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Actuators, Volume 11, Issue 8 (August 2022) – 37 articles

Cover Story (view full-size image): In a narrow surgical space, flexible surgical instruments offer advantages over rigid counterparts in terms of operational dexterity. Therefore, a flexible surgical instrument was designed in this study to realize dexterous motion using multiple segments in a series under tendon-driven operation. The forward and inverse kinematics of the instrument were solved using the geometrical method and the Newton–Raphson method. The experiments showed that the proposed method for solving flexible instrument kinematics had high precision, a unique solution, and high speed. The instrument can be well controlled to perform refined operations. In addition, the instrument could flexibly reach the designated position in a narrow and long operating space. Finally, it was verified that the prototype device had a certain load capacity. View this paper
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17 pages, 609 KiB  
Communication
Fault-Tolerant Control of Linear Systems with Unmatched Uncertainties Based on Integral Sliding Mode Technique
by Li-Ying Hao and Lian-Sheng Zhou
Actuators 2022, 11(8), 241; https://doi.org/10.3390/act11080241 - 22 Aug 2022
Cited by 2 | Viewed by 1361
Abstract
This paper proposes a novel fault-tolerant control method based on the integral sliding mode technique for unmatched uncertain linear systems with external perturbations. Differently from the existing works, the uncertainties under consideration have an unmatched norm-bounded form in the system and input matrix. [...] Read more.
This paper proposes a novel fault-tolerant control method based on the integral sliding mode technique for unmatched uncertain linear systems with external perturbations. Differently from the existing works, the uncertainties under consideration have an unmatched norm-bounded form in the system and input matrix. Based on linear matrix inequalities, the existence conditions of the sliding mode surface are presented. The unknown fault information is then estimated by some adaptive laws. On the grounds of that, an integral sliding mode controller is also obtained to guarantee the disturbance attenuation and fault tolerance for linear uncertain systems with unmatched uncertainties and actuator faults from the initial time. Finally, the comparative simulation results verify the effectiveness of our presented scheme. Full article
(This article belongs to the Special Issue Sensor and Actuator Attacks of Cyber-Physical Systems)
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22 pages, 4151 KiB  
Article
Implementation of Iterative Learning Control on a Pneumatic Actuator
by James Rwafa and Farzad Ghayoor
Actuators 2022, 11(8), 240; https://doi.org/10.3390/act11080240 - 22 Aug 2022
Cited by 1 | Viewed by 1758
Abstract
Pneumatic actuators demonstrate various nonlinear and uncertain behavior, and as a result, precise control of such actuators with model-based control schemes is challenging. The Iterative Learning Control (ILC) algorithm is a model-free control method usually used for repetitive processes. The ILC uses information [...] Read more.
Pneumatic actuators demonstrate various nonlinear and uncertain behavior, and as a result, precise control of such actuators with model-based control schemes is challenging. The Iterative Learning Control (ILC) algorithm is a model-free control method usually used for repetitive processes. The ILC uses information from previous repetitions to learn about a system’s dynamics for generating a more suitable control signal. In this paper, an ILC method to overcome the nonlinearities and uncertainties in a pneumatic cylinder-piston actuator is suggested. The actuator is modeled using MATLAB SimScape blocks, and the ILC scheme has been expanded for controlling nonlinear, non-repetitive systems so that it can be used to control the considered pneumatic system. The simulation results show that the designed ILC controller is capable of tracking a non-repetitive reference signal and can overcome the internal and payload uncertainties with the precision of 0.002 m. Therefore, the ILC can be considered as an approach for controlling the pneumatic actuators, which is challenging to obtain their mathematical modeling. Full article
(This article belongs to the Special Issue Applications of Intelligent Control in Actuators Systems)
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17 pages, 9518 KiB  
Article
High-Rate, High-Precision Wing Twist Actuation for Drone, Missile, and Munition Flight Control
by Ronald Barrett-Gonzalez and Nathan Wolf
Actuators 2022, 11(8), 239; https://doi.org/10.3390/act11080239 - 21 Aug 2022
Cited by 3 | Viewed by 1866
Abstract
This paper covers a new actuation and deflection controller configuration for high-aspect-ratio wings used on subsonic drones, missiles, and munitions. Current approaches to the flight control of these aircraft have unearthed challenges with friction, stiction, slop, bandwidth, and thick boundary layer nonlinearities, which [...] Read more.
