Machines

25 pages, 4783 KiB

Open AccessArticle

Analytical, Numerical and Experimental Analysis of a Positive Displacement Cam Mechanism—A Case Study

by Eugen Merticaru, Vasile Merticaru, Gheorghe Nagîț, Andrei Marius Mihalache, Liviu Lucian Tăbăcaru and Marius Ionuț Rîpanu

Machines 2023, 11(7), 770; https://doi.org/10.3390/machines11070770 - 24 Jul 2023

Viewed by 1271

Abstract

Cam mechanisms, covering a large structural variety, are widely used in machinery, mainly as components of automated systems. Their functioning behavior is affected by negative dynamic phenomena determined by specific high velocities and acceleration rates. Within the various types of research on the [...] Read more.

Cam mechanisms, covering a large structural variety, are widely used in machinery, mainly as components of automated systems. Their functioning behavior is affected by negative dynamic phenomena determined by specific high velocities and acceleration rates. Within the various types of research on the dynamic behavior of cam mechanisms, this study addresses the need to clarify the influence of geometrical parameters and technological conditions on some indicators of the jump phenomenon in contact loss for a cam-follower mechanism. This particularly developed case study referred to a mechanism with a profiled grooved disk cam and oscillating follower. To highlight the influence of the cam-follower contact elasticity on the jump phenomenon, two dynamic models were developed: one considering rigid elements in contact and the second considering elastic cam-follower contact. The models were tested within a virtually simulated experiment, and the numerical simulation results evidenced the influence of input factors like the applied load on the mechanism, the clearance in the cam-follower kinematic pair, and the rotational speed of the cam, and the inertia moment was reduced to the follower on some indicators of the jump phenomenon. Validation FEA and experiments were performed, proving the reliable appropriateness of the dynamic model based on elastic cam-follower contact. Full article

(This article belongs to the Section Machine Design and Theory)

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29 pages, 10330 KiB

Open AccessArticle

Enhanced Integrator with Drift Elimination for Accurate Flux Estimation in Sensorless Controlled Interior PMSM for High-Performance Full Speed Range Hybrid Electric Vehicles Applications

by Sadiq Ur Rahman and Chaoying Xia

Machines 2023, 11(7), 769; https://doi.org/10.3390/machines11070769 - 24 Jul 2023

Viewed by 1126

Abstract

Interior Permanent Magnet Synchronous Motor (IPMSM) motion-sensorless speed control necessitates precise knowledge of rotor flux, speed, and position. Due to numerous non-ideal aspects, such as converter nonlinearities, detection errors, integral initial value, and parameter mismatches, the conventional first-order integrator’s estimated rotor flux experiences [...] Read more.

Interior Permanent Magnet Synchronous Motor (IPMSM) motion-sensorless speed control necessitates precise knowledge of rotor flux, speed, and position. Due to numerous non-ideal aspects, such as converter nonlinearities, detection errors, integral initial value, and parameter mismatches, the conventional first-order integrator’s estimated rotor flux experiences a DC offset (Doff). Low-pass filters (LPF) with a constant cut-off frequency yield accurate estimates only in the medium- and high-speed range; however, at the low-speed area, both magnitude and phase estimates are inaccurate. The presented technique resolves the aforementioned issue for a broad speed range. In order to achieve precise flux estimation, this article presents an improved technique of flux estimator with two distinct drift mitigation strategies for the motion-sensorless field-oriented control (FOC) system of IPMSM. Using the orthogonality of the

α -

and

β

-axes, the proposed drift elimination system can estimate drift in different situations while maintaining a high level of dynamic performance. The stator flux linkage (SFL) computation in the synchronous coordinate is established from the estimation of the rotating shaft’s permanent magnetic flux linkage orientation and the statistical equations model of the SFL. By comparing the calculated SFL vector to the SFL vector derived from the stator winding voltage and currents integral model with a drift PI compensation loop, a feedback loop is formed to neutralize integral drift, and the rotational speed and position of an IPMSM is estimated utilizing the vector product of the two flux linkages in a phase-locked loop. Theoretical interpretation is presented, and Matlab Simulink simulations, as well as experimental outcomes, consistently demonstrate that the suggested estimation techniques can eliminate the phenomenon of flux drift. Full article

(This article belongs to the Special Issue Advanced Data Analytics in Intelligent Industry: Theory and Practice)

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19 pages, 6344 KiB

Open AccessEditor’s ChoiceArticle

Design of Z Profile Roller Tooling and Research on Roller Clearance

by Yigang Jing, Qun Sun and Ying Zhao

Machines 2023, 11(7), 767; https://doi.org/10.3390/machines11070767 - 24 Jul 2023

Viewed by 813

Abstract

In metal processing, bending forming is widely applied in various fields. To prevent excessive surface scratching and heavy indentation on the profiles, which can negatively affect the surface quality, it is often necessary to determine the clearances between the rollers and the upper [...] Read more.

In metal processing, bending forming is widely applied in various fields. To prevent excessive surface scratching and heavy indentation on the profiles, which can negatively affect the surface quality, it is often necessary to determine the clearances between the rollers and the upper and lower surfaces of the profiles using experimental methods. However, this experimental approach not only results in material waste but also fails to determine the optimal clearance value. Therefore, orthogonal experiments were conducted to design different clearances between the rollers and the upper and lower surfaces of the profiles to mitigate the issues of excessive surface scratching and poor surface quality during the bending forming process of large-section Z-profiles. Finite element simulation was employed to simulate the different experiments, and a range analysis was performed on the experimental results to obtain the optimal clearance value. The obtained results fall within the range of results obtained from traditional experimental methods, indicating its consistency with actual practice, higher accuracy, and scientific rigor compared with experimental methods. Furthermore, the roller tooling design was revised based on the optimal clearance value for the profile processing. The experimental results demonstrate that the surface quality of the profiles processed with optimal clearance is superior to those processed without it. Additionally, this study presents a comprehensive methodology for roller tooling design and investigates the influence of different loading modes on the local wrinkling deformation of the profiles. Full article

(This article belongs to the Section Advanced Manufacturing)

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29 pages, 4770 KiB

Open AccessReview

Overview of Jamming Technology for Satellite Navigation

by Xiangjun Li, Lei Chen, Zukun Lu, Feixue Wang, Wenxiang Liu, Wei Xiao and Peiguo Liu

Machines 2023, 11(7), 768; https://doi.org/10.3390/machines11070768 - 22 Jul 2023

Cited by 2 | Viewed by 3373

Abstract

The Global Navigation Satellite System (GNSS) has been applied to all aspects of social livelihood and military applications and has become an important part of national infrastructure construction. However, due to the vulnerability of GNSS, satellite navigation jamming technology can pose a serious [...] Read more.

