Next Issue
Volume 9, October
Previous Issue
Volume 9, August
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
2.1
2.6
Journals
Machines
Volume 9
Issue 9
share announcement

Machines, Volume 9, Issue 9 (September 2021) – 25 articles

Cover Story (view full-size image): Stretchable and wearable strain sensors have wide-ranging applications in human motion detection. High aspect ratio silver nanowires (AgNWs) have great potential in flexible and stretchable strain sensors due to the high conductivity and flexibility of AgNW networks. This work aims to fabricate highly stretchable, sensitive, and linear kirigami strain sensors with AgNWs. The AgNW synthesis parameters and process windows were optimized through Taguchi’s method. AgNWs were synthesized at optimized parameters using the one-pot modified polyol method. AgNW-ecoflex Kirigami strain sensors were fabricated and were able to perform up to 70% strain with moderate sensitivity (GF ~1.6) and excellent linearity (R2 = 0.99). Our sensor was capable of detecting finger movement without obvious hysteresis. View this paper.
  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Reader to open them.
Order results
Result details
Section
Show export options expand_more Show export options expand_less
Select all
Export citation of selected articles as:
16 pages, 4916 KiB  
Article
Identification of Robot Joint Torsional Stiffness Based on the Amplitude of the Frequency Response of Asynchronous Data
by Kai Xu, Xing Wu, Xiaoqin Liu and Dongxiao Wang
Machines 2021, 9(9), 204; https://doi.org/10.3390/machines9090204 - 21 Sep 2021
Cited by 3 | Viewed by 2884
Abstract
The difficulty of adding external excitation and the asynchronous data collection from the industrial robot operation limited the online parameter identification of industrial robots. In this regard, this study proposes an identification method that only uses the amplitude of the frequency response function [...] Read more.
The difficulty of adding external excitation and the asynchronous data collection from the industrial robot operation limited the online parameter identification of industrial robots. In this regard, this study proposes an identification method that only uses the amplitude of the frequency response function (FRF) of the system to identify robot joint torsional stiffness and dynamic parameters. The error criterion function shows that this method is feasible and comparable to applying the complete frequency response for identification. The Levenberg–Marquardt (L-M) algorithm is used to find the global optimal value of the error criterion function. In addition, an operational excitation method is proposed to excite the system. The speed profile is set as a triangle wave to excite the system using rectangular wave electromagnetic torques. The simulation results show that using the amplitude of the FRF to identify parameters applies to asynchronous data. The experiments on a single-degree-of-freedom articulated arm test bench show that the motion excitation method is effective, and both stiffness and inertia are identifiable. Full article
(This article belongs to the Section Robotics, Mechatronics and Intelligent Machines)
►▼ Show Figures

Figure 1

13 pages, 4787 KiB  
Article
Three-Phase Induction Motors Online Protection against Unbalanced Supply Voltages
by Khaled Laadjal, Mohamed Sahraoui, Abdeldjalil Alloui and Antonio J. Marques Cardoso
Machines 2021, 9(9), 203; https://doi.org/10.3390/machines9090203 - 20 Sep 2021
Cited by 12 | Viewed by 3773
Abstract
Three-phase induction motors (IMs) are the main workhorse in industry due to their many advantages as compared to other types of industrial motors. However, the efficiency and lifetime of IMs can be considerably affected by some operating conditions, in particular those related to [...] Read more.
Three-phase induction motors (IMs) are the main workhorse in industry due to their many advantages as compared to other types of industrial motors. However, the efficiency and lifetime of IMs can be considerably affected by some operating conditions, in particular those related to unbalanced supply voltages (USV), which is quite a common condition in industrial plants. Therefore, early detection and a precise severity estimation of the USV for all working conditions can prevent major breakdowns and increase reliability and safety of industrial facilities. This paper proposes a reliable method allowing for a precise and online detection of the USV condition, by monitoring a pertinent indicator calculated using the voltage symmetrical components. The effectiveness of the proposed method is validated experimentally for several different working conditions, and a comparison with other indicators available in the literature is also performed. Full article
(This article belongs to the Special Issue Feature Papers to Celebrate the First Impact Factor of Machines)
►▼ Show Figures

Figure 1

23 pages, 2861 KiB  
Article
Constraint-Following Servo Control for the Trajectory Tracking of Manipulator with Flexible Joints and Mismatched Uncertainty
by Fangfang Dong, Bin Yu, Xiaomin Zhao, Shan Chen and Haijun Liu
Machines 2021, 9(9), 202; https://doi.org/10.3390/machines9090202 - 19 Sep 2021
Cited by 4 | Viewed by 1648
Abstract
Trajectory tracking is a common application method for manipulators. However, the tracking performance is hard to improve if the manipulators contain flexible joints and mismatched uncertainty, especially when the trajectory is nonholonomic. On the basis of the Udwadia–Kalaba Fundamental Equation (UKFE), the prescribed [...] Read more.
Trajectory tracking is a common application method for manipulators. However, the tracking performance is hard to improve if the manipulators contain flexible joints and mismatched uncertainty, especially when the trajectory is nonholonomic. On the basis of the Udwadia–Kalaba Fundamental Equation (UKFE), the prescribed position or velocity trajectories are creatively transformed into second-order standard differential form. The constraint force generated by the trajectories is obtained in closed form with the help of UKFE. Then, a high-order fractional type robust control with an embedded fictitious signal is proposed to achieve practical stability of the system, even if the mismatched uncertainty exists. Only the bound of uncertainty is indispensable, rather than the exact information. A leakage type of adaptive law is proposed to estimate such bound. By introducing a dead-zone, the control will be simplified when the specific parameter enters a certain area. Validity of the proposed controller is verified by numerical simulation with two-link flexible joint manipulator. Full article
(This article belongs to the Section Automation and Control Systems)
►▼ Show Figures