This paper covers a new actuation and deflection controller configuration for high-aspect-ratio wings used on subsonic drones, missiles, and munitions. Current approaches to the flight control of these aircraft have unearthed challenges with friction, stiction, slop, bandwidth, and thick boundary layer nonlinearities, which degrade flight control accuracy—especially in terminal flight phases. The approach described in this paper uses directionally attached piezoelectric (DAP) actuators to actively twist a high-aspect-ratio wing for flight control. The DAP actuators were modeled analytically and computationally using linear finite element modeling. A 3″ (7.62 cm) chord × 15″ (38.1 cm) semispan rectangular wing with an NACA 0012 profile was built and structurally tested, demonstrating excellent agreement between theory and experiment. New actuation methods were used to overdrive the PZT-5H piezoelectric elements deep into the repoling range. This overdrive actuation rejuvenated the actuator elements and allowed for dramatically improved deflections with respect to configurations in previous years. Static testing demonstrated deflections in excess of ±1.6° in root-to-tip twist. Dynamic testing showed corner frequencies greater than 310 Hz. A series of wind tunnel tests at up to 180 ft/s (55 m/s, 123 mph, 107 kts, 198 kph) demonstrated excellent roll control authority, rapid manipulation of C, and lift manipulation using quasi-static deflections. The paper concludes with a summary of implications for terminal guidance for drone, missile, and munition flight control in real atmospheres. Full article
(This article belongs to the Special Issue Advanced Actuators for Aerospace Systems)
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23 pages, 5491 KiB  
Article
Friction Torque Analysis and Verification of Planetary Thread Roller Bearing
by Lu Liu, Congcong Zhang, Yanqing Guo, Yuxiang Bian, Yongling Fu, Yifan Ning and Jinjie Zhou
Actuators 2022, 11(8), 238; https://doi.org/10.3390/act11080238 - 21 Aug 2022
Cited by 3 | Viewed by 1491
Abstract
A planetary thread roller bearing (PTRB) is a state-of-the-art component in electromechanical actuators (EMA) due to its high load-bearing capacity and small volume. The study of the PTRB is a leading task in the domain of EMA application. In this study, we propose [...] Read more.
A planetary thread roller bearing (PTRB) is a state-of-the-art component in electromechanical actuators (EMA) due to its high load-bearing capacity and small volume. The study of the PTRB is a leading task in the domain of EMA application. In this study, we propose a mathematical model of PTRB friction torque on its working principle and causes. Specifically, the impact of basic properties of the PTRB on friction torque, i.e., rotating speed and external load, are modeled and analyzed. To verify the variation principle of friction torque, experiments are carried out on an actual PTRB. For the test PTRB, the rotating speed ranges from 200 to 2000 rpm with a reverse load from 2000 to 30,000 N at a constant temperature of 55 °C. Experimental results verify the effectiveness of the mathematical model under conditions of 200–2000 rpm rotating speed and 2000–30,000 N external load, which establish strong evidence for model accuracy and robustness. Full article
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14 pages, 2777 KiB  
Article
Communication-Based Train Control with Dynamic Headway Based on Trajectory Prediction
by Yijuan He, Jidong Lv and Tao Tang
Actuators 2022, 11(8), 237; https://doi.org/10.3390/act11080237 - 18 Aug 2022
Cited by 3 | Viewed by 1719
Abstract
Rail transit plays a significant role in the operation of an efficient and effective urban public transportation system. Safety and capacity are some of the most crucial objectives in railway operations. The communication-based train control (CBTC) system is a continuous and automatic train [...] Read more.
Rail transit plays a significant role in the operation of an efficient and effective urban public transportation system. Safety and capacity are some of the most crucial objectives in railway operations. The communication-based train control (CBTC) system is a continuous and automatic train control system that realizes constant and high-capacity train ground two-way communication. In this study, a dynamic headway model of the ‘softwall’ moving-block approach is proposed for CBTC to increase the track capacity and improve dispatching efficiency based on the train trajectory prediction. For this precise trajectory prediction task, we introduce a hybrid trajectory prediction model to combine Long Short-term memory (LSTM) and Kalman Filter (KF) to extract the train’s local data features and learn the long-term dependencies, respectively. Then we present a dynamic headway model to maximize the train headway and reduce the track distance. The leading trains’ information is used to construct the iterative learning control strategy, and the predicted trajectory is input into the algorithm of the headway model. We use a simulation model of the rail network in Chengdu to demonstrate the effectiveness of our proposed approach. The results show the Mean Absolute Error (MAE) of the predicted trajectory retreated to 93.97 cm and reductions in operation headway of at least 64.33% under the dynamic headway model versus the traditional moving-block model. Full article
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15 pages, 2031 KiB  
Article
Friction Parameters Dynamic Change and Compensation for a Novel Dual-Drive Micro-Feeding System
by Ziteng Lu, Xianying Feng, Zhe Su, Yandong Liu and Ming Yao
Actuators 2022, 11(8), 236; https://doi.org/10.3390/act11080236 - 17 Aug 2022
Cited by 3 | Viewed by 1618
Abstract
This paper introduces a novel dual-drive micro-feeding system (DDMS) to obtain precise micro-feed synthetic motion by rotating both the screw and the nut, which eliminates the effects of nonlinear friction at low micro-feeding speeds and has good resistance to external disturbances. For the [...] Read more.
