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Machines, Volume 9, Issue 6 (June 2021) – 21 articles

Cover Story (view full-size image): In a human–robot collaborative system, safety issues are the main pillars. Anti-collision control techniques are essential to improving operator safety and robot flexibility by preventing impacts that can occur between the robot and humans or objects found within the workspace. In this paper, a set of algorithms for dynamic collision avoidance are customized for the Universal Robots' collaborative manipulator class. Links of the robot are wrapped by adaptive cylindrical safety regions, whose radius varies according to the speed of the colliding obstacle. Three control laws are proposed, based on the type of motion admitted for the perturbation of the end-effector trajectory: the most general mode admits a 6-DOF perturbation, whereas reduced mobility modes allow for 4-DOF and 3-DOF perturbations. View this paper.
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Article
Dynamic Handling Characterization and Set-Up Optimization for a Formula SAE Race Car via Multi-Body Simulation
Machines 2021, 9(6), 126; https://doi.org/10.3390/machines9060126 - 21 Jun 2021
Viewed by 681
Abstract
There is a growing interest towards multi-body modelling and simulation that play a critical role in the development and testing of new mechanical systems, in general, and formula cars specifically to avoid expensive and time-consuming experimental track testing. Recent advances in computer-aided engineering [...] Read more.
There is a growing interest towards multi-body modelling and simulation that play a critical role in the development and testing of new mechanical systems, in general, and formula cars specifically to avoid expensive and time-consuming experimental track testing. Recent advances in computer-aided engineering packages, allows one not only to evaluate the basic properties that define the dynamic behavior of a newly-designed formula car, but as well as to investigate the impact on the performance of the many adjustable parameters that collectively are referred to as the car set-up. Therefore, by providing a rapid feedback of a given set-up expectation, optimal configurations can be obtained ensuring the highest level of performance. In this paper, a Formula SAE vehicle is expressly targeted. First, a full multi-body model of the prototype is described detailing the properties of each subassembly, e.g., suspensions and antiroll bars, steering system, and powertrain. Then, the basic handling characteristics are obtained via simulated track testing. Based on vehicle dynamics principles, the fine tuning of the vehicle setup is thoroughly discussed to gain the best performance in each of the contest events of the Formula SAE competition. For example, in the skidpad event where cars are required to drive along an eight-shaped track, an almost 2 km/h gain in the maximum travel velocity can be achieved by adjusting the camber angles of all tires. Full article
(This article belongs to the Special Issue Dynamic Analysis of Multibody Mechanical Systems)
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Review
A Review on Sliding Vane and Rolling Piston Compressors
Machines 2021, 9(6), 125; https://doi.org/10.3390/machines9060125 - 21 Jun 2021
Viewed by 359
Abstract
Rotary compressors have been employed in heating and cooling for more than a century and are ubiquitous in daily life but there has not been any comprehensive record of their development and technological advances. This review paper attempts to provide a comprehensive account [...] Read more.
Rotary compressors have been employed in heating and cooling for more than a century and are ubiquitous in daily life but there has not been any comprehensive record of their development and technological advances. This review paper attempts to provide a comprehensive account of the advances in R&D and design evolution of these rotary compressors since their inception, namely the sliding vane compressor, rolling piston compressor, and their design variants in open literature. This is to showcase the current state-of-the-art for these compressors so that researchers can use it as a basis for future work. Based on authors’ insight, inter-disciplinary research combined with advancements in ‘disruptive’ technology such as artificial intelligence and advancements in additive manufacturing might be a promising research direction to bring about improvements in rotary compressor performance to meet mankind’s growing needs for cooling and heating applications. Full article
(This article belongs to the Section Machine Design and Theory)
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Article
Selection of Optimal Magnets for Traction Motors to Prevent Demagnetization
Machines 2021, 9(6), 124; https://doi.org/10.3390/machines9060124 - 20 Jun 2021
Viewed by 415
Abstract
Currently, permanent-magnet-type traction motors drive most electric vehicles. However, the potential demagnetization of magnets in these motors limits the performance of an electric vehicle. It is well known that during severe duty, the magnets are demagnetized if they operate beyond a ‘knee point’ [...] Read more.