Figure 1

18 pages, 7650 KiB  
Article
Modelling and Stability Analysis for a Magnetically Levitated Slice Motor (MLSM) with Gyroscopic Effect and Non-Collocated Structure Based on the Extended Inverse Nyquist Stability Criterion
by Lingling Li, Yang Yu, Liang Hu, Xiaodong Ruan, Rui Su and Xin Fu
Machines 2021, 9(9), 201; https://doi.org/10.3390/machines9090201 - 18 Sep 2021
Viewed by 1802
Abstract
Stability of the rotor motion is the precondition for the reliable operation of magnetically levitated slice motors (MLSMs). However, with gyroscopic effect and non-collocated structure existing simultaneously, its stability analysis faces a tremendous challenge, because the torsional motions couple with the radial translational [...] Read more.
Stability of the rotor motion is the precondition for the reliable operation of magnetically levitated slice motors (MLSMs). However, with gyroscopic effect and non-collocated structure existing simultaneously, its stability analysis faces a tremendous challenge, because the torsional motions couple with the radial translational ones, making MLSM a multiple-input and multiple-output (MIMO) system with high order. Therefore, in this paper, we first establish a novel MIMO rotor dynamics closed-loop model and further convert it into an equivalent single-input and single-out (SISO) feedback control system by constructing complex variables, meanwhile reducing the system order by half. Beneficial from the equivalence between the MIMO and SISO systems, the sufficient and necessary conditions of the absolute stability of MLSM are derived by the extended inverse Nyquist stability criterion in the complex domain. Additionally, the effectiveness of the proposed modelling and stability analysis method is evaluated by simulation and experimental results. Thus, apart from PID parameters, this paper demonstrates that the stability of MLSM is also affected by the coupling of gyroscopic effect and non-collocated structure, which should serve as an essential guideline for system regulation of MLSM. Full article
(This article belongs to the Section Electrical Machines and Drives)
►▼ Show Figures

Figure 1

14 pages, 6514 KiB  
Article
A Simple Calibration Method for a Fringe Projection System Embedded within an Additive Manufacturing Machine
by Yue Liu, Liam Blunt, Feng Gao and Xiangqian Jiang
Machines 2021, 9(9), 200; https://doi.org/10.3390/machines9090200 - 17 Sep 2021
Cited by 3 | Viewed by 2371
Abstract
In additive manufacturing (AM), especially for advanced powder fusion machines, it is of high importance to develop an in situ inspection system to monitor the printed surface and pre-print powder bed as the build cycle proceeds. Consequently, high resolution, high precision and fast [...] Read more.
In additive manufacturing (AM), especially for advanced powder fusion machines, it is of high importance to develop an in situ inspection system to monitor the printed surface and pre-print powder bed as the build cycle proceeds. Consequently, high resolution, high precision and fast detection measurement systems need to be investigated, as such optically based measurement systems can provide feedback for manufacturing process optimisation. Fringe projection technology has a great advantage in the measurement of topography in such environments. The implementation of a fringe projection system requires that the system is pre-calibrated in order to obtain high measurement resolution and repeatability. This paper presents a simple calibration method for an AM-based in situ fringe projection system using a phase-depth calibration model. If a calibration plate with certificated marks is used, however, the texture of the plate will affect the measured phase accuracy. A simple calibration method to reduce the calibration plate texture effect in the process of calibration is outlined. Experimental results show that the proposed method can eliminated these effects and improve measurement resolution and repeatability. The proposed in situ/in process inspection technique has been implemented within a commercial electron beam powder bed fusion additive manufacturing machine (EBAM), to demonstrate the capability for effective feedback during the manufacturing process. Full article
(This article belongs to the Special Issue Precision Measurement and Machines)
►▼ Show Figures

Figure 1

16 pages, 31912 KiB  
Article
2D CNN-Based Multi-Output Diagnosis for Compound Bearing Faults under Variable Rotational Speeds
by Minh-Tuan Pham, Jong-Myon Kim and Cheol-Hong Kim
Machines 2021, 9(9), 199; https://doi.org/10.3390/machines9090199 - 14 Sep 2021
Cited by 27 | Viewed by 3781
Abstract
Bearings prevent damage caused by frictional forces between parts supporting the rotation and they keep rotating shafts in their correct position. However, the continuity of work under harsh conditions leads to inevitable bearing failure. Thus, methods for bearing fault diagnosis (FD) that can [...] Read more.
Bearings prevent damage caused by frictional forces between parts supporting the rotation and they keep rotating shafts in their correct position. However, the continuity of work under harsh conditions leads to inevitable bearing failure. Thus, methods for bearing fault diagnosis (FD) that can predict and categorize fault type, as well as the level of degradation, are increasingly necessary for factories. Owing to the advent of deep neural networks, especially convolutional neural networks (CNNs), intelligent FD methods have achieved significantly higher performance in terms of accuracy. However, in addition to accuracy, the efficiency issue still needs to be weathered in complicated diagnosis scenarios to adapt to real industrial environments. Here, we introduce a method based on multi-output classification, which utilizes the correlated features extracted for bearing compound fault type classification and crack-size classification to serve both aims. Additionally, the synergy of a time–frequency signal processing method and the proposed two-dimensional CNN helped the method perform well under the condition of variable rotational speeds. Monitoring signals of acoustic emission also had advantages for incipient FD. The experimental results indicated that utilizing correlated features in multi-output classification improved both the accuracy and efficiency of multi-task diagnosis compared to conventional CNN-based multiclass classification. Full article
(This article belongs to the Special Issue Artificial Intelligence for Fault Diagnosis of Rotating Machinery)
►▼ Show Figures