This paper introduces a novel dual-drive micro-feeding system (DDMS) to obtain precise micro-feed synthetic motion by rotating both the screw and the nut, which eliminates the effects of nonlinear friction at low micro-feeding speeds and has good resistance to external disturbances. For the DDMS system, firstly, the frictional force of the screw–ball–nut contact surface is analyzed, and the dynamic system model based on the unique frictional coupling model is established for the DDMS. Secondly, a velocity squared term is added to the Stribeck model to characterize the influence of the frictional coupling on the system. The correctness of the modified model is verified through experiments and frictional parameters identification by combining with the genetic algorithm (GA). The dynamic trend of the frictional parameters with different speed combinations is studied, and the method of fitting parameters using the modified Stribeck model is proposed. Finally, the DDMS three closed-loop error compensation model and the proportional derivative position controller with the friction feedforward compensator are put forward to realize the accurate position-tracking function. Experiment results show that the method reduces the average tracking error by about 60% compared to the conventional PD controller. Full article
(This article belongs to the Special Issue Design and Control of High-Precision Motion Systems)
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21 pages, 5231 KiB  
Article
Numerical Simulation and Torsional Vibration Mitigation of Spatial Eccentric Structures with Multiple Magnetorheological Dampers
by Yang Yang and Ying-Qing Guo
Actuators 2022, 11(8), 235; https://doi.org/10.3390/act11080235 - 16 Aug 2022
Cited by 3 | Viewed by 1601
Abstract
Eccentric structures will have torsional vibrations subjected to earthquakes, which can accelerate the damage of structures, and even become the main cause of building collapse. Semi-active control systems equipped with multiple magnetorheological (MR) dampers have been widely applied in structural vibration control. In [...] Read more.
Eccentric structures will have torsional vibrations subjected to earthquakes, which can accelerate the damage of structures, and even become the main cause of building collapse. Semi-active control systems equipped with multiple magnetorheological (MR) dampers have been widely applied in structural vibration control. In this study, numerical models of spatial eccentric structures with multiple MR dampers were established, and time history analysis was conducted to mitigate torsional vibrations of eccentric structures. Firstly, a full-scale spatial eccentric structure model with both plan asymmetry and vertical irregularity was established in OpenSEES, and the accuracy of the structure model was verified by comparisons with model results from SAP2000. Then, the mathematical model of MR dampers was introduced to the structure model using the ‘Truss’ element and self-defined material in OpenSEES, and damping forces obtained from the MR damper model were compared with experimental data. Finally, modal analysis and nonlinear time history analysis of the eccentric structure model equipped with multiple MR dampers subjected to different seismic excitations were performed. Comparisons between the seismic responses of the uncontrolled structure and the structure with multiple MR dampers were carried out to demonstrate the effectiveness of the MR control system. Numerical results show that the control system with multiple MR dampers can significantly attenuate the torsional vibrations of eccentric structures, and thus possess significant engineering application prospects. Full article
(This article belongs to the Special Issue Vibration Control and Structure Health Monitoring)
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21 pages, 8448 KiB  
Article
Evolution and Near-Wall Effect of the Vortex Structures Induced by In-Line Twin Synthetic Jets in a Crossflow
by Hongxin Wang, Degang Xu, Linwen Li, Kaiwen Zhou, Xin Wen and Hui Tang
Actuators 2022, 11(8), 234; https://doi.org/10.3390/act11080234 - 16 Aug 2022
Viewed by 1448
Abstract
This paper aims to further the understanding of the mixing process of in-line twin synthetic jets (SJs) and their impact in the near-wall region in a flat-plate laminar boundary layer. A numerical study has been carried out, in which colored fluid particles and [...] Read more.