The Global Navigation Satellite System (GNSS) has been applied to all aspects of social livelihood and military applications and has become an important part of national infrastructure construction. However, due to the vulnerability of GNSS, satellite navigation jamming technology can pose a serious threat to GNSS security applications, and this has become a research hotspot in the field of navigation countermeasures. In this paper, satellite navigation jamming technologies are divided into suppression jamming and deception jamming, and the research status of satellite navigation suppression jamming and deception jamming technologies are sorted by three aspects: jamming technology classification, jamming efficiency evaluation, and jamming source deployment. Finally, the future development trend of satellite navigation jamming technology is summarized. Full article

(This article belongs to the Section Automation and Control Systems)

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23 pages, 12311 KiB

Open AccessArticle

Study on the Influence of the Pilot Stage Swirl Intensity on the Double-Swirl Combustor’s Ignition Process via Large Eddy Simulation

by Pengfei Zhu, Hongyu Ju, Yue Li, Yue Yan, Jianqin Suo and Zhenxia Liu

Machines 2023, 11(7), 766; https://doi.org/10.3390/machines11070766 - 22 Jul 2023

Viewed by 850

Abstract

The ignition reliability of the combustion chamber is crucial for the overall performance of an engine. As the aero-engine combustion chambers continue to advance, the scope of the ignition problem has also expanded. This study employs large eddy simulation to investigate the flow [...] Read more.

The ignition reliability of the combustion chamber is crucial for the overall performance of an engine. As the aero-engine combustion chambers continue to advance, the scope of the ignition problem has also expanded. This study employs large eddy simulation to investigate the flow characteristics and ignition process of a double-swirl combustor. The non-reacting flow field and ignition propagation process are acquired using particle image velocimetry (PIV) and high-speed cameras. Experimental findings are employed to validate the numerical simulations. The results demonstrate a close relationship between the ignition process of the double-swirl combustor and the flow field within the combustor. Following the spark discharge, a core is generated at the edge of the recirculation zone. Over time, the spark gradually propagates towards the center of the combustor along the direction of swirl due to the flow. Once the flame reaches the head, the fuel and gas mixture ignited by the core within the recirculation zone stabilizes within the boundary layer of the primary and pilot stages. The flame continues to propagate throughout the combustor until complete ignition is achieved. Additionally, the swirl intensity of the pilot mode is identified as a key factor influencing the ignition propagation process of the double-swirl combustor. Full article

(This article belongs to the Section Electromechanical Energy Conversion Systems)

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22 pages, 3161 KiB

Open AccessArticle

Fault Diagnosis of Train Wheelset Bearing Roadside Acoustics Considering Sparse Operation with GA-RBF

by Jiandong Qiu, Jiajia Ran, Minan Tang, Fan Yu and Qiang Zhang

Machines 2023, 11(7), 765; https://doi.org/10.3390/machines11070765 - 22 Jul 2023

Cited by 1 | Viewed by 928

Abstract

Trackside acoustic signals are useful for non-contact measurements as well as early warnings in the diagnosis of train wheelset bearing faults. However, there are two important problems when using roadside acoustic signals to diagnose wheel-to-wheel bearing faults; one is the presence of strong [...] Read more.

Trackside acoustic signals are useful for non-contact measurements as well as early warnings in the diagnosis of train wheelset bearing faults. However, there are two important problems when using roadside acoustic signals to diagnose wheel-to-wheel bearing faults; one is the presence of strong interference from strong noise and high harmonics in the signal, and the other is the low efficiency of bearing fault identification caused by it. Therefore, from the viewpoint of solving the two problems, a sparse operation method is proposed for denoising and detuning the modulation of the roadside acoustic signal, and a machine learning classifier with a Genetic Algorithm (GA)-optimized Radial Basis Neural Network (RBFNN) is proposed to improve the rate at which the features of roadside acoustic signal faults are recognized. Firstly, the background noise is filtered out from the Doppler-corrected acoustic signal using the Sparse Representation method, and the inverse wavelet transform is reconstructed into a noiseless signal. Secondly, the interference high-harmonic signal in the signal is filtered out using the Resonant Sparse Signal Decomposition (RSSD) method. Then, the GA is selected to optimize the parameters of the RBF neural network and build a fault diagnosis model. Finally, the extracted acoustic signal feature set is trained on the network model, and the trained model is used for testing. In summary, the sparse operation on the roadside acoustic signal processing and the GA-RBFNN diagnosis model were verified as being very effective in the diagnosis of roadside acoustic train wheel pair faults through the simulation experiment. Full article

(This article belongs to the Section Machines Testing and Maintenance)

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20 pages, 1071 KiB

Open AccessReview

Hierarchical Classification of Subject-Cooperative Control Strategies for Lower Limb Exoskeletons in Gait Rehabilitation: A Systematic Review

by Jyotindra Narayan, Chaiyawan Auepanwiriyakul, Sanchit Jhunjhunwala, Mohamed Abbas and Santosha K. Dwivedy

Machines 2023, 11(7), 764; https://doi.org/10.3390/machines11070764 - 22 Jul 2023

Cited by 5 | Viewed by 1700

Abstract

Over the last decade, lower limb exoskeletons have seen significant development, with a particular focus on improving the interaction between the subject and the exoskeleton. This has been achieved by implementing advanced control strategies that enable the safe and efficient use of the [...] Read more.

Over the last decade, lower limb exoskeletons have seen significant development, with a particular focus on improving the interaction between the subject and the exoskeleton. This has been achieved by implementing advanced control strategies that enable the safe and efficient use of the exoskeleton. In this work, the control strategies for lower limb exoskeletons are divided into upper-level control (supervisory and high-level control) and lower-level control (the servo layer). Before discussing these control strategies, a brief introduction to lower limb exoskeletons and their control schemes is provided. The control hierarchy for lower limb exoskeletons is then systematically reviewed along with an overview of the techniques used. A Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) statement is used to highlight the systematic process of identifying relevant articles with inclusion and exclusion criteria. The details of supervisory control, high-level control, and servo control strategies are presented by citing relevant state-of-the-art studies, particularly from the past five years. The targeted lower limb joint, training mode, and development stage for different control strategies are highlighted in a tabulated form to articulate the overall hierarchy level. Finally, the potential opportunities and limitations of subject-cooperative control are discussed. Overall, this work aims to provide an in-depth understanding of the control strategies used in lower limb exoskeletons, focusing on subject cooperation. This knowledge can be used to improve the safety and efficacy of lower limb exoskeletons, ultimately benefiting individuals with mobility impairments. Full article

(This article belongs to the Special Issue Rehabilitation Robotics: Design, Applications and Challenges)

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13 pages, 2558 KiB

Open AccessArticle

Tendon-Driven Crawling Robot with Programmable Anisotropic Friction by Adjusting Out-of-Plane Curvature

by Hyeonsu Kim, Sumin Cho, Dongik Kam, Seong Jin Lee, Seongjae Park, Dongwhi Choi and Jongwoo Kim

Machines 2023, 11(7), 763; https://doi.org/10.3390/machines11070763 - 22 Jul 2023

Viewed by 1346

Abstract

Origami crawling robots, inspired by the principles of origami folding, have emerged as a promising approach for developing lightweight and flexible robots capable of navigating tight spaces. These robots utilize anisotropic friction, where the frictional forces between surfaces vary depending on the direction [...] Read more.