Figure 1

27 pages, 9134 KiB  
Article
Development of Infrared-Guided Missile Precision Detection Simulator
by Zhuo Wang, Zhenyu Wu, Tao Wang and Bo Zhang
Machines 2021, 9(9), 198; https://doi.org/10.3390/machines9090198 - 14 Sep 2021
Viewed by 2703
Abstract
In order to carry out various detections of system indicators during the research and development phase of infrared guided missiles, the article first analyzes several main design schemes of the infrared guided missile detection simulator and finds that it has the disadvantages of [...] Read more.
In order to carry out various detections of system indicators during the research and development phase of infrared guided missiles, the article first analyzes several main design schemes of the infrared guided missile detection simulator and finds that it has the disadvantages of difficult processing technology and low detection accuracy. The overall structure of the detection device was designed, including the design of the rotation and swing mechanism, lens mechanism, optical system and control system. The optical system error analysis is performed on the infrared guided missile detection simulator. The position of the receiving light source is obtained by analyzing the mechanism characteristics of the detection simulator and the kinematics model of the device. The phase difference analysis of the eccentricity and tilt system is obtained. The image quality was evaluated by the optical transfer function (MTF), and the system error was found to meet the requirements of imaging quality. The experiments show that the simulation of 1.7~4.9 um medium wave infrared dynamic target signals provides an accurate and reasonable experimental environment for the missile and the verification of the light source target and meets the experimental requirements. Full article
(This article belongs to the Section Machine Design and Theory)
►▼ Show Figures

Figure 1

35 pages, 771 KiB  
Review
A Survey on Fault Diagnosis and Fault-Tolerant Control Methods for Unmanned Aerial Vehicles
by George K. Fourlas and George C. Karras
Machines 2021, 9(9), 197; https://doi.org/10.3390/machines9090197 - 13 Sep 2021
Cited by 56 | Viewed by 8115
Abstract
The continuous evolution of modern technology has led to the creation of increasingly complex and advanced systems. This has been also reflected in the technology of Unmanned Aerial Vehicles (UAVs), where the growing demand for more reliable performance necessitates the development of sophisticated [...] Read more.
The continuous evolution of modern technology has led to the creation of increasingly complex and advanced systems. This has been also reflected in the technology of Unmanned Aerial Vehicles (UAVs), where the growing demand for more reliable performance necessitates the development of sophisticated techniques that provide fault diagnosis and fault tolerance in a timely and accurate manner. Typically, a UAV consists of three types of subsystems: actuators, main structure and sensors. Therefore, a fault-monitoring system must be specifically designed to supervise and debug each of these subsystems, so that any faults can be addressed before they lead to disastrous consequences. In this survey article, we provide a detailed overview of recent advances and studies regarding fault diagnosis, Fault-Tolerant Control (FTC) and anomaly detection for UAVs. Concerning fault diagnosis, our interest is mainly focused on sensors and actuators, as these subsystems are mostly prone to faults, while their healthy operation usually ensures the smooth and reliable performance of the aerial vehicle. Full article
(This article belongs to the Section Robotics, Mechatronics and Intelligent Machines)
►▼ Show Figures

Figure 1

24 pages, 15509 KiB  
Article
Optimal Design of Shift Point Strategy for DCT Based on Particle Swarm Optimization
by Houzhong Zhang, Xiangtian Yang, Xiaoqiang Sun and Jiasheng Liang
Machines 2021, 9(9), 196; https://doi.org/10.3390/machines9090196 - 10 Sep 2021
Cited by 4 | Viewed by 2376
Abstract
For a vehicle equipped with DCT, the vehicle model is established according to the existing experimental data. The traditional method is used to solve the law of economic and dynamic shift, respectively. Then, the dynamic objective function and economic objective function are designed. [...] Read more.
For a vehicle equipped with DCT, the vehicle model is established according to the existing experimental data. The traditional method is used to solve the law of economic and dynamic shift, respectively. Then, the dynamic objective function and economic objective function are designed. After normalization of the two functions, the weighted combination is carried out to get the comprehensive objective function. The traditional shift law obtained in the previous paper is regarded as the limit value of variable optimization by particle swarm optimization algorithm, and the comprehensive objective function designed in this paper is solved. The shift law obtained by the three methods is integrated into Simulink model, and the dynamic and economic verification are carried out, respectively. By comparing the acceleration time of 0–100, 0–70, and 70–120 km/h, the dynamic performance of the shift point is obtained by three methods. The final test results show that the economy of the optimized shift point is improved by 1.37% and 3.17%, respectively. The power performance increased by 4.087%, 15.28%, and −10.70%, hence, achieving the desired results. Full article
(This article belongs to the Section Vehicle Engineering)
►▼ Show Figures

Figure 1

19 pages, 9429 KiB  
Article
Investigation on the Finishing Characteristics of a Magnetic Abrasive Finishing Process with Magnetic Abrasive Slurry Circulation System
by Jiaye Xu, Yanhua Zou and Huijun Xie
Machines 2021, 9(9), 195; https://doi.org/10.3390/machines9090195 - 10 Sep 2021
Cited by 2 | Viewed by 2278
Abstract
The magnetic abrasive finishing (MAF) process is an ultra-precision surface finishing technology. In order to further improve the finishing efficiency and continuity, a magnetic abrasive finishing process using the circulatory system to renew magnetic abrasive slurry was proposed. This study investigated the mechanism [...] Read more.
The magnetic abrasive finishing (MAF) process is an ultra-precision surface finishing technology. In order to further improve the finishing efficiency and continuity, a magnetic abrasive finishing process using the circulatory system to renew magnetic abrasive slurry was proposed. This study investigated the mechanism of the compound magnetic finishing fluid in the process using the conveyor belt as the carrier to complete the circulation and finishing through simulation and theoretical analysis. The influence of the different distribution states of the magnetic finishing fluid in the conveyor belt and the finishing area on the finishing characteristics is observed and analyzed, in addition to a series of experiments to explore the feasibility of finishing polychlorotrifluoroethylene resin plate through this process. Experimental results show that as the working gap decreases, the distribution width of compound magnetic finishing fluid on the conveyor belt becomes larger, and the distribution of the points of action on the workpiece in the finishing area is significantly different and the area increases, and obtains a higher finishing force and finishing efficiency. In this study, the surface roughness of polychlorotrifluoroethylene resin plate was improved from 274 nm Ra to 34 nm Ra within 15 min. Full article
(This article belongs to the Special Issue Advances of Japanese Machine Design)
►▼ Show Figures