Currently, permanent-magnet-type traction motors drive most electric vehicles. However, the potential demagnetization of magnets in these motors limits the performance of an electric vehicle. It is well known that during severe duty, the magnets are demagnetized if they operate beyond a ‘knee point’ in the B(H) curve. We show herein that the classic knee point definition can degrade a magnet by up to 4 grades. To prevent consequent excessive loss in performance, this paper defines the knee point k as the point of intersection of the B(H) curve and a parallel line that limits the reduction in its residual flux density to 1%. We show that operating above such a knee point will not be demagnetizing the magnets. It will also prevent a magnet from degenerating to a lower grade. The flux density at such a knee point, termed demag flux density, characterizes the onset of demagnetization. It rightly reflects the value of a magnet, so can be used as a basis to price the magnets. Including such knee points in the purchase specifications also helps avoid the penalty of getting the performance of a low-grade magnet out of a high-grade magnet. It also facilitates an accurate demagnetization analysis of traction motors in the worst-case conditions. Full article
(This article belongs to the Section Vehicle Engineering)
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Article
Frequency Measurement Method of Signals with Low Signal-to-Noise-Ratio Using Cross-Correlation
Machines 2021, 9(6), 123; https://doi.org/10.3390/machines9060123 - 18 Jun 2021
Viewed by 362
Abstract
Precise frequency measurement plays an essential role in many industrial and robotic systems. However, different effects in the application’s environment cause signal noises, which make frequency measurement more difficult. In small signals or rough environments, even negative Signal-to-Noise Ratios (SNRs) are possible. Thus, [...] Read more.
Precise frequency measurement plays an essential role in many industrial and robotic systems. However, different effects in the application’s environment cause signal noises, which make frequency measurement more difficult. In small signals or rough environments, even negative Signal-to-Noise Ratios (SNRs) are possible. Thus, frequency measuring methods, which are suited for low SNR signals, are in great demand. While denoising methods such as autocorrelation do not suffice for small signal with low SNR, frequency measurement methods such as Fast-Fourier Transformation or Continuous Wavelet Transformation suffer from Heisenberg’s uncertainty principle, which makes simultaneous high frequency and time resolutions impossible. In this paper, the cross-correlation spectrum is presented as a new frequency measuring method. It can be used in any frequency domain, and provides greater denoising than autocorrelation. Furthermore, frequency and time resolutions are independent from one another, and can be set separately by the user. In simulations, it achieves an average deviation of less than 0.1% on sinusoidal signals with a SNR of −10 dB and a signal length of 1000 data points. When applied to “self-mixing”-interferometry signals, the method can reach a normalized root-mean square error of 0.2% with the aid of an estimation method and an averaging algorithm. Therefore, further research of the method is recommended. Full article
(This article belongs to the Special Issue State-of-Art in Sensors for Robotic Applications)
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Article
Numerical and Experimental Investigation of the Temperature Rise of Cutting Tools Caused by the Tool Deflection Energy
Machines 2021, 9(6), 122; https://doi.org/10.3390/machines9060122 - 18 Jun 2021
Viewed by 354
Abstract
Tool temperature variation in flank milling usually causes excessive tool wear, shortens tool life, and reduces machining accuracy. The heat source is the primary factor of the machine thermal error in the process of cutting components. Moreover, the accuracy of the thermal error [...] Read more.