Origami crawling robots, inspired by the principles of origami folding, have emerged as a promising approach for developing lightweight and flexible robots capable of navigating tight spaces. These robots utilize anisotropic friction, where the frictional forces between surfaces vary depending on the direction of motion, enabling controlled movement by changing the robot’s body orientation. While various actuation methods have been explored, such as pneumatic and magnetic systems, they suffer from limitations such as bulkiness or restricted workspace. In this paper, we propose a tendon-driven crawling robot that achieves anisotropic friction by controlling its out-of-plane curvature. By manipulating the robot’s shape and out-of-plane curvature, we can modulate the friction forces and enable efficient crawling motion. To maximize anisotropic friction, we design an asymmetric contact film composed of elastomer and polyester. We analyze the relationship between out-of-plane curvature and frictional force through experiments on flat and sloped surfaces, considering different leg angles and slope angles of the contact film. The results demonstrate the gait loss ratio of 1.96% for the optimized design, highlighting the robot’s ability to crawl efficiently with quick response times and a low-profile system. This research contributes to the advancement of origami-based crawling robots and their potential applications in confined and unstructured environments. Full article

(This article belongs to the Special Issue Soft Robotics: Fabrication, Actuation and Application)

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24 pages, 9915 KiB

Open AccessArticle

Analysis of the Influence of Downhole Drill String Vibration on Wellbore Stability

by Yonggang Shan, Qilong Xue, Jin Wang, Yafeng Li and Chong Wang

Machines 2023, 11(7), 762; https://doi.org/10.3390/machines11070762 - 22 Jul 2023

Cited by 3 | Viewed by 1274

Abstract

Most studies related to aspects of wellbore stability, such as wellbore breakage, block dropping, and wellbore expansion, revolve around the physicochemical interaction between drilling fluid and surrounding rock, but relevant studies show that drill string vibration during drilling also has a crucial and [...] Read more.

Most studies related to aspects of wellbore stability, such as wellbore breakage, block dropping, and wellbore expansion, revolve around the physicochemical interaction between drilling fluid and surrounding rock, but relevant studies show that drill string vibration during drilling also has a crucial and even decisive influence on wellbore stability. In order to thoroughly explore the influence mechanism of drill string vibration on wellbore stability, our research group established a finite element flexible simulation model of drill string dynamics and used a storage downhole vibration measurement device to collect downhole real drilling vibration data to verify the correctness of the simulation model. Then, based on the critical conditions of wellbore breakage, a wellbore stability evaluation method was established, and the wellbore stability under different drilling parameters and drilling tool combination conditions was evaluated and analyzed. The research results play an important role in revealing the influence mechanism of drill string vibration on wellbore stability and can provide theoretical guidance for engineering problems such as wellbore instability risk assessment. Full article

(This article belongs to the Topic Energy Equipment and Condition Monitoring)

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18 pages, 11369 KiB

Open AccessArticle

Analysis of E-Scooter Vibrations from Health Perspective: A Case Study

by Juan David Cano-Moreno, José María Cabanellas Becerra, José Manuel Arenas Reina and Manuel Enrique Islán Marcos

Machines 2023, 11(7), 761; https://doi.org/10.3390/machines11070761 - 21 Jul 2023

Cited by 1 | Viewed by 1379

Abstract

The impact of vibrations on health in occupational environments has been extensively studied. Although the effects of vehicle vibrations on driving comfort has been investigated, the literature on the impact of vehicle vibrations on health is scarce. Accordingly, this study aimed to investigate [...] Read more.

The impact of vibrations on health in occupational environments has been extensively studied. Although the effects of vehicle vibrations on driving comfort has been investigated, the literature on the impact of vehicle vibrations on health is scarce. Accordingly, this study aimed to investigate the influence of e-scooter vibrations on driver health by considering both whole-body vibrations (WBVs) and hand–arm vibrations (HAVs). From the perspective of health, vibration zones were defined based on the UNE-2631 and UNE-5349 standards, as well as the European Vibration Directive. Real measurements obtained from an e-scooter acceleration database were used. The results of the study on WBVs show that, on average, 87.54% and 95.47% of non-desirable vibrations are caused by driving an e-scooter on pavers and asphalt, respectively. This shows that ‘potentially non-healthy’ and ‘non-healthy’ vibrations are 25.69% and 61.85%, respectively, when driving on pavers and 85.52% and 12.96%, respectively, when driving on asphalt. Therefore, the WBV levels reached by driving an e-scooter on any pavement could potentially harm health. However, the influence of HAV on the incidence of Raynaud’s syndrome is low. The study results on WBV suggest that future e-scooter designs must be based on a more damped road–driver interface. Full article

(This article belongs to the Special Issue Modeling, Estimation, Control, and Decision for Human-Vehicle Systems)

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23 pages, 8291 KiB

Open AccessArticle

Influence of Weak Structural Vibrations on a Machine-Driven Chain of Mechanical Oscillators with Friction under Varying Normal Forces

by Paweł Olejnik

Machines 2023, 11(7), 760; https://doi.org/10.3390/machines11070760 - 21 Jul 2023

Viewed by 870

Abstract

This work presents a real mechatronic system consisting of coupled inertia oscillators affected by relatively high-frequency structural vibrations. The system’s basic mathematical description is also provided. To simulate real structural vibrations, a vibration exciter in the form of an imbalanced rotor is incorporated [...] Read more.

