Advanced Systems Engineering: Theory and Applications

Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Applied Sciences applsci	2.7	4.5	2011	16.9 Days	CHF 2400
Sensors sensors	3.9	6.8	2001	17 Days	CHF 2600
Electronics electronics	2.9	4.7	2012	15.6 Days	CHF 2400
Metals metals	2.9	4.4	2011	15 Days	CHF 2600
Energies energies	3.2	5.5	2008	16.1 Days	CHF 2600
Chips chips	-	-	2022	15.0 days *	CHF 1000

19 pages, 2861 KiB

Open AccessArticle

Finite-Time Adaptive Dynamic Surface Asymptotic Tracking Control of Uncertain Multi-Agent Systems with Unknown Control Gains

by Xiongfeng Deng and Chaocheng An

Appl. Sci. 2023, 13(17), 9552; https://doi.org/10.3390/app13179552 - 23 Aug 2023

Viewed by 770

Abstract

In this work, the finite-time asymptotic tracking control problem of uncertain multi-agent systems with unknown control gains is studied. For the unknown control gain of each subsystem in multi-agent systems, we consider using the Nussbaum gain function techniques to handle them. To deal [...] Read more.

In this work, the finite-time asymptotic tracking control problem of uncertain multi-agent systems with unknown control gains is studied. For the unknown control gain of each subsystem in multi-agent systems, we consider using the Nussbaum gain function techniques to handle them. To deal with the unknown uncertain nonlinear dynamics, the radial basis function neural network is introduced in each step of the dynamic surface control design. In addition, a nonlinear compensating term with the estimation of an unknown bounded parameter is designed to avoid repeated differentiation of each virtual control law. Then, based on the neural network control method, dynamic surface control technique, and finite-time control theory, an adaptive neural network finite-time dynamic surface control law is finally designed. Using stability analysis, it is proven that the presented adaptive control law can guarantee all signals of the closed-loop system semi-global practical finite-time stable, and the tracking error of each follower agent can converge to a small neighborhood of zero in finite time. Finally, a class of single-link robot systems is provided to illustrate the effectiveness of the designed control law. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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15 pages, 18198 KiB

Open AccessArticle

A Formal Approach to the Extraction of Permittivity and Permeability of Isotropic and Anisotropic Media Using the TM₁₁ Mode in Rectangular Waveguides

by Waldemar Susek, Andrzej Dukata and Patrycja Pomarańska

Electronics 2023, 12(13), 2899; https://doi.org/10.3390/electronics12132899 - 01 Jul 2023

Viewed by 864

Abstract

Based on our previous work on the propagation of electromagnetic waves in a layered medium placed in a rectangular waveguide, we present the theory of using the TE₁₀ and TM₁₁ modes to determine the complex parameters of isotropic and anisotropic media. [...] Read more.

Based on our previous work on the propagation of electromagnetic waves in a layered medium placed in a rectangular waveguide, we present the theory of using the TE₁₀ and TM₁₁ modes to determine the complex parameters of isotropic and anisotropic media. The Nicolson–Ross–Weir method was used. The cases of isotropic, uniaxial, and biaxial materials were considered. It has been shown that the TM₁₁ mode can be used to extract parameters of non-magnetic uniaxial anisotropy media by a single measurement, without changing the sample position. This is not possible with the previously used TE₁₀ mode. It is also possible to use the TM₁₁ mode to quickly determine whether a material is isotropic or not. Experimental results are presented for some isotropic materials. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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13 pages, 5712 KiB

Open AccessCommunication

Modelling Polarization Effects in a CdZnTe Sensor at Low Bias

by Jindřich Pipek, Roman Grill, Marián Betušiak and Kris Iniewski

Sensors 2023, 23(12), 5681; https://doi.org/10.3390/s23125681 - 17 Jun 2023

Viewed by 1197

Abstract

Semi-insulating CdTe and CdZnTe crystals fabricated into pixelated sensors and integrated into radiation detection modules have demonstrated a remarkable ability to operate under rapidly changing X-ray irradiation environments. Such challenging conditions are required by all photon-counting-based applications, including medical computed tomography (CT), airport [...] Read more.

Semi-insulating CdTe and CdZnTe crystals fabricated into pixelated sensors and integrated into radiation detection modules have demonstrated a remarkable ability to operate under rapidly changing X-ray irradiation environments. Such challenging conditions are required by all photon-counting-based applications, including medical computed tomography (CT), airport scanners, and non-destructive testing (NDT). Although, maximum flux rates and operating conditions differ in each case. In this paper, we investigated the possibility of using the detector under high-flux X-ray irradiation with a low electric field satisfactory for maintaining good counting operation. We numerically simulated electric field profiles visualized via Pockels effect measurement in a detector affected by high-flux polarization. Solving coupled drift–diffusion and Poisson’s equations, we defined the defect model, consistently depicting polarization. Subsequently, we simulated the charge transport and evaluated the collected charge, including the construction of an X-ray spectrum on a commercial 2-mm-thick pixelated CdZnTe detector with 330 µm pixel pitch used in spectral CT applications. We analyzed the effect of allied electronics on the quality of the spectrum and suggested setup optimization to improve the shape of the spectrum. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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40 pages, 9697 KiB

Open AccessArticle

Modelling and Experimental Study of Power Losses in Toothed Wheels

by Guglielmo Giannetti, Enrico Meli and Andrea Rindi

Sensors 2023, 23(12), 5541; https://doi.org/10.3390/s23125541 - 13 Jun 2023

Viewed by 756

Abstract

In recent decades, the request for more efficient performances in the aeronautical sector moved researchers to pay particular attention to all the related mechanisms and systems, especially with respect to the saving of power. In this context, the bearing modeling and design, as [...] Read more.

In recent decades, the request for more efficient performances in the aeronautical sector moved researchers to pay particular attention to all the related mechanisms and systems, especially with respect to the saving of power. In this context, the bearing modeling and design, as well as gear coupling, play a fundamental role. Moreover, the need for low power losses also concerns the study and the implementation of advanced lubrication systems, especially for high peripheral speed. With the previous aims, this paper presents a new validated model for toothed gears, added to a bearing model; with the link of these different submodels, the whole model describes the system’s dynamic behavior, taking into account the different kinds of power losses (windage losses, fluid dynamic losses, etc.) generated by the mechanical system parts (especially rolling bearings and gears). As the bearing model, the proposed model is characterized by high numerical efficiency and allows the investigation of different rolling bearings and gears with different lubrication conditions and frictions. A comparison between the experimental and simulated results is also presented in this paper. The analysis of the results is encouraging and shows a good agreement between experiments and model simulations, with particular attention to the power losses in the bearing and gears. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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20 pages, 740 KiB

Open AccessArticle

Dual-Arm Cluster Tool Scheduling for Reentrant Wafer Flows

by Tairan Song, Yan Qiao, Yunfang He, Naiqi Wu, Zhiwu Li and Bin Liu

Electronics 2023, 12(11), 2411; https://doi.org/10.3390/electronics12112411 - 26 May 2023

Cited by 2 | Viewed by 952

Abstract

Cluster tools are the key equipment in semiconductor manufacturing systems. They have been widely adopted for many wafer fabrication processes, such as chemical and physical vapor deposition processes. Reentrant wafer flows are commonly seen in cluster tool operations for deposition processes. It is [...] Read more.

Cluster tools are the key equipment in semiconductor manufacturing systems. They have been widely adopted for many wafer fabrication processes, such as chemical and physical vapor deposition processes. Reentrant wafer flows are commonly seen in cluster tool operations for deposition processes. It is very complicated to schedule cluster tools with reentrant processes. For a dual-arm cluster tool with two-time reentering, the existing studies point out that a one-wafer periodical (1-WP) schedule can be found, and it is optimal in terms of productivity. However, for some wafer fabrication processes, wafers should be processed at some PMs more than two times. This gives rise to a question of whether there still exists a 1-WP schedule for dual-arm cluster tools with the number of reentering times being more than two such that the cycle time of a tool can reach the lower bound. This problem is still open, and this is what this work wants to tackle. For a dual-arm cluster tool with the number of reentering times being k (>2) times, if there does not exist a value f ∈ {1, 2 …} such that k = 3f, theoretical proofs are given to show that a 1-WP schedule can be found, otherwise it does not exist. For cases with a 1-WP schedule, the cycle time can be obtained by analytical expressions. For the cases without a 1-WP schedule, two new methods for a three-wafer periodical schedule are proposed to improve the system productivity by comparing it with an existing three-wafer periodical schedule. The applications of the obtained results are demonstrated by examples. Wafer residency time constraints are required for some wafer fabrication processes. Note that the results obtained in this work cannot be directly applied to cluster tools with both reentrant wafer flows and wafer residency time constraints. Nevertheless, schedulablity and scheduling analyses for that applications can be conducted based on the obtained results in this work. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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16 pages, 4368 KiB

Open AccessArticle

A Requirement Quality Assessment Method Based on User Stories

by Xiangqian Xu, Yajie Dou, Liwei Qian, Zhiwei Zhang, Yufeng Ma and Yuejin Tan

Electronics 2023, 12(10), 2155; https://doi.org/10.3390/electronics12102155 - 09 May 2023

Cited by 3 | Viewed by 1383

Abstract

Agile development processes based on user stories often face issues such as incomplete, inconsistent, and inaccurate user requirements, which increase the workload of agile development teams and reduce the efficiency of product function development, ultimately resulting in the inability to respond quickly to [...] Read more.

Agile development processes based on user stories often face issues such as incomplete, inconsistent, and inaccurate user requirements, which increase the workload of agile development teams and reduce the efficiency of product function development, ultimately resulting in the inability to respond quickly to user requirements. This paper proposes a user requirement quality assessment method based on user stories to address these problems. This method relies on the agile development process, constructs a user requirement quality assessment framework, defines a user story model and a user requirement quality model, develops seven user requirement quality assessment criteria, and designs a user requirement quality assessment process. A data experiment exploring the development of smartphone requirements is used to validate the feasibility and effectiveness of the method. The experimental results demonstrate that the method improves user requirement quality to some extent, providing an automated solution for agile development teams to enhance user requirement quality. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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17 pages, 1627 KiB

Open AccessArticle

Channel Emulator Framework for Underwater Acoustic Communications

by Indrakshi Dey and Nicola Marchetti

Appl. Sci. 2023, 13(9), 5818; https://doi.org/10.3390/app13095818 - 08 May 2023

Viewed by 1177

Abstract

In this paper, we develop a tractable mathematical model and an emulation framework for communicating information through water using acoustic signals. Water is considered one of the most complex media to model due to its vastness and variety of characteristics, which depend on [...] Read more.

In this paper, we develop a tractable mathematical model and an emulation framework for communicating information through water using acoustic signals. Water is considered one of the most complex media to model due to its vastness and variety of characteristics, which depend on the scenario, the type of water body (lakes, rivers, tanks, sea, etc.), and the geographical location of the water body being considered. Our proposed mathematical model involves the concept of damped harmonic oscillators to represent the medium (water); Milne’s oscillator technique is used to map the interaction between the acoustic signal and water. Wave equations formulated for acoustic pressure and acoustic wave velocity are employed to characterise the travelling acoustic signal. The signal strength, phase shift, and time delay generated from the mathematical model are then inputted into a Simulink-based emulator framework to generate channel samples and channel impulse responses. The emulator utilises the wide sense stationary uncorrelated scattering (WSSUS) assumption and a finite sum-of-sinusoids (SOS) approach with a uniformly distributed phase to generate the channel samples. By utilising this emulator platform, it becomes feasible to generate profiles for amplitude variation, the Doppler shift, and spread experienced by any travelling signal in various underwater communication scenarios. Such a platform can be employed to simulate different communication scenarios, underwater network topologies, and data for training various learning models. Additionally, it can predict the performance of different modulation, multiplexing, error correction, and multi-access techniques for underwater acoustic communication (UWAC) systems. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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14 pages, 5325 KiB

Open AccessArticle

Simulation Analysis of the Motion of Superparamagnetic Particles in Liquid-Phase Fluid under a Magnetic Field

by Qiangqiang Zhang, Hui Song, Ruhong Song and Xianguo Hu

Appl. Sci. 2023, 13(9), 5406; https://doi.org/10.3390/app13095406 - 26 Apr 2023

Cited by 2 | Viewed by 952

Abstract

Based on the magnetic response of magnetic particles, the targeting of particles to a target area under the modulation of an external magnetic field has been used in many applications. An accurate kinematic model is helpful to achieve accurate targeting of magnetic particles [...] Read more.

Based on the magnetic response of magnetic particles, the targeting of particles to a target area under the modulation of an external magnetic field has been used in many applications. An accurate kinematic model is helpful to achieve accurate targeting of magnetic particles and to investigate the factors influencing the motion of the particles. In the present paper, a segmental magnetization model was proposed based on the real magnetization process of superparamagnetic particles to calculate the magnetic force, and this was compared with a traditional magnetization model. The effects of magnetic field strength and particle diameter on the trajectory of magnetic particles in fluids under a magnetic field were further analyzed using a finite element analysis software. The simulation results show that changing the particle size only affected the velocity of the particles and did not affect the trajectory. When magnetic field strength changed, magnetic particles showed different trajectories. Notably, when the magnetic field force in the Y direction was too large, meaning the gravity could be neglected, the trajectory of the particles no longer changed when the magnetic field strength was varied. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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19 pages, 6576 KiB

Open AccessArticle

Fault Diagnosis of Wind Turbine Planetary Gear Based on a Digital Twin

by Yi Wang, Wenlei Sun, Liqiang Liu, Bingkai Wang, Shenghui Bao and Renben Jiang

Appl. Sci. 2023, 13(8), 4776; https://doi.org/10.3390/app13084776 - 10 Apr 2023

Cited by 5 | Viewed by 2301

Abstract

Aiming at the problems of the traditional planetary gear fault diagnosis method of wind turbines, such as the poor timeliness of data transmission, weak visualization effect of state monitoring, and untimely feedback of fault information, this paper proposes a planetary gear fault diagnosis [...] Read more.

Aiming at the problems of the traditional planetary gear fault diagnosis method of wind turbines, such as the poor timeliness of data transmission, weak visualization effect of state monitoring, and untimely feedback of fault information, this paper proposes a planetary gear fault diagnosis method for wind turbines based on a digital twin. The method was used to build the digital twin model of wind turbines and analyze the wind turbines’ operating state utilizing virtual and real data. Empirical mode decomposition (EMD) was used, and an atom search optimization–support vector machine (ASO-SVM) model was established for planetary gear fault diagnosis. The digital twin model diagnoses faults and constantly revises the model based on the diagnostic results. The digital twin fault diagnosis system was implemented in the Unity3D platform. The experimental results demonstrate the feasibility of the proposed early-warning system for the real-time diagnosis of planetary gear faults in wind turbines. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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16 pages, 4383 KiB

Open AccessArticle

Piecewise Hybrid System with Cross-Correlation Spectral Kurtosis for Fault Diagnosis in Rolling Bearing of Wind Power Generator

by Shan Wang, Zijian Qiao and Pingjuan Niu

Electronics 2023, 12(7), 1548; https://doi.org/10.3390/electronics12071548 - 25 Mar 2023

Cited by 2 | Viewed by 1127

Abstract

As the core equipment of wind turbines, rolling bearings affect the normal operation of wind power generators, resulting in huge economic losses and significant social impacts in the case of faults. Most faults are not easily found because of the small vibration response [...] Read more.

As the core equipment of wind turbines, rolling bearings affect the normal operation of wind power generators, resulting in huge economic losses and significant social impacts in the case of faults. Most faults are not easily found because of the small vibration response of these rolling bearings that operate in harsh conditions. To address the problem that the fault identifications of rolling bearings are disturbed by the strong noise in wind power generators, an adaptive nonlinear method based on a piecewise hybrid stochastic resonance system with a novel cross-correlation spectral kurtosis is proposed. Then, the vibration signals collected from the fault point of the outer and inner rings are used to clarify the outstanding capability of the proposed method when compared with the maximum cross-correlation-kurtosis-based unsaturated stochastic resonance method. Furthermore, the machine learning method based on the medium tree was adopted to further prove the excellent performance of the piecewise hybrid stochastic resonance system with a novel cross-correlation spectral kurtosis for realizing the efficient detection of rolling bearing faults in wind power generators, which has important innovation significance and practical engineering value for ensuring the safe and stable operation of wind turbines. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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23 pages, 1870 KiB

Open AccessArticle

Dynamic Equivalent Model Considering Multiple Induction Motors for System Frequency Response

by Zhen Tang, Guoxing Mu, Jie Pan, Zhiwei Xue, Hong Yang, Mingyang Mei, Zhihao Zhang and Peng Kou

Energies 2023, 16(7), 2987; https://doi.org/10.3390/en16072987 - 24 Mar 2023

Viewed by 1084

Abstract

Renewable energy sources have been characterized by a persistent and rapid proliferation, which has resulted in a notable reduction in grid inertia over an extended period. There is a widely held belief that the primary source of inertia within the grid stems from [...] Read more.

Renewable energy sources have been characterized by a persistent and rapid proliferation, which has resulted in a notable reduction in grid inertia over an extended period. There is a widely held belief that the primary source of inertia within the grid stems from generation-side conventional units. However, in power consumption, a significant number of induction motors are present, which can inherently offer rotational inertia by virtue of their kinetic energy. To investigate the influence of induction motors on grid inertia, in this paper, we propose two types of models, i.e., a detailed grid model and a dynamic equivalent model that considers multiple induction motors. Specifically, the detailed grid model with multiple induction motors is first established. However, the detailed model requires the specific parameters of induction motors, which are hard to acquire in large systems. Moreover, the accuracy of the model is unsatisfactory. To fill these gaps, the dynamic equivalent model (DEM) is further proposed to emulate the detailed model. Compared with the detailed model, the proposed dynamic equivalent model is structurally simple and does not require the specific parameters of induction motors. Therefore, it is possible to apply to large systems for investigating the influence of induction motors on grid frequency dynamics. A genetic algorithm is introduced in order to figure out the parameters of the proposed dynamic equivalent model from historical frequency data. The proposed detailed model and dynamic equivalent model are evaluated on the IEEE 9-bus system in MATLAB and SimPowerSystems toolbox. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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18 pages, 10076 KiB

Open AccessArticle

The Influence of the Magnetic Field Line Curvature on Wall Erosion near the Hall Thruster Exit Plane

by Lulu Quan, Yong Cao, Bin Tian and Keyu Gong

Appl. Sci. 2023, 13(6), 3547; https://doi.org/10.3390/app13063547 - 10 Mar 2023

Cited by 1 | Viewed by 1060

Abstract

One of the main factors that limit the lifetime of the Hall effect Thrusters (HETs) is the erosion of the acceleration channel caused by the flux of energetic ions. The magnetic field that is curved and convex towards the anode has been widely [...] Read more.

One of the main factors that limit the lifetime of the Hall effect Thrusters (HETs) is the erosion of the acceleration channel caused by the flux of energetic ions. The magnetic field that is curved and convex towards the anode has been widely used in HETs because of its role in reducing the divergence angle of the ion beam and the channel wall erosion. However, the mechanism of the influence of the magnetic field line curvature on the wall erosion is not clear. Therefore, in this paper, a 2D3V numerical model based on the immersed-finite-element and particle-in-cell (IFE-PIC) method is established to simulate the radial-azimuthal plane near the exit of the Hall thruster. The effect of the tilt angle of the magnetic field line on the wall sputtering erosion rate is analyzed. The results show that compared to the case with the electric field E perpendicular to the magnetic field B, the energy of the ions hitting the channel wall is smaller and the wall erosion is weaker when the magnetic field lines are convex to the anode. As the tilt angle of the magnetic field lines increases from 0° to 60°, the erosion rate is reduced by 90%. Conversely, when the magnetic field lines are convex to the exit plane of the channel, the wall erosion is much more serious compared to the case with the orthogonal electric field E and the magnetic field B. As the tilt angle of the magnetic field line changes from 0° to 60°, the erosion rate is enhanced by 171%. The results in this paper are instructive for the design and optimization of the magnetic field of the HETs. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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16 pages, 5346 KiB

Open AccessArticle

A Digital Twin-Based State Monitoring Method of Gear Test Bench

by Jubo Li, Songlin Wang, Jianjun Yang, Huijie Zhang and Hengbo Zhao

Appl. Sci. 2023, 13(5), 3291; https://doi.org/10.3390/app13053291 - 04 Mar 2023

Cited by 4 | Viewed by 1915

Abstract

The gear test bench is important equipment for analyzing gear performance, detecting gear quality, and providing basic data for gear design and machining. In order to monitor the running state of the gear test bench, predict its running performance both timely and effectively, [...] Read more.

The gear test bench is important equipment for analyzing gear performance, detecting gear quality, and providing basic data for gear design and machining. In order to monitor the running state of the gear test bench, predict its running performance both timely and effectively, and guarantee its stable operation, a digital twin-based state monitoring method of the gear test bench is proposed in this paper. The state monitoring system of the gear test bench based on the digital twin model is constructed to simulate its normal running state in real time. On this basis, through the acquisition of physical information of the gear test bench, the developing of the state monitoring system, and the simulation of the digital twin model, the real-time state monitoring of the normal operation gear test bench is realized. The test results of the closed power flow gear test bench show that the digital twin simulation results of the gear test bench are basically consistent with it. The proposed state monitoring system can map the normal running state of the gear test bench, so as to realize the running state monitoring of the gear test bench. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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14 pages, 3543 KiB

Open AccessArticle

Development of a Reference Device for the Calibration of Optical One-Shot Time-Interval Measurements

by Dalibor Kuhinek, Tomislav Bratko, Hrvoje Vukošić and Ivica Gavranić

Electronics 2023, 12(2), 439; https://doi.org/10.3390/electronics12020439 - 14 Jan 2023

Viewed by 1094

Abstract

This paper presents the development of a device that creates two or more light pulses with a precision time delay in a range from microseconds to several seconds and for the purpose of the calibration of velocity of detonation (VOD) measurement instruments. The [...] Read more.