Tool temperature variation in flank milling usually causes excessive tool wear, shortens tool life, and reduces machining accuracy. The heat source is the primary factor of the machine thermal error in the process of cutting components. Moreover, the accuracy of the thermal error modeling is greatly influenced by the formation mechanism of the heat source. However, the tool heat caused by the potential energy of the tool bending and twisting has essentially not been taken into consideration in previous research. In this paper, a new heat source that causes the thermal error of the cutting tools is proposed. The potential energy of the tools’ bending and twisting is calculated using experimental data, and how tool potential energy is transformed into heat via friction is explored based on the energy conservation. The temperature rise of the cutting tool is simulated by a lattice-centered finite volume method. To verify the model, the temperature separation of a tool edge is measured experimentally under the given cutting load. The results of the numerical analysis show that the rise in tool temperature caused by the tool’s potential energy is related to the time and position of the cutting edge involved in milling. For the same conditions, the predicted results are consistent with the experimental results. The proportion of temperature rise due to tool potential energy is up to 6.57% of the total tool temperature rise. The results obtained lay the foundation for accurate thermal error modeling, and also provide a theoretical basis for the force–thermal coupling process. Full article
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Article
Motion Planning and Control of Redundant Manipulators for Dynamical Obstacle Avoidance
Machines 2021, 9(6), 121; https://doi.org/10.3390/machines9060121 - 18 Jun 2021
Viewed by 444
Abstract
This paper presents a framework for the motion planning and control of redundant manipulators with the added task of collision avoidance. The algorithms that were previously studied and tested by the authors for planar cases are here extended to full mobility redundant manipulators [...] Read more.
This paper presents a framework for the motion planning and control of redundant manipulators with the added task of collision avoidance. The algorithms that were previously studied and tested by the authors for planar cases are here extended to full mobility redundant manipulators operating in a three-dimensional workspace. The control strategy consists of a combination of off-line path planning algorithms with on-line motion control. The path planning algorithm is used to generate trajectories able to avoid fixed obstacles detected before the robot starts to move; this is based on the potential fields method combined with a smoothing interpolation that exploits Bézier curves. The on-line motion control is designed to compensate for the motion of the obstacles and to avoid collisions along the kinematic chain of the manipulator; this is realized using a velocity control law based on the null space method for redundancy control. Furthermore, an additional term of the control law is introduced which takes into account the speed of the obstacles, as well as their position. In order to test the algorithms, a set of simulations are presented: the redundant collaborative robot KUKA LBR iiwa is controlled in different cases, where fixed or dynamic obstacles interfere with its motion. The simulated data show that the proposed method for the smoothing of the trajectory can give a reduction of the angular accelerations of the motors of the order of 90%, with an increase of less than 15% of the calculation time. Furthermore, the dependence of the on-line control law on the speed of the obstacle can lead to reductions in the maximum speed and acceleration of the joints of approximately 50% and 80%, respectively, without significantly increasing the computational effort that is compatible for transferability to a real system. Full article
(This article belongs to the Special Issue Advances of Japanese Machine Design)
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Article
Determination of Heat Transfer Coefficient from Housing Surface of a Totally Enclosed Fan-Cooled Machine during Passive Cooling
Machines 2021, 9(6), 120; https://doi.org/10.3390/machines9060120 - 18 Jun 2021
Viewed by 533
Abstract
This paper presents the analytical calculation of the heat transfer coefficient of a complex housing shape of a Totally Enclosed Fan-Cooled (TEFC) industrial machine when it works below 20% of its nominal speed or close to stall. Therefore, passive cooling is dominant, and [...] Read more.
This paper presents the analytical calculation of the heat transfer coefficient of a complex housing shape of a Totally Enclosed Fan-Cooled (TEFC) industrial machine when it works below 20% of its nominal speed or close to stall. Therefore, passive cooling is dominant, and most of the heat is extracted by the combination of natural convection and radiation phenomena. Under these conditions, the area-based composite approach was used for the development of the analytical calculation method. A test rig using a TEFC Synchronous Reluctance Motor (SynRM) was constructed, and the collected experimental data was used to validate the proposed analytical method successfully. Full article
(This article belongs to the Special Issue Thermal Analysis of Electric Machine Drives)
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Article
Robot Grasping System and Grasp Stability Prediction Based on Flexible Tactile Sensor Array
Machines 2021, 9(6), 119; https://doi.org/10.3390/machines9060119 - 17 Jun 2021
Viewed by 467
Abstract
As an essential perceptual device, the tactile sensor can efficiently improve robot intelligence by providing contact force perception to develop algorithms based on contact force feedback. However, current tactile grasping technology lacks high-performance sensors and high-precision grasping prediction models, which limits its broad [...] Read more.
