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Actuators, Volume 10, Issue 7 (July 2021) – 32 articles

Cover Story (view full-size image): Recently, there has been growing interest in high-rate actuators for single-shot applications, such as release/deployment mechanisms and high-strain-rate mechanical testing of materials, as well as high-frequency and energy-efficient actuation in micro-scale systems. Shape memory alloy (SMA) actuators are prime candidates for such applications due to their unique high work-per-volume yield. High-rate actuation of SMA can provide improved energy efficiency, as well as shorter response and total actuation times. The present review targets the different aspects of the high-rate actuation of SMA wires to enable actuator design based on specific user requirements. The paper provides general design guidelines for obtaining high actuator performance, as well as a detailed model and simulations of actuator response that can serve as accurate design tools. View this paper.
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15 pages, 4016 KiB  
Communication
Parameter Identification of the Nonlinear Piezoelectric Shear d15 Coefficient of a Smart Composite Actuator
by Pelin Berik and Peter L. Bishay
Actuators 2021, 10(7), 168; https://doi.org/10.3390/act10070168 - 19 Jul 2021
Viewed by 2146
Abstract
The objective of this work is to characterize the nonlinear dependence of the piezoelectric d15 shear coefficient of a composite actuator on the static electric field and include this effect in finite element (FE) simulations. The Levenberg-Marquardt nonlinear least squares optimization algorithm [...] Read more.
The objective of this work is to characterize the nonlinear dependence of the piezoelectric d15 shear coefficient of a composite actuator on the static electric field and include this effect in finite element (FE) simulations. The Levenberg-Marquardt nonlinear least squares optimization algorithm implemented in MATLAB was applied to acquire the piezoelectric shear coefficient parameters. The nonlinear piezoelectric d15 shear constant of the composite actuator integrated with piezoceramic d15 patches was obtained to be 732 pC/N at 198 V. The experimental benchmark was simulated using a three-dimensional piezoelectric FE model by taking piezoelectric nonlinearity into consideration. The results revealed that the piezoelectric shear d15 coefficient increased nonlinearly under static applied electric fields over 0.5 kV/cm. A comparison between the generated transverse deflections of the linear and nonlinear FE models was also performed. Full article
(This article belongs to the Special Issue Ferroelectric Materials and Piezoelectric Actuators)
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23 pages, 5123 KiB  
Article
Development of a Bionic Dolphin Flexible Tail Experimental Device Driven by a Steering Gear
by Bo Zhang, Qingxiang Li, Tao Wang and Zhuo Wang
Actuators 2021, 10(7), 167; https://doi.org/10.3390/act10070167 - 19 Jul 2021
Cited by 2 | Viewed by 2615
Abstract
In order to study the mechanism of the tail swing of the bionic dolphin, a flexible tail experimental device based on a steering engine was developed. This study was focused on the common three joint steering gear and its use in a bionic [...] Read more.
In order to study the mechanism of the tail swing of the bionic dolphin, a flexible tail experimental device based on a steering engine was developed. This study was focused on the common three joint steering gear and its use in a bionic dolphin tail swing mechanism, and it was found that the bionic dolphin driven by the steering gear had the problem of excessive stiffness. In order to solve this problem, we designed a bionic dolphin tail swing mechanism. The tail swing mechanism was designed rationally through the combination of a steering gear drive and two flexible spines. Analysis of kinematic and dynamic modeling was further completed. Through simulation using, the research on the bionic dolphin tail swing mechanism was verified. Experiments showed that the swing curve formed by the steering gear-driven bionic dolphin tail swing mechanism with two flexible spines fit the real fish body wave curve better than the original bionic dolphin tail swing mechanism. Full article
(This article belongs to the Topic Motion Planning and Control for Robotics)
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26 pages, 62480 KiB  
Review
Soft Exoskeletons: Development, Requirements, and Challenges of the Last Decade
by Alan Francisco Pérez Vidal, Jesse Yoe Rumbo Morales, Gerardo Ortiz Torres, Felipe de Jesús Sorcia Vázquez, Alan Cruz Rojas, Jorge Aurelio Brizuela Mendoza and Julio César Rodríguez Cerda
Actuators 2021, 10(7), 166; https://doi.org/10.3390/act10070166 - 19 Jul 2021
Cited by 41 | Viewed by 9179
Abstract
In this article, various investigations on soft exoskeletons are presented and their functional and structural characteristics are analyzed. The present work is oriented to the studies of the last decade and covers the upper and lower joints, specifically the shoulder, elbow, wrist, hand, [...] Read more.
In this article, various investigations on soft exoskeletons are presented and their functional and structural characteristics are analyzed. The present work is oriented to the studies of the last decade and covers the upper and lower joints, specifically the shoulder, elbow, wrist, hand, hip, knee, and ankle. Its functionality, applicability, and main characteristics are exposed, such as degrees of freedom, force, actuators, power transmission methods, control systems, and sensors. The purpose of this work is to show the current trend in the development of soft exoskeletons, in addition to specifying the essential characteristics that must be considered in its design and the challenges that its construction implies. Full article
(This article belongs to the Special Issue Actuators on Soft Exoskeletons)
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17 pages, 6267 KiB  
Article
Performance Assessment of an Electric Power Steering System for Driverless Formula Student Vehicles
by Raffaele Manca, Salvatore Circosta, Irfan Khan, Stefano Feraco, Sara Luciani, Nicola Amati, Angelo Bonfitto and Renato Galluzzi
Actuators 2021, 10(7), 165; https://doi.org/10.3390/act10070165 - 18 Jul 2021
Cited by 8 | Viewed by 7503
Abstract
In the context of automated driving, Electric Power Steering (EPS) systems represent an enabling technology. They introduce the ergonomic function of reducing the physical effort required by the driver during the steering maneuver. Furthermore, EPS gives the possibility of high precision control of [...] Read more.