This paper presents the development of a device that creates two or more light pulses with a precision time delay in a range from microseconds to several seconds and for the purpose of the calibration of velocity of detonation (VOD) measurement instruments. The device was assembled, programmed, and tested for functionality. Measurements were conducted using a reference counter. First, a precision OCXO (oven-controlled crystal oscillator) was used as a clock source. For verification of programmed subroutines, a counter oscillator output port was used as a source of clock signal for the microcontroller. This enabled the cancellation of possible oscillator errors. The signal had to be converted from an AC sine signal to a signal with positive values only using a clamper circuit. By the proposed solution, a calculable standard of time delay between two light pulses was achieved. According to the obtained results, this device can be used to calibrate field measurement devices for VOD measurements in explosives or some other use where the measurement device records the time interval between multiple light pulses. This enables more confidence in measurement results, faster recognition of instrument drift and increases the quality of measurement. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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19 pages, 3448 KiB

Open AccessTutorial

Stability Analysis of Equilibrium Point and Limit Cycle of Two-Dimensional Nonlinear Dynamical Systems—A Tutorial

by Bin Wei

Appl. Sci. 2023, 13(2), 1136; https://doi.org/10.3390/app13021136 - 14 Jan 2023

Cited by 2 | Viewed by 2364

Abstract

The equilibrium state of a dynamical system can be divided into the equilibrium point and limit cycle. In this paper, the stability analysis of the equilibrium point and limit cycle of dynamical systems are presented through different and all possible approaches, and those [...] Read more.

The equilibrium state of a dynamical system can be divided into the equilibrium point and limit cycle. In this paper, the stability analysis of the equilibrium point and limit cycle of dynamical systems are presented through different and all possible approaches, and those approaches are compared as well. In particular, the author presented the stability analysis of the equilibrium point through phase plane approach, Lyapunov–LaSalle energy-based approach, and linearization approach, respectively, for two-dimensional nonlinear system, while the stability analysis of the limit cycle is analyzed by using the LaSalle local invariant set theorem and Poincaré–Bendixson theorem, which is only valid in two-dimensional systems. Different case studies are used to demonstrate the stability analysis of equilibrium point and limit cycle. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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22 pages, 1660 KiB

Open AccessArticle

A Hybrid Multi-Criteria Approach to the Vendor Selection Problem for Sensor-Based Medical Devices

by Constanta Zoie Radulescu and Marius Radulescu

Sensors 2023, 23(2), 764; https://doi.org/10.3390/s23020764 - 09 Jan 2023

Cited by 3 | Viewed by 1421

Abstract

Sensors for health are a dynamic technology and sensor-based medical devices (SMD) are becoming an important part of health monitoring systems in healthcare centers and ambulatory care. The rapid growth in the number, diversity and costs of medical devices and Internet of Things [...] Read more.

Sensors for health are a dynamic technology and sensor-based medical devices (SMD) are becoming an important part of health monitoring systems in healthcare centers and ambulatory care. The rapid growth in the number, diversity and costs of medical devices and Internet of Things (IoT) healthcare platforms imposes a challenge for healthcare managers: making a rational choice of SMD vendor from a set of potential SMD vendors. The aim of this paper is to develop a hybrid approach that combines a performance evaluation model and a multi-objective model for the SMD vendor selection problem. For determining the criteria weights in the performance evaluation model, an original version of the best worst method (BWM) is applied, which we call the flexible best worst method (FBWM). The multi-objective model has two objective functions; one is to maximize the SMD performance and the other is to minimize the SMD cost. A case study for the application of the hybrid approach for SMD procurement in a healthcare center is analyzed. The hybrid approach can support healthcare decision makers in their SMD procurement decisions. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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14 pages, 2481 KiB

Open AccessArticle

TEZE: A System to Enhance Safety in Highway Tunnels as a New Smartphone-Based Emergency Call Paradigm

by Romeo Giuliano, Franco Mazzenga, Emilio Tenaglia, Francesco Vatalaro, Alessandro Vizzarri and Gherardo Zei

Electronics 2023, 12(2), 333; https://doi.org/10.3390/electronics12020333 - 09 Jan 2023

Cited by 1 | Viewed by 1463

Abstract

In the European Union, the eCall system has been mandatory since 31 March 2018. The system enabled a significant increase in safety on roads and highways, making help faster in the event of an accident. However, based on circuit-switched 2G/3G communications and an [...] Read more.

In the European Union, the eCall system has been mandatory since 31 March 2018. The system enabled a significant increase in safety on roads and highways, making help faster in the event of an accident. However, based on circuit-switched 2G/3G communications and an onboard device called IVS, it is generally unavailable on legacy vehicles. Some of its limitations tend to be remedied by the future NG eCall based on 4G/5G packet-switched communications. This paper discusses why the IVS may be an Achilles’ heel of any future IVS-based eCall and analyzes the advantages of a smartphone-based system. The TEZE system, starting to be implemented and installed in Italian highway tunnels, is one first general-purpose safety system, allowing highly reliable smartphone-based emergency calls. It is based on a dedicated low-cost ground infrastructure that allows monitoring of the availability of emergency call service through the mobile radio networks of the operators present inside a tunnel. The system complies with the ISO/IEC 30141:2018 reference standard. Identifying functional/non-functional requirements and their verification criteria provides an overall validation of the analyzed system. The TEZE system has been implemented and tested on the field. We report and comment on some experimental results. The paper also examines some key functionalities for vehicular services that can be implemented in an integrated system based on smartphones and heterogeneous networks. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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12 pages, 1041 KiB

Open AccessArticle

Adaptive Dendritic Cell-Negative Selection Method for Earthquake Prediction

by Wen Zhou, Wuyang Lan, Zhiwei Ye, Zhe Ming, Jingliang Chen and Qiyi He

Electronics 2023, 12(1), 9; https://doi.org/10.3390/electronics12010009 - 20 Dec 2022

Cited by 1 | Viewed by 1644

Abstract

Earthquake prediction (EQP) is an extremely difficult task, which has been overcome by adopting various technologies, with no further transformation so far. The negative selection algorithm (NSA) is an artificial intelligence method based on the biological immune system. It is widely used in [...] Read more.

Earthquake prediction (EQP) is an extremely difficult task, which has been overcome by adopting various technologies, with no further transformation so far. The negative selection algorithm (NSA) is an artificial intelligence method based on the biological immune system. It is widely used in anomaly detection due to its advantages of requiring little normal data to detect anomalies, including historical seismic-events-based EQP. However, NSA can suffer from the undesirable effect of data drift, resulting in outdated normal patterns learned from data. To tackle this problem, the data changes must be detected and processed, stimulating fast algorithmic adaptation strategies. This study proposes a dendritic cell algorithm (DCA)-based adaptive learning method for drift detection and negative selection algorithm (DC-NSA) that dynamically adapts to new input data. First, this study adopts the Gutenberg–Richter (GR) law and other earthquake distribution laws to preprocess input data. Then, the NSA is employed for EQP, and then, the dendritic cell algorithm (DCA) is employed to detect changes to trigger gradient descent strategies and update the self-set in NSA. Finally, the proposed approach is implemented to predict the earthquakes of MW > 5 in Sichuan and the surroundings during the next month. The experimental results demonstrate that our proposed DC-NSA is superior to the existing state-of-the-art EQP approaches. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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16 pages, 1052 KiB

Open AccessArticle

Flexible IoT Agriculture Systems for Irrigation Control Based on Software Services

by Eva Palomar-Cosín and Marisol García-Valls

Sensors 2022, 22(24), 9999; https://doi.org/10.3390/s22249999 - 19 Dec 2022

Cited by 3 | Viewed by 2153

Abstract

IoT technology applied to agriculture has produced a number of contributions in the recent years. Such solutions are, most of the time, fully tailored to a particular functional target and focus extensively on sensor-hardware development and customization. As a result, software-centered solutions for [...] Read more.

IoT technology applied to agriculture has produced a number of contributions in the recent years. Such solutions are, most of the time, fully tailored to a particular functional target and focus extensively on sensor-hardware development and customization. As a result, software-centered solutions for IoT system development are infrequent. This is not suitable, as the software is the bottleneck in modern computer systems, being the main source of performance loss, errors, and even cyber attacks. This paper takes a software-centric perspective to model and design IoT systems in a flexible manner. We contribute a software framework that supports the design of the IoT systems’ software based on software services in a client–server model with REST interactions; and it is exemplified on the domain of efficient irrigation in agriculture. We decompose the services’ design into the set of constituent functions and operations both at client and server sides. As a result, we provide a simple and novel view on the design of IoT systems in agriculture from a sofware perspective: we contribute simple design structure based on the identification of the front-end software services, their internal software functions and operations, and their interconnections as software services. We have implemented the software framework on an IoT irrigation use case that monitors the conditions of the field and processes the sampled data, detecting alarms when needed. We demonstrate that the temporal overhead of our solution is bounded and suitable for the target domain, reaching a response time of roughly 11 s for bursts of 3000 requests. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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21 pages, 8273 KiB

Open AccessFeature PaperArticle

Influence of the Main Geometrical Parameters on the Design and Performance of Mixed Inflow Turbines

by Mohammed Amine Chelabi, Sergey Dobrotvorskiy, Yevheniia Basova, Borys A. Aleksenko, Milan Edl, Jan Zdebor and José Machado

Appl. Sci. 2022, 12(23), 12165; https://doi.org/10.3390/app122312165 - 28 Nov 2022

Cited by 2 | Viewed by 1247

Abstract

The blade shape is of great interest to hybrid turbine designers, due to its significant and direct impact on turbine performance. The inlet and outlet diameters of the vane affect the size of the rotor, which is limited because of the small space [...] Read more.

The blade shape is of great interest to hybrid turbine designers, due to its significant and direct impact on turbine performance. The inlet and outlet diameters of the vane affect the size of the rotor, which is limited because of the small space available in internal combustion engines. The effect of the ratio of the average inlet diameter and the average exducer inlet diameter on the performance of a mixed inlet turbine will be the focus of this study, which consists of two cases included herein for the purpose of illustrating the means of improving rotor performances and controlling the flow mass rate. In the first case, we achieved this by changing the average diameter of the exducer inlet, while, in the second one, we achieved this by changing the average inlet diameter. Additionally, the angles of the inlet and outlet blades were recalculated to preserve the same blade profile and to eliminate the effect of curvilinearity. It was noted that the shape of the blade was very sensitive to changes in the ratio of the investigated diameters, and—in both cases—interesting results were obtained. First, an increase in output work and in total static isentropic efficiency by 2.16% and 2.15%, respectively, was generated, with a saving of 3.52% of the used mass flow and a lighter rotor compared to one that used to take up the same space by using fixed average inlet diameter blades. In the second case, there was an increase in the output work by 3.31%, and in the total static isentropic efficiency by 3.34%, but the rotor became heavier and required an increase in the mass flow used. Since inter-blade flows are very complex, three-dimensional and viscous—featuring various types of secondary and eddy flows—the CFX.15-CFD code was used in all models to solve the averaged Navier–Stokes equations. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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15 pages, 1869 KiB

Open AccessArticle

Efficient Weighted Ensemble Method for Predicting Peak-Period Postal Logistics Volume: A South Korean Case Study

by Eunhye Kim, Tsatsral Amarbayasgalan and Hoon Jung

Appl. Sci. 2022, 12(23), 11962; https://doi.org/10.3390/app122311962 - 23 Nov 2022

Viewed by 1297

Abstract

Demand prediction for postal delivery services is useful for managing logistic operations optimally. Particularly for holiday periods, namely the Lunar New Year and Korean Thanksgiving Day (Chuseok) in South Korea, the logistics service increases sharply compared with the usual period, which makes it [...] Read more.

Demand prediction for postal delivery services is useful for managing logistic operations optimally. Particularly for holiday periods, namely the Lunar New Year and Korean Thanksgiving Day (Chuseok) in South Korea, the logistics service increases sharply compared with the usual period, which makes it hard to provide reliable operation in mail centers. This study proposes a Multilayer Perceptron-based weighted ensemble method for predicting the accepted parcel volumes during special periods. The proposed method consists of two main phases: the first phase enriches the training dataset via synthetic samples using unsupervised learning; the second phase builds two Multilayer Perceptron models using internal and external factor-derived features for prediction. The final result is estimated by the weighted average predictions of these models. We conducted experiments on 25 Korean mail center datasets. The experimental study on the dataset provided by Korea Post shows better performance than other compared methods. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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21 pages, 5444 KiB

Open AccessArticle

Optimizable Control Barrier Functions to Improve Feasibility and Add Behavior Diversity while Ensuring Safety

by Shilei Li, Zhimin Yuan, Yun Chen, Fang Luo, Zhichao Yang, Qing Ye, Wei Fu and Yu Fu

Electronics 2022, 11(22), 3657; https://doi.org/10.3390/electronics11223657 - 09 Nov 2022

Viewed by 1626

Abstract

Ensuring safety while retaining maximum performance is a basic requirement for automatic cyber-physical systems, especially for safety-critical applications. A quadratic programming optimization framework called MPC-CBF has recently been presented, which directly unifies model predictive control (MPC) with control barrier functions (CBFs) over the [...] Read more.

Ensuring safety while retaining maximum performance is a basic requirement for automatic cyber-physical systems, especially for safety-critical applications. A quadratic programming optimization framework called MPC-CBF has recently been presented, which directly unifies model predictive control (MPC) with control barrier functions (CBFs) over the prediction time horizon. However, the conservative nature of CBFs can lead to feasibility problems in real applications. Based on the analysis of the role of the decay rate and the conservative accumulation phenomenon in standard CBF formulations, this paper proposes to directly optimize CBF constraints within the MPC framework. By regarding CBFs as a safety restriction level indicator and an optimizable constraint within the MPC framework, the trade-off between feasibility and safety can be adaptively optimized. The proposed Optimizable CBF (OCBF) model removes the hyper-parameters selection problem in standard CBFs and can adaptively adjust the safety restriction level and increase behavior diversity by adding the corresponding objects in the cost function in MPC. To eliminate the accumulation effects of actual values of the CBF constraints in previous time steps, this paper further proposes a General OCBF (GOCBF) formulation. Compared with existing formulations, the safety margin defined in our GOCBF has intuitive physical meanings and thus provides a more flexible and intuitive mechanism to compromise different objects in terms of ensuring safety while not undermining basic feasibility. Experimental results demonstrate that our algorithm provides a more flexible and intuitive mechanism to achieve this, thus improving feasibility and adding behavior diversity in the MPC-CBF framework. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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19 pages, 2299 KiB

Open AccessArticle

Design and Implementation of a Cloud PACS Architecture

by Jacek Kawa, Bartłomiej Pyciński, Michał Smoliński, Paweł Bożek, Marek Kwasecki, Bartosz Pietrzyk and Dariusz Szymański

Sensors 2022, 22(21), 8569; https://doi.org/10.3390/s22218569 - 07 Nov 2022

Cited by 4 | Viewed by 5395

Abstract

The limitations of the classic PACS (picture archiving and communication system), such as the backward-compatible DICOM network architecture and poor security and maintenance, are well-known. They are challenged by various existing solutions employing cloud-related patterns and services. However, a full-scale cloud-native PACS has [...] Read more.

The limitations of the classic PACS (picture archiving and communication system), such as the backward-compatible DICOM network architecture and poor security and maintenance, are well-known. They are challenged by various existing solutions employing cloud-related patterns and services. However, a full-scale cloud-native PACS has not yet been demonstrated. The paper introduces a vendor-neutral cloud PACS architecture. It is divided into two main components: a cloud platform and an access device. The cloud platform is responsible for nearline (long-term) image archive, data flow, and backend management. It operates in multi-tenant mode. The access device is responsible for the local DICOM (Digital Imaging and Communications in Medicine) interface and serves as a gateway to cloud services. The cloud PACS was first implemented in an Amazon Web Services environment. It employs a number of general-purpose services designed or adapted for a cloud environment, including Kafka, OpenSearch, and Memcached. Custom services, such as a central PACS node, queue manager, or flow worker, also developed as cloud microservices, bring DICOM support, external integration, and a management layer. The PACS was verified using image traffic from, among others, computed tomography (CT), magnetic resonance (MR), and computed radiography (CR) modalities. During the test, the system was reliably storing and accessing image data. In following tests, scaling behavior differences between the monolithic Dcm4chee server and the proposed solution are shown. The growing number of parallel connections did not influence the monolithic server’s overall throughput, whereas the performance of cloud PACS noticeably increased. In the final test, different retrieval patterns were evaluated to assess performance under different scenarios. The current production environment stores over 450 TB of image data and handles over 4000 DICOM nodes. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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23 pages, 9182 KiB

Open AccessReview

Roof Fall Hazard Monitoring and Evaluation—State-of-the-Art Review

by Krzysztof Fuławka, Lech Stolecki, Marcin Szumny, Witold Pytel, Izabela Jaśkiewicz-Proć, Michel Jakić, Michael Nöger and Philipp Hartlieb

Energies 2022, 15(21), 8312; https://doi.org/10.3390/en15218312 - 07 Nov 2022

Cited by 4 | Viewed by 2387

Abstract

A roof fall hazard is still one of the major threats in the underground mining industry. Each such type of event always brings great risk to miners and causes serious interruptions in the process of rock excavation. In general, the possibility of roof [...] Read more.

A roof fall hazard is still one of the major threats in the underground mining industry. Each such type of event always brings great risk to miners and causes serious interruptions in the process of rock excavation. In general, the possibility of roof fall hazard occurrence is directly related to the local geology, the presence of horizontal stresses as well as the type of excavation method and the efficacy of the utilized roof support. Due to the complexity of this process, it is important to continuously evaluate the roof fall risk, especially in long life-time places where a mining crew is often present. Within this article, a detailed review of the current methods of monitoring and evaluating roof fall risk was presented. Based on the extensive literature survey, different types of devices were described, and their advantages and disadvantages were pointed out. Furthermore, new trends in the area of roof fall risk monitoring were described and discussed. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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13 pages, 420 KiB

Open AccessArticle

Stability Analysis for Linear Systems with a Differentiable Time-Varying Delay via Auxiliary Equation-Based Method

by Zongming Yin, Xiefu Jiang, Ning Zhang and Weihua Zhang

Electronics 2022, 11(21), 3492; https://doi.org/10.3390/electronics11213492 - 27 Oct 2022

Cited by 1 | Viewed by 1051

Abstract

This paper concentrates on the stability problem for linear systems with a differentiable time-varying delay via an auxiliary equation-based method. By supposing that the second-order derivative of the system state is available, an auxiliary equation is obtained. On the basis of the system [...] Read more.

This paper concentrates on the stability problem for linear systems with a differentiable time-varying delay via an auxiliary equation-based method. By supposing that the second-order derivative of the system state is available, an auxiliary equation is obtained. On the basis of the system equation and the auxiliary equation, we define a suitable delay-product-type augmented Lyapunov-Krasovskii functional (LKF), under which more delay and system state information can be exploited. Based on the LKF, by utilizing some vital lemmas, adding zero terms, and the convex analysis method, we propose a new stability condition that is less conservative. Finally, to illustrate the merit of the obtained stability condition, two typical numerical examples are given. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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16 pages, 3904 KiB

Open AccessArticle

Modeling and Analysis of a Thermophotovoltaic Integrated Self-Powered Furnace

by Praveen Cheekatamarla, Stephen Kowalski, Ahmad Abu-Heiba, Timothy LaClair and Kyle Gluesenkamp

Energies 2022, 15(19), 7090; https://doi.org/10.3390/en15197090 - 27 Sep 2022

Viewed by 1422

Abstract

This work investigates the energy efficiency and carbon reduction potential of self-powered residential building heating equipment using a thermodynamic modeling approach. An integrated thermophotovoltaic power module and residential scale furnace system (40,000 Btu/h) were modeled and studied in detail to assess the influence [...] Read more.

This work investigates the energy efficiency and carbon reduction potential of self-powered residential building heating equipment using a thermodynamic modeling approach. An integrated thermophotovoltaic power module and residential scale furnace system (40,000 Btu/h) were modeled and studied in detail to assess the influence of different design configurations on primary energy efficiency. Operational characteristics such as total power generation, electrical efficiency, and heat recovery were examined in a self-powered system configuration. A sensitivity analysis was conducted to determine the influence of the electric grid’s carbon dioxide footprint (carbon intensity) and the cost of electricity on the environmental, as well as the economic, benefit associated with the self-powered configuration. Compared with a traditional furnace powered by an electric grid at a carbon intensity of 0.5 kg CO_2eq/kWh_EL, the self-powered furnace was shown to decrease the annual carbon dioxide emissions by approximately 550 kg (~75% reduction), while also saving more than USD 200 in utility expenses, annually. Additionally, the carbon emission reduction potential of blending different concentrations of hydrogen in natural gas fuel was also studied. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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12 pages, 798 KiB

Open AccessArticle

Implementation and Review of the Axisymmetric Equilibrium System of RFX-Mod2 within the MARTe2 Framework

by Nicolò Ferron, Claudio Finotti, Gabriele Manduchi, Giuseppe Marchiori, Paolo Bettini, Domenico Abate and Roberto Cavazzana

Electronics 2022, 11(17), 2751; https://doi.org/10.3390/electronics11172751 - 01 Sep 2022

Cited by 1 | Viewed by 957

Abstract

A major refurbishment of the toroidal complex of the RFX-mod device is in progress and it will include the removal of the Inconel vacuum vessel and a modification of the stainless steel supporting structure to be made vacuum-tight. The axisymmetric equilibrium control in [...] Read more.

A major refurbishment of the toroidal complex of the RFX-mod device is in progress and it will include the removal of the Inconel vacuum vessel and a modification of the stainless steel supporting structure to be made vacuum-tight. The axisymmetric equilibrium control in RFX-mod was responsible for the control of the plasma current, horizontal and vertical position along with its stability and the plasma shape. The new implementation framework, both hardware and software, is described. The system has been fully reviewed and modified, if needed, for its prospective use in RFX-mod2. In order to run tests in an operation-like context, the updated system has also been implemented in the MARTe2 framework, to be deployed for the real-time applications of RFX-mod2. The results of the previous versions were reproduced and the cycle-time requirements were met. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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23 pages, 9008 KiB

Open AccessArticle

Autonomous Vehicle with Emergency Braking Algorithm Based on Multi-Sensor Fusion and Super Twisting Speed Controller

by Turki Alsuwian, Rana Basharat Saeed and Arslan Ahmed Amin

Appl. Sci. 2022, 12(17), 8458; https://doi.org/10.3390/app12178458 - 24 Aug 2022

Cited by 12 | Viewed by 7626

Abstract

The automobile revolution and growth in the number of cars produced several issues, and vehicle accidents remain one of the most serious road-related issues. Human mistakes and a failure to brake quickly are the main causes of accidents. There may be serious outcomes [...] Read more.