This work presents a real mechatronic system consisting of coupled inertia oscillators affected by relatively high-frequency structural vibrations. The system’s basic mathematical description is also provided. To simulate real structural vibrations, a vibration exciter in the form of an imbalanced rotor is incorporated into the model. The dynamic behavior of the contacting solid bodies is significantly influenced by the rotating imbalanced mass, which is in frictional contact with the body. The vertical acceleration component resulting from the rotational motion of the imbalance leads to a faster breakage of the sliding contact between the block and the belt, causing a shorter duration of the contact pair in the stick phase. Additionally, the softly coupled pendulum solid body can be utilized to effectively detect weak vibration modes of the self-excited friction oscillator that would otherwise be challenging to observe. Full article

(This article belongs to the Section Machines Testing and Maintenance)

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17 pages, 6826 KiB

Open AccessEditor’s ChoiceArticle

Design, Modelling and Optimization of a High Power Density Axial Flux SRM with Reduced Torque Ripple for Electric Vehicles

by Akbar Mohammadi Ajamloo, Mohamed N. Ibrahim and Peter Sergeant

Machines 2023, 11(7), 759; https://doi.org/10.3390/machines11070759 - 20 Jul 2023

Cited by 4 | Viewed by 1537

Abstract

Switched reluctance machines (SRMs) are potential candidates for use in the propulsion systems of electric vehicles. However, they suffer from low power density and high torque ripple. In this paper, a segmented rotor double-sided axial flux SRM (DSAFSRM) is chosen for detailed analysis. [...] Read more.

Switched reluctance machines (SRMs) are potential candidates for use in the propulsion systems of electric vehicles. However, they suffer from low power density and high torque ripple. In this paper, a segmented rotor double-sided axial flux SRM (DSAFSRM) is chosen for detailed analysis. A hybrid design algorithm is proposed to take the effects of iron non-linearity into account. The proposed design procedure benefits from simplicity and high accuracy at the same time. A two-step optimization procedure is presented which minimizes the torque ripple of the DSAFSRM without jeopardizing its efficiency. The torque ripple is reduced from 120% to 35% after optimization. In the two-step optimization procedure, both geometrical and switching related parameters are investigated. Moreover, a double-sided radial flux SRM is designed and compared with the proposed DSAFSRM in terms of torque ripple, average torque, efficiency and power density. The results indicate superior performance of the optimized DSAFSRM, especially in terms of average torque, which is 26% higher than the torque produced by the double-sided radial flux SRM. Full article

(This article belongs to the Special Issue Future Trends in Advanced Design of Electrical Machines, Drives and Electric Vehicles Using Additive Manufacturing Approaches)

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19 pages, 5953 KiB

Open AccessArticle

A Method for Rotor Speed Measurement and Operating State Identification of Hydro-Generator Units Based on YOLOv5

by Jiajun Liu, Lei Xiong, Ji Sun, Yue Liu, Rui Zhang and Haokun Lin

Machines 2023, 11(7), 758; https://doi.org/10.3390/machines11070758 - 20 Jul 2023

Viewed by 933

Abstract

With the rapid development of artificial intelligence, machine vision and other information technologies in the construction of smart power plants, the requirements of power plants for the state monitoring of hydro-generator units (HGU) are becoming higher and higher. Based on this, this paper [...] Read more.

With the rapid development of artificial intelligence, machine vision and other information technologies in the construction of smart power plants, the requirements of power plants for the state monitoring of hydro-generator units (HGU) are becoming higher and higher. Based on this, this paper applies YOLOv5 to the state monitoring scenario of HGU, and proposes a method for rotor speed measurement (RSM) and operating state identification (OSI) of HGUs based on the YOLOv5. The proposed method is applied to the actual RSM and OSI of HGUs. The experimental results show that the Precision and Recall of the proposed method for rotor image are 99.5% and 100%, respectively. Compared with the traditional methods, the online image monitoring based on machine vision not only realizes high-precision RSM and the real-time and accurate determination of operating states, but also realizes video image monitoring of the rotor, the operation trend prediction of the rotor and the early warning of abnormal operating states, so that staff can find the hidden dangers in time and ensure the safe operation of the HGU. Full article

(This article belongs to the Topic Hydroelectric Power)

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21 pages, 16883 KiB

Open AccessArticle

Torque-Based Control of a Bio-Inspired Modular Climbing Robot

by Carlos Prados, Miguel Hernando, Ernesto Gambao and Alberto Brunete

Machines 2023, 11(7), 757; https://doi.org/10.3390/machines11070757 - 19 Jul 2023

Viewed by 1368

Abstract

This article presents a generalizable, low computational cost, simple, and fast gravity compensation method for legged robots with a variable number of legs. It is based on the static problem, which is a reduction in the dynamic model of the robot that takes [...] Read more.

This article presents a generalizable, low computational cost, simple, and fast gravity compensation method for legged robots with a variable number of legs. It is based on the static problem, which is a reduction in the dynamic model of the robot that takes advantage of the low velocity of climbing robots. To solve it, we propose a method that computes the torque to be applied by each actuator to compensate for the gravitational forces without using the Jacobian matrix for the forces exerted by the end-effector and without using analytical methods for the gravitational components of the model. We compare our method with the most popular method and conclude that ours is twice as fast. Using the proposed gravity compensator, we present a torque-based PD controller for the position of the leg modules, and a body velocity control without dynamic compensation. In addition, we validate the method with both hardware and a simulated version of the ROMERIN robot, a modular legged and climbing robot. Furthermore, we compare our controller with the usual kinematic inverse controllers, demonstrating that the mean angular and linear error is significantly reduced, as well as the power requirements of the actuators. Full article

(This article belongs to the Special Issue Intelligent Bio-Inspired Robots: New Trends and Future Perspectives)

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18 pages, 7609 KiB

Open AccessEditor’s ChoiceArticle

A Novel Sleeve Design to Reduce the Eddy Current Loss of High-Speed Electrical Machines

by Seung-Heon Lee, Si-Woo Song, Min-Jae Jeong, Won-Ho Kim and Dong-Hoon Jung

Machines 2023, 11(7), 756; https://doi.org/10.3390/machines11070756 - 19 Jul 2023

Cited by 1 | Viewed by 1225

Abstract

Demand for high-speed motors is increasing. Surface-mounted permanent magnet synchronous motors (SPMSM) used in high-speed applications have magnets attached to the rotor, so there is a risk of damage and scattering due to centrifugal force as the speed increases. For this reason, applying [...] Read more.