In the context of automated driving, Electric Power Steering (EPS) systems represent an enabling technology. They introduce the ergonomic function of reducing the physical effort required by the driver during the steering maneuver. Furthermore, EPS gives the possibility of high precision control of the steering system, thus paving the way to autonomous driving capability. In this context, the present work presents a performance assessment of an EPS system designed for a full-electric all-wheel-drive electric prototype racing in Formula Student Driverless (FSD) competitions. Specifically, the system is based on the linear actuation of the steering rack by using a ball screw. The screw nut is rotated through a belt transmission driven by a brushless DC motor. Modeling and motion control techniques for this system are presented. Moreover, the numerical model is tuned through a grey-box identification approach. Finally, the performance of the proposed EPS system is tested experimentally on the vehicle through both sine-sweep profiles and co-simulated driverless sessions. The system performance is assessed in terms of reference tracking capability, thus showing favorable results for the proposed actuation solution. Full article
(This article belongs to the Special Issue Actuators for Intelligent Electric Vehicles)
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17 pages, 2888 KiB  
Article
Analysis and Synthesis in the Design of Magnetic Switching Electric Machines
by Nikolay Shaitor, Michal Kelemen and Boris Yakimovich
Actuators 2021, 10(7), 164; https://doi.org/10.3390/act10070164 - 16 Jul 2021
Cited by 2 | Viewed by 2730
Abstract
A systematic approach to the design of electrical machines is implemented by solving problems of analysis and synthesis in various combinations at different stages and stages of design. The questions of the formulation and implementation of synthesis and analysis problems in the study [...] Read more.
A systematic approach to the design of electrical machines is implemented by solving problems of analysis and synthesis in various combinations at different stages and stages of design. The questions of the formulation and implementation of synthesis and analysis problems in the study and design of modular-type magnetically commutated electrical machines are considered. They are aimed at reducing weight, size and cost while improving the performance of these newly designed machines. A complex method of parametric synthesis and an automated program containing a calculated mathematical model of an electric machine has been developed. On the basis of numerical full factorial experiments, the optimization parameter is determined, and a regression analysis is performed with the construction of an optimization model. It allows you to find a narrow range of variation of significant factors, at which the optimization parameter satisfies the specified conditions. On the example of studying an inductor generator of axial-radial configuration, new approaches to the formulation and solution of typical problems of analysis and synthesis of modular-type electrical machines are shown. The use of complex parametric synthesis makes it possible to significantly reduce the masses of the designed modular machines in comparison with drum-type inductor machines of the same power. Full article
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17 pages, 4411 KiB  
Article
Fluid-Structure Interaction Modelling of a Soft Pneumatic Actuator
by Duraikannan Maruthavanan, Arthur Seibel and Josef Schlattmann
Actuators 2021, 10(7), 163; https://doi.org/10.3390/act10070163 - 15 Jul 2021
Cited by 14 | Viewed by 4306
Abstract
This paper presents a fully coupled fluid-structure interaction (FSI) simulation model of a soft pneumatic actuator (SPA). Previous research on modelling and simulation of SPAs mostly involves finite element modelling (FEM), in which the fluid pressure is considered as pressure load uniformly acting [...] Read more.
This paper presents a fully coupled fluid-structure interaction (FSI) simulation model of a soft pneumatic actuator (SPA). Previous research on modelling and simulation of SPAs mostly involves finite element modelling (FEM), in which the fluid pressure is considered as pressure load uniformly acting on the internal walls of the actuator. However, FEM modelling does not capture the physics of the fluid flow inside an SPA. An accurate modelling of the physical behaviour of an SPA requires a two-way FSI analysis that captures and transfers information from fluid to solid and vice versa. Furthermore, the investigation of the fluid flow inside the flow channels and chambers of the actuator are vital for an understanding of the fluid energy distribution and the prediction of the actuator performance. The FSI modelling is implemented on a typical SPA and the flow behaviour inside the actuator is presented. Moreover, the bending behaviour of the SPA from the FSI simulation results is compared with a corresponding FEM simulation. Full article
(This article belongs to the Section Actuators for Robotics)
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19 pages, 5582 KiB  
Article
Robust Model Reference Adaptive Control for Tail-Sitter VTOL Aircraft
by Ahmed R. Ajel, Amjad J. Humaidi, Ibraheem Kasim Ibraheem and Ahmad Taher Azar
Actuators 2021, 10(7), 162; https://doi.org/10.3390/act10070162 - 15 Jul 2021
Cited by 23 | Viewed by 3273
Abstract
This study presents a control design of roll motion for a vertical take-off and landing unmanned air vehicle (VTOL-UAV) design based on the Model Reference Adaptive Control (MRAC) scheme in the hovering flight phase. The adaptive laws are developed for the UAV system [...] Read more.
This study presents a control design of roll motion for a vertical take-off and landing unmanned air vehicle (VTOL-UAV) design based on the Model Reference Adaptive Control (MRAC) scheme in the hovering flight phase. The adaptive laws are developed for the UAV system under nonparametric uncertainty (gust and wind disturbance). Lyapunov-based stability analysis of the adaptive controlled UAV system under roll motion has been conducted and the adaptive laws have been accordingly developed. The Uniform Ultimate Boundness (UUB) of tracking error has been proven and the stability analysis showed that the incorporation of dead-zone modification in adaptive laws could guarantee the uniform boundness of all signals. The computer simulation has been conducted based on a proposed controller for tracking control of the roll motion. The results show that the drift, which appears in estimated gain behaviors due to the application of gust and wind disturbance, could be stopped by introducing dead-zone modification in adaptive laws, which leads to better robustness characteristics of the adaptive controller. Full article
(This article belongs to the Section Control Systems)
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13 pages, 5227 KiB  
Article
Additive Manufacturing of Flexible Material for Pneumatic Actuators Application
by Miranda Fateri, João Falcão Carneiro, Achim Frick, João Bravo Pinto and Fernando Gomes de Almeida
Actuators 2021, 10(7), 161; https://doi.org/10.3390/act10070161 - 15 Jul 2021
Cited by 3 | Viewed by 2523
Abstract
In this paper, endurance of peristaltic linear pneumatic actuators was studied using different hose geometries. Towards this goal, different hose geometries were additively manufactured using Fused Layer Manufacturing techniques of Thermoplastic Polyurethane Elastomer. Material properties of the elastomer were studied using Differential Scanning [...] Read more.