This paper aims to further the understanding of the mixing process of in-line twin synthetic jets (SJs) and their impact in the near-wall region in a flat-plate laminar boundary layer. A numerical study has been carried out, in which colored fluid particles and the Q criterion are used to track the SJ-induced vortex structures at the early stage of the evolution. Interacting vortex structures at four selected phase differences are presented and analyzed. It is found that the fluid injected at the early stage of the blowing stroke mainly contributes to the formation of the hairpin legs, the fluid injected near the maximum blowing mainly contributes to the formation of the hairpin head, and the fluid injected at the late stage of the blowing stroke contributes very little to the formation of the hairpin vortex. It is also confirmed that, irrespective of the phase difference, the hairpin vortex issued from the upstream actuator is more capable of maintaining its coherence than its counterpart issued from the downstream actuator. The influence of the interacting vortex structures on the boundary layer is also studied through investigating excess wall shear stress. In all cases, a pair of streaks of high wall shear stress can be observed with similar size. Among them, the streaks have the strongest wall shear stress, with the largest gap at phase difference 0 when partially interacting vortex structures are produced. The findings can provide valuable guiding information for the applications of synthetic jets in heat transfer, mixing control, and flow control in a crossflow. Full article
(This article belongs to the Special Issue Active Flow Control: Recent Advances in Fundamentals and Applications)
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16 pages, 1675 KiB  
Article
Switching Model Predictive Control for Thin McKibben Muscle Servo Actuator
by Mohd Akmal Mhd Yusoff, Ahmad Athif Mohd Faudzi, Mohd Shukry Hassan Basri, Mohd Fuaad Rahmat, Mohd Ibrahim Shapiai and Shahrol Mohamaddan
Actuators 2022, 11(8), 233; https://doi.org/10.3390/act11080233 - 15 Aug 2022
Viewed by 1618
Abstract
Dynamic characteristics and control of thin McKibben muscle (TMM) have not yet been fully investigated, especially on the translational antagonistic pair system. Therefore, the objective of this study is to propose a Switching Model Predictive Control (SMPC) based on a Piecewise Affine (PWA) [...] Read more.
Dynamic characteristics and control of thin McKibben muscle (TMM) have not yet been fully investigated, especially on the translational antagonistic pair system. Therefore, the objective of this study is to propose a Switching Model Predictive Control (SMPC) based on a Piecewise Affine (PWA) system model to control a translational antagonistic-pair TMM servo actuator. A novel configuration enables the servo actuator to achieve a position control of 40 mm within a small footprint. The result shows that the feedback system gives minimal steady-state errors when tracking staircase and setpoint references ranging from 0 to 3.5 cm. The controller also produces better transient and steady-state responses than our previously developed Gain-scheduled Proportional–Integral–Derivative (GSPID) controller. The evidence from this study suggests that a predictive control for a TMM servo actuator is feasible. Full article
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53 pages, 71001 KiB  
Review
Soft Gloves: A Review on Recent Developments in Actuation, Sensing, Control and Applications
by Monica Tiboni and Cinzia Amici
Actuators 2022, 11(8), 232; https://doi.org/10.3390/act11080232 - 10 Aug 2022
Cited by 9 | Viewed by 5095
Abstract
Interest in soft gloves, both robotic and haptic, has enormously grown over the past decade, due to their inherent compliance, which makes them particularly suitable for direct interaction with the human hand. Robotic soft gloves have been developed for hand rehabilitation, for ADLs [...] Read more.
Interest in soft gloves, both robotic and haptic, has enormously grown over the past decade, due to their inherent compliance, which makes them particularly suitable for direct interaction with the human hand. Robotic soft gloves have been developed for hand rehabilitation, for ADLs assistance, or sometimes for both. Haptic soft gloves may be applied in virtual reality (VR) applications or to give sensory feedback in combination with prostheses or to control robots. This paper presents an updated review of the state of the art of soft gloves, with a particular focus on actuation, sensing, and control, combined with a detailed analysis of the devices according to their application field. The review is organized on two levels: a prospective review allows the highlighting of the main trends in soft gloves development and applications, and an analytical review performs an in-depth analysis of the technical solutions developed and implemented in the revised scientific research. Additional minor evaluations integrate the analysis, such as a synthetic investigation of the main results in the clinical studies and trials referred in literature which involve soft gloves. Full article
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24 pages, 8530 KiB  
Article
Design, Development, and Control of a Novel Upper-Limb Power-Assist Exoskeleton System Driven by Pneumatic Muscle Actuators
by Hsien-Ru Chu, Shean-Juinn Chiou, I-Hsum Li and Lian-Wang Lee
Actuators 2022, 11(8), 231; https://doi.org/10.3390/act11080231 - 10 Aug 2022
Cited by 2 | Viewed by 2124
Abstract
An innovative wearable upper-limb power-assist exoskeleton system (UPES) was designed for laborers to improve work efficiency and reduce the risk of musculoskeletal disorders. This novel wearable UPES consists of four joints, each comprising a single actuated pneumatic muscle actuator (PMA) and a torsion [...] Read more.