Demand for high-speed motors is increasing. Surface-mounted permanent magnet synchronous motors (SPMSM) used in high-speed applications have magnets attached to the rotor, so there is a risk of damage and scattering due to centrifugal force as the speed increases. For this reason, applying the retaining sleeve to the rotor is essential. However, when using sleeves, there is a problem of reducing efficiency due to eddy current loss. In this paper, a study was conducted on a motor for a 100 kW building air conditioning system operating at a speed of 20,000 rpm. The purpose of the study is to reduce eddy current loss by optimizing the sleeve geometry. To this end, 3D finite element analysis (FEA) using JMAG 22.1 was conducted to analyze eddy current loss, the minimum safety factor was analyzed through mechanical stiffness analysis using ANSYS Workbench, and the validity of sleeve shape was proved through cause analysis. Through the research results, it is expected that the shape change of the sleeve will have the effect of reducing eddy current loss. Full article

(This article belongs to the Section Electrical Machines and Drives)

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18 pages, 1758 KiB

Open AccessArticle

A qLPV-MPC Control Strategy for Trajectory Tracking of Quadrotors

by Daniel Rodriguez-Guevara, Antonio Favela-Contreras and Oscar Julian Gonzalez-Villarreal

Machines 2023, 11(7), 755; https://doi.org/10.3390/machines11070755 - 19 Jul 2023

Cited by 1 | Viewed by 1266

Abstract

This article proposes a model predictive control (MPC) strategy for a quadrotor drone trajectory tracking based on a compact state-space model based on a quasi-linear parameter varying (qLPV) representation of the nonlinear quadrotor. The use of a qLPV representation allows for faster execution [...] Read more.

This article proposes a model predictive control (MPC) strategy for a quadrotor drone trajectory tracking based on a compact state-space model based on a quasi-linear parameter varying (qLPV) representation of the nonlinear quadrotor. The use of a qLPV representation allows for faster execution times, which can be suitable for real-time applications and for solving the optimization problem using quadratic programming (QP). The estimation of future values of the scheduling parameters along the prediction horizon is made by using the planned trajectory based on the previous optimal control actions. The performance of the proposed approach is tested by following different trajectories in simulation to show the effectiveness of the proposed control scheme. Full article

(This article belongs to the Special Issue Nonlinear and Adaptive Control of Intelligent Machines)

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19 pages, 10959 KiB

Open AccessArticle

Vibration and Position Control of a Two-Link Flexible Manipulator Using Reinforcement Learning

by Minoru Sasaki, Joseph Muguro, Fumiya Kitano, Waweru Njeri, Daiki Maeno and Kojiro Matsushita

Machines 2023, 11(7), 754; https://doi.org/10.3390/machines11070754 - 19 Jul 2023

Viewed by 1213

Abstract

In recent years, industries have increasingly emphasized the need for high-speed, energy-efficient, and cost-effective solutions. As a result, there has been growing interest in developing flexible link manipulator robots to meet these requirements. However, reducing the weight of the manipulator leads to increased [...] Read more.

In recent years, industries have increasingly emphasized the need for high-speed, energy-efficient, and cost-effective solutions. As a result, there has been growing interest in developing flexible link manipulator robots to meet these requirements. However, reducing the weight of the manipulator leads to increased flexibility which, in turn, causes vibrations. This research paper introduces a novel approach for controlling the vibration and motion of a two-link flexible manipulator using reinforcement learning. The proposed system utilizes trust region policy optimization to train the manipulator’s end effector to reach a desired target position, while minimizing vibration and strain at the root of the link. To achieve the research objectives, a 3D model of the flexible-link manipulator is designed, and an optimal reward function is identified to guide the learning process. The results demonstrate that the proposed approach successfully suppresses vibration and strain when moving the end effector to the target position. Furthermore, the trained model is applied to a physical flexible manipulator for real-world control verification. However, it is observed that the performance of the trained model does not meet expectations, due to simulation-to-real challenges. These challenges may include unanticipated differences in dynamics, calibration issues, actuator limitations, or other factors that affect the performance and behavior of the system in the real world. Therefore, further investigations and improvements are recommended to bridge this gap and enhance the applicability of the proposed approach. Full article

(This article belongs to the Section Automation and Control Systems)

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15 pages, 4218 KiB

Open AccessArticle

Kinematic Modeling and Simulation of a New Robot for Wingbox Internal Fastening Application

by Jiefeng Jiang, Jingjing You and Yunbo Bi

Machines 2023, 11(7), 753; https://doi.org/10.3390/machines11070753 - 18 Jul 2023

Cited by 2 | Viewed by 904

Abstract

At present, the fastener installation in a wingbox facing a narrow space must be performed manually. Using a robot is an appropriate solution for automatic assembly. However, the existing robots cannot meet the internal fastening requirements. A new robot with a prismatic joint [...] Read more.

At present, the fastener installation in a wingbox facing a narrow space must be performed manually. Using a robot is an appropriate solution for automatic assembly. However, the existing robots cannot meet the internal fastening requirements. A new robot with a prismatic joint and four revolute joints (1P4R) was developed to perform the positioning and operation in the wingbox. A compact arm link was designed, and mechanical frame structures were set up. The control system was also set up for the robot’s motion. Then, the forward kinematic model was carried out with the matrix transformation method, and in the analysis the workspace entirely covered the wingbox. The inverse kinematic model was established using the geometric method, and through calculation and simulation, the inverse kinematic equations were verified and refined. Full article

(This article belongs to the Section Automation and Control Systems)

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15 pages, 4435 KiB

Open AccessArticle

A CNN-Based Methodology for Identifying Mechanical Faults in Induction Motors Using Thermography

by Omar Trejo-Chavez, Irving A. Cruz-Albarran, Emmanuel Resendiz-Ochoa, Alejandro Salinas-Aguilar, Luis A. Morales-Hernandez, Jesus A. Basurto-Hurtado and Carlos A. Perez-Ramirez

Machines 2023, 11(7), 752; https://doi.org/10.3390/machines11070752 - 18 Jul 2023

Viewed by 1244

Abstract

Infrared thermography (IRT) has become an interesting alternative for performing condition assessments of different types of induction motor (IM)-based equipment when it operates under harsh conditions. The reported results from state-of-the-art articles that have analyzed thermal images do not consider (1): the presence [...] Read more.

Infrared thermography (IRT) has become an interesting alternative for performing condition assessments of different types of induction motor (IM)-based equipment when it operates under harsh conditions. The reported results from state-of-the-art articles that have analyzed thermal images do not consider (1): the presence of more than one fault, and (2) the inevitable noise-corruption the images suffer. Bearing in mind these reasons, this paper presents a convolutional neural network (CNN)-based methodology that is specifically designed to deal with noise-corrupted images for detecting the failures that have the highest incidence rate: bearing and broken bar failures; moreover, rotor misalignment failure is also considered, as it can cause a further increase in electricity consumption. The presented results show that the proposal is effective in detecting healthy and failure states, as well as identifying the failure nature, as a 95% accuracy is achieved. These results allow considering the proposal as an interesting alternative for using IRT images obtained in hostile environments. Full article

(This article belongs to the Special Issue Monitoring and Fault Identification Based on Artificial Intelligence Methods)

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21 pages, 5877 KiB

Open AccessEditor’s ChoiceReview

Research Progress on the Dynamic Characteristics of Planetary Gear Transmission in a Non-Inertial System

by Bingwei Gao, Yongkang Wang and Guangbin Yu

Machines 2023, 11(7), 751; https://doi.org/10.3390/machines11070751 - 18 Jul 2023

Viewed by 1412

Abstract

Planetary gear systems have many advantages over other gear systems. Previous studies on its dynamic characteristics mostly used Earth as the reference system, which is inconsistent with the actual working conditions of many planetary gear systems, such as aircraft maneuvering, vehicle movement changes, [...] Read more.