In this paper, endurance of peristaltic linear pneumatic actuators was studied using different hose geometries. Towards this goal, different hose geometries were additively manufactured using Fused Layer Manufacturing techniques of Thermoplastic Polyurethane Elastomer. Material properties of the elastomer were studied using Differential Scanning Calorimetry and the tensile test. The relations between the sample’s print temperature and build direction on the actuator endurance were investigated. Lastly, the relation between the geometry design of the PLPA actuator and its endurance is also discussed. Based on this methodology, authors present results showing that the use of a customized shaped hose with geometrical reinforcement at sides leads to a considerable rise in the hose endurance, when compared with the conventional circular design. Full article
(This article belongs to the Special Issue Peristaltic Linear Pneumatic Actuators)
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15 pages, 5329 KiB  
Article
Effects of Trailing Edge Deflections Driven by Shape Memory Alloy Actuators on the Transonic Aerodynamic Characteristics of a Super Critical Airfoil
by Binbin Lv, Yuanjing Wang and Pengxuan Lei
Actuators 2021, 10(7), 160; https://doi.org/10.3390/act10070160 - 15 Jul 2021
Cited by 4 | Viewed by 2009
Abstract
A smart structure to actuate a morphing trailing edge based on the super critical airfoil NASA sc-0714(2) was designed and verified in a transonic wind tunnel. The pressure distribution over the wing was measured to evaluate the structure ability and effects of trailing [...] Read more.
A smart structure to actuate a morphing trailing edge based on the super critical airfoil NASA sc-0714(2) was designed and verified in a transonic wind tunnel. The pressure distribution over the wing was measured to evaluate the structure ability and effects of trailing edge deflections on the aerodynamic characteristics. In the experiment, Mach number was from 0.4 to 0.8, and the angle of attack was from 0° to 6°. The results showed that the smart structure based on shape memory alloy could carry aerodynamic loads under transonic flow and deflect the trailing edge. When the driving force was constant, deformation would be influenced by the Mach number and angle of attack. Increasing the Mach number weakened the actuation capability of the smart structure, which decreased the deflection angle and rate of the trailing edge. The influence of the angle of attack is more complex, and couples with the influence of the Mach number. The higher the Mach number, the stronger the influence of the angles of attack. Additionally, the trailing edge deflection would dramatically change the flow structure over the airfoil, such as the shock wave position and strength. If separation was caused by the trailing edge deflection, the limitation of the smart structure would be further found. Full article
(This article belongs to the Special Issue Shape Memory Alloy Actuators)
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14 pages, 4926 KiB  
Article
Modular Capsules with Assembly and Separation Mechanism: Proof of Concept
by Zhenyu Li, Manh Cuong Hoang, Chang-Sei Kim, Eunpyo Choi, Doyeon Bang, Jong-Oh Park and Byungjeon Kang
Actuators 2021, 10(7), 159; https://doi.org/10.3390/act10070159 - 12 Jul 2021
Cited by 3 | Viewed by 2062
Abstract
As wireless capsule endoscope (WCE) technology has advanced, various studies were published on WCEs with functional modules for the diagnosis and treatment of problems in the digestive system. However, when additional functional modules are added the physical size of the WCEs will increase, [...] Read more.
As wireless capsule endoscope (WCE) technology has advanced, various studies were published on WCEs with functional modules for the diagnosis and treatment of problems in the digestive system. However, when additional functional modules are added the physical size of the WCEs will increase, making them more difficult for patients to comfortably swallow. Moreover, there are limitations when it comes to adding multi-functional modules to the WCEs due to the size of the digestive tract itself. This article introduces a controllable modular capsule endoscope driven by an electromagnetic actuation (EMA) system. The modular capsules are divided into a driving capsule and a functional capsule. Capsules with different functions are swallowed in sequence and then recombination, transportation and separation functions are carried out under the control of the EMA system while in the stomach, this approach solves the size limitation issues faced by multi-functional capsule endoscopes. The recombination and separation functions make use of a characteristic of soft magnetic materials so that their magnetization direction can be changed easily. These functions are made possible by the addition of a soft magnet to the capsule together with the precise control of magnetic fields provided by the EMA system. Full article
(This article belongs to the Special Issue Smart Actuators for Endoscopic Robots)
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13 pages, 5487 KiB  
Article
Efficiency Model for Traveling Wave-Type Ultrasonic Motors Based on Contact Variables and Preload
by Haoyu Sun, Hao Yin, Jiang Liu and Xilong Zhang
Actuators 2021, 10(7), 158; https://doi.org/10.3390/act10070158 - 12 Jul 2021
Viewed by 2142
Abstract
The contact interface variables are difficult to measure for an ultrasonic motor. When the ultrasonic motor works under different preloads, the error between the traditional efficiency model and the real output is quite large. In order to solve these two problems, we propose [...] Read more.
The contact interface variables are difficult to measure for an ultrasonic motor. When the ultrasonic motor works under different preloads, the error between the traditional efficiency model and the real output is quite large. In order to solve these two problems, we propose a novel efficiency model. It takes measured preload and the feedback voltage data as the input, which may offer better accuracy and on-line ability. Firstly, the effect of the preload on the drive characteristics is investigated, and the relationship between preload and the change in motor energy input is analyzed. Secondly, a contact model based on measured preload and feedback voltage is built, providing a more accurate description of the contact variables. Finally, an efficiency model was developed with a new composite stator structure. A preload test rig for a 60 mm ultrasonic motor is built and real operating conditions are measured. The results show that the correlation coefficient of the present model is 0.991, larger than 0.925 of the conventional model. The proposed model is more consistent with the real working conditions for the motor. Full article
(This article belongs to the Special Issue Miniature and Micro-Actuators)
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35 pages, 11519 KiB  
Article
Reconfigurable Slip Vectoring Control in Four In-Wheel Drive Electric Vehicles
by Gerardo Amato and Riccardo Marino
Actuators 2021, 10(7), 157; https://doi.org/10.3390/act10070157 - 10 Jul 2021
Cited by 6 | Viewed by 2854
Abstract
Controllability, maneuverability, fault-tolerance/isolation and safety are significantly enhanced in electric vehicles (EV) equipped with the redundant actuator configuration of four-in-wheel electric motors (4IWM). A highly reconfigurable architecture is proposed and illustrated for the adaptive, nonmodel-based control of 4IWM-EVs. Given the longitudinal force, yaw-moment [...] Read more.