As an essential perceptual device, the tactile sensor can efficiently improve robot intelligence by providing contact force perception to develop algorithms based on contact force feedback. However, current tactile grasping technology lacks high-performance sensors and high-precision grasping prediction models, which limits its broad application. Herein, an intelligent robot grasping system that combines a highly sensitive tactile sensor array was constructed. A dataset that can reflect the grasping contact force of various objects was set up by multiple grasping operation feedback from a tactile sensor array. The stability state of each grasping operation was also recorded. On this basis, grasp stability prediction models with good performance in grasp state judgment were proposed. By feeding training data into different machine learning algorithms and comparing the judgment results, the best grasp prediction model for different scenes can be obtained. The model was validated to be efficient, and the judgment accuracy was over 98% in grasp stability prediction with limited training data. Further, experiments prove that the real-time contact force input based on the feedback of the tactile sensor array can periodically control robots to realize stable grasping according to the real-time grasping state of the prediction model. Full article
(This article belongs to the Section Mechatronic and Intelligent Machines)
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Article
Simulation of the Circulating Motion of the Working Medium and Metal Removal during Multi-Energy Processing under the Action of Vibration and Centrifugal Forces
Machines 2021, 9(6), 118; https://doi.org/10.3390/machines9060118 - 17 Jun 2021
Viewed by 354
Abstract
The rotational motion of the medium granules under the influence of an impeller installed in the bottom of a cylindrical reservoir is considered. The dependencies of the circulation velocity of the abrasive granules, as well as the dependence of the pressure in the [...] Read more.
The rotational motion of the medium granules under the influence of an impeller installed in the bottom of a cylindrical reservoir is considered. The dependencies of the circulation velocity of the abrasive granules, as well as the dependence of the pressure in the circulation flow of the granules on the radius of the vibrating machine cylindrical reservoir for different speeds of the impeller rotation are obtained. Furthermore, the velocities of the abrasive granules at various distances from the center of the cylindrical reservoir of the vibrating machine have been determined. The amplitudes of the tangential and radial components of the velocity of movement of pseudo-gas from abrasive granules are obtained. The total pressure on the surface of the processed part and the average velocity of the abrasive granules colliding with it are determined. The graphical dependencies of the integral metal removal on the amplitude and frequency of oscillations of the walls of the vibrating machine reservoir are given for various values of the angular velocities of the impeller rotation. Full article
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Article
Dimensional (Parametric) Synthesis of the Hexapod-Type Parallel Mechanism with Reconfigurable Design
Machines 2021, 9(6), 117; https://doi.org/10.3390/machines9060117 - 12 Jun 2021
Viewed by 577
Abstract
The study provides a solution to a dimensional synthesis problem for a hexapod-type reconfigurable parallel mechanism, which can change its configuration to realize different trajectories of its output link while having a single drive. The work presents an original procedure to find the [...] Read more.
The study provides a solution to a dimensional synthesis problem for a hexapod-type reconfigurable parallel mechanism, which can change its configuration to realize different trajectories of its output link while having a single drive. The work presents an original procedure to find the dimensions of some mechanism’s links and their initial configuration to reproduce these trajectories. After describing the mechanism, the paper examines kinematic relations representing the basis for the subsequent synthesis algorithm. Next, the obtained expressions are extended and provide a system of equations to be solved. The structure of this equation system allows it to be solved effectively by numerical methods, which is demonstrated with an example. The proposed algorithm of dimensional synthesis does not require solving the optimization problems, in contrast to the familiar methods of dimensional synthesis of parallel mechanisms. Further, the suggested approach to the synthesis problem allows finding solution in a fast and computationally efficient manner. Full article
(This article belongs to the Special Issue Robotic Machine Tools)
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Article
Optimizing the Formation of Hydraulic Cylinder Surfaces, Taking into Account Their Microrelief Topography Analyzed during Different Operations
Machines 2021, 9(6), 116; https://doi.org/10.3390/machines9060116 - 10 Jun 2021
Viewed by 401
Abstract
Causes of the in-service damage to hydrocylinder liners were investigated, and the requirements to their working surfaces were systematized. Roughness parameter Ra was found not to provide a precise estimate of the surface quality because its reduction did not affect surface microgeometry. Additionally, [...] Read more.