Planetary gear systems have many advantages over other gear systems. Previous studies on its dynamic characteristics mostly used Earth as the reference system, which is inconsistent with the actual working conditions of many planetary gear systems, such as aircraft maneuvering, vehicle movement changes, etc. By analyzing representative research papers, this study summarizes the lumped-parameter, finite element, and rigid–flexible coupling models commonly used in studying the traditional dynamic characteristics. Then, the research status of gear–rotor and planetary gear systems in inertial and non-inertial systems is summarized. The research progress of load characteristics, vibration characteristics, and vibration control of the traditional planetary gear system is summarized. Finally, some suggestions for future development are put forward. There are a few studies on the non-inertial dynamics of planetary gear systems. The three analysis models have distinct characteristics and applications but can all be used in non-inertial systems. The dynamic analysis method of non-inertial rotor systems can be combined with the dynamic study of gear systems. It is of practical significance to study the non-inertial dynamic characteristics of planetary gear systems. Scholars can refer to the non-inertial dynamic research of the gear–rotor system, select the analysis model according to the needs, and continue to study the dynamic characteristics of the planetary gear system under the non-inertial system. Full article

(This article belongs to the Special Issue Research on Rotor Dynamics and Vibration Control)

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36 pages, 5025 KiB

Open AccessReview

Intelligent Approaches for Anomaly Detection in Compressed Air Systems: A Systematic Review

by Jasmine Mallia, Emmanuel Francalanza, Peter Xuereb and Paul Refalo

Machines 2023, 11(7), 750; https://doi.org/10.3390/machines11070750 - 18 Jul 2023

Cited by 2 | Viewed by 1508

Abstract

Inefficiencies within compressed air systems (CASs) call for the integration of Industry 4.0 technologies for financially viable and sustainable operations. A systematic literature review of intelligent approaches within CASs was carried out, in which the research methodology was based on the PRISMA guidelines. [...] Read more.

Inefficiencies within compressed air systems (CASs) call for the integration of Industry 4.0 technologies for financially viable and sustainable operations. A systematic literature review of intelligent approaches within CASs was carried out, in which the research methodology was based on the PRISMA guidelines. The search was carried out on 1 November 2022 within two databases: Scopus and Web of Science. The research methodology resulted in 37 papers eligible for a qualitative and bibliometric analysis based on a set of research questions. These aimed to identify specific characteristics of the selected publications. Thus, the review performed a comprehensive analysis on mathematical approaches, multiple machine learning (ML) methods, the implementation of neural networks (NNs), the development of time-series techniques, comparative analysis, and hybrid techniques. This systematic literature review allowed the comparison of these approaches, while widening the perspective on how such methods can be implemented within CASs for a more intelligent approach. Any limitations or challenges faced were mitigated through an unbiased procedure of involving multiple databases, search terms, and researchers. Therefore, this systematic review resulted in discussions and implications for the definition of future implementations of intelligent approaches that could result in sustainable CASs. Full article

(This article belongs to the Special Issue Assessing New Trends in Sustainable and Smart Manufacturing)

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19 pages, 6294 KiB

Open AccessArticle

Effects of Abrasive Waterjet Machining on the Quality of the Surface Generated on a Carbon Fibre Reinforced Polymer Composite

by Andrew Rowe, Alokesh Pramanik, Animesh Kumar Basak, Chander Prakash, Shankar Subramaniam, Amit Rai Dixit and N. Radhika

Machines 2023, 11(7), 749; https://doi.org/10.3390/machines11070749 - 18 Jul 2023

Cited by 2 | Viewed by 1127

Abstract

The effect of the water pressure, traverse speed, and abrasive feed rate on the circularity, cylindricity, kerf taper, and surface roughness of holes produced by abrasive waterjet machining (AWJM) of a carbon-fibre-reinforced polymer (CFRP) composite was investigated in the current study. It was [...] Read more.

The effect of the water pressure, traverse speed, and abrasive feed rate on the circularity, cylindricity, kerf taper, and surface roughness of holes produced by abrasive waterjet machining (AWJM) of a carbon-fibre-reinforced polymer (CFRP) composite was investigated in the current study. It was found that the circularity deviation decreased as the water pressure was increased. Cylindricity was affected by all three parameters, although the abrasive feed rate caused the largest deviations as it increased. The surface roughness was affected by all three, but a clear connection was not able to be concluded. The kerf taper ratio reduced with an increase in water pressure, while it increased with an increase in the abrasive feed rate and an increase in the traverse speed. To obtain optimum results, the water pressure should be increased, the traverse speed should be decreased, and the abrasive feed rate can remain constant but is recommended to be slightly reduced. Full article

(This article belongs to the Special Issue Machining Challenges towards Pico-Precision)

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23 pages, 7201 KiB

Open AccessArticle

Multi-Objective Optimization of AISI P20 Mold Steel Machining in Dry Conditions Using Machine Learning—TOPSIS Approach

by Adel T. Abbas, Neeraj Sharma, Zeyad A. Alsuhaibani, Abhishek Sharma, Irfan Farooq and Ahmed Elkaseer

Machines 2023, 11(7), 748; https://doi.org/10.3390/machines11070748 - 18 Jul 2023

Cited by 4 | Viewed by 1048

Abstract

In the present research, AISI P20 mold steel was processed using the milling process. The machining parameters considered in the present work were speed, depth of cut (DoC), and feed (F). The experiments were designed according to an L₂₇ orthogonal array; therefore, [...] Read more.