An innovative wearable upper-limb power-assist exoskeleton system (UPES) was designed for laborers to improve work efficiency and reduce the risk of musculoskeletal disorders. This novel wearable UPES consists of four joints, each comprising a single actuated pneumatic muscle actuator (PMA) and a torsion spring module driven via a steel cable. Unlike most single-joint applications, where dual-PMAs are driven by antagonism, this design aims to combine a torsion spring module with a single-PMA via a steel cable for a 1-degree of freedom (1-DOF) joint controlled by a proportional-pressure regulator. The proposed four driving degrees of freedom wearable UPES is suitable for power assistance in work and characterizes a simple structure, safety, and compliance with the motion of an upper limb. However, due to the hysteresis, time-varying characteristics of the PMA, and non-linear movement between joint flexion and extension, the model parameters are difficult to identify accurately, resulting in unmeasurable uncertainties and disturbances of the wearable UPES. To address this issue, we propose an improved proxy-based sliding mode controller integrated with a linear extended state observer (IPSMC-LESO) to achieve accurate power-assisted control for the upper limb and ensure safe interaction between the UPES and the wearer. This control method can slow the underdamped dynamic recovery motion to tend the target trajectory without overshoots from large tracking errors that result in actuator saturation, and without deteriorating the power assist effect during regular operation. The experimental results show that IPSMC-LESO can effectively control a 4-DOF wearable UPES, observe the unknown states and total disturbance online of the system, and adapt to the external environment and load changes to improve system control performance. The results prove that the joint torsion spring module combining the single-PMA can reduce the number of PMAs and proportional-pressure regulators by half and obtain a control response similar to that of the dual-PMA structure. Full article
(This article belongs to the Special Issue Actuation Solutions for Wearable Robots)
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13 pages, 4132 KiB  
Article
Control Design and Testing for a Finger Exoskeleton Mechanism
by Adithya Prakash Damarla, Matteo Russo and Marco Ceccarelli
Actuators 2022, 11(8), 230; https://doi.org/10.3390/act11080230 - 10 Aug 2022
Cited by 1 | Viewed by 2522
Abstract
This paper describes a control strategy for a linkage finger exoskeleton mechanism with two degrees of freedom. To characterise the performance of the proposed finger motion assistance device, a replica of a human finger is prototyped to mimic human finger motion and to [...] Read more.
This paper describes a control strategy for a linkage finger exoskeleton mechanism with two degrees of freedom. To characterise the performance of the proposed finger motion assistance device, a replica of a human finger is prototyped to mimic human finger motion and to the testing effect of assistance provided by the novel exoskeleton with results from grasp tests. A feasible control design is developed to achieve a robust grasp of an object using the proposed exoskeleton mechanism, which is validated with simulated and experimental results that show how the proposed control algorithm maintains the force within 3% of the desired value. The aim of the paper is to present a control design for the ExoFinger exoskeleton with low-cost easy operation features that are aligned with the similar characteristics of the mechanical design. Full article
(This article belongs to the Special Issue Advanced Robots: Design, Control and Application)
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16 pages, 1476 KiB  
Article
Analytical Derivation and Analysis of Vertical and Lateral Installation Ratios for Swing Axle, McPherson and Double Wishbone Suspension Architectures
by Francesco Bucchi and Basilio Lenzo
Actuators 2022, 11(8), 229; https://doi.org/10.3390/act11080229 - 9 Aug 2022
Cited by 1 | Viewed by 3823
Abstract
In the context of suspension design, the installation ratio (or motion ratio) is a parameter that relates wheel movement with spring deflection, quite an important kinematic property of a suspension. Yet, no study in the literature provides a clear relationship between the installation [...] Read more.
In the context of suspension design, the installation ratio (or motion ratio) is a parameter that relates wheel movement with spring deflection, quite an important kinematic property of a suspension. Yet, no study in the literature provides a clear relationship between the installation ratio and the geometrical features of a suspension. This paper employs rigid body kinematics and appropriate geometrical schematics to fill such a gap. Analytical expressions of the installation ratio are derived for three suspension layouts: swing axle, McPherson, double wishbone. Key concepts such as instant center, roll center and camber gain are harnessed to provide insightful analyses for relevant case studies of suspension passenger cars. Among the key results, the typical assumption of a McPherson installation ratio close to 1 is supported by a formal demonstration, and the new concept of “lateral” installation ratio is introduced which, alongside the classical “vertical” installation ratio, further characterizes suspension motion. Numerical results obtained through a multibody software support the findings of this paper. In conclusion, this study provides valuable insights for suspension design engineers. Full article
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17 pages, 5309 KiB  
Article
Design, Modeling, Testing, and Control of a Novel Fully Flexure-Based Displacement Reduction Mechanism Driven by Voice Coil Motor
by Yunzhuang Chen and Leijie Lai
Actuators 2022, 11(8), 228; https://doi.org/10.3390/act11080228 - 8 Aug 2022
Cited by 1 | Viewed by 2505
Abstract
This paper presents a flexure-based displacement reduction mechanism driven by a voice coil motor to improve the motion resolution and eliminate the hysteresis nonlinearity of the traditional piezo-actuated micropositioning/nanopositioning stages. The mechanism is composed of three groups of compound bridge-type displacement reduction mechanisms, [...] Read more.