Causes of the in-service damage to hydrocylinder liners were investigated, and the requirements to their working surfaces were systematized. Roughness parameter Ra was found not to provide a precise estimate of the surface quality because its reduction did not affect surface microgeometry. Additionally, the surface quality was assessed by the Abbott-Firestone curve during the finishing operation. The optimized manufacturing technology for obtaining hydrocylinder liners was offered based on having the required microgeometry and surface quality provided by cutting operations. The quality and service characteristics of internal surfaces of hydrocylinder liners were improved by changing technological operations. In particular, the semi-finish turning was chosen to provide for the surface roughness parameter Ra within 6.3–8.0 μm and the roughness pitch parameter S within 0.4–0.6 mm and homogeneous surface structure. The finishing rolling was replaced by burnishing to form a regular microrelief. Full article
(This article belongs to the Section Advanced Manufacturing)
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Article
Analysis of the Vibration Suppression of Double-Beam System via Nonlinear Switching Piezoelectric Network
Machines 2021, 9(6), 115; https://doi.org/10.3390/machines9060115 - 08 Jun 2021
Viewed by 465
Abstract
In this paper, a method to suppress the vibration of a double-beam system with nonlinear synchronized switch damping on the inductor via a network (SSDI-net) is proposed. Unlike the classical linear piezoelectric shunt damping, SSDI-net is a nonlinear piezoelectric damping. A double-beam system [...] Read more.
In this paper, a method to suppress the vibration of a double-beam system with nonlinear synchronized switch damping on the inductor via a network (SSDI-net) is proposed. Unlike the classical linear piezoelectric shunt damping, SSDI-net is a nonlinear piezoelectric damping. A double-beam system with SSDI-net was simplified to a lumped parameter electromechanical coupling model and analyzed by using the multi-harmonic balance method, at first with alternating frequency–time techniques (MHBM/AFT). Then, a new lower-power autonomous switching control circuit board was designed, based on SSD technique, and vibration control experiments using a double-beam system with an SSDI network are conducted, to verify the validity of the proposed analysis method and its calculation results. The nonlinear switching piezoelectric network proposed in this article can increase the voltage inversion factor. Furthermore, future applications of this switching piezoelectric network technology in the vibration suppression of bladed-disk structures in aero engines can reduce the number of switches by at least half and obtain almost the same damping effect. Full article
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Article
A Comparative Study on the Condensation Heat Transfer of R-513A as an Alternative to R-134a
Machines 2021, 9(6), 114; https://doi.org/10.3390/machines9060114 - 06 Jun 2021
Viewed by 556
Abstract
This paper presents the two-phase condensation heat transfer and pressure drop characteristics of R-513A as an alternative refrigerant to R-134a in a 9.52-mm OD horizontal microfin copper tube. The test facility had a straight, horizontal test section with an active length of 2.0 [...] Read more.