In the present research, AISI P20 mold steel was processed using the milling process. The machining parameters considered in the present work were speed, depth of cut (DoC), and feed (F). The experiments were designed according to an L₂₇ orthogonal array; therefore, a total of 27 experiments were conducted with different settings of machining parameters. The response parameters investigated in the present work were material removal rate (MRR), surface roughness (Ra, Rt, and Rz), power consumption (PC), and temperature (Temp). The machine learning (ML) approach was implemented for the prediction of response parameters, and the corresponding error percentage was investigated between experimental values and predicted values (using the ML approach). The technique for order of preference by similarity to ideal solution (TOPSIS) approach was used to normalize all response parameters and convert them into a single performance index (Pi). An analysis of variance (ANOVA) was conducted using the design of experiments, and the optimized setting of machining parameters was investigated. The optimized settings suggested by the integrated ML–TOPSIS approach were as follows: speed, 150 m/min; DoC, 1 mm; F, 0.06 mm/tooth. The confirmation results using these parameters suggested a close agreement and confirmed the suitability of the proposed approach in the parametric evaluation of a milling machine while processing P20 mold steel. It was found that the maximum percentage error between the predicted and experimental values using the proposed approach was 3.43%. Full article

(This article belongs to the Special Issue Precision Engineering in Manufacturing: Challenges and Future)

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19 pages, 8010 KiB

Open AccessArticle

Enhancing sEMG-Based Finger Motion Prediction with CNN-LSTM Regressors for Controlling a Hand Exoskeleton

by Mirco Vangi, Chiara Brogi, Alberto Topini, Nicola Secciani and Alessandro Ridolfi

Machines 2023, 11(7), 747; https://doi.org/10.3390/machines11070747 - 17 Jul 2023

Cited by 1 | Viewed by 1260

Abstract

In recent years, the number of people with disabilities has increased hugely, especially in low- and middle-income countries. At the same time, robotics has made significant advances in the medical field, and many research groups have begun to develop low-cost wearable solutions. The [...] Read more.

In recent years, the number of people with disabilities has increased hugely, especially in low- and middle-income countries. At the same time, robotics has made significant advances in the medical field, and many research groups have begun to develop low-cost wearable solutions. The Mechatronics and Dynamic Modelling Lab of the Department of Industrial Engineering at the University of Florence has recently developed a new version of a wearable hand exoskeleton for assistive purposes. In this paper, we will present a new regression method to predict the finger angle position of the first joint from the value of the sEMG of the forearm and the previous position of the finger itself. To acquire the dataset necessary to train the regressor a specific graphical user interface was developed which was able to acquire sEMG data from a Myo armband and the finger position from a Leap Motion Controller. Two long short-term memory (LSTM) models were compared, one in its standard configuration and the other with a convolutional layer, yielding significantly better performance for the second one, with an increase in

R^{2}

coefficient from an average value of

0.746

to

0.825

, leading to the conclusion that a convolutional layer could increase performance when few sensors are available. Full article

(This article belongs to the Special Issue Design and Control of Wearable Mechatronics Devices)

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23 pages, 4723 KiB

Open AccessArticle

Convolutional-Transformer Model with Long-Range Temporal Dependencies for Bearing Fault Diagnosis Using Vibration Signals

by Hosameldin O. A. Ahmed and Asoke K. Nandi

Machines 2023, 11(7), 746; https://doi.org/10.3390/machines11070746 - 17 Jul 2023

Cited by 1 | Viewed by 1363

Abstract

Fault diagnosis of bearings in rotating machinery is a critical task. Vibration signals are a valuable source of information, but they can be complex and noisy. A transformer model can capture distant relationships, which makes it a promising solution for fault diagnosis. However, [...] Read more.

Fault diagnosis of bearings in rotating machinery is a critical task. Vibration signals are a valuable source of information, but they can be complex and noisy. A transformer model can capture distant relationships, which makes it a promising solution for fault diagnosis. However, its application in this field has been limited. This study aims to contribute to this growing area of research by proposing a novel deep-learning architecture that combines the strengths of CNNs and transformer models for effective fault diagnosis in rotating machinery. Thus, it captures both local and long-range temporal dependencies in the vibration signals. The architecture starts with CNN-based feature extraction, followed by temporal relationship modelling using the transformer. The transformed features are used for classification. Experimental evaluations are conducted on two datasets with six and ten health conditions. In both case studies, the proposed model achieves high accuracy, precision, recall, F1-score, and specificity all above 99% using different training dataset sizes. The results demonstrate the effectiveness of the proposed method in diagnosing bearing faults. The convolutional-transformer model proves to be a promising approach for bearing fault diagnosis. The method shows great potential for improving the accuracy and efficiency of fault diagnosis in rotating machinery. Full article

(This article belongs to the Special Issue Machine Learning and Artificial Intelligence in Machinery Condition Monitoring)

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16 pages, 7454 KiB

Open AccessArticle

Stability Analysis of a Vehicle–Cargo Securing System for Autonomous Trucks Based on 6-SPS-Type Parallel Mechanisms

by Guosheng Zhang, Tao Wang, Han Wang, Shilei Wu and Zhongxi Shao

Machines 2023, 11(7), 745; https://doi.org/10.3390/machines11070745 - 15 Jul 2023

Cited by 1 | Viewed by 981

Abstract

Stability prediction of the securing system for autonomous trucks is an important prerequisite for achieving safety monitoring of large cargo transportation and improving logistics efficiency. Considering the side slide risk of large cargo and the inability to predict stability using the existing under-constrained [...] Read more.

Stability prediction of the securing system for autonomous trucks is an important prerequisite for achieving safety monitoring of large cargo transportation and improving logistics efficiency. Considering the side slide risk of large cargo and the inability to predict stability using the existing under-constrained friction securing model, this paper proposes a new vehicle–cargo securing model based on the 6-SPS parallel mechanism. By establishing an analytical 3-DOF model, the dynamics performance of the vehicle–cargo system is analyzed based on the response solution under sinusoidal excitations. To verify the correctness of the analytical model, a multi-body dynamics model of the whole vehicle–cargo system based on the three-dimensional geometric model and the 6-SPS parallel mechanism is established for simulation in ADAMS. According to road class, pavement roughness is modeled by a white noise power spectrum method as the excitation in the simulation. The results show that the dynamics response of the analytical model accords well with that of the simulation model, with relative errors of 8.34% and 0.036% in amplitude and frequency, respectively. The proposed method can provide theoretical support for accurate stability prediction and for achieving safety monitoring of large cargo transportation for autonomous trucks. Full article

(This article belongs to the Special Issue Advances in Autonomous Vehicles Dynamics and Control)

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13 pages, 4985 KiB

Open AccessArticle

Stator Inter-Turn Short-Circuits Fault Diagnostics in Three-Phase Line-Start Permanent Magnet Synchronous Motors Fed by Unbalanced Voltages

by D. S. B. Fonseca, Hugo R. P. Antunes and Antonio J. Marques Cardoso

Machines 2023, 11(7), 744; https://doi.org/10.3390/machines11070744 - 15 Jul 2023

Cited by 2 | Viewed by 918

Abstract

This paper addresses the diagnostics of stator faults in three-phase line-start permanent magnet synchronous motors. More traditional fault diagnostic methodologies are unable to properly diagnose stator inter-turn short-circuit faults in three-phase motors under unbalanced supply voltage conditions, since both conditions impact the fault [...] Read more.