Figure 1

20 pages, 4692 KiB  
Article
Robust Vibration Control Based on Rigid-Body State Observer for Modular Joints
by Qiang Xin, Chongchong Wang, Chin-Yin Chen, Guilin Yang and Long Chen
Machines 2021, 9(9), 194; https://doi.org/10.3390/machines9090194 - 10 Sep 2021
Cited by 4 | Viewed by 1800
Abstract
The vibration caused by resonance modes frequently occurs during acceleration and deceleration of the modular joint integrated with flexible harmonic drive. The conventional equivalent rigid-body velocity method with observer can suppress the residual vibration induced by resonant frequency but has poor robustness to [...] Read more.
The vibration caused by resonance modes frequently occurs during acceleration and deceleration of the modular joint integrated with flexible harmonic drive. The conventional equivalent rigid-body velocity method with observer can suppress the residual vibration induced by resonant frequency but has poor robustness to model uncertainties and external disturbances. Moreover, it cannot eliminate the torque ripple caused by the harmonic drive during low-speed uniform motion, reducing the velocity tracking accuracy. Hence, a velocity controller with a rigid-body state observer and an adjustable damper is designed to improve the robust performance and velocity tracking accuracy. The designed rigid-body state observer allows a higher gain so that the bandwidth of the observer can increase, and the equivalent rigid-body velocity can be acquired more accurately. Notably, the high gain observer reduces the sensitivity to model uncertainties and exotic disturbances, especially near the resonant frequency. In addition, the observer combined with an adjustable damper can suppress the residual vibration and torque ripple simultaneously. The proposed method is compared experimentally with a PI method and two other rigid-body velocity methods, such as the conventional equivalent rigid-body observer method and the self-resonance cancellation method, to verify its advantages. Full article
(This article belongs to the Section Automation and Control Systems)
►▼ Show Figures

Figure 1

34 pages, 1563 KiB  
Article
Blockchain-Empowered Digital Twins Collaboration: Smart Transportation Use Case
by Radhya Sahal, Saeed H. Alsamhi, Kenneth N. Brown, Donna O’Shea, Conor McCarthy and Mohsen Guizani
Machines 2021, 9(9), 193; https://doi.org/10.3390/machines9090193 - 09 Sep 2021
Cited by 55 | Viewed by 6250
Abstract
Digital twins (DTs) is a promising technology in the revolution of the industry and essential for Industry 4.0. DTs play a vital role in improving distributed manufacturing, providing up-to-date operational data representation of physical assets, supporting decision-making, and avoiding the potential risks in [...] Read more.
Digital twins (DTs) is a promising technology in the revolution of the industry and essential for Industry 4.0. DTs play a vital role in improving distributed manufacturing, providing up-to-date operational data representation of physical assets, supporting decision-making, and avoiding the potential risks in distributed manufacturing systems. Furthermore, DTs need to collaborate within distributed manufacturing systems to predict the risks and reach consensus-based decision-making. However, DTs collaboration suffers from single failure due to attack and connection in a centralized manner, data interoperability, authentication, and scalability. To overcome the above challenges, we have discussed the major high-level requirements for the DTs collaboration. Then, we have proposed a conceptual framework to fulfill the DTs collaboration requirements by using the combination of blockchain, predictive analysis techniques, and DTs technologies. The proposed framework aims to empower more intelligence DTs based on blockchain technology. In particular, we propose a concrete ledger-based collaborative DTs framework that focuses on real-time operational data analytics and distributed consensus algorithms. Furthermore, we describe how the conceptual framework can be applied using smart transportation system use cases, i.e., smart logistics and railway predictive maintenance. Finally, we highlighted the future direction to guide interested researchers in this interesting area. Full article
(This article belongs to the Special Issue Smart Manufacturing)
►▼ Show Figures

Figure 1

16 pages, 5407 KiB  
Article
Minimization Method for 3D Surface Roughness Evaluation Area
by Viktor Molnár
Machines 2021, 9(9), 192; https://doi.org/10.3390/machines9090192 - 08 Sep 2021
Cited by 11 | Viewed by 2196
Abstract
3D surface roughness measurement is still a less mature procedure than its 2D version. The size of the evaluation area is not as standardized as the measurement length in the 2D version. The purpose of this study is to introduce a method for [...] Read more.
3D surface roughness measurement is still a less mature procedure than its 2D version. The size of the evaluation area is not as standardized as the measurement length in the 2D version. The purpose of this study is to introduce a method for minimizing the evaluated surface area. This could help industrial applications in minimizing the time and cost of measurements. Machining experiments (hard turning and infeed grinding) and surface roughness measurements were carried out for automotive industrial parts to demonstrate the introduced method. Some frequently used roughness parameters were analyzed. Basic statistical calculations were applied to analyze the relationship between the surface area and the roughness parameter values and regression analyses were applied to validate the results in case of the applied technological data. The main finding of the study is that minimum evaluation areas can be clearly designated and, depending on the different roughness parameter–procedure version, different evaluation sizes (Sa: 1.3 × 1.3 mm; Sq: 1.4 × 1.4 mm; Ssk and Sku: 2 × 2 m; Sp and Sv: 1.7 × 1.7 mm) are recommended. Full article
(This article belongs to the Section Material Processing Technology)
►▼ Show Figures