This paper presents the two-phase condensation heat transfer and pressure drop characteristics of R-513A as an alternative refrigerant to R-134a in a 9.52-mm OD horizontal microfin copper tube. The test facility had a straight, horizontal test section with an active length of 2.0 m and was cooled by cold water circulated in a surrounding annular space. The annular-side heat transfer coefficients were obtained using the Wilson plot method. The average heat transfer coefficient and pressure drop data are presented at the condensation temperature of 35 °C in the range of 100–440 kg·m−2·s−1 mass flux. The test data of R-513A are compared with those of R-134a, R-1234yf, and R-1234ze(E). The average condensation heat transfer coefficients of the R-513A and R-1234ze(E) refrigerants were similar to R-134a at the lower mass flux (100~150 kg·m−2·s−1), while they were up to 10% higher than R-134a as the mass flux increased. The pressure drop of R-513A was similar to R-1234yf and 10% lower than that of R-134a at the higher mass flux. The R-1234ze(E) pressure drops were 20 % higher compared to those of R-134a at the higher mass flux. Full article
(This article belongs to the Section Energy and Power Engineering)
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Article
Adaptive Obstacle Avoidance for a Class of Collaborative Robots
Machines 2021, 9(6), 113; https://doi.org/10.3390/machines9060113 - 03 Jun 2021
Viewed by 672
Abstract
In a human–robot collaboration scenario, operator safety is the main problem and must be guaranteed under all conditions. Collision avoidance control techniques are essential to improve operator safety and robot flexibility by preventing impacts that can occur between the robot and humans or [...] Read more.
In a human–robot collaboration scenario, operator safety is the main problem and must be guaranteed under all conditions. Collision avoidance control techniques are essential to improve operator safety and robot flexibility by preventing impacts that can occur between the robot and humans or with objects inadvertently left within the operational workspace. On this basis, collision avoidance algorithms for moving obstacles are presented in this paper: inspired by algorithms already developed by the authors for planar manipulators, algorithms are adapted for the 6-DOF collaborative manipulators by Universal Robots, and some new contributions are introduced. First, in this work, the safety region wrapping each link of the manipulator assumes a cylindrical shape whose radius varies according to the speed of the colliding obstacle, so that dynamical obstacles are avoided with increased safety regions in order to reduce the risk, whereas fixed obstacles allow us to use smaller safety regions, facilitating the motion of the robot. In addition, three different modalities for the collision avoidance control law are proposed, which differ in the type of motion admitted for the perturbation of the end-effector: the general mode allows for a 6-DOF perturbation, but restrictions can be imposed on the orientation part of the avoidance motion using 4-DOF or 3-DOF modes. In order to demonstrate the effectiveness of the control strategy, simulations with dynamic and fixed obstacles are presented and discussed. Simulations are also used to estimate the required computational effort in order to verify the transferability to a real system. Full article
(This article belongs to the Special Issue Collaborative Robotics and Adaptive Machines)
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Communication
A Product Pose Tracking Paradigm Based on Deep Points Detection
Machines 2021, 9(6), 112; https://doi.org/10.3390/machines9060112 - 28 May 2021
Viewed by 627
Abstract
The paper at hand presents a novel and versatile method for tracking the pose of varying products during their manufacturing procedure. By using modern Deep Neural Network techniques based on Attention models, the most representative points to track an object can be automatically [...] Read more.
The paper at hand presents a novel and versatile method for tracking the pose of varying products during their manufacturing procedure. By using modern Deep Neural Network techniques based on Attention models, the most representative points to track an object can be automatically identified using its drawing. Then, during manufacturing, the body of the product is processed with Aluminum Oxide on those points, which is unobtrusive in the visible spectrum, but easily distinguishable from infrared cameras. Our proposal allows for the inclusion of Artificial Intelligence in Computer-Aided Manufacturing to assist the autonomous control of robotic handlers. Full article
(This article belongs to the Special Issue Intelligent Mechatronics Systems)
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Article
An Offset Laser Measurement Method for the Deviation Analysis of Cylindrical Gears
Machines 2021, 9(6), 111; https://doi.org/10.3390/machines9060111 - 28 May 2021
Viewed by 716
Abstract
Generally, in the laser measurement of gears, the laser beam passes through the center of the gear, and the laser displacement sensor reads the spatial distance from the gear involute tooth surface to the laser displacement sensor. However, in this method, the angle [...] Read more.