This paper addresses the diagnostics of stator faults in three-phase line-start permanent magnet synchronous motors. More traditional fault diagnostic methodologies are unable to properly diagnose stator inter-turn short-circuit faults in three-phase motors under unbalanced supply voltage conditions, since both conditions impact the fault indicators used for inter-turn short-circuit fault diagnostics in a similar way. In this paper, the relation between the symmetrical components of the three-phase quantities and the harmonic components of the Extended Park’s Vector Approach (EPVA) is established. It is proved that the negative component and the EPVA harmonic component at a frequency twice the supply frequency are directly related to the fault occurrence. It is also proved that the healthy motor negative impedance is constant and not load-dependent. Based on this, the negative impedance/admittance is indirectly analyzed, through the combined use of the Extended Park´s Vector Approach of both voltage and current, and is explored for the fault diagnostics. Experimental results, obtained for different load torques, unbalanced supply voltage values, and fault severity levels, show that inter-turn short-circuit fault diagnostics can be achieved even under unbalanced supply voltage conditions based on the analysis of the motor admittance, at a frequency twice the supply frequency, that is the negative sequence admittance. Full article

(This article belongs to the Special Issue Fault-Tolerant PM Motors and Drives)

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20 pages, 12070 KiB

Open AccessArticle

Performance Optimization of Ultralow-Frequency Electromagnetic Energy Harvester Driven by Eccentric mass

by Jintao Liang, Chao Zhang and Kangqi Fan

Machines 2023, 11(7), 743; https://doi.org/10.3390/machines11070743 - 15 Jul 2023

Cited by 1 | Viewed by 848

Abstract

Driven by an eccentric mass through a two-layered cantilevered plectrum, the electromagnetic energy harvester (EEH) can convert low-frequency mechanical vibrations into continuous uni-directional rotation. To optimize the performance of the EEH, electromagnetic analysis of the EEH was conducted. Three-phase winding permanent magnet (PM) [...] Read more.

Driven by an eccentric mass through a two-layered cantilevered plectrum, the electromagnetic energy harvester (EEH) can convert low-frequency mechanical vibrations into continuous uni-directional rotation. To optimize the performance of the EEH, electromagnetic analysis of the EEH was conducted. Three-phase winding permanent magnet (PM) topology was employed, and combinations of different coils and magnet pole numbers were designed. Then, the finite element method (FEM) was applied to analyze the influence of the combinations of the coils and pole numbers as well as the PM dimensions on the three-phase induced voltage. Prototypes with different configurations were fabricated and the analysis effectiveness was confirmed. Furthermore, different types of stator yokes were designed to enhance the magnetic field. Compared to the original prototype, the output voltage of the optimal prototype increased by 0.5 V with the same rotation speed, and the harmonic components were sufficiently low. Then, experiments with excitation by linear reciprocating motions and swing motions were conducted. Under different exciting conditions, the optimal prototype can also induce the highest voltage amplitude. With an increase in the weight of the eccentric mass, a long duration can be reached that lasts up to 12 s. In summary, the proposed optimization can achieve a high-efficiency and high-power density EEH. Full article

(This article belongs to the Special Issue Mechatronic Systems: Developments and Applications)

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14 pages, 2149 KiB

Open AccessArticle

A Reliable Life Consumption Assessment and Individual Life Monitoring Method for Rolling Bearings

by Yueshuai Fu, Huimin Fu and Qiong Wu

Machines 2023, 11(7), 742; https://doi.org/10.3390/machines11070742 - 14 Jul 2023

Cited by 1 | Viewed by 974

Abstract

Rolling bearings are critical rotating components in aerospace and high-speed trains. The service loads of rolling bearings are generally different from each other, causing significant differences in their damage degrees and reliable life potential. To ensure bearing reliability during service, a reliable life [...] Read more.

Rolling bearings are critical rotating components in aerospace and high-speed trains. The service loads of rolling bearings are generally different from each other, causing significant differences in their damage degrees and reliable life potential. To ensure bearing reliability during service, a reliable life consumption assessment and individual life monitoring method is proposed. Firstly, a small-sample reliable life evaluation method is established based on an accelerated life test conducted at a constant load or load block spectrum before delivery, by which the lower confidence limit of the reliable life of the rolling bearing under any service load can be calculated with the required confidence and reliability. Then, the confidence limits of the reliable life consumption percentage and remaining reliable life percentage for each rolling bearing can be evaluated in real time according to their online monitoring loads and Miner’s law. By this means, individual life monitoring and online life management can be conveniently realized. Compared with traditional bearing life management methods, which do not consider service load differences, this method can more effectively ensure service safety and simultaneously maximize the life potential of bearings. Full article

(This article belongs to the Section Machines Testing and Maintenance)

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21 pages, 11280 KiB

Open AccessArticle

A Planning Framework for Robotic Insertion Tasks via Hydroelastic Contact Model

by Lin Yang, Mohammad Zaidi Ariffin, Baichuan Lou, Chen Lv and Domenico Campolo

Machines 2023, 11(7), 741; https://doi.org/10.3390/machines11070741 - 14 Jul 2023

Cited by 1 | Viewed by 1515

Abstract

Robotic contact-rich insertion tasks present a significant challenge for motion planning due to the complex force interaction between robots and objects. Although many learning-based methods have shown success in contact tasks, most methods need sampling or exploring to gather sufficient experimental data. However, [...] Read more.

Robotic contact-rich insertion tasks present a significant challenge for motion planning due to the complex force interaction between robots and objects. Although many learning-based methods have shown success in contact tasks, most methods need sampling or exploring to gather sufficient experimental data. However, it is both time-consuming and expensive to conduct real-world experiments repeatedly. On the other hand, while the virtual world enables low cost and fast computations by simulators, there still exists a huge sim-to-real gap due to the inaccurate point contact model. Although finite element analysis might generate accurate results for contact tasks, it is computationally expensive. As such, this study proposes a motion planning framework with bilevel optimization to leverage relatively accurate force information with fast computation time. This framework consists of Dynamic Movement Primitives (DMPs) used to parameterize motion trajectories, Black-Box Optimization (BBO), a derivative-free approach, integrated to improve contact-rich insertion policy with hydroelastic contact model, and simulated variability to account for visual uncertainty in the real world. The accuracy of the simulated model is then validated by comparing our contact results with a benchmark Peg-in-Hole task. Using these integrated DMPs and BBO with hydroelastic contact model, the motion trajectory generated in planning is capable of guiding the robot towards successful insertion with iterative refinement. Full article

(This article belongs to the Special Issue Recent Trends in Robot Motion Planning and Control)

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