This paper presents a flexure-based displacement reduction mechanism driven by a voice coil motor to improve the motion resolution and eliminate the hysteresis nonlinearity of the traditional piezo-actuated micropositioning/nanopositioning stages. The mechanism is composed of three groups of compound bridge-type displacement reduction mechanisms, which adopt distributed-compliance rectangular beams to reduce the concentration of stress and improve the dynamic performance of the mechanism. The symmetrical distribution of the structure can eliminate the parasitic displacement of the mechanism and avoid the bending moment and lateral stress applied to the voice coil motor. Firstly, the analytical model of the mechanism is obtained by the stiffness matrix method. The theoretical displacement reduction ratio, input stiffness, and natural frequency of the displacement reduction mechanism are obtained by solving the analytical model. Then, through the static analysis and modal analysis of the mechanism with the Ansys software, the accuracy of the analytical model is verified, and the experimental prototype is also constructed for performance tests. The results show that the maximum stroke of the mechanism is 197.43 μm with motion resolution of 40 nm. The natural frequency is 291 Hz, and the input stiffness is 28.50 N/mm. Finally, the trajectory tracking experiment is carried out to verify the positioning performance of the mechanism. The experimental results show that the designed feedback controller has good stability, and the introduction of the feedforward controller and disturbance observer can greatly reduce the tracking errors. Full article
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15 pages, 4230 KiB  
Article
Dielectric Elastomer-Driven Bionic Inchworm Soft Robot Realizes Forward and Backward Movement and Jump
by Zeying Jing, Qingzhong Li, Wentai Su and Yuan Chen
Actuators 2022, 11(8), 227; https://doi.org/10.3390/act11080227 - 8 Aug 2022
Cited by 4 | Viewed by 2327
Abstract
To produce multi-modal mobility in complicated situations is a significant issue for soft robots. In this study, we show the conception, construction, and operation of an inchworm-impersonating dielectric elastomer-activated soft robot. The robot is small and lightweight, weighing only 3.5 g, and measuring [...] Read more.
To produce multi-modal mobility in complicated situations is a significant issue for soft robots. In this study, we show the conception, construction, and operation of an inchworm-impersonating dielectric elastomer-activated soft robot. The robot is small and lightweight, weighing only 3.5 g, and measuring an overall 110 mm by 50 mm by 60 mm (length, width, and height). The three mobility modes for the robot are each equipped with a detailed mechanism. When the excitation voltage is 5 kV, the robot runs forward under a frequency of stimulation of 1–9 Hz, and its direction of motion changes to a backwards motion at >10 Hz. When the excitation voltage of 5.5 kV is applied to the robot, the robot runs forward at 1–12 Hz frequency and moves in the opposite direction at 13 Hz, reaching the fastest reverse speed of 240 mm/s. When the excitation voltage rises to 6 kV, the robot reaches its fastest running speed of 270 mm/s at 14 Hz. Motivated by high voltage and high duty cycle, the robot can jump over obstacles of 5 mm. In order to assess the performance of backward running, the speed achieved by the robot under a 30% duty cycle and a 50% duty cycle was compared, as well as the speed of the robot with or without the use of a counterweight. The robot has a simpler design and construction than earlier soft robots of the same kind, as well as a quicker speed, a wider variety of movement modes, and other notable advantages. Full article
(This article belongs to the Section Actuators for Robotics)
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24 pages, 6346 KiB  
Article
Eight-DOF Dynamic Modeling of EMA Mechanical Transmission and Spalling Fault Characteristic Analysis
by Zhengyang Yin, Yi Yang, Guoji Shen, Ling Chen and Niaoqing Hu
Actuators 2022, 11(8), 226; https://doi.org/10.3390/act11080226 - 6 Aug 2022
Viewed by 1572
Abstract
Electromechanical actuators (EMAs), as the critical actuator system of next-generation aircraft, have attracted the attention of many institutions and enterprises around the world. However, due to harsh working conditions, their reliability cannot satisfy the requirements of widespread application in aircraft. Therefore, in order [...] Read more.