Controllability, maneuverability, fault-tolerance/isolation and safety are significantly enhanced in electric vehicles (EV) equipped with the redundant actuator configuration of four-in-wheel electric motors (4IWM). A highly reconfigurable architecture is proposed and illustrated for the adaptive, nonmodel-based control of 4IWM-EVs. Given the longitudinal force, yaw-moment requests and the reconfiguration matrix, each IWM is given a slip reference according to a Slip Vectoring (SV) allocation strategy, which minimizes the overall slip vector norm. The distributed electric propulsion and the slip vector reference allow for a decentralized online estimation of the four-wheel torque-loads, which are uncertain depending on loading and road conditions. This allows for the allocation of four different torques depending on individual wheel conditions and to determine in which region (linear/nonsaturated or nonlinear/saturated) of the torque/slip characteristics each wheel is operating. Consequently, the 4IWMs can be equalized or reconfigured, including actuator fault-isolation as a special case, so that they are enforced to operate within the linear tire region. The initial driving-mode selection can be automatically adjusted and restored among eighteen configurations to meet the safety requirements of linear torque/slip behavior. Three CarSim realistic simulations illustrate the equalization algorithm, the quick fault-isolation capabilities and the importance of a continuous differential action in a critical double-lane-change maneuver. Full article
(This article belongs to the Special Issue Vehicle Modeling and Control)
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16 pages, 3443 KiB  
Article
Direct Drive Servovalves Actuated by Amplified Piezo-Stacks: Assessment through a Detailed Numerical Analysis
by Paolo Tamburrano, Elia Distaso, Andrew R. Plummer, Francesco Sciatti, Pietro De Palma and Riccardo Amirante
Actuators 2021, 10(7), 156; https://doi.org/10.3390/act10070156 - 07 Jul 2021
Cited by 5 | Viewed by 2331
Abstract
This paper presents a feasibility study using commercially available amplified piezo-stacks for the direct actuation of four-way three-position (4/3) direct drive servovalves. The prospect of using amplified piezo-stacks in place of linear force motors is very attractive by virtue of their fast response [...] Read more.
This paper presents a feasibility study using commercially available amplified piezo-stacks for the direct actuation of four-way three-position (4/3) direct drive servovalves. The prospect of using amplified piezo-stacks in place of linear force motors is very attractive by virtue of their fast response speed and low weight. Piezo-stacks equipped with mechanical amplification systems can give levels of displacement suitable for this application. A very effective amplification system has recently been produced by some manufacturers and is based on a temperature-independent diamond structure. This paper details simulations of a 4/3 servovalve directly actuated by such a piezoelectric actuator with a diamond structure. To this end, well-established equations, implemented in Simulink by means of the libraries of Simscape Fluids, are used. The proposed architecture shows simplicity of construction; in addition, very good step response speed and frequency response are predicted by the simulations. Full article
(This article belongs to the Special Issue Recent Advances on Servovalves)
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13 pages, 7974 KiB  
Article
Design and Simulation of Novel 3-DOF Spherical Voice Coil Motor
by Yi-Hsuan Lin, Chien-Sheng Liu and Chiu-Nung Yeh
Actuators 2021, 10(7), 155; https://doi.org/10.3390/act10070155 - 07 Jul 2021
Cited by 7 | Viewed by 3821
Abstract
Multi-DOF motion is realized in the eyes and joints of robots mostly through the combination of multiple one-degree-of-freedom (1-DOF) motors. However, this results in reduced efficiency, a large volume, reduced response speed, and inaccurate positioning. To solve these problems, this study proposes a [...] Read more.
Multi-DOF motion is realized in the eyes and joints of robots mostly through the combination of multiple one-degree-of-freedom (1-DOF) motors. However, this results in reduced efficiency, a large volume, reduced response speed, and inaccurate positioning. To solve these problems, this study proposes a novel 3-DOF spherical voice coil motor (VCM). In this VCM, 16 coils and a radially oriented ring magnet are used to generate a Lorentz force to achieve motion. In particular, coils for Z-axis rotation are sandwiched between the coils for X- and Y-axis rotation. Furthermore, the proposed VCM can achieve 360° rotation about the Z-axis. The commercial software ANSYS was used to design and verify the performance of the proposed VCM. Simulation results indicate that this VCM affords improved power efficiency because only a suitable combination of coils, rather than all coils, needs to be powered on. The results demonstrate the feasibility of the proposed 3-DOF spherical VCM. Full article
(This article belongs to the Special Issue Design and Application of Actuators with Multi-DOF Movement)
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12 pages, 2641 KiB  
Article
Backstepping Sliding-Mode Control of Piezoelectric Single-Piston Pump-Controlled Actuator
by Bin Wang, Pengda Ren and Xinhao Huang
Actuators 2021, 10(7), 154; https://doi.org/10.3390/act10070154 - 07 Jul 2021
Cited by 2 | Viewed by 1923
Abstract
A piston piezoelectric (PZT) pump has many advantages for the use of light actuators. How to deal with the contradiction between the intermittent oil supplying and position control precision is essential when designing the controller. In order to accurately control the output of [...] Read more.
A piston piezoelectric (PZT) pump has many advantages for the use of light actuators. How to deal with the contradiction between the intermittent oil supplying and position control precision is essential when designing the controller. In order to accurately control the output of the actuator, a backstepping sliding-mode control method based on the Lyapunov function is introduced, and the controller is designed on the basis of establishing the mathematical model of the system. The simulation results show that, compared with fuzzy PID and ordinary sliding-mode control, backstepping sliding-mode control has a stronger anti-jamming ability and tracking performance, and improves the control accuracy and stability of the piezoelectric pump-controlled actuator system. Full article
(This article belongs to the Section Miniaturized and Micro Actuators)
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16 pages, 1906 KiB  
Article
Design Method of Bearingless Permanent Magnet Slice Motor for Maglev Centrifugal Pump Based on Performance Metric Cluster
by Yifan Zhang, Liang Hu, Rui Su and Xiaodong Ruan
Actuators 2021, 10(7), 153; https://doi.org/10.3390/act10070153 - 05 Jul 2021
Cited by 5 | Viewed by 2568
Abstract
Different from ordinary AC machines, the design of a bearingless permanent magnet slice motor (BPMSM) considers not only the torque performance, but also the passive and active suspension properties. In addition, BPMSM for a maglev centrifugal pump has unique design characteristics due to [...] Read more.