The automobile revolution and growth in the number of cars produced several issues, and vehicle accidents remain one of the most serious road-related issues. Human mistakes and a failure to brake quickly are the main causes of accidents. There may be serious outcomes to driving when distracted. To address the aforementioned issues, an autonomous emergency braking system (AEBS) was developed. To support such an AEBS, scalable, reliable, secure, fault-tolerant, and interoperable technologies are required. An advanced emergency braking system (EBS) with sensor fusion is proposed in this paper that can autonomously identify a probable forward collision and activate the vehicle braking system to brake the vehicle to avoid or mitigate a collision. Additionally, it provides a non-linear speed controller that facilitates the AEBS to apply the brakes in an emergency. Sensor fusion using lidar, radar, and vision sensors makes the AEBS more efficient and more reliable to detect vehicles or obstacles and decreases the chance of collision to a minimum level. A MATLAB/Simulink environment was used for simulation experiments and the results demonstrated the stable operation of the AEBS to avoid forward collisions in the event of an error in the measurement of any one sensor while any vehicle is detected. The presented work establishes that the EBS sensor fusion unit is a highly reliable solution for detecting the leading vehicle at the proper time and the AEBS controller can apply the brake in the situation of forwarding obstacle detection. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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16 pages, 2554 KiB

Open AccessArticle

Consensus Problem and Formation Control for Heterogeneous Multi-Agent Systems with Switching Topologies

by Chunping Wang, Jiaqi Wang, Ping Wu and Jinfeng Gao

Electronics 2022, 11(16), 2598; https://doi.org/10.3390/electronics11162598 - 19 Aug 2022

Cited by 4 | Viewed by 1402

Abstract

The cooperative control problem of discrete-time multi-agent systems (MASs) is discussed, and bounded uncertain time-delays and directed switching topologies are considered. By applying model transformations and matrix theory, an augmented system method is introduced to handle a heterogeneous time-delay MAS. Then, the consensus [...] Read more.

The cooperative control problem of discrete-time multi-agent systems (MASs) is discussed, and bounded uncertain time-delays and directed switching topologies are considered. By applying model transformations and matrix theory, an augmented system method is introduced to handle a heterogeneous time-delay MAS. Then, the consensus problem of the system is turned to the convergence issue of the product of innumerable row stochastic matrices. Sufficient conditions for asymptotic consensus of the system under directed switching topologies are obtained. Moreover, a novel consensus-based formation control strategy is designed to gain sufficient and necessary conditions for the formation control of a second-order differential robot system. Finally, the effectiveness of the obtained results is verified through simulations. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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15 pages, 3340 KiB

Open AccessArticle

A Modeling Method of Agents and SOA in Advanced Avionics System Based on AADL

by Pingyu Deng, Qing Zhou, Dong An, Shihai Wang and Kui Li

Appl. Sci. 2022, 12(16), 8157; https://doi.org/10.3390/app12168157 - 15 Aug 2022

Cited by 3 | Viewed by 1468

Abstract

The modeling method of agents and service-oriented architecture (SOA) in avionics systems describes agents and SOA in avionics systems with models. To our knowledge, however, the current modeling methods cannot describe the behavior of agents and SOA accurately and do not fit well [...] Read more.

The modeling method of agents and service-oriented architecture (SOA) in avionics systems describes agents and SOA in avionics systems with models. To our knowledge, however, the current modeling methods cannot describe the behavior of agents and SOA accurately and do not fit well with the existing avionics system models. This paper addresses the above problems by presenting a modeling method based on architecture analysis and design language (AADL). In this method, the working states of agents are described by the mode components, with the working process being triggered by the input of agents; and the services are described by the process component. The application of the software system is described by the system components that contain several process components. Moreover, different modes of the system are used to describe different applications, and the transitions of application are triggered by specific application requests. Software architecture of an avionics system is modeled by the proposed method. This case demonstrates that the proposed method can accurately describe how agents and SOA work in a new way and fit well with the existing avionics system models. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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7 pages, 2130 KiB

Open AccessArticle

Calculation of Three-dimensional Energy Product for Isotropic Nd₂Fe₁₄B Magnet

by Namkyu Kim, Hee-Sung Han, Chul-Jin Choi, Ki-Suk Lee and Jihoon Park

Appl. Sci. 2022, 12(15), 7887; https://doi.org/10.3390/app12157887 - 05 Aug 2022

Viewed by 1582

Abstract

A conventional energy product calculated by the product of the B-field and the H-field is not sufficient for representing the performance of a magnet because it considers the homogeneous and only the uniaxial magnetic properties of the magnet. The conventional energy [...] Read more.

A conventional energy product calculated by the product of the B-field and the H-field is not sufficient for representing the performance of a magnet because it considers the homogeneous and only the uniaxial magnetic properties of the magnet. The conventional energy product has been compared with another energy product obtained by integrating the scalar product of the B-field and the H-field of each cell composed of the three-dimensional components. We investigated a model system by micromagnetic simulation using finite differential method (FDM) and calculated the full hysteresis of the magnet. The model system of a Nd₂Fe₁₄B magnet composed of grains with a diameter of about 100 nm was assumed. In the case of the isotropic multi-grain magnet, the energy product calculated by the integration method was 28% larger than the energy product obtained by the conventional way, although a discrepancy between the distribution of the magnetizations and the demagnetizing fields at the reversal process resulted in the decrease of the energy product. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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16 pages, 22444 KiB

Open AccessArticle

3D Measurement Method for Saturated Highlight Characteristics on Surface of Fuel Nozzle

by Yeni Li, Liang Hou and Yun Chen

Sensors 2022, 22(15), 5661; https://doi.org/10.3390/s22155661 - 28 Jul 2022

Cited by 1 | Viewed by 1417

Abstract

Saturated highlights on metal surfaces reduce the detection accuracy of fuel nozzles. In this paper, we propose an image inpainting method with a saturated highlight based on the statistics of similar patches used in prior segmentation of the subregion. The sequence image acquisition [...] Read more.

Saturated highlights on metal surfaces reduce the detection accuracy of fuel nozzles. In this paper, we propose an image inpainting method with a saturated highlight based on the statistics of similar patches used in prior segmentation of the subregion. The sequence image acquisition is based on the shape from focus in the five-axis platform. By our method, the focus measure (FM) operator and the window size are evaluated using the sharpness evaluation curve and calculating time. We observe that the detection accuracy is improved when the highlight area is filled by the highlight-free area within the same segmentation region. There are fewer deviation points in the three-dimensional (3D) point cloud that are extracted from the sequence images. The inlet circle and the outlet circle of the fuel nozzle are both detected by the two-dimensional (2D) Hough Transform (HT) method. Our experiments show that the method yields better results in 3D detection of the key parameters of fuel nozzles with the saturated highlight characteristics. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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15 pages, 5423 KiB

Open AccessArticle

Research on Wire-to-Two Fin Configuration for Positive Atmospheric Plasma by Electrokinetic Blower

by Mar Cogollo de Cádiz, Pedro Martí Balsalobre and Andrés Díaz Lantada

Energies 2022, 15(15), 5443; https://doi.org/10.3390/en15155443 - 27 Jul 2022

Cited by 1 | Viewed by 1166

Abstract

Interest in the development of electro-fluid-dynamic devices (EFDs) based on corona discharge is growing due to their advantages and applicability across different industrial sectors. On the one hand, their performance as forced convection motors, in terms of weight, volume, and absence of noise [...] Read more.

Interest in the development of electro-fluid-dynamic devices (EFDs) based on corona discharge is growing due to their advantages and applicability across different industrial sectors. On the one hand, their performance as forced convection motors, in terms of weight, volume, and absence of noise and moving parts, make them competitive against traditional systems such as fans. On the other hand, the actions of the corona discharge, in terms of elimination of viruses and bacteria, are already known. This paper studies the characteristics of corona discharge in terms of air flow for a new proposed configuration and geometry of electrodes. A systematic study is performed through a parametric study of the distances, power consumption, and size of the corona electrode. The characteristic voltage–current (CVCCs) and flow–pressure curves obtained provide design rules to use the generated corona discharge and the device itself, as a silent air propeller, which may also sterilize the surrounding environment and surfaces. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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17 pages, 1143 KiB

Open AccessArticle

Improving Security of Web Servers in Critical IoT Systems through Self-Monitoring of Vulnerabilities

by Linxuan Song and Marisol García-Valls

Sensors 2022, 22(13), 5004; https://doi.org/10.3390/s22135004 - 02 Jul 2022

Cited by 4 | Viewed by 2523

Abstract

IoT (Internet of Things) systems are complex ones that may comprise large numbers of sensing and actuating devices; and servers that store data and further configure the operation of such devices. Usually, these systems involve real-time operation as they are closely bound to [...] Read more.

IoT (Internet of Things) systems are complex ones that may comprise large numbers of sensing and actuating devices; and servers that store data and further configure the operation of such devices. Usually, these systems involve real-time operation as they are closely bound to particular physical processes. This real-time operation is often threatened by the security solutions that are put in place to alleviate the ever growing attack surface in IoT. This paper focuses on critical IoT domains where less attention has been paid to the web security aspects. The main reason is that, up to quite recently, web technologies have been considered unreliable and had to be avoided by design in critical systems. In this work, we focus on the server side and on how attacks propagate from server to client as vulnerabilities and from client to unprotected servers; we describe the concerns and vulnerabilities introduced by the intensive usage of web interfaces in IoT from the server templating engines perspective. In this context, we propose an approach to perform self monitoring on the server side, propagating the self monitoring to the IoT system devices; the aim is to provide rapid detection of security vulnerabilities with a low overhead that is transparent to the server normal operation. This approach improves the control over the vulnerability detection. We show a set of experiments that validate the feasibility of our approach. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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16 pages, 2299 KiB

Open AccessArticle

State Estimation of Gas-Lifted Oil Well Using Nonlinear Filters

by Ojonugwa Adukwu, Darci Odloak, Amir Muhammed Saad and Fuad Kassab Junior

Sensors 2022, 22(13), 4875; https://doi.org/10.3390/s22134875 - 28 Jun 2022

Cited by 3 | Viewed by 1506

Abstract

The focus of this work is the extension of nonlinear state estimation methods to gas-lifted systems. The extended Kalman filter (EKF), unscented Kalman filter (UKF) and particle filter (PF) were used to estimate the nonlinear states. Brief descriptions of the filters were first [...] Read more.

The focus of this work is the extension of nonlinear state estimation methods to gas-lifted systems. The extended Kalman filter (EKF), unscented Kalman filter (UKF) and particle filter (PF) were used to estimate the nonlinear states. Brief descriptions of the filters were first presented starting from the linear Kalman filter. Hypothesis tests on the expectation of the residuals were performed to show how close to optimal the estimation methods are and it showed the UKF estimates to be slightly better than EKF while PF performs the worst. The PF has poor accuracy using residual visualisation, hypothesis test and the root mean squared error (RMSE) values of the residuals. The gas-lifted system exhibits casing heading instability where the states show oscillatory behaviour depending on the value of the input but the results here do not change in a known way for each filter as the input is changed from the non-oscillatory region to the oscillatory region. Therefore, for this noise distribution and model assumption, either the EKF or UKF can be used for nonlinear state estimation with UKF better preferred if computational cost is not considered when control solutions are used in gas-lifted system. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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13 pages, 2746 KiB

Open AccessArticle

Resource Allocation for TDD Cell-Free Massive MIMO Systems

by Xuanhong Lin, Fangmin Xu, Jingzhao Fu and Yue Wang

Electronics 2022, 11(12), 1914; https://doi.org/10.3390/electronics11121914 - 20 Jun 2022

Cited by 4 | Viewed by 1784

Abstract

In this paper, we investigate a joint resource allocation algorithm in a time-division duplex (TDD)-based cell-free massive MIMO (CFMM) system, which has great potential to improve spectrum efficiency and throughput. Because the throughput of the system is a bottleneck due to the sharing [...] Read more.

In this paper, we investigate a joint resource allocation algorithm in a time-division duplex (TDD)-based cell-free massive MIMO (CFMM) system, which has great potential to improve spectrum efficiency and throughput. Because the throughput of the system is a bottleneck due to the sharing of the pilot, we attempted to alleviate pilot contamination. We propose a pilot assignment approach called user-distance-ordering-based pilot assignment (UDOPA) based on the distance between users and the center, which can be calculated by the K-means method. Then, using an access point (AP) selection algorithm, only the APs having a major impact on the macro diversity gain of a user are selected as the serving APs. In contrast to the existing AP selection algorithms, users with the same pilot are not allowed to share the same serving AP in the proposed AP selection algorithm, which also significantly reduces the complexity of data processing. Finally, a modified max–min power control scheme with teaching–learning-based optimization (TLBO) is proposed to further improve the performance of the systems and guarantee the minimum user rate. Simulation results show that the proposed joint resource allocation scheme can effectively enhance CFMM systems’ performance. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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30 pages, 9373 KiB

Open AccessArticle

Design and Fabrication of an Isolated Two-Stage AC–DC Power Supply with a 99.50% PF and ZVS for High-Power Density Industrial Applications

by Ahmed H. Okilly and Jeihoon Baek

Electronics 2022, 11(12), 1898; https://doi.org/10.3390/electronics11121898 - 16 Jun 2022

Cited by 3 | Viewed by 3400

Abstract

Power quality in terms of power factor (PF), efficiency, and total harmonic distortions (THDs) is an important consideration in power supplies designed for 5G telecom servers. This paper presents a different magnetic parts design and manufacturing techniques of power supplies, design and selection [...] Read more.

Power quality in terms of power factor (PF), efficiency, and total harmonic distortions (THDs) is an important consideration in power supplies designed for 5G telecom servers. This paper presents a different magnetic parts design and manufacturing techniques of power supplies, design and selection criteria of switching elements as well as the optimal design of control loops based on small-signal stability modeling and an appropriate stability criterion. The designed telecom power supply consists of the power factor correction (PFC) stage to increase the input power factor and the isolated phase-shift pulse width modulation (PWM) zero-voltage switching (ZVS) DC–DC converter stage to regulate the supply voltage to the specified load value while maintaining a high conversion efficiency. A two-stage outdoor telecom power supply with a power rating of 2 kW was designed and fabricated on a printed circuit board (PCB). The distinct two-stage power components of the power supply were subjected to loss analysis. Furthermore, PSIM simulation and experiments were used to demonstrate the total harmonic distortions (THDs), voltage ripples, power efficiency, and PF performance of the supply current for the proposed power supply under various operating situations. This work produces an industrial high power density power supply with a high PF, low THD and high conversion efficiency which is suitable for telecom power server applications. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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12 pages, 6575 KiB

Open AccessArticle

Monitoring the Geometric Position of Transition Zones to Increase the Quality and Safety of Railway Lines

by Stanislav Hodas, Jana Izvoltova, Jakub Chromcak and Dasa Bacova

Appl. Sci. 2022, 12(12), 6038; https://doi.org/10.3390/app12126038 - 14 Jun 2022

Cited by 9 | Viewed by 2145

Abstract

Transition zones on railway lines are localities with gradual changes in the construction layers in the connections between a fixed track and ballasted track or between a wide track and various railway objects, e.g., tunnels, bridges, culverts, etc. The different type of construction [...] Read more.

Transition zones on railway lines are localities with gradual changes in the construction layers in the connections between a fixed track and ballasted track or between a wide track and various railway objects, e.g., tunnels, bridges, culverts, etc. The different type of construction of transition zones causes a shock wave when the train passes, which can cause undesired effects on the stability of its construction, durability, and passengers’ comfort. For this reason, railway opera-tors pay increased attention to the construction inspection of these transition sections. The research deals with the description of the transition zones, methods, and results of their monitoring in experimental sections of the railway corridors. Innovative aspects are the measurements made using precise geodetic instruments as well as continuous measurements with the KRAB trolley. The analyses of measurements in the experimental sections of the track show whether the stability of the geometric spatial position is ensured. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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15 pages, 4123 KiB

Open AccessArticle

An Adaptive Bi-Mutation-Based Differential Evolution Algorithm for Multi-Threshold Image Segmentation

by Yu Sun and Yingying Yang

Appl. Sci. 2022, 12(11), 5759; https://doi.org/10.3390/app12115759 - 06 Jun 2022

Cited by 8 | Viewed by 1637

Abstract

Aiming at solving the problems of large calculation, time-consuming, and low segmentation accuracy of multi-threshold image segmentation, an adaptive threshold value based differential evolution algorithm is proposed in this paper. Firstly, an opposite learning strategy is introduced into the initial population to improve [...] Read more.

Aiming at solving the problems of large calculation, time-consuming, and low segmentation accuracy of multi-threshold image segmentation, an adaptive threshold value based differential evolution algorithm is proposed in this paper. Firstly, an opposite learning strategy is introduced into the initial population to improve the quality of the initial population; secondly, a threshold-value-based mutation strategy is proposed to balance the exploration and development capabilities of the algorithm, and the number of successfully evolved individuals is considered as a threshold value to adaptively adjust the evolution of superior and inferior individuals. Experiments demonstrate that the proposed algorithm has better performance in enhancing accuracy and speeding up the convergence. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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20 pages, 9692 KiB

Open AccessArticle

Factor Design for the Oxide Etching Process to Reduce Edge Particle Contamination in Capacitively Coupled Plasma Etching Equipment

by Ching-Ming Ku and Stone Cheng

Appl. Sci. 2022, 12(11), 5684; https://doi.org/10.3390/app12115684 - 03 Jun 2022

Cited by 3 | Viewed by 7988

Abstract

During the oxide layer etching process, particles in capacitively coupled plasma etching equipment adhere to the wafer edge and cause defects that reduce the yield from semiconductor wafers. To reduce edge particle contamination in plasma etching equipment, we propose changes in the voltage [...] Read more.

During the oxide layer etching process, particles in capacitively coupled plasma etching equipment adhere to the wafer edge and cause defects that reduce the yield from semiconductor wafers. To reduce edge particle contamination in plasma etching equipment, we propose changes in the voltage and temperature of the electrostatic chuck, plasma discharge sequence, gas flow, and pressure parameters during the etching process. The proposed edge particle reduction method was developed by analyzing particle maps after wafer etching. Edge particle adherence in plasma etching equipment can be reduced by decreasing the voltage and temperature changes of the electrostatic chuck and generating a plasma sheath with a continuous discharge sequence of radio-frequency plasma. The gas pressure and flow rate also affect the number of wafer edge particles. Experimental results were used to optimize the equipment parameters to reduce edge particle contamination and improve edge wafer defects after dry etching. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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27 pages, 8115 KiB

Open AccessArticle

Diagnosing the Machine Set Rotor Using Its Relative Vibrations

by Piotr Jan Bielawski

Appl. Sci. 2022, 12(11), 5660; https://doi.org/10.3390/app12115660 - 02 Jun 2022

Viewed by 1362

Abstract

The efficiency and dependability of machine set depends on the quality of maintenance of functional units of the machine set rotor. Diagnosing the functional units of the machine set can significantly increase the effectiveness and efficiency of the maintenance of the machine set. [...] Read more.

The efficiency and dependability of machine set depends on the quality of maintenance of functional units of the machine set rotor. Diagnosing the functional units of the machine set can significantly increase the effectiveness and efficiency of the maintenance of the machine set. The purpose of the study was to substantiate the separation of the machine set rotor and demonstrate the possibility of diagnosing such a functional unit using non-contact measurements of its relative vibrations. The measure of the wear margin of the machine set rotor was analyzed, and the symptoms of this measure were examined. Finally, the configuration of the relative vibration sensors of the machine set rotor was investigated. Three models of the relationship between the wear margin measures and the measures of the machine set rotor symptoms were developed for the machine set rotor with a crankshaft supported in slide bearings. One new sensors head (shaft position sensors head) of the relative vibration of the machine set rotor was designed. In each machine set, the rotor of the machine set can be distinguished. The developed models of relationships and designed sensors head can be used as parts of the diagnostic system of the supported slide bearings rotor of the machine set with the crankshaft. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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14 pages, 426 KiB

Open AccessArticle

Quantitative Assessment and Grading of Hardware Trojan Threat Based on Rough Set Theory

by Daming Yang, Cheng Gao and Jiaoying Huang

Appl. Sci. 2022, 12(11), 5576; https://doi.org/10.3390/app12115576 - 31 May 2022

Cited by 1 | Viewed by 1084

Abstract

The globalization of integrated circuit (IC) design and fabrication has given rise to severe concerns with respect to modeling strategic interaction between malicious attackers and Hardware Trojan (HT) defenders using game theory. The quantitative assessment of attacker actions has made the game very [...] Read more.

The globalization of integrated circuit (IC) design and fabrication has given rise to severe concerns with respect to modeling strategic interaction between malicious attackers and Hardware Trojan (HT) defenders using game theory. The quantitative assessment of attacker actions has made the game very challenging. In this paper, a novel rough set theory framework is proposed to analyze HT threat. The problem is formulated as an attribute weight calculation and element assessment in an information system without decision attributes. The proposed method introduces information content in the rough set that allows calculation of the weight of both core attributes and non-core attributes. For quantitative assessment, the HT threat is characterized by the closeness coefficient. In order to allow HT defenders to use fast and effective countermeasures, a threat classification method based on the k-means algorithm is proposed, and the Best Workspace Prediction (BWP) index is used to determine the number of clusters. Statistical tests were performed on the benchmark circuits in Trust-hub in order to demonstrate the effectiveness of the proposed technique for assessing HT threat. Compared with k-means, equidistant division-based k-means, and k-means++, our method shows a significant improvement in both cluster accuracy and running time. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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11 pages, 2933 KiB

Open AccessArticle

Determination of Pressure Drop Correlation for Air Flow through Packed Bed of Sinter Particles in Terms of Euler Number

by Junsheng Feng, Liang Zhao, Haitao Wang, Zude Cheng, Yongfang Xia and Hui Dong

Energies 2022, 15(11), 4034; https://doi.org/10.3390/en15114034 - 31 May 2022

Cited by 1 | Viewed by 1332

Abstract

In order to clearly understand the air flow resistance characteristics in vertical tanks for sinter waste heat recovery in the steel industry, experimental research on the air flow pressure drop (FPD) performance in a sinter bed layer (BL) was conducted. Based on a [...] Read more.