Generally, in the laser measurement of gears, the laser beam passes through the center of the gear, and the laser displacement sensor reads the spatial distance from the gear involute tooth surface to the laser displacement sensor. However, in this method, the angle between the laser beam and the normal vector of the measured tooth surface is too large, which affects the accuracy of the measurement and the stability of the data. This paper proposes an offset laser measurement method. The laser beam is offset from the center of the gear by a certain distance to form a larger incident angle with the tooth surface, which can effectively address the problem and increase the measurement accuracy. Through a selection of the optimal offset distance, the range of optimal offset measurement positions was obtained and clarified by experiments. We solved the data conversion problem caused by the change in measuring position, and we measured the pitch deviation and helix angle of the gear to confirm the feasibility of this method. According to the theoretical calculation and experimental verification, it was found that this method has the advantages of better measurement accuracy and less fluctuation in measurement data. It is, thus, suitable for precision gear measurement. Full article
(This article belongs to the Special Issue Precision Measurement and Machines)
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Article
Mechanical Design and Analysis of the End-Effector Finger Rehabilitation Robot (EFRR) for Stroke Patients
Machines 2021, 9(6), 110; https://doi.org/10.3390/machines9060110 - 26 May 2021
Viewed by 892
Abstract
Most existing finger rehabilitation robots are structurally complex and cannot be adapted to multiple work conditions, such as clinical and home. In addition, there is a lack of attention to active adduction/abduction (A/A) movement, which prevents stroke patients from opening the joint in [...] Read more.
Most existing finger rehabilitation robots are structurally complex and cannot be adapted to multiple work conditions, such as clinical and home. In addition, there is a lack of attention to active adduction/abduction (A/A) movement, which prevents stroke patients from opening the joint in time and affects the rehabilitation process. In this paper, an end-effector finger rehabilitation robot (EFRR) with active A/A motion that can be applied to a variety of applications is proposed. First, the natural movement curve of the finger is analyzed, which is the basis of the mechanism design. Based on the working principle of the cam mechanism, the flexion/extension (F/E) movement module is designed and the details used to ensure the safety and reliability of the device are introduced. Then, a novel A/A movement module is proposed, using the components that can easily individualized design to achieve active A/A motion only by one single motor, which makes up for the shortcomings of the existing devices. As for the control system, a fuzzy proportional-derivative (PD) adaptive impedance control strategy based on the position information is proposed, which can make the device more compliant, avoid secondary injuries caused by excessive muscle tension, and protect the fingers effectively. Finally, some preliminary experiments of the prototype are reported, and the results shows that the EFRR has good performance, which lays the foundation for future work. Full article
(This article belongs to the Special Issue Design and Control of Advanced Mechatronics Systems)
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Article
System Identification and Controller Design of a Novel Autonomous Underwater Vehicle
Machines 2021, 9(6), 109; https://doi.org/10.3390/machines9060109 - 26 May 2021
Cited by 1 | Viewed by 451
Abstract
Autonomous underwater vehicle is an effective tool for humans to explore the ocean. It can be used for the monitoring of underwater structures and facilities, which puts forward more accurate and stable requirements for the system operation of the autonomous underwater vehicle. This [...] Read more.
Autonomous underwater vehicle is an effective tool for humans to explore the ocean. It can be used for the monitoring of underwater structures and facilities, which puts forward more accurate and stable requirements for the system operation of the autonomous underwater vehicle. This paper studies the system and structural design, including the parameter identification design and control system design, of a novel autonomous underwater vehicle called “Arctic AUV”. The dynamic mathematical model of the “Arctic AUV” was established, and the system parameter identification method based on the multi-sensor least squares centralized fusion algorithm was proposed. The simplification of the mathematical model of the robot was theoretically derived, and the online parameter identification and motion control were combined, so that the robot could cope with the influence of the arctic water velocity and external turbulence. Based on the hybrid control scheme of adaptive PID and predictive control, the accurate motion control of the “Arctic AUV” was realized. A prototype of “Arctic AUV” was developed, and system parameter identification experiments were carried out in indoor pool water. Hybrid adaptive and predictive control experiments were also carried out. The validity of the parametric design method in this paper was verified, and by comparative experiment, the effect of the control method proposed in this paper was better than the traditional method. Full article
(This article belongs to the Section Automation Systems)
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Article
Dual Resource Constrained Flexible Job Shop Scheduling Based on Improved Quantum Genetic Algorithm
Machines 2021, 9(6), 108; https://doi.org/10.3390/machines9060108 - 24 May 2021
Viewed by 593
Abstract
Aiming at solving the problem of dual resource constrained flexible job shop scheduling problem (DRCFJSP) with differences in operating time between operators, an artificial intelligence (AI)-based DRCFJSP optimization model is developed in this paper. This model introduces the differences between the loading and [...] Read more.