Different from ordinary AC machines, the design of a bearingless permanent magnet slice motor (BPMSM) considers not only the torque performance, but also the passive and active suspension properties. In addition, BPMSM for a maglev centrifugal pump has unique design characteristics due to the integration of the pump head and sensors. This paper investigates evaluation and design techniques based on a cluster of performance metrics targeting on developing BPMSM for a maglev centrifugal pump. The cluster of performance metrics for BPMSM, including passive stiffness (kz, kz/kx, kz/ky, kα, and kβ) and active factors (ki and cm), is first proposed and an evaluation function fiSi,Li is constructed. Then, practical configurations of BPMSM for a maglev centrifugal pump are summarized. Based on the cluster of performance metrics, the finite-element method (FEM) is used to explore the impact of the rotor magnetization (sinusoidal, diametric, and radial method) on motor properties. Subsequently, the complete design process of BPMSM for a maglev centrifugal pump is introduced and key differences (including three crucial geometric parameters: ratio of rotor height to diameter λ, magnetic gap length δ, and stator tooth width αst) in the design considerations between BPMSM and general bearingless motors are analyzed. Finally, the upgraded performance (kz, kα, kβ, ki, cm, and fiSi,Li increased by about 29%, 38%, 33%, 31%, 21%, and 15%, respectively) of the designed candidate is obtained, which verifies the effectiveness of the proposed design methods. Full article
(This article belongs to the Special Issue Magnetic Bearings: From Theory to Applications)
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15 pages, 3067 KiB  
Article
MCI Detection Using Kernel Eigen-Relative-Power Features of EEG Signals
by Yu-Tsung Hsiao, Chia-Fen Tsai, Chien-Te Wu, Thanh-Tung Trinh, Chun-Ying Lee and Yi-Hung Liu
Actuators 2021, 10(7), 152; https://doi.org/10.3390/act10070152 - 04 Jul 2021
Cited by 7 | Viewed by 2929
Abstract
Classification between individuals with mild cognitive impairment (MCI) and healthy controls (HC) based on electroencephalography (EEG) has been considered a challenging task to be addressed for the purpose of its early detection. In this study, we proposed a novel EEG feature, the kernel [...] Read more.
Classification between individuals with mild cognitive impairment (MCI) and healthy controls (HC) based on electroencephalography (EEG) has been considered a challenging task to be addressed for the purpose of its early detection. In this study, we proposed a novel EEG feature, the kernel eigen-relative-power (KERP) feature, for achieving high classification accuracy of MCI versus HC. First, we introduced the relative powers (RPs) between pairs of electrodes across 21 different subbands of 2-Hz width as the features, which have not yet been used in previous MCI-HC classification studies. Next, the Fisher’s class separability criterion was applied to determine the best electrode pairs (five electrodes) as well as the frequency subbands for extracting the most sensitive RP features. The kernel principal component analysis (kernel PCA) algorithm was further performed to extract a few more discriminating nonlinear principal components from the optimal RPs, and these components form a KERP feature vector. Results carried out on 51 participants (24 MCI and 27 HC) show that the newly introduced subband RP feature showed superior classification performance to commonly used spectral power features, including the band power, single-electrode relative power, and also the RP based on the conventional frequency bands. A high leave-one-participant-out cross-validation (LOPO-CV) classification accuracy 86.27% was achieved by the RP feature, using a simple linear discriminant analysis (LDA) classifier. Moreover, with the same classifier, the proposed KERP further improved the accuracy to 88.24%. Finally, cascading the KERP feature to a nonlinear classifier, the support vector machine (SVM), yields a high MCI-HC classification accuracy of 90.20% (sensitivity = 87.50% and specificity = 92.59%). The proposed method demonstrated a high accuracy and a high usability (only five electrodes are required), and therefore, has great potential to further develop an EEG-based computer-aided diagnosis system that can be applied for the early detection of MCI. Full article
(This article belongs to the Special Issue Actuators in Robotic Control)
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16 pages, 4274 KiB  
Article
Friction Prediction and Validation of a Variable Stiffness Lower Limb Exosuit Based on Finite Element Analysis
by Zhuo Ma, Siyang Zuo, Baojun Chen and Jianbin Liu
Actuators 2021, 10(7), 151; https://doi.org/10.3390/act10070151 - 02 Jul 2021
Cited by 2 | Viewed by 2477
Abstract
The variable stiffness exosuit has great potential for human augmentation and medical applications. However, the model of the variable stiffness mechanism in exosuits is far from satisfactory for the accurate prediction and control of friction force. This paper presents a friction prediction model [...] Read more.
The variable stiffness exosuit has great potential for human augmentation and medical applications. However, the model of the variable stiffness mechanism in exosuits is far from satisfactory for the accurate prediction and control of friction force. This paper presents a friction prediction model of a variable stiffness lower limb exosuit, verifies its prediction performance, and identifies its applicability. The friction force model was established by the Coulomb friction hypothesis. The equivalent coefficient, which is the core parameter of the model, was determined based on friction and squeezing force data obtained by tests and an ANSYS simulation. Experiments show that the prediction error of the proposed model can reach 15% with a proper structural dimension change constraint. The friction force control test showed that the achieved model can shorten the settling time of the step response by 26% and eliminate the steady-state error. Verifications indicate that the proposed method can provide guidance to the modeling of other friction/stiffness structures, especially friction-based wearable robot structure models and predictions. Full article
(This article belongs to the Special Issue Actuators on Soft Exoskeletons)
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15 pages, 4040 KiB  
Article
Experimental and Analytical Study of Secondary Path Transfer Function in Active Hydraulic Mount with Solenoid Actuator
by Rang-Lin Fan, Yu-Fei Dou, Fang-Hua Yao, Song-Qiang Qi and Chen Han
Actuators 2021, 10(7), 150; https://doi.org/10.3390/act10070150 - 02 Jul 2021
Cited by 1 | Viewed by 2037
Abstract
The active hydraulic mount with solenoid actuator (AHM-SNA) does not require permanent magnets, is of low cost, and has attracted wide attention. This paper focuses on each link of the secondary path in AHM-SNA, the transfer functions (TFs) were studied one by one, [...] Read more.