In order to clearly understand the air flow resistance characteristics in vertical tanks for sinter waste heat recovery in the steel industry, experimental research on the air flow pressure drop (FPD) performance in a sinter bed layer (BL) was conducted. Based on a self-made experimental device, the measurement values of air FPD for different experimental conditions were determined firstly, and then the concept of Euler number (Eu) in heat exchangers was introduced into the study of air FPD in BL; the change rules of Eu under different particle diameters were analyzed. Finally, the air FPD correlation in sinter BL was obtained and described in the form of Eu, and the error analysis of obtained air FPD correlation was performed. The results show that, the air FPD increases as a second power relationship with the increase in air superficial velocity when the particle diameter is constant. The decrease amplitude of Eu gradually dwindles when increasing the Reynolds number (Re), and the decrease in the Eu shows a reciprocal relationship with the Re. As the bed geometry factor increases, the FPD coefficient, A, decreases as an exponential relationship, while the FPD coefficient, B, increases as a first power relationship. The obtained air FPD correlation in the form of Eu in the experiment is well compatible with the measurement values, and the mean deviation of obtained correlation is 4.67%, showing good originality. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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20 pages, 7015 KiB

Open AccessArticle

An Industrial Fault Diagnostic System Based on a Cubic Dynamic Uncertain Causality Graph

by Xusong Bu, Hao Nie, Zhan Zhang and Qin Zhang

Sensors 2022, 22(11), 4118; https://doi.org/10.3390/s22114118 - 28 May 2022

Cited by 5 | Viewed by 1774

Abstract

This study presents an industrial fault diagnosis system based on the cubic dynamic uncertain causality graph (cubic DUCG) used to model and diagnose industrial systems without sufficient data for model training. The system is developed based on cloud native technology. It contains two [...] Read more.

This study presents an industrial fault diagnosis system based on the cubic dynamic uncertain causality graph (cubic DUCG) used to model and diagnose industrial systems without sufficient data for model training. The system is developed based on cloud native technology. It contains two main parts, the diagnostic knowledge base and the inference method. The knowledge base was built by domain experts modularly based on professional knowledge. It represented the causality between events in the target industrial system in a visual and graphical form. During the inference, the cubic DUCG algorithm could dynamically generate the cubic causal graph according to the real-time data and perform the logic and probability calculations based on the generated cubic DUCG models, visually displaying the dynamic causal evolution of faults. To verify the system’s feasibility, we rebuild a fault-diagnosis model of the secondary circuit system of No. 1 at the Ningde nuclear power plant based on the new system. Twenty-four fault cases were used to test the diagnostic accuracy of the system, and all faults were correctly diagnosed. The results showed that it was feasible to use the cubic DUCG platform for fault diagnosis. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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24 pages, 4351 KiB

Open AccessArticle

Optimization Workflows for Linking Model-Based Systems Engineering (MBSE) and Multidisciplinary Analysis and Optimization (MDAO)

by Christian Habermehl, Gregor Höpfner, Jörg Berroth, Stephan Neumann and Georg Jacobs

Appl. Sci. 2022, 12(11), 5316; https://doi.org/10.3390/app12115316 - 24 May 2022

Cited by 9 | Viewed by 2837

Abstract

Developing modern products involves numerous domains (controlling, production, engineering, etc.) and disciplines (mechanics, electronics, software, etc.). The products have become increasingly complex while their time to market has decreased. These challenges can be overcome by Model-Based Systems Engineering (MBSE), where all development data [...] Read more.

Developing modern products involves numerous domains (controlling, production, engineering, etc.) and disciplines (mechanics, electronics, software, etc.). The products have become increasingly complex while their time to market has decreased. These challenges can be overcome by Model-Based Systems Engineering (MBSE), where all development data (requirements, architecture, etc.) is stored and linked in a system model. In an MBSE system model, product requirements at the system level can lead to numerous technical variants with conflicting objectives at the parameter level. To determine the best technical variants or tradeoffs, Multidisciplinary Analysis and Optimization (MDAO) is already being used today. Linking MBSE and MDAO allows for mutually beneficial synergies to be expected that have not yet been fully exploited. In this paper, a new approach to link MBSE and MDAO is proposed. The novelty compared to existing approaches is the reuse of existing MBSE system model data. Models developed during upstream design and test activities already linked to the MBSE system model were integrated into an MDAO problem. Benefits are reduced initial and reconfiguration efforts and the resolution of the MDAO black-box behavior. For the first time, the MDAO problem was modeled as a workflow using activity diagrams in the MBSE system model. For a given system architecture, this workflow finds the design variable values that allow for the best tradeoff of objectives. The structure and behavior of the workflow were formally described in the MBSE system model with SysML. The presented approach for linking MBSE and MDAO is demonstrated using an example of an electric coolant pump. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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15 pages, 13132 KiB

Open AccessArticle

Performance Analysis of Acceleration and Inertial Force of Electromagnetic Suspension Inertial Stabilizer

by Sumei Gao, Longxiang Xu and Chaowu Jin

Appl. Sci. 2022, 12(11), 5304; https://doi.org/10.3390/app12115304 - 24 May 2022

Viewed by 1212

Abstract

In this paper, the structural characteristics of electromagnetic suspension (EMS) inertial stabilizers are analyzed firstly, and then a mechanical analysis of a single mass block and double mass block is carried out. The relationship model between the inertial anti-rolling mass block and inertial [...] Read more.

In this paper, the structural characteristics of electromagnetic suspension (EMS) inertial stabilizers are analyzed firstly, and then a mechanical analysis of a single mass block and double mass block is carried out. The relationship model between the inertial anti-rolling mass block and inertial force transmitted to the ship is established. The inertial force is determined by the number of coil turns, coil current, mass block, mass of the ship, electromagnet current, rate of change of the electromagnet current, air gap between the electromagnet and inertial mass block, and rotational angular speed. Through theoretical analysis, it is found that the response speed of inertia force is directly related to the electromagnetic coil current, the voltage at both ends of the electromagnetic coil, the coil resistance and the air gap. It is concluded that the response speed of the inertia force can be controlled by controlling the coil current, adjusting the voltage at both ends of the coil and adjusting the air gap. The inductance of the electromagnetic coil will also increase the nonlinearity of the inertial anti-roll system. On the basis of theoretical analysis, a digital simulation of EMS inertial stabilizer is carried out by MATLAB and ANSYS MAXWELL2D. Finally, a single mass block system of EMS inertial stabilizer is designed and tested. During the test, a 1.5 V sinusoidal excitation voltage is added to the electromagnetic coil after the mass block is suspended stably, and the maximum acceleration values of the inertial anti-rolling mass block and hull are 10.29 m/s² and 1.27 m/s². Finally, the theoretical analysis results, digital simulation results and experimental results are analyzed, which verifies the correctness of the acceleration and inertia force performance analysis of the EMS inertial stabilizer. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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15 pages, 2907 KiB

Open AccessArticle

Measurement of Large-Sized-Pipe Diameter Based on Stereo Vision

by Pu Liu, Lieshan Zhang and Meibao Wang

Appl. Sci. 2022, 12(10), 5277; https://doi.org/10.3390/app12105277 - 23 May 2022

Cited by 2 | Viewed by 2189

Abstract

To address the lack of fast and high-precision in situ measurement of large-sized pipes in current industrial applications, a pipe-diameter-measurement method based on stereo vision is designed in this paper. By using multiple sets of binocular cameras to perform 3D reconstruction and integration [...] Read more.

To address the lack of fast and high-precision in situ measurement of large-sized pipes in current industrial applications, a pipe-diameter-measurement method based on stereo vision is designed in this paper. By using multiple sets of binocular cameras to perform 3D reconstruction and integration of multiple laser markers projected on measured cross sections of pipes, the pipe diameter can be estimated. In this method, a measurement algorithm is adopted to enable automatic matching of feature points through affine distance transformation, and an optimized point-cloud-registration algorithm with normal-vector constraints is used to ensure measurement robustness. To verify the feasibility of the method, an experimental system was built under laboratory conditions, and three types of pipes with outer diameters from 285 mm to 325 mm were measured. The experimental results show that the relative error is within ±0.570% and the maximum repeatability standard deviation is 0.551 mm. The experimental results basically meet industrial standards, and the proposed method therefore has good application prospects. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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15 pages, 6915 KiB

Open AccessArticle

General Mass Property Measurement Equipment for Large-Sized Aircraft

by Xiaolin Zhang, Hang Yu, Wenyan Tang and Jun Wang

Sensors 2022, 22(10), 3912; https://doi.org/10.3390/s22103912 - 21 May 2022

Cited by 5 | Viewed by 2344

Abstract

The accurate measurement of aircraft mass properties, such as the mass, centroid, and moment of inertia (MOI), plays a key role in the precise control of aircraft. In order to obtain high-precision information on the parameters of the mass, centroid, and MOI of [...] Read more.

The accurate measurement of aircraft mass properties, such as the mass, centroid, and moment of inertia (MOI), plays a key role in the precise control of aircraft. In order to obtain high-precision information on the parameters of the mass, centroid, and MOI of an aircraft using a single instrument, an integrated mass property measurement system was developed in this study by analyzing and comparing the latest technologies, especially the function-switching device, which switches the measurement states between the center of mass and the MOI. The purpose of mass property measurement was achieved through single clamping. In addition, the system has strong versatility and expansion and can be used with different tooling or adapter rings to measure the mass properties of aircraft with different shapes. In this paper, the main mechanical structure of the measurement system, the measurement method of relevant mass parameters, and the solution method of the transformation matrix are introduced, and the standard parts and the aircraft were verified experimentally. The test results showed that the mass measurement accuracy was 0.03%, the centroid measurement error was within ±0.2 mm, and the measurement accuracy of the MOI was within 0.2%, all of which meet the high-precision measurement requirements for the mass properties. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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20 pages, 1859 KiB

Open AccessArticle

The Regression Model and the Problem of Inventory Centralization: Is the “Square Root Law” Applicable?

by Dariusz Milewski and Tomasz Wiśniewski

Appl. Sci. 2022, 12(10), 5152; https://doi.org/10.3390/app12105152 - 20 May 2022

Viewed by 2019

Abstract

The research problem undertaken by the authors of this article concerns the optimization of the size of the distribution network (the number of warehouses). The authors developed regression models, which are an alternative to the classical “Square Root law” optimization formula. The models [...] Read more.

The research problem undertaken by the authors of this article concerns the optimization of the size of the distribution network (the number of warehouses). The authors developed regression models, which are an alternative to the classical “Square Root law” optimization formula. The models were built for the two distributions of demand most commonly used in the literature: Gaussian and Gamma distribution. They allow the calculation of the level of inventory with a given number of warehouses and the level of stock availability as a measure of logistic customer service. The aim was to create a useful tool for decision-makers in companies. The models were elaborated on the base of the simulations carried out for various products (loading parameters, value), sales volumes, number of warehouses, and different standard deviations. Both regression models were statistically significant; the coefficients of determination are relevant. A slightly better value was obtained in the case of Gaussian distribution. The results obtained with the use of the classic “Square Root law” were in some cases quite similar. However, the type of distribution and the variability of demand, measured by standard deviation, have a significant influence here. Thus, the authors believe that the models developed may give more accurate results and that the “Square Root law” formula should be modified taking into account the characteristics of the demand. After completing the regression models with cost components, the total costs were calculated for selected cases of product groups (food, electronics, garments), different levels of the availability of stocks, and different number of warehouses. As it turned out, centralization may not necessarily be the optimal strategy for the most expensive goods. Loading parameters are also important, as they have a significant impact on the costs of storage and, above all, transport. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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19 pages, 3460 KiB

Open AccessArticle

Advanced Fault-Tolerant Anti-Surge Control System of Centrifugal Compressors for Sensor and Actuator Faults

by Turki Alsuwian, Arslan Ahmed Amin, Muhammad Taimoor Maqsood, Muhammad Bilal Qadir, Saleh Almasabi and Mohammed Jalalah

Sensors 2022, 22(10), 3864; https://doi.org/10.3390/s22103864 - 19 May 2022

Cited by 7 | Viewed by 2293

Abstract

Faults frequently occur in the sensors and actuators of process machines to cause shutdown and process interruption, thereby creating costly production loss. centrifugal compressors (CCs) are the most used equipment in process industries such as oil and gas, petrochemicals, and fertilizers. A compressor [...] Read more.

Faults frequently occur in the sensors and actuators of process machines to cause shutdown and process interruption, thereby creating costly production loss. centrifugal compressors (CCs) are the most used equipment in process industries such as oil and gas, petrochemicals, and fertilizers. A compressor control system called an anti-surge control (ASC) system based on many critical sensors and actuators is used for the safe operation of CCs. In this paper, an advanced active fault-tolerant control system (AFTCS) has been proposed for sensor and actuator faults of the anti-surge control system of a centrifugal compressor. The AFTCS has been built with a dedicated fault detection and isolation (FDI) unit to detect and isolate the faulty part as well as replace the faulty value with the virtual redundant value from the observer model running in parallel with the other healthy sensors. The analytical redundancy is developed from the mathematical modeling of the sensors to provide estimated values to the controller in case the actual sensor fails. Dual hardware redundancy has been proposed for the anti-surge valve (ASV). The simulation results of the proposed Fault-tolerant control (FTC) for the ASC system in the experimentally validated CC HYSYS model reveal that the system continued to operate in the event of faults in the sensors and actuators maintaining system stability. The proposed FTC for the ASC system is novel in the literature and significant for the process industries to design a highly reliable compressor control system that would continue operation despite faults in the sensors and actuators, hence preventing costly production loss. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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19 pages, 9840 KiB

Open AccessArticle

Research on Dynamic Characteristics of the RBBH System Based on Dynamics Model and Vibration Data Fusion

by Shuilin Lin, Jianliang Sun, Chen Zhao and Yan Peng

Sensors 2022, 22(10), 3806; https://doi.org/10.3390/s22103806 - 17 May 2022

Cited by 4 | Viewed by 1525

Abstract

The roll-bearing-bearing housing (RBBH) system is one of the most common kernel structures used to determine strip mill stability and product surface quality in modern metallurgical machinery. To better understand dynamic characteristics of the RBBH system, this paper provides a nonlinear dynamic model [...] Read more.

The roll-bearing-bearing housing (RBBH) system is one of the most common kernel structures used to determine strip mill stability and product surface quality in modern metallurgical machinery. To better understand dynamic characteristics of the RBBH system, this paper provides a nonlinear dynamic model and designs an engineering test platform on the RBBH system in the whole rolling process. First, a nonlinear dynamic model of the RBBH system supported by four-row rolling bearings under high speed and heavy load is established. Then, the method of combining Riccati transfer matrix and Newmark-β numerical integration is employed to solve nonlinear dynamic equations. After that, the engineering test platform is designed and assembled to capture and analyze the vibration signals of weathering steel (SPA-H) with finished thicknesses of 1.6 and 3.2 mm. Finally, the dynamic characteristics of the RBBH system are studied with the method of the dynamic model and vibration data fusion. The results show that the SPA-H with a finished thickness of 1.6 mm is rolled, the RBBH system fluctuates violently in both horizontal and vertical directions, and numerical results are highly consistent with experimental results in acceleration response, velocity response, and displacement response. In addition, the dynamic performance parameters of the four-row rolling bearing will also fluctuate greatly. Finally, there is significant interest to gain the benefits for the RBBH system design and mill stable rolling purposes. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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18 pages, 3123 KiB

Open AccessArticle

An Electric Fence-Based Intelligent Scheduling Method for Rebalancing Dockless Bike Sharing Systems

by Lulu Jia, Dezhen Yang, Yi Ren, Qiang Feng, Bo Sun, Cheng Qian, Zhifeng Li and Chenchen Zeng

Appl. Sci. 2022, 12(10), 5031; https://doi.org/10.3390/app12105031 - 16 May 2022

Cited by 3 | Viewed by 1819

Abstract

With a new generation of bike sharing services emerging, the development of dockless bike sharing services results in considerable socioeconomic and environmental benefits but also creates new issues, such as inappropriate parking behaviors and bike imbalances. To solve the inappropriate parking problem, electric [...] Read more.

With a new generation of bike sharing services emerging, the development of dockless bike sharing services results in considerable socioeconomic and environmental benefits but also creates new issues, such as inappropriate parking behaviors and bike imbalances. To solve the inappropriate parking problem, electric fences have been introduced to guide users to park bikes in designated zones. Considering the role of electric fences in restricting user parking behaviors, an electric fence-based intelligent scheduling method for rebalancing dockless bike sharing systems is proposed in this paper. As a dynamic method that considers the real-time usage of bike sharing systems, an electric fence adjusts its capacity based on real-time information, which guides users to return bikes to electric fences with greater urgency. Because existing approaches require prespecified models and are unable to consider all the intricacies in the dynamic optimization problem, a model-free intelligent scheduling approach based on deep Q-learning that can adapt to the changing distributions of customer arrivals, available bikes, bike locations, and user travel times is used to solve the problem. Finally, a case study involving Beihang University is employed, which shows that the method performs well in rebalancing the bike sharing system and improving the mean utilization (MU) and customer satisfaction (CS). Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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12 pages, 4511 KiB

Open AccessArticle

Research on Permanent Magnet Synchronous Motor Control System Based on Adaptive Kalman Filter

by Jiadong Cui, Wenhao Xing, Huibin Qin, Yongzhu Hua, Xin Zhang and Xinran Liu

Appl. Sci. 2022, 12(10), 4944; https://doi.org/10.3390/app12104944 - 13 May 2022

Cited by 8 | Viewed by 1839

Abstract

A sensorless control system of a permanent magnet synchronous motor based on an extended Kalman filter (EKF) algorithm faces problems with inaccurate or mismatched process noise statistics. This problem affects the performance of the filter, resulting in an inaccurate estimation of motor speed. [...] Read more.

A sensorless control system of a permanent magnet synchronous motor based on an extended Kalman filter (EKF) algorithm faces problems with inaccurate or mismatched process noise statistics. This problem affects the performance of the filter, resulting in an inaccurate estimation of motor speed. To address the above problem, this paper proposes a parameter-adaptive Kalman filter algorithm that does not depend on precise noise system covariance. This method can significantly reduce the negative impact of the noise statistical mismatch on motor speed estimation. In addition, the method uses adaptive covariance prediction and removes the original covariance checks in the EKF, thus reducing the calculation burden. The simulation results show that, compared with the traditional EKF algorithm, the algorithm proposed in this article can effectively reduce the steady-state jitter and improve the filtering adaptability and calculation accuracy. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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14 pages, 2675 KiB

Open AccessArticle

An Input–Output Analysis of the Water–Energy–Food Nexus Based on the Intensity and Quantity Index System—A Case Study of 30 Provinces in China

by Ke Zhang, Zihao Shen and Chengshuang Sun

Energies 2022, 15(10), 3591; https://doi.org/10.3390/en15103591 - 13 May 2022

Cited by 3 | Viewed by 1748

Abstract

In the study of the water–energy–food nexus (WEF nexus), the importance of the intensity and quantity index system has been widely recognized. In order to study the impact of WEF on the economy, this paper establishes an intensity index system and a quantity [...] Read more.

In the study of the water–energy–food nexus (WEF nexus), the importance of the intensity and quantity index system has been widely recognized. In order to study the impact of WEF on the economy, this paper establishes an intensity index system and a quantity index system, taking account of the impact of environmental pollution. Using a DEA model and China’s provincial data from 2019, this paper calculated the efficiency of the WEF nexus with the developed intensity and quantity index systems. The results show that the efficiency is not high in areas with a high economic development level, and efficiency is not the lowest in areas with a relatively low economic development level. When considering environmental pollution, the efficiency of some provinces has increased significantly, indicating that the WEF nexus has not caused environmental damage and is conducive to sustainable economic development. In the two intensity index systems, the efficiency of the production system is significantly lower than that of the consumption system, indicating that there is a serious waste of cultivated land per capita. Compared with the intensity index system, the efficiency of the quantity index system is low, and the polarization is obvious. A high level of GDP does not mean a high level of economic development. There may be a low level of resource utilization technology or environmental pollution underlying it. It is unscientific to evaluate local economic development only by GDP. When evaluating the urban economy and national economy, we should conduct an overall study of WEF and reasonably allocate WEF resources, which will not only help to alleviate the current situation of resource shortage in various countries but also effectively promote the coordinated development of national and regional economies. At the same time, environmental protection should also be taken into account. Compared with the economic development model of developing the economy first and then solving environmental problems, developing and solving at the same time is more conducive to the sustainable development of the national economy. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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17 pages, 4231 KiB

Open AccessArticle

Investigation of the Relationship between Vibration Signals Due to Oil Impurity and Cavitation Bubbles in Hydraulic Pumps

by Özgür Yılmaz, Murat Aksoy and Zehan Kesilmiş

Electronics 2022, 11(10), 1549; https://doi.org/10.3390/electronics11101549 - 12 May 2022

Cited by 1 | Viewed by 1893

Abstract

Although hydraulic pumps are frequently used in daily life, improper use due to oil analysis or oil contamination is ignored. There is no instantaneous inspection; instead, the oil is changed periodically at certain times, whether it is contaminated or not. Hydraulic systems operate [...] Read more.