Figure 1

15 pages, 2069 KiB  
Review
Systematic Literature Review Predictive Maintenance Solutions for SMEs from the Last Decade
by Sepideh Hassankhani Dolatabadi and Ivana Budinska
Machines 2021, 9(9), 191; https://doi.org/10.3390/machines9090191 - 07 Sep 2021
Cited by 14 | Viewed by 4701
Abstract
Today, small- and medium-sized enterprises (SMEs) play an important role in the economy of societies. Although environmental factors, such as COVID-19, as well as non-environmental factors, such as equipment failure, make these industries more vulnerable, they can be minimized by better understanding the [...] Read more.
Today, small- and medium-sized enterprises (SMEs) play an important role in the economy of societies. Although environmental factors, such as COVID-19, as well as non-environmental factors, such as equipment failure, make these industries more vulnerable, they can be minimized by better understanding the concerns and threats these industries face. Only a few SMEs have the capacity to implement the innovative manufacturing technologies of Industry 4.0. The system must be highly adaptable to any equipment, have low costs, avoid the need of doing complex integrations and setups, and have future reliability due to the rapid growth of technology. The goal of this study was to provide an overview of past articles (2010–2020), highlighting the major expectations, requirements, and challenges for SMEs regarding the implementation of predictive maintenance (PdM). The proposed solutions to meet these expectations, requirements, and challenges are discussed. In general, in this study, we attempted to overcome the challenges and limitations of using smart manufacturing—PdM, in particular—in small- and medium-sized enterprises by summarizing the solutions offered in different industries and with various conditions. Moreover, this literature review enables managers and stakeholders of organizations to find solutions from previous studies for a specific category, with consideration for their expectations and needs. This can be significantly helpful for small- and medium-sized organizations to save time due to time-consuming maintenance processes. Full article
(This article belongs to the Section Machines Testing and Maintenance)
►▼ Show Figures

Figure 1

20 pages, 8162 KiB  
Article
A Smart Tool Holder Calibrated by Machine Learning for Measuring Cutting Force in Fine Turning and Its Application to the Specific Cutting Force of Low Carbon Steel S15C
by Liang-Wei Tseng, Teng-Shan Hu and Yuh-Chung Hu
Machines 2021, 9(9), 190; https://doi.org/10.3390/machines9090190 - 06 Sep 2021
Cited by 3 | Viewed by 3909
Abstract
Real-time monitoring of the cutting force in the machining process is critical for improving machining accuracy, optimizing the machining process, and optimizing tool lifetime; however, the dynamometers are too expensive to be widely used by machine tool users. Therefore, this paper presents a [...] Read more.
Real-time monitoring of the cutting force in the machining process is critical for improving machining accuracy, optimizing the machining process, and optimizing tool lifetime; however, the dynamometers are too expensive to be widely used by machine tool users. Therefore, this paper presents a simple and cheap apparatus—a smart tool holder—to measure the cutting force of turning tools in the finishing turning. The apparatus does not change the structure of the turning tool. It consists of a tool holder and a piezoresistive force sensor foil, and transmits the signal through Bluetooth wireless communication. Instead of dealing with the circuit hardware, this paper uses the Artificial Neural Network (ANN) model to successfully calibrate the warm-up shift problem of the piezoresistive force sensor. Such a software method is simple, and considerably cheaper than the hardware method. For the force measurement capability of the smart tool holder, the cross-interference between orthogonal forces are very small and thus can be ignored. The force reading of the smart tool holder possesses high repeatability for the same turning parameters and high accuracy within the experiment groups. The authors apply the smart tool holder to cut the low carbon steel S15C, and to determine its specific cutting force in fine turning. The resulting fine turning force model agrees very well with the measurement. Its mean absolute deviation is 3.87% and its standard deviation is 1.55%, which reveals that the accuracy and precision of the smart tool holder and the fine turning force model are both good. Full article
(This article belongs to the Section Advanced Manufacturing)
►▼ Show Figures

Figure 1

24 pages, 10187 KiB  
Article
A Vibration Suppression Method for the Multistage Rotor of an Aero-Engine Based on Assembly Optimization
by Yue Chen, Jiwen Cui and Xun Sun
Machines 2021, 9(9), 189; https://doi.org/10.3390/machines9090189 - 05 Sep 2021
Cited by 5 | Viewed by 1765
Abstract
The assembly quality of the multistage rotor is an essential factor affecting its vibration level. The existing optimization methods for the assembly angles of the rotors at each stage can ensure the concentricity and unbalance meet the requirements, but it cannot directly ensure [...] Read more.
The assembly quality of the multistage rotor is an essential factor affecting its vibration level. The existing optimization methods for the assembly angles of the rotors at each stage can ensure the concentricity and unbalance meet the requirements, but it cannot directly ensure its vibration responses meet the indexes. Therefore, in this study, we first derived the excitation formulas of the geometric and mass eccentricities on the multistage rotor and introduced it into the dynamics model of the multistage rotor system. Then, the coordinate transfer model of the geometric and mass eccentricities errors, including assembly angles of the rotors at all stages, was established. Moreover, the mathematical relationship between the assembly angles of the rotors at all stages and the nodal vibration responses was established by combining the error transfer model with the dynamics model of the multistage rotor system. Furthermore, an optimization function was developed, which takes the assembly angles as the optimization variables and the maximum vibration velocity at the bearings as the optimization objective. Finally, a simplified four-stage high-pressure rotor system was assembled according to the optimal assembly angles calculated in the simulations. The experimental results showed that the maximum vibration velocity at the bearings under the optimal assembly was reduced by 69.6% and 45.5% compared with that under the worst assembly and default assembly. The assembly optimization method proposed in this study has a significant effect on the vibration suppression of the multistage rotor of an aero-engine. Full article
(This article belongs to the Section Machines Testing and Maintenance)
►▼ Show Figures