The active hydraulic mount with solenoid actuator (AHM-SNA) does not require permanent magnets, is of low cost, and has attracted wide attention. This paper focuses on each link of the secondary path in AHM-SNA, the transfer functions (TFs) were studied one by one, and a simple and efficient expression for the total secondary path is discussed. First, based on the mathematical model of the hydraulic mount with inertia track and decoupling membrane, the TF from actuator active force to output force at frame side was analyzed, the results show that the TF was constant in the mid-frequency band. Second, based on the geometric parameters and cone air gap of solenoid actuator, it was obtained that the TF from the square of current to actuator active force is also constant; based on the relationship that the active force frequency is twice of the harmonic current frequency, the full-wave-rectified current was introduced. Utilizing the fact that the second harmonic component of the current is the main component, it was concluded that the total TF of the secondary path from current to active force and then to output force at frame side was constant in the mid-frequency band. Finally, two sets of experiments with full-wave-rectified current as the excitation were carried out, and the analytical conclusion was verified that the TF of the secondary path was constant as a proportional link and was convenient for the active control algorithms. Full article
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21 pages, 21060 KiB  
Article
Dynamic Parameter Estimation of Large Space Debris Based on Inertial and Visual Data Fusion
by Jinming Yao, Yuqiang Liu, Huibo Zhang and Shijie Dai
Actuators 2021, 10(7), 149; https://doi.org/10.3390/act10070149 - 02 Jul 2021
Cited by 2 | Viewed by 2410
Abstract
Most large space debris has large residual angular momentum, and the de-tumbling and capturing operation can easily cause instability and failure of tracking satellites. Therefore, it is necessary to perform real-time dynamic parameter identification of space debris prior to the imminent de-tumbling and [...] Read more.
Most large space debris has large residual angular momentum, and the de-tumbling and capturing operation can easily cause instability and failure of tracking satellites. Therefore, it is necessary to perform real-time dynamic parameter identification of space debris prior to the imminent de-tumbling and capture operation, thus improving the efficiency and success of active debris removal (ADR) missions. A method for identifying dynamic parameters based on the fusion of visual and inertial data is proposed. To obtain the inertial data, the inertial measurement units (IMU) with light markers were fixed on the debris surface by space harpoon, which has been experimentally proven in space, and the binocular vision was placed at the front of a tracking satellite to obtain coordinates of the light markers. A novel method for denoising inertial data is proposed, which will eliminate the interference from the space environment. Furthermore, based on the denoised data and coordinates of the light markers, the mass-center location is estimated. The normalized angular momentum is calculated using the Euler–Poinsot motion characteristics, and all active debris removal parameters are determined. Simulations with Gaussian noise and experiments in the controlled laboratory have been conducted, the results indicate that this method can provide accurate dynamic parameters for the ADR mission. Full article
(This article belongs to the Special Issue Actuation for Space Applications)
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14 pages, 4171 KiB  
Article
Data-Driven Tuning of PID Controlled Piezoelectric Ultrasonic Motor
by Sarah Makarem, Bülent Delibas and Burhanettin Koc
Actuators 2021, 10(7), 148; https://doi.org/10.3390/act10070148 - 29 Jun 2021
Cited by 21 | Viewed by 4753
Abstract
Ultrasonic motors employ resonance to amplify the vibrations of piezoelectric actuator, offering precise positioning and relatively long travel distances and making them ideal for robotic, optical, metrology and medical applications. As operating in resonance and force transfer through friction lead to nonlinear characteristics [...] Read more.
Ultrasonic motors employ resonance to amplify the vibrations of piezoelectric actuator, offering precise positioning and relatively long travel distances and making them ideal for robotic, optical, metrology and medical applications. As operating in resonance and force transfer through friction lead to nonlinear characteristics like creep and hysteresis, it is difficult to apply model-based control, so data-driven control offers a good alternative. Data-driven techniques are used here for iterative feedback tuning of a proportional integral derivative (PID) controller parameters and comparing between different motor driving techniques, single source and dual source dual frequency (DSDF). The controller and stage system used are both produced by the company Physik Instrumente GmbH, where a PID controller is tuned with the help of four search methods: grid search, Luus–Jaakola method, genetic algorithm, and a new hybrid method developed that combines elements of grid search and Luus–Jaakola method. The latter method was found to be quick to converge and produced consistent result, similar to the Luus–Jaakola method. Genetic Algorithm was much slower and produced sub optimal results. The grid search has also proven the DSDF driving method to be robust, less parameter dependent, and produces far less integral position error than the single source driving method. Full article
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16 pages, 5311 KiB  
Article
Permanent Magnet Synchronous Motor Speed Control Based on Improved Active Disturbance Rejection Control
by Zhaoyao Shi, Pan Zhang, Jiachun Lin and Hongyu Ding
Actuators 2021, 10(7), 147; https://doi.org/10.3390/act10070147 - 29 Jun 2021
Cited by 11 | Viewed by 3885
Abstract
An improved active disturbance rejection control (I-ADRC) to improve the disturbance attenuation of a permanent magnet synchronous motor speed controller was proposed in this paper. A nonlinear function with improved smoothness was adopted to design the controller. The Lyapunov stability of the improved [...] Read more.
An improved active disturbance rejection control (I-ADRC) to improve the disturbance attenuation of a permanent magnet synchronous motor speed controller was proposed in this paper. A nonlinear function with improved smoothness was adopted to design the controller. The Lyapunov stability of the improved tracking differentiator, the improved extended state observer, and the controller were analysed. Moreover, simulations and experiments confirmed the effectiveness of the proposed controller. The results demonstrate that the proposed controller has a smaller steady-state error and a stronger disturbance attenuation ability than the proportional integral derivative (PID) controller. Full article
(This article belongs to the Section Control Systems)
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20 pages, 5685 KiB  
Article
A Novel Deep Learning Model for Mechanical Rotating Parts Fault Diagnosis Based on Optimal Transport and Generative Adversarial Networks
by Xuanquan Wang, Xiongjun Liu, Ping Song, Yifan Li and Youtian Qie
Actuators 2021, 10(7), 146; https://doi.org/10.3390/act10070146 - 28 Jun 2021
Cited by 4 | Viewed by 2252
Abstract
To solve the poor real-time performance of the existing fault diagnosis algorithms on transmission system rotating components, this paper proposes a novel high-dimensional OT-Caps (Optimal Transport–Capsule Network) model. Based on the traditional capsule network algorithm, an auxiliary loss is introduced during the offline [...] Read more.