Although hydraulic pumps are frequently used in daily life, improper use due to oil analysis or oil contamination is ignored. There is no instantaneous inspection; instead, the oil is changed periodically at certain times, whether it is contaminated or not. Hydraulic systems operate based on Pascal’s law, which states that the fluid will distribute the pressure equally to every point in a closed area. The fluid oil taken from an oil reservoir is moved into the pump by engine power. During this movement, as it passes through different pressure areas and different sections, undesirable events such as viscosity change and gas formation occur in the hydraulic oil. These formations collide with the outer walls and cause cavitation with respect to unwanted oil impurities. This cavitation causes unwanted vibration signals to occur in the normal working order of the system. As a result of cavitation, the particles that affect the lubricity and fluidity of the oil in the oil are mixed into the liquid and circulate freely. At the connection points, the blockage caused by the liquid in the pump cylinder block or the valve plate and the collisions of particles is effective. As a result, it creates vibrations of different frequencies. The frequency and amplitudes of these vibrations differ according to the degree of oil contamination. A method has been developed to find the degree of contamination of the oil circulating in the pump by looking at the amplitude and frequency of these vibrations measured from the motor body. There exist standards about the pollution of hydraulic fluid. With these standards, the maximum number of particles allowed for a given pollution level is defined. This topic is discussed in the conclusion to this study. This method has also been proven experimentally. Error and vibration analysis studies on pumps using a different approach are available in the literature. In these studies, pressure variation, total energy transmission, or artificial intelligence models were used to detect anomalies in the pump. In this study, the impurity rate of the oil was set at five different levels and the operating regime of the pump at each level was investigated experimentally. Rayleigh–Plesset and Zwart–Gerber–Belamri models, which are the most common cavitation models, were used to explain the bubble formation in the moving oil and the relationship of these bubbles with vibration. Frequency components were examined by the Discrete Fast Fourier Analysis method, where the operation of the pump was affected by the increase in oil impurity. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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17 pages, 7070 KiB

Open AccessArticle

Effective Attention-Based Feature Decomposition for Cross-Age Face Recognition

by Suli Li and Hyo Jong Lee

Appl. Sci. 2022, 12(10), 4816; https://doi.org/10.3390/app12104816 - 10 May 2022

Cited by 5 | Viewed by 2147

Abstract

Deep-learning-based, cross-age face recognition has improved significantly in recent years. However, when using the discriminative method, it is still challenging to extract robust age-invariant features that can reduce the interference caused by age. In this paper, we propose a novel, effective, attention-based feature [...] Read more.

Deep-learning-based, cross-age face recognition has improved significantly in recent years. However, when using the discriminative method, it is still challenging to extract robust age-invariant features that can reduce the interference caused by age. In this paper, we propose a novel, effective, attention-based feature decomposition model, the age-invariant features extraction network, which can learn more discriminative feature representations and reduce the disturbance caused by aging. Our method uses an efficient channel attention block-based feature decomposition module to extract age-independent identity features from facial representations. Our end-to-end framework learns the age-invariant features directly, which is more convenient and can greatly reduce training complexity compared with existing multi-stage training methods. In addition, we propose a direct sum loss function to reduce the interference of age-related features. Our method achieves a comparable and stable performance. Experimental results demonstrate superior performance on four benchmarked datasets over the state-of-the-art. We obtain the relative improvements of 0.06%, 0.2%, and 2.2% on the cross-age datasets CACD-VS, AgeDB, and CALFW, respectively, and a relative 0.03% improvement on a general dataset LFW. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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20 pages, 1797 KiB

Open AccessArticle

Thermal Stability and Thermodynamic Performances of Pure Siloxanes and Their Mixtures in Organic Rankine Cycles

by Gioele Di Marcoberardino, Costante Mario Invernizzi, Paolo Iora, Luca Arosio, Marcello Canavese, Angelo Lunghi and Antonella Mazzei

Energies 2022, 15(10), 3498; https://doi.org/10.3390/en15103498 - 10 May 2022

Cited by 6 | Viewed by 1870

Abstract

Organic Rankine cycles are often the best solution for the conversion of thermal energy. The many working fluids include silicon oils. One crucial issue that determines the choice of a working fluid is its thermochemical stability, as this sets a limit to the [...] Read more.

Organic Rankine cycles are often the best solution for the conversion of thermal energy. The many working fluids include silicon oils. One crucial issue that determines the choice of a working fluid is its thermochemical stability, as this sets a limit to the maximum temperature at which the fluid can be used in a power plant. A second subject, much debated today, is the use of mixtures in ORCs. In the first part of this study, an investigation into the thermal stability of siloxanes using two different approaches was carried out. The results confirmed a limit working temperature for the considered siloxanes of about 300 °C, with a degradation that advanced significantly over time at 350 °C. In the second part of the study, an analysis of the thermodynamic performances of some siloxane mixtures was carried out. It was found that the efficiencies of the corresponding thermodynamic cycles were substantially the same as for the pure fluids used today. By changing the composition of the mixture, it was also possible to vary, within reasonable limits, the values of the condensation pressure, adapting the thermodynamic cycle to the different situations that can be encountered in current practice. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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18 pages, 10210 KiB

Open AccessArticle

Effect of Stator Slots on Electromagnetic Performance of a High-Voltage Line-Start Permanent Magnet Synchronous Motor

by Dongming Li, Guihong Feng, Wei Li, Bingyi Zhang and Jiaxu Zhang

Energies 2022, 15(9), 3358; https://doi.org/10.3390/en15093358 - 05 May 2022

Cited by 7 | Viewed by 3423

Abstract

It is well known that the use of slotted stators in motors produces undesirable effects, such as magnetic flux distortion, additional losses, ripple torque, and vibration. However, a large number of studies pay more attention to stator slots and magnetic slot wedges (MSW) [...] Read more.

It is well known that the use of slotted stators in motors produces undesirable effects, such as magnetic flux distortion, additional losses, ripple torque, and vibration. However, a large number of studies pay more attention to stator slots and magnetic slot wedges (MSW) in asynchronous motors and permanent magnet motors, ignoring the same problems in large capacity high voltage line start permanent magnet synchronous motors (HVLSPMSM). In order to disclose the effect of the stator slot on HVLSPMSMs, the no-load air gap magnetic field distribution and stator leakage reactance are studied. Meanwhile, the differences in the starting torque, pull-in torque and pull-out torque of four slot models are compared, and the starting performance is more affected by stator slot. In practical manufacturing, the application of MSWs is the main way to change the electromagnetic performance of stator slots, so the influence of MSWs under different permeabilities on the performance of HVLSPMSMs is investigated. Finally, the effect of a stator slot on the motor starting performance and the rated performance are verified by prototypes and experimental tests, which provide a reference for the application of MSWs in HVLSPMSMs. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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9 pages, 3659 KiB

Open AccessArticle

An Improved Phase Deviation Discriminator for Carrier Synchronization of APSK Signal in Satellite-to-Ground Communication Systems

by Yuyao Shen, Xuesen Shi, Shiqi Zhao and Yongqing Wang

Electronics 2022, 11(9), 1472; https://doi.org/10.3390/electronics11091472 - 04 May 2022

Cited by 2 | Viewed by 1638

Abstract

The conventional phase deviation discriminator used in the decision feedback loop for carrier synchronization of APSK signal requires symbol decision for every constellation symbol. When the number of constellation symbols used for coherent integration becomes larger, the complexity would increase greatly. To solve [...] Read more.

The conventional phase deviation discriminator used in the decision feedback loop for carrier synchronization of APSK signal requires symbol decision for every constellation symbol. When the number of constellation symbols used for coherent integration becomes larger, the complexity would increase greatly. To solve this problem, this work proposes an improved phase deviation discriminator based on symbol decisions. It firstly executes doubling frequency on the APSK signal to reduce the modulation order and eliminate the modulation phase of the received signal. Then, it rotates the constellation clockwise and selects the constellation symbols that on the X-axis to execute coherent integration and phase deviation extraction. Compared to the conventional discriminator in the decision feedback loop, the proposed discriminator can reduce the symbol decision times and steps. Therefore, when a large number of constellation symbols are used for coherent integration, it can reduce the computational complexity significantly. Moreover, with a large number of constellation symbols, the proposed discriminator achieves better BER and RMSE performance than other existing feedback loops. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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15 pages, 3275 KiB

Open AccessArticle

A Novel Route to Optimize Placement Equipment Kinematics by Coupling Capacitive Accelerometers

by João Veiga, Susana Lima, Luís Silva, Vítor Hugo Carneiro, Mário Pinhão, Arminda Manuela Gonçalves, Maria Teresa Malheiro, Álvaro Miguel Sampaio, José Meireles, António J. Pontes and José Machado

Sensors 2022, 22(9), 3423; https://doi.org/10.3390/s22093423 - 29 Apr 2022

Viewed by 1713

Abstract

Machine end-effector kinematic analysis is critical to optimizing transporting components where inertial forces are the main loads. While displacements may be measured with relatively high accuracy in transportation equipment motors, the inertial forces in the transported components are seldom optimized. This is especially [...] Read more.

Machine end-effector kinematic analysis is critical to optimizing transporting components where inertial forces are the main loads. While displacements may be measured with relatively high accuracy in transportation equipment motors, the inertial forces in the transported components are seldom optimized. This is especially relevant in electronic component placement systems, where the components have a wide range of configurations (i.e., geometry and mass) and the deployment dimensional/geometric tolerances are remarkably good. The optimization of these systems requires the monitoring of the real position of the accelerometers relative to the measurement point of interest with sufficient accuracy that allows the assembly position to be predicted instantaneously. This study shows a novel method to calibrate this equipment using triaxial accelerometers on a surface mount machine to measure the end-effector accelerations and velocities in its planar motion. The dynamic equations of the system and the method for integration are presented to address the uncertainty on the exact position of the accelerometer sensors relative to the measuring point of interest exist and allow the position correction to optimize response and accuracy. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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13 pages, 914 KiB

Open AccessArticle

A Chinese Grammatical Error Correction Method Based on Iterative Training and Sequence Tagging

by Hailan Kuang, Kewen Wu, Xiaolin Ma and Xinhua Liu

Appl. Sci. 2022, 12(9), 4364; https://doi.org/10.3390/app12094364 - 26 Apr 2022

Cited by 1 | Viewed by 2271

Abstract

Chinese grammatical error correction (GEC) is under continuous development and improvement, and this is a challenging task in the field of natural language processing due to the high complexity and flexibility of Chinese grammar. Nowadays, the iterative sequence tagging approach is widely applied [...] Read more.

Chinese grammatical error correction (GEC) is under continuous development and improvement, and this is a challenging task in the field of natural language processing due to the high complexity and flexibility of Chinese grammar. Nowadays, the iterative sequence tagging approach is widely applied to Chinese GEC tasks because it has a faster inference speed than sequence generation approaches. However, the training phase of the iterative sequence tagging approach uses sentences for only one round, while the inference phase is an iterative process. This makes the model focus only on the current sentence’s current error correction results rather than considering the results after multiple rounds of correction. In order to address this problem of mismatch between the training and inference processes, we propose a Chinese GEC method based on iterative training and sequence tagging (CGEC-IT). First, in the iterative training phase, we dynamically generate the target tags for each round by using the final target sentences and the input sentences of the current round. The final loss is the average of each round’s loss. Next, by adding conditional random fields for sequence labeling, we ensure that the model pays more attention to the overall labeling results. In addition, we use the focal loss to solve the problem of category imbalance caused by the fact that most words in text error correction do not need error correction. Furthermore, the experiments on NLPCC 2018 Task 2 show that our method outperforms prior work by up to 2% on the F0.5 score, which verifies the efficiency of iterative training on the Chinese GEC model. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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23 pages, 8243 KiB

Open AccessArticle

Experimental Thermofluidic Characterization of Different Metallic Regenerators Crossed by Alternating Air Flow

by Mohamed Said Kahaleras, Guillaume Layes, François Lanzetta and Steve Djetel-Gothe

Appl. Sci. 2022, 12(9), 4264; https://doi.org/10.3390/app12094264 - 23 Apr 2022

Cited by 3 | Viewed by 1300

Abstract

The regenerator is one of the most important elements of a thermal machine operating in an alternating flow regime. The present study constituted an experiment on the dynamic characterization of different metallic regenerators crossed by alternating air flow. During an experiment, gas temperature, [...] Read more.

The regenerator is one of the most important elements of a thermal machine operating in an alternating flow regime. The present study constituted an experiment on the dynamic characterization of different metallic regenerators crossed by alternating air flow. During an experiment, gas temperature, velocity, and pressure were measured at both ends of the regenerator. The acquisition frequency was set at 1 kHz for each temperature, pressure, and velocity signal. This enabled us to fully characterize an oscillating flow cycle. Experiments were performed for different regenerators (structures and porosities), frequencies, temperature gradients, and displaced air volumes. The experimental results showed that the density ratio is significant at high frequencies for all structures. The friction coefficient is determined based on a classical correlation at the time of maximum velocity. The friction factor

f

seems to decrease with the kinetic Reynolds number

R e_{ω}

for a 30% porosity regenerator. For the other tested regenerators (35% and 40% porosity), we observed that it is almost constant with a little dispersion. To minimize the dispersion effects, another definition was proposed to calculate the friction factor at the time of maximum pressure drop. The results showed that for all regenerators a single clear trend is the function of the kinetic Reynolds number. A significant phase shift was observed between the velocity and pressure drop. It increases with the increasing kinetic Reynolds number. It was found that the phase shift only depends on frequency. Finally, a correlation equation was proposed to predict the phase shift of different regenerator structures. It was found that the effect of the kinetic Reynolds number

R e_{ω}

on the phase shift is more dominant than that of the hydraulic diameter to length ratio

D_{h} / L

. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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15 pages, 13789 KiB

Open AccessArticle

Simulation Research on Deadbeat Direct Torque and Flux Control of Permanent Magnet Synchronous Motor

by Jie Chen, Jiajun Wang and Bo Yan

Energies 2022, 15(9), 3009; https://doi.org/10.3390/en15093009 - 20 Apr 2022

Cited by 4 | Viewed by 1650

Abstract

Direct torque control (DTC) is widely used in a permanent-magnet synchronous motor (PMSM), but it has its own shortcomings caused by high torque ripple. Deadbeat-direct torque and flux control (DB-DTFC) is a new torque and flux method compared with DTC. However, the traditional [...] Read more.

Direct torque control (DTC) is widely used in a permanent-magnet synchronous motor (PMSM), but it has its own shortcomings caused by high torque ripple. Deadbeat-direct torque and flux control (DB-DTFC) is a new torque and flux method compared with DTC. However, the traditional DB-DTFC is often based on rotor-flux-oriented control. The reference voltage of the stator is computed in a rotor-flux-oriented coordinate system, and the solution involves solving quadratic equations, which will increase the burden of computational processing. To improve the computation of the reference voltages and the control performance, this paper proposes a new DB-DTFC algorithm and introduces its basic principles. First, the proposed DB-DTFC algorithm uses the forward Euler equation to solve the reference voltage in a stator-flux-oriented coordinate system. Second, the discrete mathematical model is used to predict the next control current to achieve deadbeat control. Third, the structural model of the proposed DB-DTFC is constructed. Finally, the simulation model of the proposed DB-DTFC algorithm is built with a MATLAB/Simulink platform. The simulation results prove that the proposed DB-DTFC algorithm can achieve better control performance in torque and flux control compared with the DTC algorithm and SVM-based direct torque and flux control (SVM-DTFC) algorithm. In particular, the torque index of DB-DTFC is reduced about 6% in a limited speed range in comparison with the DTC algorithm. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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19 pages, 4669 KiB

Open AccessArticle

Active Disturbance Rejection Control in Magnetic Bearing Rotor Systems with Redundant Structures

by Baixin Cheng, Xin Cheng, Shao Song, Huachun Wu, Yefa Hu, Rougang Zhou and Shuai Deng

Sensors 2022, 22(8), 3012; https://doi.org/10.3390/s22083012 - 14 Apr 2022

Cited by 4 | Viewed by 1801

Abstract

At present, magnetic bearings are a better energy-saving choice than mechanical bearings in industrial applications. However, there are strongly coupled characteristics in magnetic bearing–rotor systems with redundant structures, and uncertain disturbances in the electrical system as well as external disturbances, and these unfavorable [...] Read more.

At present, magnetic bearings are a better energy-saving choice than mechanical bearings in industrial applications. However, there are strongly coupled characteristics in magnetic bearing–rotor systems with redundant structures, and uncertain disturbances in the electrical system as well as external disturbances, and these unfavorable factors degrade the performance of the system. To improve the anti-interference performance of magnetic bearing systems, this paper proposes the inverse of the current distribution matrix W⁻¹ meaning that the active disturbance rejection control simulation model can be carried out without neglecting the current of each coil. Firstly, based on the working mechanism of magnetic bearings with redundant structures and the nonlinear electromagnetic force model, the current and displacement stiffness models of magnetic bearings are established, and a dynamic model of the rotor is constructed. Then, according to the dynamic model of the rotor and the mapping relationship between the current of each coil and the electromagnetic force of the magnetic bearing, we established the equivalent control loop of the magnetic bearing–rotor system with redundant structures. Finally, on the basis of the active disturbance rejection control (ADRC) strategy, we designed a linear active disturbance rejection controller (LADRC) for magnetic bearings with redundant structures under the condition of no coil failure, and a corresponding simulation was carried out. The results demonstrate that compared to PID+current distribution control strategy, the LADRC+current distribution control strategy proposed in this paper is able to effectively improve the anti-interference performance of the rotors supported by magnetic bearings with redundant structures. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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13 pages, 499 KiB

Open AccessArticle

Adaptive Neural Partial State Tracking Control for Full-State-Constrained Uncertain Singularly Perturbed Nonlinear Systems and Its Applications to Electric Circuit

by Hao Wang, Xiaomin Liu and Chunyu Yang

Electronics 2022, 11(8), 1209; https://doi.org/10.3390/electronics11081209 - 11 Apr 2022

Viewed by 1285

Abstract

This paper is concerned with the adaptive neural network (NN) partial tracking control problem for a class of completely unknown multi-input multi-output (MIMO) singularly perturbed nonlinear systems possessing time-varying asymmetric state constraints. To satisfy the constraints, we utilize the state-depended transformation technique to [...] Read more.

This paper is concerned with the adaptive neural network (NN) partial tracking control problem for a class of completely unknown multi-input multi-output (MIMO) singularly perturbed nonlinear systems possessing time-varying asymmetric state constraints. To satisfy the constraints, we utilize the state-depended transformation technique to convert the original state-constrained system to an equivalent unconstrained one, then the state constraint problem can be solved by ensuring its stability. Partial state tracking can be achieved without the violation of state constraints. The adaptive tracking controllers are designed by using singular perturbation theory and the adaptive control method, in which NNs are used to approximate unknown nonlinear functions. The ill-conditioned numerical problems lurking in the controller design process are averted and the closed-loop system stability can be guaranteed by introducing an appropriate Lyapunov function with singular perturbation parameter. Finally, a practical example is given to demonstrate the effectiveness of our proposed adaptive NN tracking control scheme. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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14 pages, 1306 KiB

Open AccessArticle

A Lyapunov Stability Analysis of Modified HOSM Controllers Using a PID-Sliding Surface Applied to an ABS Laboratory Setup

by Christopher Javier García Torres, Luis Adrián Ferré Covantes, Claudia Carolina Vaca García, Juan Carlos Estrada Gutiérrez, Antonio Navarrete Guzmán and Cuauhtémoc Acosta Lúa

Appl. Sci. 2022, 12(8), 3796; https://doi.org/10.3390/app12083796 - 09 Apr 2022

Cited by 1 | Viewed by 1304

Abstract

The antilock braking system (ABS) is a mechatronic system that helps a driver maintain the maneuverability of a vehicle while braking by preventing wheel lock-ups. However, the design of high-performance controllers for this type of system is complicated because of its highly nonlinear [...] Read more.

The antilock braking system (ABS) is a mechatronic system that helps a driver maintain the maneuverability of a vehicle while braking by preventing wheel lock-ups. However, the design of high-performance controllers for this type of system is complicated because of its highly nonlinear dynamics. The problem becomes even more difficult to resolve when uncertainties in the parameters appear in its dynamics. In this paper, an ABS laboratory setup mimicking a quarter car model is considered. A modified high-order sliding mode (HOSM) controller using a proportional-integral-differential (PID) control as a sliding surface was designed. This controller provides a reference value of a tire slip. The proposed controller uses a tracking error to define the slip surface through the PID controller structure, and the modified HOSM controller holds the system on the previously designed slip surface. The closed-loop system stability has been proven in the sense of Lyapunov. Finally, the ABS laboratory setup allows for experimentally checking the performance of the modified HOSM controller using a PID-sliding surface, showing a considerable increase in the efficiency of the control system compared with a PID-like controller. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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19 pages, 4962 KiB

Open AccessArticle

Velocity-Free Formation Control and Collision Avoidance for UUVs via RBF: A High-Gain Approach

by Zheping Yan, Anzuo Jiang, Chonglang Lai and Heng Li

Electronics 2022, 11(8), 1170; https://doi.org/10.3390/electronics11081170 - 07 Apr 2022

Cited by 1 | Viewed by 1376

Abstract

This paper designs an adaptive formation control system for unmanned underwater vehicles (UUVs) in the presence of unmeasurable states and environmental disturbance. To solve the problem of unmeasurable UUV states, a filtered high-gain observer (FHGO) is employed to estimate the states, despite measurement [...] Read more.

This paper designs an adaptive formation control system for unmanned underwater vehicles (UUVs) in the presence of unmeasurable states and environmental disturbance. To solve the problem of unmeasurable UUV states, a filtered high-gain observer (FHGO) is employed to estimate the states, despite measurement noise. Then, an adaptive control scheme is designed to achieve UUV formation collision avoidance. The radial basis function (RBF) is used to estimate the unknown disturbance. The stability of UUV formation with collision avoidance is proven by using the Lyapunov theorem. Numerical simulation is carried out to demonstrate that the proposed filtered high-gain observer is successful in estimating the states of UUVs. The control law can keep the UUV formation from collision with good performance. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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13 pages, 19010 KiB

Open AccessArticle

The Resulting Effect of Flow Pulsations on Calibration Constant of Acoustic Path in Ultrasonic Flowmeters

by Anna Goltsman and Ilya Saushin

Sensors 2022, 22(7), 2815; https://doi.org/10.3390/s22072815 - 06 Apr 2022

Cited by 4 | Viewed by 1831

Abstract

The present paper compares, for the first time, the regimes of a pulsating turbulent flow in a smooth pipe in terms of 0.001 ≤ ω⁺ ≤ 0.0346 and 0.16 ≤ β ≤ 0.63 at Re ≈ 7000 with the uncertainty in estimating [...] Read more.