Figure 1

24 pages, 77464 KiB  
Article
Proximity Sensor for Thin Wire Recognition and Manipulation
by Andrea Cirillo, Gianluca Laudante and Salvatore Pirozzi
Machines 2021, 9(9), 188; https://doi.org/10.3390/machines9090188 - 03 Sep 2021
Cited by 3 | Viewed by 2977
Abstract
In robotic grasping and manipulation, the knowledge of a precise object pose represents a key issue. The point acquires even more importance when the objects and, then, the grasping areas become smaller. This is the case of Deformable Linear Object manipulation application where [...] Read more.
In robotic grasping and manipulation, the knowledge of a precise object pose represents a key issue. The point acquires even more importance when the objects and, then, the grasping areas become smaller. This is the case of Deformable Linear Object manipulation application where the robot shall autonomously work with thin wires which pose and shape estimation could become difficult given the limited object size and possible occlusion conditions. In such applications, a vision-based system could not be enough to obtain accurate pose and shape estimation. In this work the authors propose a Time-of-Flight pre-touch sensor, integrated with a previously designed tactile sensor, for an accurate estimation of thin wire pose and shape. The paper presents the design and the characterization of the proposed sensor. Moreover, a specific object scanning and shape detection algorithm is presented. Experimental results support the proposed methodology, showing good performance. Hardware design and software applications are freely accessible to the reader. Full article
(This article belongs to the Special Issue State-of-Art in Sensors for Robotic Applications)
►▼ Show Figures

Figure 1

18 pages, 5962 KiB  
Article
Research on the Multi-Robot Cooperative Pursuit Strategy Based on the Zero-Sum Game and Surrounding Points Adjustment
by Gang Chen, Wenqian Xu, Zixing Li, Yuqiang Liu and Xin Liu
Machines 2021, 9(9), 187; https://doi.org/10.3390/machines9090187 - 03 Sep 2021
Cited by 1 | Viewed by 2202
Abstract
Making full use of the cooperation of multi-robots can improve the success rate of apursuit task. Therefore, this paper proposes a multi-robot cooperative pursuit strategy based on the zero-sum game and surrounding points adjustment. First, a mathematical description of the multi-robot pursuit problem [...] Read more.
Making full use of the cooperation of multi-robots can improve the success rate of apursuit task. Therefore, this paper proposes a multi-robot cooperative pursuit strategy based on the zero-sum game and surrounding points adjustment. First, a mathematical description of the multi-robot pursuit problem is constructed, and the zero-sum game model is established considering the cooperation of the pursuit robots and the confrontation between the pursuit robots and the escape robot. By solving the game model, the optimal movement strategies of the pursuit robots and the escape robot are obtained. Then, the position adjustment method of the pursuit robots is studied based on the Hungarian algorithm, and the pursuit robots are controlled to surround the escape robot. Based on this, a multi-robot cooperative pursuit strategy is proposed that divides the pursuit process into two stages: pursuit robot position adjustment and game pursuit. Finally, the correctness and effectiveness of the multi-robot cooperative pursuit strategy are verified with simulation experiments. The multi-robot cooperative pursuit strategy allows the pursuit robots to capture the escape robot successfully without conflicts among the pursuit robots. It can be seen from the documented simulation experiments that the success rate of the pursuit task using the strategy proposed in this paper is 100%. Full article
(This article belongs to the Collection Machines, Mechanisms and Robots: Theory and Applications)
►▼ Show Figures

Figure 1

9 pages, 1853 KiB  
Communication
Highly Stretchable and Kirigami-Structured Strain Sensors with Long Silver Nanowires of High Aspect Ratio
by Huiyan Huang, Catherine Jiayi Cai, Bok Seng Yeow, Jianyong Ouyang and Hongliang Ren
Machines 2021, 9(9), 186; https://doi.org/10.3390/machines9090186 - 03 Sep 2021
Cited by 5 | Viewed by 2537
Abstract
Stretchable, skin-interfaced, and wearable strain sensors have risen in recent years due to their wide-ranging potential applications in health-monitoring devices, human motion detection, and soft robots. High aspect ratio (AR) silver nanowires (AgNWs) have shown great potential in the flexible and stretchable strain [...] Read more.
Stretchable, skin-interfaced, and wearable strain sensors have risen in recent years due to their wide-ranging potential applications in health-monitoring devices, human motion detection, and soft robots. High aspect ratio (AR) silver nanowires (AgNWs) have shown great potential in the flexible and stretchable strain sensors due to the high conductivity and flexibility of AgNW conductive networks. Hence, this work aims to fabricate highly stretchable, sensitive, and linear kirigami strain sensors with high AR AgNWs. The AgNW synthesis parameters and process windows have been identified by Taguchi’s design of experiment and analysis. Long AgNWs with a high AR of 1556 have been grown at optimized synthesis parameters using the one-pot modified polyol method. Kirigami sensors were fabricated via full encapsulation of AgNWs with Ecoflex silicon rubber. Kirigami-patterned strain sensors with long AgNWs show high stretchability, moderate sensitivity, excellent linearity (R2 = 0.99) up to 70% strain and can promptly detect finger movement without obvious hysteresis. Full article
(This article belongs to the Special Issue Smart Machines: Applications and Advances in Human Motion Analysis)
►▼ Show Figures