To solve the poor real-time performance of the existing fault diagnosis algorithms on transmission system rotating components, this paper proposes a novel high-dimensional OT-Caps (Optimal Transport–Capsule Network) model. Based on the traditional capsule network algorithm, an auxiliary loss is introduced during the offline training process to improve the network architecture. Simultaneously, an optimal transport theory and a generative adversarial network are introduced into the auxiliary loss, which accurately depicts the error distribution of the fault characteristic. The proposed model solves the low real-time performance of the capsule network algorithm due to complex architecture, long calculation time, and oversized hardware resource consumption. Meanwhile, it ensures the high precision, early prediction, and transfer aptitude of fault diagnosis. Finally, the model’s effectiveness is verified by the public data sets and the actual faults data of the transmission system, which provide technical support for the application. Full article
(This article belongs to the Special Issue Health Monitoring and Fault Diagnosis on Actuation Systems)
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26 pages, 6749 KiB  
Review
Current Trends and Prospects in Compliant Continuum Robots: A Survey
by Shiyao Li and Guangbo Hao
Actuators 2021, 10(7), 145; https://doi.org/10.3390/act10070145 - 28 Jun 2021
Cited by 28 | Viewed by 5701
Abstract
Compliant continuum robots (CCRs) have slender and elastic bodies. Compared with a traditional serial robot, they have more degrees of freedom and can deform their flexible bodies to go through a constrained environment. In this paper, we classify CCRs according to basic transmission [...] Read more.
Compliant continuum robots (CCRs) have slender and elastic bodies. Compared with a traditional serial robot, they have more degrees of freedom and can deform their flexible bodies to go through a constrained environment. In this paper, we classify CCRs according to basic transmission units. The merits, materials and potential drawbacks of each type of CCR are described. Drive systems depend on the basic transmission units significantly, and their advantages and disadvantages are reviewed and summarized. Variable stiffness and intrinsic sensing are desired characteristics of CCRs, and the methods of obtaining the two characteristics are discussed. Finally, we discuss the friction, buckling, singularity and twisting problems of CCRs, and emphasise the ways to reduce their effects, followed by several proposing perspectives, such as the collaborative CCRs. Full article
(This article belongs to the Special Issue Soft and Compliant Actuators and Their Robotic Applications)
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24 pages, 9857 KiB  
Article
UWB Based Relative Planar Localization with Enhanced Precision for Intelligent Vehicles
by Mingyang Wang, Xinbo Chen, Pengyuan Lv, Baobao Jin, Wei Wang and Yong Shen
Actuators 2021, 10(7), 144; https://doi.org/10.3390/act10070144 - 26 Jun 2021
Cited by 4 | Viewed by 2109
Abstract
Along with the rapid development of advanced driving assistance systems for intelligent vehicles, essential functions such as forward collision warning and collaborative cruise control need to detect the relative positions of surrounding vehicles. This paper proposes a relative planar localization system based on [...] Read more.
Along with the rapid development of advanced driving assistance systems for intelligent vehicles, essential functions such as forward collision warning and collaborative cruise control need to detect the relative positions of surrounding vehicles. This paper proposes a relative planar localization system based on the ultra-wideband (UWB) ranging technology. Three UWB modules are installed on the top of each vehicle. Because of the limited space on the vehicle roof compared with the ranging error, the traditional triangulation method leads to significant positioning errors. Therefore, an optimal localization algorithm combining homotopy and the Levenberg–Marquardt method is first proposed to enhance the precision. The triangular side lengths and directed area are introduced as constraints. Secondly, a UWB sensor error self-correction method is presented to further improve the ranging accuracy. Finally, we carry out simulations and experiments to show that the presented algorithm in this paper significantly improves the relative position and orientation precision of both the pure UWB localization system and the fusion system integrated with dead reckoning. Full article
(This article belongs to the Special Issue Actuators for Intelligent Electric Vehicles)
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16 pages, 1160 KiB  
Article
Parameter Identification of BLDC Motor Using Electromechanical Tests and Recursive Least-Squares Algorithm: Experimental Validation
by Jose Jimenez-Gonzalez, Felipe Gonzalez-Montañez, Victor Manuel Jimenez-Mondragon, Jesús Ulises Liceaga-Castro, Rafael Escarela-Perez and Juan Carlos Olivares-Galvan
Actuators 2021, 10(7), 143; https://doi.org/10.3390/act10070143 - 25 Jun 2021
Cited by 10 | Viewed by 4565
Abstract
In this article, the parameter identification of a brushless DC motor (BLDC) is presented. The approach here presented is based on a direct identification considering a three-phase line-to-line voltage electromagnetic torque as function of the electric currents and rotor speed. The estimation is [...] Read more.
In this article, the parameter identification of a brushless DC motor (BLDC) is presented. The approach here presented is based on a direct identification considering a three-phase line-to-line voltage electromagnetic torque as function of the electric currents and rotor speed. The estimation is divided into two stages. First, the electrical parameters are estimated by well-known no-load and DC tests. Consequently, estimation of mechanical parameters is performed using a recursive Least Square Algorithm. The proposed approach is validated by comparing model responses to motor real time responses. Additionally, the design, digital simulation and real time implementation of a PI rotor speed controller, based on the estimated model, validate the identification proposal presented here. Full article
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17 pages, 6630 KiB  
Article
Numerical and Experimental Study of a Flexible Trailing Edge Driving by Pneumatic Muscle Actuators
by Shiwei Zhao, Daochun Li, Jin Zhou and Enlai Sha
Actuators 2021, 10(7), 142; https://doi.org/10.3390/act10070142 - 24 Jun 2021
Cited by 7 | Viewed by 2367
Abstract
A static aeroelastic analysis of the flexible trailing edge is conducted to calculate the deformed shape, aerodynamic coefficients and corresponding driving pressure. A physical flexible trailing edge model is manufactured using a honeycomb structure, which is measured based on binocular vision. The quadratic [...] Read more.