The present paper compares, for the first time, the regimes of a pulsating turbulent flow in a smooth pipe in terms of 0.001 ≤ ω⁺ ≤ 0.0346 and 0.16 ≤ β ≤ 0.63 at Re ≈ 7000 with the uncertainty in estimating the flow rate by an ultrasonic flowmeter. It was revealed that the classification of pulsating flow regimes according to the dimensionless angular frequency ω⁺ does not have a direct relation with the K parameter equal to the ratio of the phase-average calibration constant in pulsating flow to the corresponding value in steady flow. The results of data processing showed that K depends on the relative amplitude of pulsations β and the position of the chord of the ultrasonic beam trajectory (L/R is distance L from the pipe center to the chord to the pipe radius R). In the coordinates β and L/R, there is a rather wide area where the uncertainty in flow rate estimation of pulsating flows should not exceed 0.5%. An increase in β or L/R leads to an increase in measurement uncertainty, which in the limiting case β, L/R → 1 can reach 5% or more. Favorable and unfavorable areas of the pipe section were identified when scanning pulsating flows and the effectiveness of using multi-path scanning schemes was estimated to reduce the resulting effect of flow pulsations on flow measurement uncertainty. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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13 pages, 16357 KiB

Open AccessArticle

Fuzzy Compensation and Load Disturbance Adaptive Control Strategy for Electro-Hydraulic Servo Pump Control System

by Yu Song, Zhongwang Hu and Chao Ai

Electronics 2022, 11(7), 1159; https://doi.org/10.3390/electronics11071159 - 06 Apr 2022

Cited by 7 | Viewed by 1853

Abstract

Aiming at the high-precision position control of electro-hydraulic servo pump control system, a compensation control algorithm based on fuzzy control theory is proposed based on the classical PID control algorithm for the control of factors such as oil compression and system leakage. Firstly, [...] Read more.

Aiming at the high-precision position control of electro-hydraulic servo pump control system, a compensation control algorithm based on fuzzy control theory is proposed based on the classical PID control algorithm for the control of factors such as oil compression and system leakage. Firstly, a mathematical model of the system was established, and online identification of load disturbance was carried out. Then, oil compression and system leakage compensation controllers were established, and the position error caused by the load disturbance was compensated based on fuzzy control rules. Finally, the position control effect was verified using an experimental platform. The results show that the load disturbance compensation control strategy can significantly reduce the influence of load disturbance of the system. The steady-state accuracy of the system reached ±0.01 mm, which significantly enhanced the anti-disturbance ability of the system. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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34 pages, 5155 KiB

Open AccessArticle

Time Connection of Subsequent Construction Processes Estimated by Statistical Method

by Stanislav Smugala and Darja Kubečková

Appl. Sci. 2022, 12(7), 3529; https://doi.org/10.3390/app12073529 - 30 Mar 2022

Viewed by 1208

Abstract

An integral part of managing the construction of investment units is the monitoring of labor productivity using statistical methods in combination with construction software. Such a combination includes a number of methods and modeling, among which is a method for determining the probability [...] Read more.

An integral part of managing the construction of investment units is the monitoring of labor productivity using statistical methods in combination with construction software. Such a combination includes a number of methods and modeling, among which is a method for determining the probability of the completion of construction processes based on the recorded mean value of labor productivity and its variations. For investment units consisting of two or more objects, it is necessary to assess the probability of the completion of construction processes related to follow-up activities and which are carried out by the same work crews. Based on the selected probability modeling, the aim of this contribution was to show how statistical methods and software support can contribute to savings in resources, both human and time, in construction production. The aspect is documented in a case study of residential buildings. The Lindeberg–Lévy and Moivre–Laplace theory and the Bernoulli principle were used for mathematical modeling. The CONTEC construction software was applied as the software support. The performed modeling showed a decrease in the mean value of performance for all the processes examined compared to the planned values, except for the implementation of reinforced concrete monolithic structures. For these reasons, the working capacities had to be increased in order to meet construction milestones. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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11 pages, 1214 KiB

Open AccessArticle

Training Data Selection by Categorical Variables for Better Rare Event Prediction in Multiple Products Production Line

by Dongting Xu, Zhisheng Zhang and Jinfei Shi

Electronics 2022, 11(7), 1056; https://doi.org/10.3390/electronics11071056 - 28 Mar 2022

Cited by 5 | Viewed by 2231

Abstract

Manufacturers are struggling to use data from multiple products production lines to predict rare events. Improving the quality of training data is a common way to improve the performance of algorithms. However, there is little research about how to select training data quantitatively. [...] Read more.

Manufacturers are struggling to use data from multiple products production lines to predict rare events. Improving the quality of training data is a common way to improve the performance of algorithms. However, there is little research about how to select training data quantitatively. In this study, a training data selection method is proposed to improve the performance of deep learning models. The proposed method can represent different time length multivariate time series spilt by categorical variables and measure the (dis)similarities by the distance matrix and clustering method. The contributions are: (1) The proposed method can find the changes to the training data caused by categorical variables in a multivariate time series dataset; (2) according to the proposed method, the multivariate time series data from the production line can be clustered into many small training datasets; and (3) same structure but different parameters prediction models are built instead of one model which is different from the traditional way. In practice, the proposed method is applied in a real multiple products production line dataset and the result shows it can not only significantly improve the performance of the reconstruction model but it can also quantitively measure the (dis)similarities of the production behaviors. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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13 pages, 1995 KiB

Open AccessArticle

Resource Allocation for Throughput versus Fairness Trade-Offs under User Data Rate Fairness in NOMA Systems in 5G Networks

by Osama Abuajwa, Mardeni Roslee, Zubaida Binti Yusoff, Lee Loo Chuan and Pang Wai Leong

Appl. Sci. 2022, 12(7), 3226; https://doi.org/10.3390/app12073226 - 22 Mar 2022

Cited by 6 | Viewed by 1758

Abstract

In this work, we present a resource allocation scheme for managing trade-offs between total throughput maximisation and system fairness in a non-orthogonal multiple access (NOMA) system for 5G networks. Our proposed approach is designed to improve throughput and fairness as performance metrics of [...] Read more.

In this work, we present a resource allocation scheme for managing trade-offs between total throughput maximisation and system fairness in a non-orthogonal multiple access (NOMA) system for 5G networks. Our proposed approach is designed to improve throughput and fairness as performance metrics of NOMA in 5G networks. We apply integer linear programming for user pairing and adopt particle swarm optimisation as the power allocation scheme for reducing resource allocation complexity. To formulate the multi-objective problem, we use scalarisation of multi-objective optimisation, which exhibits flexibility in assigning different weights to a single objective—in the case of this study, either sum rate or fairness. Moreover, the problem is formulated with a penalty function to prevent optimisation violating the constraints of the optimisation function. Simulation results show that the proposed model outperformed the conventional approach by at least 17% in terms of throughput maximisation and fairness rate. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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13 pages, 2527 KiB

Open AccessArticle

The Study of Novel Self-Rewetting Fluid Application to Loop Heat Pipe

by Jhih-Huang Gao, Shen-Chun Wu, Ya-Wei Lee, Ta-Li Chou and Yan-Chun Chen

Appl. Sci. 2022, 12(6), 3121; https://doi.org/10.3390/app12063121 - 18 Mar 2022

Cited by 3 | Viewed by 1641

Abstract

The purpose of this paper is to develop SRF formulations for LHP performance enhancement. In this paper, the solute of SRF is prepared, and butanol and its isomer, 2-butanol, are selected. In this paper, concentrations of the 2-butanol aqueous solution (10%, 15%, and [...] Read more.

The purpose of this paper is to develop SRF formulations for LHP performance enhancement. In this paper, the solute of SRF is prepared, and butanol and its isomer, 2-butanol, are selected. In this paper, concentrations of the 2-butanol aqueous solution (10%, 15%, and 20%) plus the butanol 6% aqueous solution were used to measure the surface tension of four different formulations of SRF and water. It was found that the higher the solute concentration became, the stronger the Marangoni effect was, and the more obvious the surface tension change of the 2-butanol 20% aqueous solution was. Water, the butanol 6% aqueous solution and the 2-butanol 20% aqueous solution were filled into LHP respectively, and the heat transfer performance was measured. The 2-Butanol 20% aqueous solution improved LHP performance by about three times compared with water, and the lowest total thermal resistance was only 1/4 that of water. Therefore, the 2-butanol 20% SRF aqueous solution is an ideal formula for improving the LHP heat transfer performance. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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19 pages, 5652 KiB

Open AccessArticle

Semantic Modeling Approach Supporting Process Modeling and Analysis in Aircraft Development

by Junda Ma, Guoxin Wang, Jinzhi Lu, Shaofan Zhu, Jingjing Chen and Yan Yan

Appl. Sci. 2022, 12(6), 3067; https://doi.org/10.3390/app12063067 - 17 Mar 2022

Cited by 3 | Viewed by 1658

Abstract

With the increasing complexity of aircraft development programs, the development processes of aircraft and their subsystems are continuously becoming complicated, leading to the growing risks of development cost across the entire life cycle. In this study, we proposed a model-based systems engineering approach [...] Read more.

With the increasing complexity of aircraft development programs, the development processes of aircraft and their subsystems are continuously becoming complicated, leading to the growing risks of development cost across the entire life cycle. In this study, we proposed a model-based systems engineering approach to support process modeling of aircraft development using a multi-architecture modeling language KARMA. Simultaneously, property verification and hybrid automata simulation were used to implement the static cost analysis of each work task and dynamic cost analysis of the entire development process. Finally, a development process model of aircraft avionics system was created using a case study, in which cost analysis is implemented by the KARMA language. From the result, we found that the KARMA language enables the integration of the process modeling with static and dynamic analyses of the development process in a multi-architecture modeling tool MetaGraph 2.0. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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14 pages, 4759 KiB

Open AccessArticle

Wearable Sensor for Forearm Motion Detection Using a Carbon-Based Conductive Layer-Polymer Composite Film

by Kiwon Park

Sensors 2022, 22(6), 2236; https://doi.org/10.3390/s22062236 - 14 Mar 2022

Cited by 2 | Viewed by 2774

Abstract

In this study, we developed a fabrication method for a bracelet-type wearable sensor to detect four motions of the forearm by using a carbon-based conductive layer-polymer composite film. The integral material used for the composite film is a polyethylene terephthalate polymer film with [...] Read more.

In this study, we developed a fabrication method for a bracelet-type wearable sensor to detect four motions of the forearm by using a carbon-based conductive layer-polymer composite film. The integral material used for the composite film is a polyethylene terephthalate polymer film with a conductive layer composed of a carbon paste. It is capable of detecting the resistance variations corresponding to the flexion changes of the surface of the body due to muscle contraction and relaxation. To effectively detect the surface resistance variations of the film, a small sensor module composed of mechanical parts mounted on the film was designed and fabricated. A subject wore the bracelet sensor, consisting of three such sensor modules, on their forearm. The surface resistance of the film varied corresponding to the flexion change of the contact area between the forearm and the sensor modules. The surface resistance variations of the film were converted to voltage signals and used for motion detection. The results demonstrate that the thin bracelet-type wearable sensor, which is comfortable to wear and easily applicable, successfully detected each motion with high accuracy. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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18 pages, 1534 KiB

Open AccessArticle

The Measurement Uncertainty in Determining of Electrical Resistance Value by Applying Direct-Comparison Method

by Vladimir Pleština, Vedran Boras and Hrvoje Turić

Energies 2022, 15(6), 2115; https://doi.org/10.3390/en15062115 - 14 Mar 2022

Cited by 4 | Viewed by 2910

Abstract

This paper considers the unknown electrical resistance (measurand) as the numerical result of the measurement that was carried out by means of the well-known direct comparison measurement method using an appropriate standard resistor and voltmeter. In the literature, this measurement method is also [...] Read more.

This paper considers the unknown electrical resistance (measurand) as the numerical result of the measurement that was carried out by means of the well-known direct comparison measurement method using an appropriate standard resistor and voltmeter. In the literature, this measurement method is also referred to as a series comparison method. This method of measurement is one of the indirect methods and is suitable for measuring low resistance. This paper presents two approaches for evaluating the unknown electrical resistance and its associated combined standard uncertainty. The entire process of evaluating the combined standard uncertainty that is associated with the measurand and the standard uncertainties that are associated with the analyzed input quantities has been entirely performed in accordance with the applicable international recommendations and guidelines for the uncertainty of measurement. The analyzed approaches for evaluating the combined standard uncertainty are designed to be universal and valid both for the mutually non-correlated input quantities and for the mutually correlated input quantities, which can be obtained from a single observation, or repeated observations or by other means. This paper can substantially contribute to the measurements in electrical engineering and education. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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18 pages, 11036 KiB

Open AccessArticle

A Study on the Grain Refining Mechanisms and Melt Superheat Treatment of Aluminum-Bearing Mg Alloys

by Sung Su Jung, Yong Guk Son, Yong Ho Park and Young Cheol Lee

Metals 2022, 12(3), 464; https://doi.org/10.3390/met12030464 - 10 Mar 2022

Cited by 5 | Viewed by 2053

Abstract

Grain refinement of magnesium (Mg) alloys has been a major research topic over the past decades as one of the effective approaches to increase their strength and ductility simultaneously. In this study, a brief review of the grain refinement of aluminum-bearing Mg alloys [...] Read more.

Grain refinement of magnesium (Mg) alloys has been a major research topic over the past decades as one of the effective approaches to increase their strength and ductility simultaneously. In this study, a brief review of the grain refinement of aluminum-bearing Mg alloys is included to provide an in-depth understanding of the detailed mechanisms of grain refinement of Mg alloys. Additionally, the effect of melt superheating on the grain refining of Mg–Al-based alloys has been investigated. It was confirmed that melt superheating caused a significant grain refining effect in the commercial purity (CP) of AZ91 alloy (0.25% Mn). Undercooling of 1.3 °C was observed before superheating and was noticeably reduced after the superheating process. A vacuum filtering experiment was conducted, which involves filtering the melts using fine metal porous filters to separate the particles in the melts. It was observed that a large amount of Al₈Mn₅ particles were generated in the commercial purity AZ91 alloy by the superheating process. However, because of the poor crystallographic matching between Al₈Mn₅ and Mg, Al₈Mn₅ was not considered the nucleation site for Mg grains. A master alloy containing ε-AlMn particles, which are in good crystallographic matching with Mg, was added, and it was found that the grain size of the commercial-grade AZ91 alloy was reduced. Therefore, it is suggested that Al₈Mn₅ particles, existing as a solid phase in the molten metal of the commercial AZ91 alloy could be transformed into ε-AlMn particles by the superheating process, and these particles can be effective nucleation sites for Mg grains. The transformation of Al₈Mn₅ into ε-AlMn is considered the main mechanism of grain refinement of the commercial purity of AZ91 alloy by superheating. Notably, the effect of grain refinement by superheating was not observed in the high-purity (HP) AZ91 alloy (0.006% Mn) because Al–Mn particles were likely not formed due to a very small quantity of manganese. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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16 pages, 4200 KiB

Open AccessArticle

Study on Flow Characteristics and Mass Transfer Mechanism of Kettle Taylor Flow Reactor

by Li Ye, Tengfei Wan, Xiaohui Xie and Lin Hu

Energies 2022, 15(6), 2028; https://doi.org/10.3390/en15062028 - 10 Mar 2022

Cited by 2 | Viewed by 2282

Abstract

A scheme of a gas–liquid mixed jet is designed by installing gas distributor at the bottom of a stirred tank reactor to generate Taylor vortex. The eddy flow characteristics and mass transfer mechanism in the reactor are analyzed by numerical simulation and experiment. [...] Read more.

A scheme of a gas–liquid mixed jet is designed by installing gas distributor at the bottom of a stirred tank reactor to generate Taylor vortex. The eddy flow characteristics and mass transfer mechanism in the reactor are analyzed by numerical simulation and experiment. The results show that the evolution law of Taylor vortex in a stirred tank reactor with a rotating Reynolds number is similar to that in a conventional Taylor reactor. The Taylor vortex generated in the stirred tank reactor creates a partial plug flow region in the original complete mixing flow pattern, which reduces back mixing, the plug flow area expands with the increase of rotating Reynolds number. Under the condition of a critical rotating Reynolds number (Re_cr), the gas phase homogeneity of the reactor is increased by 28% and the dissolved oxygen rate is increased by about 5 times, which effectively improves the flow condition in the reactor and strengthens the mass transfer efficiency between the gas and liquid. The research results provide a theoretical basis for breaking through the limitation of small reaction space of conventional Taylor flow reactor and expanding production scale. The refit of kettle reactor is universal and easy to operate. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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12 pages, 3919 KiB

Open AccessArticle

Detection of Lower Body for AGV Based on SSD Algorithm with ResNet

by Xinbiao Gao, Junhua Xu, Chuan Luo, Jun Zhou, Panling Huang and Jianxin Deng

Sensors 2022, 22(5), 2008; https://doi.org/10.3390/s22052008 - 04 Mar 2022

Cited by 10 | Viewed by 2551

Abstract

Detection of human lower body provides an implementation idea for the automatic tracking and accurate relocation of automatic vehicles. Based on traditional SSD and ResNet, this paper proposes an improved detection algorithm R-SSD for human lower body detection, which utilizes ResNet50 instead of [...] Read more.

Detection of human lower body provides an implementation idea for the automatic tracking and accurate relocation of automatic vehicles. Based on traditional SSD and ResNet, this paper proposes an improved detection algorithm R-SSD for human lower body detection, which utilizes ResNet50 instead of VGG16 to improve the feature extraction level of the model. According to the application of acquisition equipment, the model input resolution is increased to 448 × 448 and the model detection range is expanded. Six feature maps of the updated resolution network are selected for detection and the lower body image dataset is clustered into five categories for aspect ratio, which are evenly distributed to each feature detection map. The experimental results show that the model R-SSD detection accuracy after training reaches 85.1% mAP. Compared with the original SSD, the detection accuracy is improved by 7% mAP. The detection confidence in practical application reaches more than 99%, which lays the foundation for subsequent tracking and relocation for automatic vehicles. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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13 pages, 11132 KiB

Open AccessArticle

Spectral Map-Based Tool for Backhaul Rural Network Optimization and Indirect Estimation of Demographic Behaviors

by Claudia Lucía Cortés, Mauricio Alejandro Montaño-Argote and Neil Guerrero-González

Appl. Sci. 2022, 12(5), 2508; https://doi.org/10.3390/app12052508 - 28 Feb 2022

Viewed by 1820

Abstract

In this article, both the optimization of a backhaul network and the indirect estimation of demographic behaviors from spectral analysis are proposed. Electromagnetic spectrum in 5 GHz frequency band was scanned, and graphs generation associated with the spectral map were obtained using AirView [...] Read more.

In this article, both the optimization of a backhaul network and the indirect estimation of demographic behaviors from spectral analysis are proposed. Electromagnetic spectrum in 5 GHz frequency band was scanned, and graphs generation associated with the spectral map were obtained using AirView Spectrum Analyzer software incorporated into Ubiquiti devices; these devices were installed in Ovejas and Chalán municipalities as part of a rural backhaul network located in Sucre, Colombia to bridge the digital divide in rural areas. In addition to telecommunications system working frequency optimization between Almagra and La Ceiba nodes, which was configured at 5790 MHz—spectral analysis is presented as a non-traditional information source of demographic behavior, an indirect measure of population data from rural and difficult access areas. Initially, power intensity levels measured in Almagra and La Ceiba nodes based on the spectral map are presented as a tool to continuously measure the demographic behavior relating telecommunications equipment use to population density. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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27 pages, 4549 KiB

Open AccessArticle

Robust Super-Twisting Sliding Mode Backstepping Control Blended with Tracking Differentiator and Nonlinear Disturbance Observer for an Unknown UAV System

by Sungbum Park and Seongik Han

Appl. Sci. 2022, 12(5), 2490; https://doi.org/10.3390/app12052490 - 27 Feb 2022

Cited by 6 | Viewed by 1866

Abstract

In this study, we examined the robust super-twisting sliding mode backstepping control (SBSC) method, which employed a tracking differentiator and nonlinear disturbance observer for a hexacopter unmanned aerial vehicle (UAV) system. To realize robust tracking control performance for a highly coupled nonlinear hexacopter [...] Read more.

In this study, we examined the robust super-twisting sliding mode backstepping control (SBSC) method, which employed a tracking differentiator and nonlinear disturbance observer for a hexacopter unmanned aerial vehicle (UAV) system. To realize robust tracking control performance for a highly coupled nonlinear hexacopter UAV system, a super-twisting sliding mode control method was combined with designing stabilizing controls of backstepping control (BSC) applied to the UAV system. Furthermore, the differentiation issue of the virtual control and compensation of transformation error in the conventional BSC design were bypassed via a new continuous tracking differentiator structure. Additionally, a new disturbance observer based on the proposed tracking differentiator was considered to estimate uncertainties of the hexacopter UAV. Comparative simulation results demonstrated that the proposed tracking-differentiator-based SBSC scheme (PTSBSC) blended with the tracking differentiator and nonlinear disturbance observer exhibits improved performance when compared to that of conventional BSC and disturbance observer systems. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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22 pages, 2434 KiB

Open AccessArticle

Scalable Path Search for Automated Test Case Generation

by Enze Ma, Xiufeng Fu and Xi Wang

Electronics 2022, 11(5), 727; https://doi.org/10.3390/electronics11050727 - 26 Feb 2022

Cited by 4 | Viewed by 2022

Abstract

Test case generation is an important task during software testing. In this paper, we present a new test-case generation framework for C programs. This approach combines dataflow analysis and dynamic symbolic execution together, and more importantly, it efficiently searches the program path space [...] Read more.

Test case generation is an important task during software testing. In this paper, we present a new test-case generation framework for C programs. This approach combines dataflow analysis and dynamic symbolic execution together, and more importantly, it efficiently searches the program path space for potential faults based on the tabu search strategy and the program fault statistics. Unlike the traditional symbolic execution, which explores the program space exhaustively and is difficult to apply to complicated programs effectively, our approach automatically explores the feasible paths of hidden faults with high probability. The scalable and efficient path search strategy facilitates bug finding with much fewer test cases generated. We implemented this approach, and the experimental results presented in this paper are attractive. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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11 pages, 3906 KiB

Open AccessArticle

An Estimation of the Backscattering Strength of Artificial Bubbles Using an Acoustic Doppler Current Profiler

by Ho Seuk Bae, Won-Ki Kim, Su-Uk Son, Woo-Shik Kim and Joung-Soo Park

Sensors 2022, 22(5), 1812; https://doi.org/10.3390/s22051812 - 25 Feb 2022

Cited by 5 | Viewed by 1822

Abstract

Acoustic Doppler current profilers (ADCPs) were developed to acquire water current velocities, as well as depth-dependent echo intensities. As the backscattering strength of an underwater object can be estimated from the measured echo intensity, the ADCP can be used to estimate plankton populations [...] Read more.