Figure 1

13 pages, 1582 KiB  
Article
Numerical and Experimental Investigation of Temperature Distribution for Dry-Clutches
by Fei Meng and Junqiang Xi
Machines 2021, 9(9), 185; https://doi.org/10.3390/machines9090185 - 03 Sep 2021
Cited by 8 | Viewed by 2389
Abstract
The temperature rise of the engaging clutch during shifting depends heavily on the transmitted torque. Precisely estimating the clutch temperature not only improves clutch control but also the optimal design of the clutch. However, the contact surface of the friction lining is closed, [...] Read more.
The temperature rise of the engaging clutch during shifting depends heavily on the transmitted torque. Precisely estimating the clutch temperature not only improves clutch control but also the optimal design of the clutch. However, the contact surface of the friction lining is closed, and the surface temperature is often difficult to measure accurately. In this study, a theoretical model of a two-dimensional transient temperature field for the friction disc has been established. In the radial and axial directions under different launching conditions, the temperature field of a friction disc is investigated. Four stages of clutch engagement have been determined, and finite-element analysis has been used to study the temperature field of a single clutch and to determine its duration.Then, the latest internationally developed distributed optical fiber sensing technology is used to perform measurement tests on the designed dry clutch friction characteristic test rig. The distributed fiber-optic temperature measurement technology can accomplish accurate temperature measurement with fast response speed and can acquire temperature value on different radii of friction discs with high spatial resolution. Such temperature sensing technology is very suitable for clutch working conditions. By analyzing the simulation and experimental results of temperature variation of different radii, different working conditions and different components, an important reference is provided for the establishment of the clutch temperature model and the optimization of the clutch heat dissipation structure design. Full article
(This article belongs to the Section Vehicle Engineering)
►▼ Show Figures

Figure 1

18 pages, 7880 KiB  
Article
The Thermal Error Estimation of the Machine Tool Spindle Based on Machine Learning
by Yu-Cheng Chiu, Po-Hsun Wang and Yuh-Chung Hu
Machines 2021, 9(9), 184; https://doi.org/10.3390/machines9090184 - 30 Aug 2021
Cited by 16 | Viewed by 2903
Abstract
Thermal error is one of the main sources of machining error of machine tools. Being a key component of the machine tool, the spindle will generate a lot of heat in the machining process and thereby result in a thermal error of itself. [...] Read more.
Thermal error is one of the main sources of machining error of machine tools. Being a key component of the machine tool, the spindle will generate a lot of heat in the machining process and thereby result in a thermal error of itself. Real-time measurement of thermal error will interrupt the machining process. Therefore, this paper presents a machine learning model to estimate the thermal error of the spindle from its feature temperature points. The authors adopt random forests and Gaussian process regression to model the thermal error of the spindle and Pearson correlation coefficients to select the feature temperature points. The result shows that random forests collocating with Pearson correlation coefficients is an efficient and accurate method for the thermal error modeling of the spindle. Its accuracy reaches to 90.49% based on only four feature temperature points—two points at the bearings and two points at the inner housing—and the spindle speed. If the accuracy requirement is not very onerous, one can select just the temperature points of the bearings, because the installation of temperature sensors at these positions is acceptable for the spindle or machine tool manufacture, while the other positions may interfere with the cooling pipeline of the spindle. Full article
(This article belongs to the Section Robotics, Mechatronics and Intelligent Machines)
►▼ Show Figures

Figure 1

17 pages, 8058 KiB  
Article
Kinematic Analysis of a Gear-Driven Rotary Planting Mechanism for a Six-Row Self-Propelled Onion Transplanter
by Md Nasim Reza, Md Nafiul Islam, Milon Chowdhury, Mohammod Ali, Sumaiya Islam, Shafik Kiraga, Seung-Jin Lim, Il-Su Choi and Sun-Ok Chung
Machines 2021, 9(9), 183; https://doi.org/10.3390/machines9090183 - 30 Aug 2021
Cited by 4 | Viewed by 2970
Abstract
The purpose of this study was to develop a kinematic model of a gear-driven rotary planting mechanism for a self-propelled onion transplanter. The kinematic model was simulated using a commercial mechanical design and a simulation software package, and was validated through an on-site [...] Read more.
The purpose of this study was to develop a kinematic model of a gear-driven rotary planting mechanism for a self-propelled onion transplanter. The kinematic model was simulated using a commercial mechanical design and a simulation software package, and was validated through an on-site performance test. Torque and acceleration sensors were installed with an input power shaft and hopper jaws, respectively. Through kinematic analysis and simulation, the appropriate length combinations for primary, connecting, and planting arm were determined as 90, 70, and 190 mm, respectively. The diameters of the driver, driven, and idler gears in the primary arm were 56, 48, and 28 mm, respectively. For the secondary link, the diameters of the driver, idler, and driven gears were 28, 28, and 56 mm, respectively. The length of the planting hopper was selected as 190 mm and remained constant during the kinematic analysis. The maximum magnitude of the velocity and acceleration of the planting mechanism were determined as 1032 mm/s and 6501 mm/s2, respectively. The power consumption was measured as 35.4 W at 60 rpm. The single- and double-unit assembly of the studied rotary planting mechanism can transplant 60 and 120 seedlings/min, respectively. Full article
(This article belongs to the Section Machine Design and Theory)
►▼ Show Figures