Electromechanical actuators (EMAs), as the critical actuator system of next-generation aircraft, have attracted the attention of many institutions and enterprises around the world. However, due to harsh working conditions, their reliability cannot satisfy the requirements of widespread application in aircraft. Therefore, in order to conduct fault diagnosis on EMAs, in this paper, we establish a comprehensive dynamic model under numerous assumptions to study the fault characteristics that may occur in the displacement and acceleration responses of EMA systems. First, an eight-DOF dynamic model containing typical mechanical components of an EMA is established. Then, by obtaining the impact forces between balls and the spalling fault and the nonlinear relationship between the total elastic restoring forces and the change of ball deformation when the fault occurs, a faulty dynamic model is established. Comparison of the simulation results between the normal and faulty model reveals that the acceleration amplitude at the third harmonic of the ball passage frequency increases when fault occurs. Based on this phenomenon, a numerical calculation method of fault characteristics is proposed. Finally, the effectiveness of the established models and the identified phenomenon are verified by experiments conducted on an EMA test rig in a laboratory environment. Full article
(This article belongs to the Section Aircraft Actuators)
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20 pages, 16501 KiB  
Article
Shock-Induced Vibration of Composite Truss Core Sandwich Plates with Distributed Nonlinear Absorbers by Optimal Locations
by Wei Zhang, Weixing Zhang, Zhong Luo, Jianen Chen and Xiangying Guo
Actuators 2022, 11(8), 225; https://doi.org/10.3390/act11080225 - 6 Aug 2022
Cited by 1 | Viewed by 1473
Abstract
In order to solve the problems of limited installation space and strict additional quality, the effects of internal distributed nonlinear energy sinks (NES) considering optimal locations on a composite truss core sandwich plate are investigated in this paper. Choose five NESs here and [...] Read more.
In order to solve the problems of limited installation space and strict additional quality, the effects of internal distributed nonlinear energy sinks (NES) considering optimal locations on a composite truss core sandwich plate are investigated in this paper. Choose five NESs here and inset them in the different places of the sandwich plate to suppress the vibration of the plate, which is excited by a half-wave shock. The coupled dynamic equations of the system are derived by the principle of conservation of energy. Then, the vibration-control performances of five NESs are discussed by numerical simulation. The distributions of the five NESs are analyzed, and the optimal position distributions are obtained. Based on the optimal location, the transient responses of the system are studied. Moreover, the performances of five NESs and a single NES are compared in different dimensions. Finally, it is found that the selection of parameters has a great impact on the effectiveness of the five NESs. The new distribution way is introduced to improve the suppression effects of the five NESs in the sandwich plate. Full article
(This article belongs to the Special Issue Advanced Spacecraft Structural Dynamics and Actuation Control)
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12 pages, 8623 KiB  
Article
Resonant Adaptive MEMS Mirror
by Amr Kamel, Samed Kocer, Lyazzat Mukhangaliyeva, Resul Saritas, Ahmet Gulsaran, Alaa Elhady, Mohamed Basha, Parsin Hajireza, Mustafa Yavuz and Eihab Abdel-Rahman
Actuators 2022, 11(8), 224; https://doi.org/10.3390/act11080224 - 5 Aug 2022
Cited by 3 | Viewed by 2779
Abstract
A novel MEMS continuous deformable mirror (DM) is presented. The mirror can be integrated into optical systems to compensate for monochromatic and chromatic aberrations. It is comprised of a 1.6 mm circular plate supported by eight evenly spaced flexural springs. Unlike traditional bias [...] Read more.
A novel MEMS continuous deformable mirror (DM) is presented. The mirror can be integrated into optical systems to compensate for monochromatic and chromatic aberrations. It is comprised of a 1.6 mm circular plate supported by eight evenly spaced flexural springs. Unlike traditional bias actuated DMs, it uses resonant electrostatic actuation (REA) to realize low- and high-order Zernike modes with a single drive signal. Instead of the hundreds or thousands of electrodes deployed by traditional DMs, the proposed DM employs only 49 electrodes and eliminates the need for spatial control algorithms and associated hardware, thereby providing a compact low-cost alternative. It also exploits dynamic amplification to reduce power requirements and increase the stroke by driving the DM at resonance. The DM was fabricated using a commercial silicon-on-insulator (SOI) MEMS process. Experimental modal analysis was carried out using laser Doppler vibrometry (LDV) to identify mode shapes of the DM and their natural frequencies. We are able to observe all of the lowest eight Zernike modes. Full article
(This article belongs to the Special Issue Micro/Nano Electromechanical Sensors and Actuators)
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13 pages, 823 KiB  
Article
A Computational Geometric Parameter Optimization of the Thermomechanical Deicing Concept
by Ozan Tamer, Fabian Walter, Michael Sinapius and Markus Böl
Actuators 2022, 11(8), 223; https://doi.org/10.3390/act11080223 - 5 Aug 2022
Cited by 3 | Viewed by 1475
Abstract
Ice formation on aerodynamic surfaces is a safety-related issue in aviation. Thermal, mechanical, or hybrid systems are used to prevent or eliminate ice formation. To increase energy efficiency, new methods are being researched and tested, using new materials. This article aims to investigate [...] Read more.