Acoustic Doppler current profilers (ADCPs) were developed to acquire water current velocities, as well as depth-dependent echo intensities. As the backscattering strength of an underwater object can be estimated from the measured echo intensity, the ADCP can be used to estimate plankton populations and distributions. In this study, the backscattering strength of bubble clusters in a water tank was estimated using the commercial ADCP as a proof-of-concept. Specifically, the temporal variations in the backscattering strength and the duration of bubble existence were quantitatively evaluated. Additionally, the PDSL (population density spectrum level) and VF (void fraction) of the artificial bubbles were characterized based on the obtained distribution characteristics using a PDPA (phase Doppler particle analyzer). Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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21 pages, 3937 KiB

Open AccessArticle

Three-Dimensional Measuring Device and Method of Underground Displacement Based on Double Mutual Inductance Voltage Contour Method

by Nanying Shentu, Feng Wang, Qing Li, Guohua Qiu, Renyuan Tong and Siguang An

Sensors 2022, 22(5), 1725; https://doi.org/10.3390/s22051725 - 23 Feb 2022

Cited by 8 | Viewed by 1734

Abstract

Landslide is a very common and destructive geo-hazard, and displacement monitoring of it is integral for risk assessment and engineering prevention. Given the shortcomings of current landslide displacement monitor technologies, a new three-dimensional underground displacement monitoring technology is proposed based on the double [...] Read more.

Landslide is a very common and destructive geo-hazard, and displacement monitoring of it is integral for risk assessment and engineering prevention. Given the shortcomings of current landslide displacement monitor technologies, a new three-dimensional underground displacement monitoring technology is proposed based on the double mutual inductance voltage contour method. The underground displacement measuring device mainly consists of an information processing unit and sensing array, connected by power and RS-485 communication lines. An underground displacement measurement model to convert the double mutual inductance voltages and the inter-axis angle into the relative displacement between adjacent sensing units is established based on the interval-interpolation and contour-modeling. Under the control of the information processing unit, the relative displacement between any two adjacent sensing units can be calculated through the underground displacement measurement model, so as to obtain the total displacement from underground depth to surface, and the measurement data can be further sent to the Internet of things cloud platform through the 4G module; thus the remote real-time monitoring of underground displacement three-dimensional measurement for the rock and soil mass from underground depth to the surface is realized. The measurement model is verified by building an experimental platform to simulate the underground displacement of rock and soil mass. The experimental results show that for each measuring unit, when the horizontal displacement and vertical displacement are within the measurement range of 0–50 mm, the maximum measurement error will not exceed 1 mm, which can meet the accuracy requirements of underground displacement monitoring of landslide. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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18 pages, 3841 KiB

Open AccessArticle

Optimization of Indoor Luminaire Layout for General Lighting Scheme Using Improved Particle Swarm Optimization

by Ji-Qing Qu, Qi-Lin Xu and Ke-Xue Sun

Energies 2022, 15(4), 1482; https://doi.org/10.3390/en15041482 - 17 Feb 2022

Cited by 5 | Viewed by 1794

Abstract

An improved mathematical model and an improved particle swarm optimization (IPSO) are proposed for the complex design parameters and conflicting design goals of the indoor luminaire layout (ILL) problem. The ILL problem is formulated as a nonlinear constrained mixed-variable optimization problem that has [...] Read more.

An improved mathematical model and an improved particle swarm optimization (IPSO) are proposed for the complex design parameters and conflicting design goals of the indoor luminaire layout (ILL) problem. The ILL problem is formulated as a nonlinear constrained mixed-variable optimization problem that has four decision variables. For a general lighting scheme (GLS), the number and location of luminaires can be uniquely determined by optimizing four decision variables, which avoid using program loops to determine the number of luminaires. We improve the particle swarm optimization (PSO) in three aspects: (1) up-down probabilistic rounding (UDPR) method proposed to solve mixed integer, (2) improving the velocity of the best global particle, and (3) using nonlinear inertia weights with random items. The IPSO has better optimization results in an office study compared with the PSO and genetic algorithm (GA). The results are validated by DIALux simulation software, and a maximum deviation of 2.2% is found. The validated results show that the method using four decision variables increased the speed by 10.6% and the success rate by 23.33%. Furthermore, Indoor Luminaire Layout System APP is designed to provide guidelines visually for lighting designers and related researchers. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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11 pages, 2543 KiB

Open AccessArticle

Simplistic, Efficient, and Low-Cost Crack Detection of Dielectric Materials Based on Millimeter-Wave Interference

by Liangping Chen, Liangjie Bi, Yong Yin, Yu Qin, Minsheng Song, Bin Wang, Hailong Li and Lin Meng

Electronics 2022, 11(4), 583; https://doi.org/10.3390/electronics11040583 - 15 Feb 2022

Cited by 2 | Viewed by 1410

Abstract

This paper proposes a simplistic, efficient, and low-cost method of millimeter-wave nondestructive testing (NDT) of dielectric material cracks based on millimeter-wave interference. A relationship between combining efficiency, phase difference, and amplitude difference was analyzed. We found that phase difference was the main factor [...] Read more.

This paper proposes a simplistic, efficient, and low-cost method of millimeter-wave nondestructive testing (NDT) of dielectric material cracks based on millimeter-wave interference. A relationship between combining efficiency, phase difference, and amplitude difference was analyzed. We found that phase difference was the main factor that affects combining efficiency. A change in combining efficiency of more than 1% was caused by a phase-difference altering of greater than 1.2° in a specific range. A relevant model was simulated with CST, and the operating frequency and antenna spacing were optimized to enhance sensitivity of the measuring system. Then, a Ka-band NDT system was built to test the combining efficiencies of different cracks. The experimental results showed that for polytetrafluoroethylene (PTFE) plates with a thickness of 5 mm, cracks with a width of about 0.4 mm, which is about 0.07 λ_g, could be detected at 35 GHz. Experimental results, simulation results, and theoretical derivation are basically consistent. Large-scale online applications of this NDT method in various industries appear feasible due to the above characteristics. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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21 pages, 7308 KiB

Open AccessArticle

Solid-State Transformer-Based DC Power Distribution Network for Shipboard Applications

by Abdelrahman Ismail, Mahmoud S. Abdel-Majeed, Mohamed Y. Metwly, Ayman S. Abdel-Khalik, Mostafa S. Hamad, Shehab Ahmed, Eman Hamdan and Noha A. Elmalhy

Appl. Sci. 2022, 12(4), 2001; https://doi.org/10.3390/app12042001 - 14 Feb 2022

Cited by 8 | Viewed by 2379

Abstract

Due to simplicity, efficiency, and the ability to accommodate energy storage devices, DC distribution networks have been seen as an optimal alternative to AC distribution networks, especially aboard future electric ships. The emerging distribution DC system entails new control and management techniques. Therefore, [...] Read more.

Due to simplicity, efficiency, and the ability to accommodate energy storage devices, DC distribution networks have been seen as an optimal alternative to AC distribution networks, especially aboard future electric ships. The emerging distribution DC system entails new control and management techniques. Therefore, an integrated DC power distribution network aboard an electric ship is selected as the case study in this paper. To meet the requirements of such a large-scale mobile power system, a multiport solid-state transformer (SST) based on silicon carbide (SiC) switches/MOSFETs is proposed. Thus, the system embodiment can significantly be reduced. Moreover, at the DC distribution level, a high penetration of renewable generation with energy storage is allowed and a six-phase asymmetrical induction machine (IM) can directly be integrated. Simulations have been conducted based on a 2 MW shipboard distribution network. The effects of the propulsion system dynamics on the SST are highlighted as well. Finally, a 2 kW lab-scale prototype has been implemented to validate the theoretical findings. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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12 pages, 655 KiB

Open AccessArticle

Coverage Probability Analysis for Device-to-Device Communication Underlaying Cellular Networks

by Fangmin Xu, Yuqin Hu, Zhirui Hu and Haiyan Cao

Electronics 2022, 11(3), 464; https://doi.org/10.3390/electronics11030464 - 04 Feb 2022

Viewed by 1626

Abstract

As one of the most promising techniques in wireless communication systems, device-to-device (D2D) has drawn much attention due to its superior performance. Meanwhile, the interference between cellular users and D2D users is still a challenging problem and needs to be mitigated effectively. A [...] Read more.

As one of the most promising techniques in wireless communication systems, device-to-device (D2D) has drawn much attention due to its superior performance. Meanwhile, the interference between cellular users and D2D users is still a challenging problem and needs to be mitigated effectively. A large number of simulation experiments for D2D communications have been studied to reduce the impact of the interference in the existing literature. However, theoretical research is still lacking. Thus, in this paper, we use stochastic geometry to evaluate the uplink performance of users by considering the impact of the previous moment on the next moment, which captures the effect of temporal and the spatial correlation of the interference in D2D communication underlaying cellular networks. Using a Poisson point process to model locations of D2D users, we derive an analytic expression for conditional probability and unconditional probability of link success, and prove that the probability of link success is temporally correlated. Moreover, we provide a theoretical framework for interference mitigation in D2D underlaying cellular networks. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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12 pages, 3662 KiB

Open AccessArticle

Determination of the Activation Energy for Hydride Decomposition Using a Sieverts-Type Apparatus and the Kissinger Equation

by Myoung-Youp Song and Young-Jun Kwak

Metals 2022, 12(2), 265; https://doi.org/10.3390/met12020265 - 31 Jan 2022

Cited by 4 | Viewed by 2185

Abstract

We developed a method to determine the activation energy for hydride decomposition using a Sieverts-type apparatus and the Kissinger equation, not using thermal analysis methods. The quantity of hydrogen released from the sample and the temperature of the reactor were first measured as [...] Read more.

We developed a method to determine the activation energy for hydride decomposition using a Sieverts-type apparatus and the Kissinger equation, not using thermal analysis methods. The quantity of hydrogen released from the sample and the temperature of the reactor were first measured as a function of time at different heating rates (Φ) in a Sieverts-type apparatus. The dehydriding rates were calculated according to time and the temperature T_m (at which the dehydriding rate was the highest). Φ and T_m were then applied to the Kissinger equation. The dehydriding rate of Mg-5Ni samples obeyed a first-order law, and the Kissinger equation could thus be used to determine the activation energy. On a heating rate of 3 K/min, the decomposition rate of hydride was the highest at 590.0 K. From a plot of ln (Φ/T_m²) versus 1/T_m, the obtained activation energy for hydride decomposition was 174 kJ/mole. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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21 pages, 8233 KiB

Open AccessArticle

Torque Ripple Suppression of Brushless DC Motor Drive System Based on Improved Harmonic Injection Active Disturbance Rejection Control

by Jinglun He, Changxiang Yan and Xiaodong Wang

Sensors 2022, 22(3), 1069; https://doi.org/10.3390/s22031069 - 29 Jan 2022

Cited by 5 | Viewed by 2142

Abstract

The positioning accuracy and speed stability of the brushless DC motor (BLDC motor), as the drive element of the optomechanically scanned system (OMSS), are closely interrelated to the final imaging quality of the system. Active disturbance rejection control (ADRC) with strong anti-interference ability, [...] Read more.

The positioning accuracy and speed stability of the brushless DC motor (BLDC motor), as the drive element of the optomechanically scanned system (OMSS), are closely interrelated to the final imaging quality of the system. Active disturbance rejection control (ADRC) with strong anti-interference ability, fast response and good robustness is one of the extensively used control strategies. However, the performance of ADRC working in a complicated environment will be limited due to the controller structure, parameter tuning and the influence of multi-source nonlinear disturbance. Therefore, an improved ADRC method is proposed, which can switch between ‘point-to-point control mode’ and ‘stable speed control mode’ according to the system requirements. To further suppress the torque ripple and improve the control performance of the system, an improved harmonic injection scheme is added, and the parameters of improved ADRC are tuned by a slime mould algorithm based on a Levy flight operator (LF-SMA). The stability of the proposed ADRC is proved by Lyapunov stability theory. The experimental results show that the proposed control scheme could be available to reduce the torque ripple of the system. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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24 pages, 12095 KiB

Open AccessArticle

Study on Thermophysical Properties of Arc Plasma for Melting Magnesium Oxide Crystals at Atmospheric Pressure

by Zhongyuan Chi, Weijun Zhang and Qiangda Yang

Energies 2022, 15(3), 1036; https://doi.org/10.3390/en15031036 - 29 Jan 2022

Viewed by 1895

Abstract

The thermodynamic and transport properties of magnesium oxide crystal arc plasma have been researched under local thermodynamic equilibrium in this paper. The pure CO₂ plasma in the arc initiation stage and Mg-CO mixtures plasma in the stable melting stage were selected. The [...] Read more.

The thermodynamic and transport properties of magnesium oxide crystal arc plasma have been researched under local thermodynamic equilibrium in this paper. The pure CO₂ plasma in the arc initiation stage and Mg-CO mixtures plasma in the stable melting stage were selected. The parameter-variation method combined with Levenberg–Marquardt algorithm (PVM-LMA) is used to solve the plasma equilibrium compositions model established by mass action law from higher to lower temperature in sequence. Taking Mg50%-CO50% plasma as an example, the plasma number density of 7500 K is calculated according to 8000 K. The results show that the PVM-LMA algorithm has the advantages of fast and high precision. The comparisons to the results of pure CO₂ in previous literature are displayed and our work shows better agreement with theirs. The results of Mg-CO mixtures indicate that the chemical properties of Mg atoms are more active and easier to ionize, which can effectively improve the electrical conductivity and thermal conductivity of plasma and reduce its viscosity. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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14 pages, 12082 KiB

Open AccessArticle

3D Placement of a New Tethered UAV to UAV Relay System for Coverage Maximization

by Nour El-Din Safwat, Ismail Mohammed Hafez and Fatma Newagy

Electronics 2022, 11(3), 385; https://doi.org/10.3390/electronics11030385 - 27 Jan 2022

Cited by 6 | Viewed by 2660

Abstract

In this paper, a new relay system that uses the UAV as a relay station between the tethered UAV and ground user (TU2U2G) is proposed. The TU2U2G system uses a TUAV as a viable alternative to replace BS and provide seamless service over [...] Read more.

In this paper, a new relay system that uses the UAV as a relay station between the tethered UAV and ground user (TU2U2G) is proposed. The TU2U2G system uses a TUAV as a viable alternative to replace BS and provide seamless service over a cable that simultaneously supplies stable power and a reliable wired data-link connection from a ground control station. Compared to the BS, TUAV improves system coverage due to its high altitude. Also, it overcomes the antenna down-tilting, which increases the path loss between BS and UAV in the cellular system. In addition, it overcomes the UAV drawback of the batteries’ limited capacity. Therefore, TUAV can achieve the main requirements of a reliable cellular BS in terms of endurance, backhaul link quality, and the advantage of the UAV’s high altitude. After that, the optimization problem is formulated to maximize UAV relay station coverage under the power budget and maximum UAV height constraints. For simplicity, the 3D placement of the UAV is decoupled to the vertical and horizontal placement. Then, a 3D placement algorithm for the system is proposed. The UAV placement in the TU2U2G system compared to the cellular system shows better results in terms of optimum UAV height, maximum coverage radius, and maximum relaying distance. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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28 pages, 5416 KiB

Open AccessReview

Photovoltaic Thermal Collectors Integrated with Phase Change Materials: A Comprehensive Analysis

by Muthanna Mohammed Awad, Omer Khalil Ahmed, Obed Majeed Ali, Naseer T. Alwan, Salam J. Yaqoob, Anand Nayyar, Mohamed Abouhawwash and Adel Fahad Alrasheedi

Electronics 2022, 11(3), 337; https://doi.org/10.3390/electronics11030337 - 22 Jan 2022

Cited by 15 | Viewed by 5335

Abstract

The target of the current study was to review and analyze the research activities of previous studies on cooling techniques for thermal photovoltaic (PV) systems using phase-change materials. These materials have the ability to absorb and release certain amounts of potential heat energy [...] Read more.

The target of the current study was to review and analyze the research activities of previous studies on cooling techniques for thermal photovoltaic (PV) systems using phase-change materials. These materials have the ability to absorb and release certain amounts of potential heat energy by changing their state from phase to phase (solid–liquid) within a small temperature range. These materials have been used to regulate and lower the temperature, increase the efficiency, and extend the life of solar cells. A host of improvements have been made to phase-changing materials through the combined utilization of phase-change materials and fins in addition to nanoscale fluids to enhance electrical efficiency. When using PCMs, the thermal, electrical, and overall efficiency improved by 26.87%, 17.33%, and 40.59%, respectively. The addition of nanomaterials increased phase-change materials’ specific heat capacity and thermal conductivity, thus reducing the plate temperature and increasing the electrical efficiency. It was found that using of nanoparticles together with a microcapsule had better performance in terms of energy efficiency. Studies indicated that variable phase materials were not used because of their high cost and lack of stable operational design. Therefore, the effect of phase-change materials on PV/thermal (PVT) system performance needs further investigation and study. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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11 pages, 8623 KiB

Open AccessArticle

Facial Recognition Method Based on Thin-Film Solar Cells

by Ruei-Tang Chen and Fong-Long Wu

Appl. Sci. 2022, 12(3), 1157; https://doi.org/10.3390/app12031157 - 22 Jan 2022

Viewed by 1642

Abstract

In this study, we developed a new facial recognition system using thin-film solar cells as sensors. When the face of a user is illuminated by LED lights on the left and right sides of the system and the reflected light enters the cells [...] Read more.

In this study, we developed a new facial recognition system using thin-film solar cells as sensors. When the face of a user is illuminated by LED lights on the left and right sides of the system and the reflected light enters the cells at the corresponding positions, differences in facial skin colors and 3D contours lead to different output voltages and currents of the thin-film solar cells. This is the basis of facial feature identification. We found that the accuracy of thin-film-solar-cell-based facial recognition can be improved by precisely controlling changes in LED light intensity. The facial features of six different users were successfully distinguished by this method, thus verifying that thin-film solar cells can be used for green power generation, as well as for facial recognition. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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28 pages, 3867 KiB

Open AccessReview

Applications, Operational Architectures and Development of Virtual Power Plants as a Strategy to Facilitate the Integration of Distributed Energy Resources

by Juan C. Sarmiento-Vintimilla, Esther Torres, Dunixe Marene Larruskain and María José Pérez-Molina

Energies 2022, 15(3), 775; https://doi.org/10.3390/en15030775 - 21 Jan 2022

Cited by 19 | Viewed by 5346

Abstract

In this article, we focus on the development and scope of virtual power plants (VPPs) as a strategy to facilitate the integration of distributed energy resources (DERs) in the power system. Firstly, the concepts about VPPs and their scope and limitations are introduced. [...] Read more.

In this article, we focus on the development and scope of virtual power plants (VPPs) as a strategy to facilitate the integration of distributed energy resources (DERs) in the power system. Firstly, the concepts about VPPs and their scope and limitations are introduced. Secondly, smart management systems for the integration of DERs are considered and a scheme of DER management through a bottom-up strategy is proposed. Then, we analyze the coordination of VPPs with the system operators and their commercial integration in the electricity markets. Finally, the challenges that must be overcome to achieve the large-scale implementation of VPPs in the power system are identified and discussed. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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20 pages, 3263 KiB

Open AccessArticle

A Novel Method for Space Circular Target Detection in Machine Vision

by Wenxue Hu, Jiannan Chi, Jiahui Liu and Zuoyun Yang

Sensors 2022, 22(3), 769; https://doi.org/10.3390/s22030769 - 20 Jan 2022

Cited by 3 | Viewed by 2033

Abstract

Computer-vision-based space circular target detection has a wide range of applications in visual measurement, object detection, and other fields. The space circular target is projected into an ellipse in the camera for localization. Traditional methods based on monocular vision use a precise calculation [...] Read more.

Computer-vision-based space circular target detection has a wide range of applications in visual measurement, object detection, and other fields. The space circular target is projected into an ellipse in the camera for localization. Traditional methods based on monocular vision use a precise calculation model to calculate the center coordinate and normal vector of the space circular target according to the image’s elliptic parameters. However, this accurate calculation method has the disadvantage of poor anti-interference ability in practical application. Aiming at the shortcomings of the above traditional calculation method, this paper proposes an optimization method for fitting the circular target in 3D space, where the image ellipse is projected back into 3D space and then detects the center coordinate and normal vector of the space circular target. Unlike the traditional method, this approach is not sensitive to the image’s elliptic parameters; it has stronger noise resistance performance and notable application value. The feasibility and effectiveness of the proposed method were verified by both simulation and practical experimental results. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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33 pages, 4913 KiB

Open AccessArticle

ARIMA-FEM Method with Prediction Function to Solve the Stress–Strain of Perforated Elastic Metal Plates

by Wenxing Chen, Shuyang Dai and Baojuan Zheng

Metals 2022, 12(2), 179; https://doi.org/10.3390/met12020179 - 19 Jan 2022

Cited by 5 | Viewed by 2043

Abstract

Stress analysis and deformation prediction have always been the focuses of the field of mechanics. The accurate force prediction in plate deformation plays important role in the production, processing and performance analysis of materials. In this paper, we propose an ARIMA-FEM method, which [...] Read more.