Figure 1

19 pages, 20281 KiB  
Article
An Improved Invariant Kalman Filter for Lie Groups Attitude Dynamics with Heavy-Tailed Process Noise
by Jiaolong Wang, Chengxi Zhang, Jin Wu and Ming Liu
Machines 2021, 9(9), 182; https://doi.org/10.3390/machines9090182 - 27 Aug 2021
Cited by 6 | Viewed by 2537
Abstract
Attitude estimation is a basic task for most spacecraft missions in aerospace engineering and many Kalman type attitude estimators have been applied to the guidance and navigation of spacecraft systems. By building the attitude dynamics on matrix Lie groups, the invariant Kalman filter [...] Read more.
Attitude estimation is a basic task for most spacecraft missions in aerospace engineering and many Kalman type attitude estimators have been applied to the guidance and navigation of spacecraft systems. By building the attitude dynamics on matrix Lie groups, the invariant Kalman filter (IKF) was developed according to the invariance properties of symmetry groups. However, the Gaussian noise assumption of Kalman theory may be violated when a spacecraft maneuvers severely and the process noise might be heavy-tailed, which is prone to degrade IKF’s performance for attitude estimation. To address the attitude estimation problem with heavy-tailed process noise, this paper proposes a hierarchical Gaussian state-space model for invariant Kalman filtering: The probability density function of state prediction is defined based on student’s t distribution, while the conjugate prior distributions of the scale matrix and degrees of freedom (dofs) parameter are respectively formulated as the inverse Wishart and Gamma distribution. For the constructed hierarchical Gaussian attitude estimation state-space model, the Lie groups rotation matrix of spacecraft attitude is inferred together with the scale matrix and dof parameter using the variational Bayesian iteration. Numerical simulation results illustrate that the proposed approach can significantly improve the filtering robustness of invariant Kalman filter for Lie groups spacecraft attitude estimation problems with heavy-tailed process uncertainty. Full article
(This article belongs to the Special Issue Modeling, Sensor Fusion and Control Techniques in Applied Robotics)
►▼ Show Figures

Figure 1

17 pages, 10667 KiB  
Article
RISE-Based Composite Adaptive Control of Electro-Hydrostatic Actuator with Asymptotic Stability
by Yaowen Ge, Xiaowei Yang, Wenxiang Deng and Jianyong Yao
Machines 2021, 9(9), 181; https://doi.org/10.3390/machines9090181 - 26 Aug 2021
Cited by 7 | Viewed by 2008
Abstract
The electro-hydrostatic actuator (EHA), the actuator of electric drive and hydraulic transmission, is competitive since it is small in size, light in weight and high in power density. However, the existence of the velocity loop error of servo motors, unmodeled dynamics and highly [...] Read more.
The electro-hydrostatic actuator (EHA), the actuator of electric drive and hydraulic transmission, is competitive since it is small in size, light in weight and high in power density. However, the existence of the velocity loop error of servo motors, unmodeled dynamics and highly nonlinear uncertainties restrict the improvement of the tracking accuracy of the EHA system. In order to achieve high-precision motion control of EHAs, a RISE-based composite adaptive control scheme is proposed in this paper. In the proposed composite adaptive control design, a novel parameter adaptive law is synthesized to compensate for the parametric uncertainties and a robust integral of the sign of error (RISE) feedback is utilized to suppress the adverse effects caused by the lumped disturbances, including the velocity loop error of a servo motor and other unmodeled dynamics. The synthesized parameter adaptive law possesses the advantage of fast convergence, which is beneficial to achieve transient tracking performance improvement. In addition, the proposed controller is more suitable for practical applications since it is chattering free. The closed-loop system stability analysis shows that the proposed control scheme guarantees an excellent asymptotic tracking performance. Finally, comparative simulations are conducted to verify the high-performance nature of the proposed controller. Full article
(This article belongs to the Special Issue Advanced Control of Industrial Electro-Hydraulic Systems)
►▼ Show Figures

Figure 1

15 pages, 5624 KiB  
Article
On-Machine Measurement and Error Compensation for 6061 Aluminum Alloy Hexagonal Punch Using a Turn-Milling Machine
by Cheng-Hsien Kuo and Po-Cheng Chen
Machines 2021, 9(9), 180; https://doi.org/10.3390/machines9090180 - 25 Aug 2021
Cited by 3 | Viewed by 2866
Abstract
For machining parts with complex shapes, consisting of computer numerical control (CNC) machine tools, different CNC machine tools will be used according to the machining method. If the workpiece is removed for off-machine measurement after machining, when the size is incorrect, it will [...] Read more.
For machining parts with complex shapes, consisting of computer numerical control (CNC) machine tools, different CNC machine tools will be used according to the machining method. If the workpiece is removed for off-machine measurement after machining, when the size is incorrect, it will need to be returned to the CNC machine tool for secondary machining. In this case, the workpiece surface quality and machining accuracy will be affected, which is very time-consuming. On-machine measurement and complex machine center is a key to solve this problem. In the recent researches that the touch probe was integrated on three or five axis machine for error compensation and shape construction based on on-machine measurement, but turning-milling machine was rare. In addition, the most types of parts were thin-walled parts or thin web parts. In this study, a contact measurement system is integrated into a CNC combined turning-milling machine for on-machine measuring. Macro-programming is used to design the machining path of A6061-T6 aluminum alloy hexagonal punch, and the action of probe measurement is added to the machining path. As the measured data exceed the tolerance range, the calculated data are fed back to the controller for machining improvement by compensation. The finished hexagonal punch is measured in a 3D coordinate measuring machine and the error is compared. The experimental results show that the contact probe needs to be corrected before machining, and the size of the corrected workpiece can reach the tolerance range of ±0.01 mm. The size error of rough machining is larger than that of fined machining, and the size error of rough machining will increase with the length of the workpiece. Full article
(This article belongs to the Special Issue Advances and Trends in Non-conventional, Abrasive and Precision Machining 2021)
►▼ Show Figures

Figure 1

Show export options expand_more Show export options expand_less
Select all
Export citation of selected articles as:
 
Displaying articles 1-25
Previous Issue
Next Issue
Back to TopTop