Aiming at solving the problem of dual resource constrained flexible job shop scheduling problem (DRCFJSP) with differences in operating time between operators, an artificial intelligence (AI)-based DRCFJSP optimization model is developed in this paper. This model introduces the differences between the loading and unloading operation time of workers before and after the process. Subsequently, the quantum genetic algorithm (QGA) is used as the carrier; the process is coded through quantum coding; and the niche technology is used to initialize the population, adaptive rotation angle, and quantum mutation strategy to improve the efficiency of the QGA and avoid premature convergence. Lastly, through the Kacem standard calculation example and the reliability analysis of the factory workshop processing process example, performance evaluation is conducted to show that the improved QGA has good convergence and does not fall into premature ability, the improved QGA can solve the problem of reasonable deployment of machines and personnel in the workshop, and the proposed method is more effective for the DRCFJSP than some existing methods. The findings can provide a good theoretical basis for actual production and application. Full article
(This article belongs to the Section Machines Testing and Maintenance)
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Article
Multi-Objective Lightweight Optimization of Parameterized Suspension Components Based on NSGA-II Algorithm Coupling with Surrogate Model
Machines 2021, 9(6), 107; https://doi.org/10.3390/machines9060107 - 24 May 2021
Cited by 1 | Viewed by 511
Abstract
In order to reduce the negative effect of lightweighting of suspension components on vehicle dynamic performance, the control arm and torsion beam widely used in front and rear suspensions were taken as research objects for studying the lightweight design method of suspension components. [...] Read more.
In order to reduce the negative effect of lightweighting of suspension components on vehicle dynamic performance, the control arm and torsion beam widely used in front and rear suspensions were taken as research objects for studying the lightweight design method of suspension components. Mesh morphing technology was employed to define design variables. Meanwhile, the rigid–flexible coupling vehicle model with flexible control arm and torsion beam was built for vehicle dynamic simulations. The total weight of control arm and torsion beam was taken as optimization objective, as well as ride comfort and handling stability performance indexes. In addition, the fatigue life, stiffness, and modal frequency of control arm and torsion beam were taken as the constraints. Then, Kriging model and NSGA-II were adopted to perform the multi-objective optimization of control arm and torsion beam for determining the lightweight scheme. By comparing the optimized and original design, it indicates that the weight of the optimized control arm and torsion beam are reduced 0.505 kg and 1.189 kg, respectively, while structural performance and vehicle performance satisfy the design requirement. The proposed multi-objective optimization method achieves a remarkable mass reduction, and proves to be feasible and effective for lightweight design of suspension components. Full article
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Article
An Optimal Choice of Profile Shift Coefficients for Spur Gears
Machines 2021, 9(6), 106; https://doi.org/10.3390/machines9060106 - 22 May 2021
Viewed by 700
Abstract
Methods used earlier for choosing profile shift coefficients were based on presumed advantages without physical proof justifying them. In this paper, a new method is proposed which guarantees a positive influence on gear failures and the operational conditions of gear pairs. The author [...] Read more.
Methods used earlier for choosing profile shift coefficients were based on presumed advantages without physical proof justifying them. In this paper, a new method is proposed which guarantees a positive influence on gear failures and the operational conditions of gear pairs. The author proposes the introduction of a new concept: the cumulative effectiveness of profile shift coefficients. Full article
(This article belongs to the Section Machine Design and Theory)
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