Stress analysis and deformation prediction have always been the focuses of the field of mechanics. The accurate force prediction in plate deformation plays important role in the production, processing and performance analysis of materials. In this paper, we propose an ARIMA-FEM method, which can be used to solve some mechanical problems of 2D porous elastic plate. We have given a detailed theory and solving steps of ARIMA-FEM. In addition, three numerical examples are given to predict the stress–strain of thin porous elastic metal plates. This article uses CST, LST and Q4 elements to discrete the rectangular plates, square plates and circle plates with holes. As for variable force prediction, this paper compared with linear regression, nonlinear regression and neural network prediction, and the results show that the ARIMA method has a higher prediction accuracy. Furthermore, we calculate the numerical solution at four mesh scales, and the numerical convergence is consistent with the theoretical convergence, which also shows the effectiveness of our method. The image smoothing algorithm is applied to keep edge information with high resolution, which can more concisely describe the plate internal changes. Finally, the application scope of ARIMA-FEM, model expansion, superconvergence analysis and other issues have been given enlightening views in the discussion section. In fact, this algorithm combined statistics and mechanics. It also reflects the knowledge integration of interdisciplinary and uses it better to serve practical applications. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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17 pages, 7702 KiB

Open AccessArticle

A 3D Attitude Estimation Method Based on Attitude Angular Partial Feedback for Polarization-Based Integrated Navigation System

by Pengwei Hu, Panpan Huang, Zhenbing Qiu, Jian Yang and Xin Liu

Sensors 2022, 22(3), 710; https://doi.org/10.3390/s22030710 - 18 Jan 2022

Cited by 5 | Viewed by 1812

Abstract

Polarization (POL) navigation is inspired by insects’ behavior of precepting celestial polarization patterns to orient themselves. It has the advantages of being autonomous and having no accumulative error, which allows it to be used to correct the errors of the inertial navigation system [...] Read more.

Polarization (POL) navigation is inspired by insects’ behavior of precepting celestial polarization patterns to orient themselves. It has the advantages of being autonomous and having no accumulative error, which allows it to be used to correct the errors of the inertial navigation system (INS). The integrated navigation system of the POL-based solar vector with INS is capable of 3D attitude determination. However, the commonly used POL-based integrated navigation system generally implements the attitude update procedure without considering the performance difference with different magnitudes of the angles between the solar-vector and body-axes of the platform (S-B angles). When one of the S-B angles is small enough, the estimated accuracy of the attitude angle by the INS/POL is worse than that of the strapdown inertial navigation system. To minimize the negative impact of POL in this situation, an attitude angular adaptive partial feedback method is proposed. The S-B angles are used to construct a partial feedback factor matrix to adaptively adjust the degree of error correction for INS. The results of simulation and real-world experiments demonstrate that the proposed method can improve the accuracy of 3D attitude estimation compared with the conventional all-feedback method for small S-B angles especially for yaw angle estimation. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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16 pages, 3396 KiB

Open AccessArticle

Enhancement of the Evaporation and Condensation Processes of a Solar Still with an Ultrasound Cotton Tent and a Thermoelectric Cooling Chamber

by Naseer T. Alwan, Ayad S. Ahmed, Milia H. Majeed, Sergey E. Shcheklein, Salam J. Yaqoob, Anand Nayyar, Yunyoung Nam and Mohamed Abouhawwash

Electronics 2022, 11(2), 284; https://doi.org/10.3390/electronics11020284 - 17 Jan 2022

Cited by 6 | Viewed by 2086

Abstract

In this paper, an experimental investigation study was conducted to show the effect of enhancing the evaporation and condensation processes inside a modified solar still by placing ultrasonic humidifiers inside a cotton mesh tent in the basin water and by installing a cooling [...] Read more.

In this paper, an experimental investigation study was conducted to show the effect of enhancing the evaporation and condensation processes inside a modified solar still by placing ultrasonic humidifiers inside a cotton mesh tent in the basin water and by installing a cooling chamber with thermoelectric elements on top of the solar still. Various parameters were recorded every hour, such as temperatures at different points within the solar still, the weather conditions (e.g., solar irradiance intensity, ambient air temperature, and wind speed), the yield of distilled water, and thermal efficiency on 29 July 2021 at the Ural Federal University (Russia). The production cost of distilled water from modified and traditional solar stills was also estimated. The experimental results showed that the productivity of the modified solar still increased by 124% compared with the traditional solar still, and the highest thermal efficiency was recorded at 2:00 p.m. (approximately 95.8% and 35.6% for modified and traditional solar stills, respectively). Finally, the productivity cost of distillate water (1 L) was approximately 0.040 and 0.042 $/L for the modified and traditional solar stills, respectively. The current work has contributed to increasing solar still productivity by applying simple and new technologies with the lowest possible capital and operational costs. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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10 pages, 2291 KiB

Open AccessArticle

Suppression of Frequency Modulation to Amplitude Modulation Conversion with Modified Group Velocity Dispersion Compensation Device in the Front End of High-Power Lasers

by Xinlei Qian, Xiaochao Wang, Xinghua Lu, Tianyu Zhang and Wei Fan

Appl. Sci. 2022, 12(2), 884; https://doi.org/10.3390/app12020884 - 16 Jan 2022

Cited by 1 | Viewed by 1887

Abstract

The group velocity dispersion (GVD) occurring in the front end of high-power lasers is one of the primary factors leading to the conversion of frequency modulation (FM) to amplitude modulation (AM). In this paper, we propose a modified, active, closed-loop feedback compensation device [...] Read more.

The group velocity dispersion (GVD) occurring in the front end of high-power lasers is one of the primary factors leading to the conversion of frequency modulation (FM) to amplitude modulation (AM). In this paper, we propose a modified, active, closed-loop feedback compensation device for GVD-induced FM–AM conversion, using a two-dimensional, electric, adjustable mirror mount and parallel grating pair to improve the long-term stability, efficiency of adjustment, and accuracy of compensation. Experimental results of a 12 h FM–AM depth test revealed that the depth varied between 2.28% and 5.22%. Moreover, we formulated a mathematical relationship between the dispersion parameters and temperature in optical fibers to analyze the intrinsic effect of temperature on FM–AM. The related simulation and experimental results consistently validated the quantitative relationship between the temperature and FM–AM depth. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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16 pages, 4676 KiB

Open AccessArticle

Research on Homogeneous Charge Compression Ignition Combustion of Intake Port Exhaust Gas Recirculation Based on Cam Drive Hydraulic Variable Valve Actuation Mechanism

by Linghai Han, Jiaquan Duan, Dingchao Qian, Yanfeng Gong, Yaodong Wang, Fangxi Xie and Yan Su

Energies 2022, 15(2), 438; https://doi.org/10.3390/en15020438 - 08 Jan 2022

Cited by 5 | Viewed by 1376

Abstract

The thermal efficiency of an efficient gasoline engine is only about 40% and it will produce a large number of harmful products. Curbing harmful emissions and enhancing thermal efficiency have always been the goals pursued and emission regulations are also being tightened gradually. [...] Read more.

The thermal efficiency of an efficient gasoline engine is only about 40% and it will produce a large number of harmful products. Curbing harmful emissions and enhancing thermal efficiency have always been the goals pursued and emission regulations are also being tightened gradually. As one of the main consumers of fossil fuels, automobile engines must further reduce fuel consumption and emissions to comply with the concept of low-carbon development, which will also help them compete with electric vehicles. Homogeneous charge compression ignition (HCCI) combustion combined with variable valve actuation (VVA) technology is one of the important ways to improve engine emissions and economy. HCCI combustion based on VVA can only be realized at small and medium loads. The actual application on the entire vehicle needs to be combined with spark ignition (SI) combustion to achieve full working condition coverage. Therefore, HCCI combustion needs fast valve response characteristics; however, the valve lift and timing of the existing VVA mechanisms are mostly controlled separately, resulting in poor valve response. In order to solve this problem, the cam driven hydraulic variable valve actuation (CDH-VVA) mechanism was designed. The valve lift and timing can be adjusted at the same time and the switching of valve lift and timing can be completed in 1~2 cycles. A set of combustion mode switching data is selected to show the response characteristics of the CDH-VVA mechanism. When switching from spark ignition (SI) to HCCI, it switches to HCCI combustion after only one combustion cycle and it switches to stable HCCI combustion after two combustion cycles, which proves the fast response characteristics of the CDH-VVA mechanism. At the same time, the CDH-VVA mechanism can form the intake port exhaust gas recirculation (EGR), as one type of internal EGR. This paper studies the HCCI combustion characteristics of the CDH-VVA mechanism in order to optimize it in the future and enable it to realize more forms of HCCI combustion. At 1000 rpm, if the maximum lift of the exhaust valve (MLEV) is higher than 5.0 mm or lower than 1.5 mm, HCCI combustion cannot operate stably, the range of excess air coefficient (λ) is largest when the MLEV is 4.5 mm, ranging from 1.0~1.5. Then, as the MLEV decreases, the range of λ becomes smaller. When the MLEV drops to 1.5 mm, the range of λ shortens to 1.0~1.3. The maximum value of the MLEV remains the same at the three engine speeds (1000 rpm, 1200 rpm and 1400 rpm), which is 5.0 mm. The minimum value of the MLEV gradually climbs as the engine speed increase, 1000 rpm: 1.5 mm, 1200 rpm: 2.0 mm, 1400 rpm: 3.0 mm. With the increase of engine speed, the range of indicated mean effective pressure (IMEP) gradually declines, 3.53~6.31 bar (1000 rpm), 4.11~6.75 bar (1200 rpm), 5.02~6.09 bar (1400 rpm), which proves that the HCCI combustion loads of the intake port EGR are high and cannot be extended to low loads. The cyclic variation of HCCI combustion basically climbs with the decrease of the MLEV and slightly jumps with the increase of the engine speed. At 1000 rpm, when the MLEV is 5.0 mm, the cyclic variation range is 0.94%~1.5%. As the MLEV drops to 1.5 mm, the cyclic variation range rises to 3.5%~4.5%. Taking the maximum value of the MLEV as an example, the cyclic variation range of 1000 rpm is 0.94%~1.5%, 1200 rpm becomes 1.5%~2.3% and 1400 rpm rises to 2.0%~2.5%. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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17 pages, 14856 KiB

Open AccessArticle

Steering a Robotic Wheelchair Based on Voice Recognition System Using Convolutional Neural Networks

by Mohsen Bakouri, Mohammed Alsehaimi, Husham Farouk Ismail, Khaled Alshareef, Ali Ganoun, Abdulrahman Alqahtani and Yousef Alharbi

Electronics 2022, 11(1), 168; https://doi.org/10.3390/electronics11010168 - 05 Jan 2022

Cited by 19 | Viewed by 5345

Abstract

Many wheelchair people depend on others to control the movement of their wheelchairs, which significantly influences their independence and quality of life. Smart wheelchairs offer a degree of self-dependence and freedom to drive their own vehicles. In this work, we designed and implemented [...] Read more.

Many wheelchair people depend on others to control the movement of their wheelchairs, which significantly influences their independence and quality of life. Smart wheelchairs offer a degree of self-dependence and freedom to drive their own vehicles. In this work, we designed and implemented a low-cost software and hardware method to steer a robotic wheelchair. Moreover, from our method, we developed our own Android mobile app based on Flutter software. A convolutional neural network (CNN)-based network-in-network (NIN) structure approach integrated with a voice recognition model was also developed and configured to build the mobile app. The technique was also implemented and configured using an offline Wi-Fi network hotspot between software and hardware components. Five voice commands (yes, no, left, right, and stop) guided and controlled the wheelchair through the Raspberry Pi and DC motor drives. The overall system was evaluated based on a trained and validated English speech corpus by Arabic native speakers for isolated words to assess the performance of the Android OS application. The maneuverability performance of indoor and outdoor navigation was also evaluated in terms of accuracy. The results indicated a degree of accuracy of approximately 87.2% of the accurate prediction of some of the five voice commands. Additionally, in the real-time performance test, the root-mean-square deviation (RMSD) values between the planned and actual nodes for indoor/outdoor maneuvering were 1.721 × 10⁻⁵ and 1.743 × 10⁻⁵, respectively. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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26 pages, 41806 KiB

Open AccessArticle

POSIT vs. Floating Point in Implementing IIR Notch Filter by Enhancing Radix-4 Modified Booth Multiplier

by Anwar A. Esmaeel, Sa’ed Abed, Bassam J. Mohd and Abbas A. Fairouz

Electronics 2022, 11(1), 163; https://doi.org/10.3390/electronics11010163 - 05 Jan 2022

Cited by 2 | Viewed by 2370

Abstract

The increased demand for better accuracy and precision and wider data size has strained current the floating point system and motivated the development of the POSIT system. The POSIT system supports flexible formats and tapered precision and provides equivalent accuracy with fewer bits. [...] Read more.

The increased demand for better accuracy and precision and wider data size has strained current the floating point system and motivated the development of the POSIT system. The POSIT system supports flexible formats and tapered precision and provides equivalent accuracy with fewer bits. This paper examines the POSIT and floating point systems, comparing the performance of 32-bit POSIT and 32-bit floating point systems using IIR notch filter implementation. Given that the bulk of the calculations in the filter are multiplication operations, an Enhanced Radix-4 Modified Booth Multiplier (ERMBM) is implemented to increase the calculation speed and efficiency. ERMBM enhances area, speed, power, and energy compared to the POSIT regular multiplier by 26.80%, 51.97%, 0.54%, and 52.22%, respectively, without affecting the accuracy. Moreover, the Taylor series technique is adopted to implement the division operation along with cosine arithmetic unit for POSIT numbers. After comparing POSIT with floating point, the accuracy of POSIT is 92.31%, which is better than floating point’s accuracy of 23.08%. Moreover, POSIT reduces area by 21.77% while increasing the delay. However, when the ERMBM is utilized instead of the POSIT regular multiplier in implementing the filter, POSIT outperforms floating point in all the performance metrics including area, speed, power, and energy by 35.68%, 20.66%, 31.49%, and 45.64%, respectively. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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28 pages, 4610 KiB

Open AccessFeature PaperArticle

Stabilization of the Cart–Inverted-Pendulum System Using State-Feedback Pole-Independent MPC Controllers

by Lotfi Messikh, El-Hadi Guechi and Sašo Blažič

Sensors 2022, 22(1), 243; https://doi.org/10.3390/s22010243 - 29 Dec 2021

Cited by 5 | Viewed by 3901

Abstract

In this paper, a pole-independent, single-input, multi-output explicit linear MPC controller is proposed to stabilize the fourth-order cart–inverted-pendulum system around the desired equilibrium points. To circumvent an obvious stability problem, a generalized prediction model is proposed that yields an MPC controller with four [...] Read more.

In this paper, a pole-independent, single-input, multi-output explicit linear MPC controller is proposed to stabilize the fourth-order cart–inverted-pendulum system around the desired equilibrium points. To circumvent an obvious stability problem, a generalized prediction model is proposed that yields an MPC controller with four tuning parameters. The first two parameters, namely the horizon time and the relative cart–pendulum weight factor, are automatically adjusted to ensure a priori prescribed system gain margin and fast pendulum response while the remaining two parameters, namely the pendulum and cart velocity weight factors, are maintained as free tuning parameters. The comparison of the proposed method with some optimal control methods in the absence of disturbance input shows an obvious advantage in the average peak efficiency in favor of the proposed SIMO MPC controller at the price of slightly reduced speed efficiency. Additionally, none of the compared controllers can achieve a system gain margin greater than 1.63, while the proposed one can go beyond that limit at the price of additional degradation in the speed efficiency. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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27 pages, 1938 KiB

Open AccessArticle

Extended Hierarchical Fuzzy Interpreted Petri Net

by Michał Markiewicz, Lesław Gniewek and Dawid Warchoł

Sensors 2021, 21(24), 8433; https://doi.org/10.3390/s21248433 - 17 Dec 2021

Viewed by 2086

Abstract

Petri nets (PNs) have many advantages such as graphical representation, formal description, and the possibility of sequential and concurrent control. An important aspect of using PNs is hierarchical modeling, which may be provided in different ways. In this paper, a new concept and [...] Read more.

Petri nets (PNs) have many advantages such as graphical representation, formal description, and the possibility of sequential and concurrent control. An important aspect of using PNs is hierarchical modeling, which may be provided in different ways. In this paper, a new concept and definition of the hierarchical structure for Fuzzy Interpreted Petri Net (FIPN) are proposed. The concept of macroplace with several input, output, and input-output places is introduced to the net. The functionality of the macroplace instances and the hierarchy graph are also proposed. They are implemented in a computer simulator called HFIPN-SML. In this study, FIPN is employed since it allows the use of analogue sensors directly for process control. Better visualization and more precise control are among advantages of the introduced approach. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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19 pages, 9644 KiB

Open AccessArticle

A Modified Multi-Winding DC–DC Flyback Converter for Photovoltaic Applications

by Cristián Pesce, Javier Riedemann, Rubén Peña, Michele Degano, Javier Pereda, Rodrigo Villalobos, Camilo Maury, Hector Young and Iván Andrade

Appl. Sci. 2021, 11(24), 11999; https://doi.org/10.3390/app112411999 - 16 Dec 2021

Cited by 3 | Viewed by 2988

Abstract

DC–DC power converters have generated much interest, as they can be used in a wide range of applications. In micro-inverter applications, flyback topologies are a relevant research topic due to their efficiency and simplicity. On the other hand, solar photovoltaic (PV) systems are [...] Read more.

DC–DC power converters have generated much interest, as they can be used in a wide range of applications. In micro-inverter applications, flyback topologies are a relevant research topic due to their efficiency and simplicity. On the other hand, solar photovoltaic (PV) systems are one of the fastest growing and most promising renewable energy sources in the world. A power electronic converter (either DC/DC or DC/AC) is needed to interface the PV array with the load/grid. In this paper, a modified interleaved-type step-up DC–DC flyback converter is presented for a PV application. The topology is based on a multi-winding flyback converter with N parallel connected inputs and a single output. Each input is supplied by an independent PV module, and a maximum power point tracking algorithm is implemented in each module to maximize solar energy harvesting. A single flyback transformer is used, and it manages only 1/N of the converter rated power, reducing the size of the magnetic core compared to other similar topologies. The design of the magnetic core is also presented in this work. Moreover, the proposed converter includes active snubber networks to increase the efficiency, consisting of a capacitor connected in series with a power switch, to protect the main switches from damaging dv/dt when returning part of the commutation energy back to the source. In this work, the operating principle of the topology is fully described on a mathematical basis, and an efficiency analysis is also included. The converter is simulated and experimentally validated with a 1 kW prototype considering three PV panels. The experimental results are in agreement with the simulations, verifying the feasibility of the proposal. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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18 pages, 2838 KiB

Open AccessArticle

Methodology for Defining the Interaction between Product Characteristics and Specific Product Complexity—Evaluated on Electrodes for Lithium-Ion Batteries

by Sina Rahlfs, Filip Vysoudil, Franz Dietrich and Thomas Vietor

Appl. Sci. 2021, 11(24), 11961; https://doi.org/10.3390/app112411961 - 15 Dec 2021

Viewed by 1812

Abstract

This study is about a method for evaluating specific product complexity. In this context, an efficient and scalable method for the development of a specific complexity assessment of highly complex products is presented. Furthermore, existing evaluation methods are analysed according to effort and [...] Read more.

This study is about a method for evaluating specific product complexity. In this context, an efficient and scalable method for the development of a specific complexity assessment of highly complex products is presented. Furthermore, existing evaluation methods are analysed according to effort and benefit, thus showing the research gap and the need for the method to be developed. The procedure for the development of an indicator for the specific evaluation of product complexity is presented in five steps and an exemplary complexity indicator for lithium ion battery cells is developed. This index is then applied, and the complexity of commercial battery cells from the application is evaluated. Based on these evaluations, final potentials of the method are shown and a recommendation for a reduction in product complexity is provided. The developed method for complexity assessment is scalable in its effort and offers implementation into existing complexity management. The method allows quick adaptation or extension and, thus, well-founded decision making. By standardizing the evaluation and taking objectively measurable complexity characteristic values as a basis, a holistic and objective evaluation tool is shown, which can thus become a decisive success factor for manufacturers of complex products. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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19 pages, 2756 KiB

Open AccessReview

Construction Planning and Operation of Battery Swapping Stations for Electric Vehicles: A Literature Review

by Yu Feng and Xiaochun Lu

Energies 2021, 14(24), 8202; https://doi.org/10.3390/en14248202 - 07 Dec 2021

Cited by 22 | Viewed by 6467

Abstract

The popularity of electric vehicles has been limited by factors such as range, long charging times and fast power failure in winter. In order to overcome these challenges, battery swapping stations (BSS) have been constructed and greatly promoted in recent years. In this [...] Read more.

The popularity of electric vehicles has been limited by factors such as range, long charging times and fast power failure in winter. In order to overcome these challenges, battery swapping stations (BSS) have been constructed and greatly promoted in recent years. In this paper, the related literature on electric vehicle service is reviewed and the co-occurrence of keywords is analyzed using CiteSpace. The literature is classified according to clustering results and recurring themes, such as the location of BSS, inventory decisions, charging strategies and BSS assignment. In each topic, typical optimization models and algorithms proposed in previous studies are summarized. Then, this paper gives a case about the business model and revenue capacity calculation of BSS. Finally, it points out the future research direction of battery swapping stations for electric vehicles. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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14 pages, 1048 KiB

Open AccessArticle

Concisely Indexed Multi-Keyword Rank Search on Encrypted Cloud Documents

by Tai-Lin Chin and Wan-Ni Shih

Appl. Sci. 2021, 11(23), 11529; https://doi.org/10.3390/app112311529 - 05 Dec 2021

Viewed by 1464

Abstract

With the advent of cloud computing, the low-cost and high-capacity cloud storages have attracted people to move their data from local computers to the remote facilities. People can access and share their data with others at anytime, from anywhere. However, the convenience of [...] Read more.

With the advent of cloud computing, the low-cost and high-capacity cloud storages have attracted people to move their data from local computers to the remote facilities. People can access and share their data with others at anytime, from anywhere. However, the convenience of cloud storages also comes with new problems and challenges. This paper investigates the problem of secure document search on the cloud. Traditional search schemes use a long index for each document to facilitate keyword search in a large dataset, but long indexes can reduce the search efficiency and waste space. Another concern to prevent people from using cloud storages is the security and privacy problem. Since cloud services are usually run by third party providers, data owners desire to avoid the leakage of their confidential information, and data users desire to protect their privacy when performing search. A trivial solution is to encrypt the data before outsourcing the data to the cloud. However, the encryption could make the search difficult by plain keywords. This paper proposes a secure multi-keyword search scheme with condensed index for encrypted cloud documents. The proposed scheme resolves the issue of long document index and the problem of searching documents over encrypted data, simultaneously. Extended simulations are conducted to show the improvements in terms of time and space efficiency for cloud data search. Full article

(This article belongs to the Topic Advanced Systems Engineering: Theory and Applications)

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