A static aeroelastic analysis of the flexible trailing edge is conducted to calculate the deformed shape, aerodynamic coefficients and corresponding driving pressure. A physical flexible trailing edge model is manufactured using a honeycomb structure, which is measured based on binocular vision. The quadratic response surface method is adopted to establish the pneumatic artificial muscle actuator model. The wire-pulley transmission model is built to identify the existence of equivalent forces and produce the equivalent forces as the substitute of actuation force. A finite element model of the flexible trailing edge is established, which is validated by the test data. A nonlinear relationship is found between the driving pressure and deflection angle. The pressure needed to bear the structural stiffness is found to be much larger than that of the aerodynamic load. With the increase in pressure, the magnitude of the lift coefficient increases less. However, the magnitude of the drag coefficient increases more with the increase in pressure under 0.2 MPa. When the driving pressure exceeds 0.2 MPa, the relationship between them is nearly linear. Full article
(This article belongs to the Special Issue Pneumatic Muscle Actuators)
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16 pages, 4782 KiB  
Article
Develop Real-Time Robot Control Architecture Using Robot Operating System and EtherCAT
by Wei-Li Chuang, Ming-Ho Yeh and Yi-Liang Yeh
Actuators 2021, 10(7), 141; https://doi.org/10.3390/act10070141 - 24 Jun 2021
Cited by 7 | Viewed by 5816
Abstract
This paper presents the potential of combining ROS (Robot Operating System), its state-of-art software, and EtherCAT technologies to design real-time robot control architecture for human–robot collaboration. For this, the advantages of an ROS framework here are it is easy to integrate sensors for [...] Read more.
This paper presents the potential of combining ROS (Robot Operating System), its state-of-art software, and EtherCAT technologies to design real-time robot control architecture for human–robot collaboration. For this, the advantages of an ROS framework here are it is easy to integrate sensors for recognizing human commands and the well-developed communication protocols for data transfer between nodes. We propose a shared memory mechanism to improve the communication between non-real-time ROS nodes and real-time robot control tasks in motion kernel, which is implemented in the ARM development board with a real-time operating system. The jerk-limited trajectory generation approach is implemented in the motion kernel to obtain a fine interpolation of ROS MoveIt planned robot path to motor. EtherCAT technologies with precise multi-axis synchronization performance are used to exchange real-time I/O data between motion kernel and servo drive system. The experimental results show the proposed architecture using ROS and EtherCAT in hard real-time environment is feasible for robot control application. With the proposed architecture, a user can efficiently send commands to a robot to complete tasks or read information from the robot to make decisions, which is helpful to reach the purpose of human–robot collaboration in the future. Full article
(This article belongs to the Special Issue Actuators in Robotic Control)
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36 pages, 3475 KiB  
Review
Use the Force: Review of High-Rate Actuation of Shape Memory Alloys
by Asaf Dana, Shahaf Vollach and Doron Shilo
Actuators 2021, 10(7), 140; https://doi.org/10.3390/act10070140 - 24 Jun 2021
Cited by 18 | Viewed by 3619
Abstract
Typical shape memory alloy actuators provide a unique combination of large stresses and strains that result in work-per-volume larger by more than two orders of magnitude than all other actuation methods that are based on active materials. High-rate actuation of shape memory alloys [...] Read more.
Typical shape memory alloy actuators provide a unique combination of large stresses and strains that result in work-per-volume larger by more than two orders of magnitude than all other actuation methods that are based on active materials. High-rate actuation of shape memory alloys can provide improved energy efficiency, and shorter response and total actuation times, along with large travel-per-wire-length, with respect to slow-rate SMA applications. In this article, we review the different aspects of high-rate actuation of shape memory alloy wires in the high-driving-force regime. We briefly survey previous experimental results about the kinetics and thermodynamics of the phase transformation in view of its practical implications. New experimental results, regarding energy efficiency, total actuation time, repeatability, and fatigue, are presented and discussed. The paper provides general design guidelines for obtaining high actuator performance, as well as guidelines for selecting the source of the electric pulse and its parameters. Finally, we construct and solve detailed simulations of actuator response that can serve as accurate design tools. Full article
(This article belongs to the Section Actuator Materials)
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19 pages, 5690 KiB  
Article
Design and Experimental Verification of Pressurized Cylinders in Hydraulic Rubber Hose Pressure Washers
by Xiaoxiao Niu, Guangfa Hao, Chengliang Zhang and Lei Li
Actuators 2021, 10(7), 139; https://doi.org/10.3390/act10070139 - 24 Jun 2021
Cited by 3 | Viewed by 2439
Abstract
Hydraulic rubber hoses are subject to great hydraulic impact during the actual working process, which causes a great potential safety hazard. Therefore, it is necessary to carry out pressure tests on hose assemblies to ensure its quality, so providing a high pressure for [...] Read more.
Hydraulic rubber hoses are subject to great hydraulic impact during the actual working process, which causes a great potential safety hazard. Therefore, it is necessary to carry out pressure tests on hose assemblies to ensure its quality, so providing a high pressure for the hydraulic hose has become the key technology of this problem. Aiming at solving the problem of detection of pressure resistance in hydraulic rubber hose cleaning machines, this paper analyzed the pressurization mechanism of the hydraulic pressurized cylinder and proposed a method of continuous pressurization. This paper also theoretically analyzed the pressure expansion of the rubber hose, and the conclusion is that for the maximum hose capacity (hose size is Φ25 mm × 6 m), the volume of water required to provide water in the hose from 10 MPa to 100 MPa is 0.59 L. The pressurized cylinder was designed and checked theoretically and analyzed by the finite element method. It is concluded that the maximum stress of the pressurized cylinder is concentrated at the bottom of the high-pressure chamber, and the outlet hole at the bottom of the cylinder barrel of the high-pressure chamber is the weakest part of the pressurized cylinder. The performance of the supercharging cylinder is verified by experiments, which proves the feasibility, rapidity and stability of the supercharging cylinder. Full article
(This article belongs to the Special Issue Advanced Fluid Power Systems and Actuators)
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