Ice formation on aerodynamic surfaces is a safety-related issue in aviation. Thermal, mechanical, or hybrid systems are used to prevent or eliminate ice formation. To increase energy efficiency, new methods are being researched and tested, using new materials. This article aims to investigate in detail the geometrical parameters of a novel thermomechanical deicing concept based on the shape memory effect. The thermomechanical behavior of a shape memory alloy wire embedded in an elastomer can be described, using the transformation expansion coefficient. The approach includes the nonlinear phase transformation and the linear expansion of the alloy. Simulation results using the above approach are compared with experimental results. In addition, a parameter study of the geometric quantities is presented, where the individual effects of these quantities are investigated assuming that there is a block-like ice layer on the surface. The results for the behavior of the SMA show promising results in terms of describing the thermomechanical behavior of the wire. However, deviations are still observed in the thermal behavior of the embedding matrix. Full article
(This article belongs to the Special Issue Shape Memory Alloy Actuators)
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19 pages, 2388 KiB  
Article
Adaptive Transition Gait Planning of Snake Robot Based on Polynomial Interpolation Method
by Xiongding Liu, Guangjie Lin and Wu Wei
Actuators 2022, 11(8), 222; https://doi.org/10.3390/act11080222 - 5 Aug 2022
Cited by 7 | Viewed by 2272
Abstract
This paper mainly studies the transition gait planning by updating the parameters of snack robot motion control function through ROS nodes, including a straight running gait into a turning gait. In the practical scenario, when changing the control parameters, the joint angle of [...] Read more.
This paper mainly studies the transition gait planning by updating the parameters of snack robot motion control function through ROS nodes, including a straight running gait into a turning gait. In the practical scenario, when changing the control parameters, the joint angle of the snake robot will increase or decrease sharply, and the angular velocity and angular acceleration of the driving joints will also change, which results in oscillation and sideslip of the body. In the turning scene, the visual tracking will loss if the head joint of the snake robot causes the lateral movement and oscillation. To solve those problems, firstly, the dynamic model of the snake robot’s gait of serpentine movement is established. Then, we propose a method based on polynomial interpolation compensation to solve the body oscillation and sideslip caused by nodes updating. To further improve the efficiency of snake robot’s gait switching, an optimal dichotomy interpolation time search is proposed to realize the snake robot’s adaptive transition gait. Finally, some simulation experiments are verified the effectiveness of the proposed method. Full article
(This article belongs to the Special Issue Applications of Intelligent Control in Actuators Systems)
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21 pages, 3990 KiB  
Article
Mathematical Modeling of a Multi-Chamber Pneumatic Soft Actuator
by Eduardo Miguel Sierra and Jose Luis Ordoñez-Avila
Actuators 2022, 11(8), 221; https://doi.org/10.3390/act11080221 - 5 Aug 2022
Cited by 9 | Viewed by 2493
Abstract
Owing to their compliance with most shapes, soft actuators are regarded as cost-effective solutions for grasping irregular objects. The material properties of nonlinear elastic polymers are considered necessary for the correct implementation of these actuators. The analysis tends to be complex even for [...] Read more.
Owing to their compliance with most shapes, soft actuators are regarded as cost-effective solutions for grasping irregular objects. The material properties of nonlinear elastic polymers are considered necessary for the correct implementation of these actuators. The analysis tends to be complex even for simple movements defined by theoretically infinite degrees of freedom. This study offers a mathematical model that outlines a relationship between the energy provided by a pressure source and the expected behavior of multi-chamber pneumatic soft actuators through hyper-elastic material deformation interpretation, geometric approximations, and the vectorial representations of their segments. Digitally analyzed empirical results measured through lateral pictures of an actuator were taken at different pressure references. Direct comparisons between the average value of the tested angles and those calculated through the tuned mathematical model provide a maximum error of 0.647° for small deformations and an improved accuracy at higher pressure inputs. This study offers a valid tool applicable to the design of soft actuators and their further analysis without the need for overly complex methods. Full article
(This article belongs to the Section Actuators for Robotics)
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17 pages, 1158 KiB  
Article
LESO-Based Nonlinear Continuous Robust Stabilization Control of Underactuated TORA Systems
by Yihao Wang, Changzhong Pan, Jinsen Xiao, Zhijing Li and Chenchen Cui
Actuators 2022, 11(8), 220; https://doi.org/10.3390/act11080220 - 4 Aug 2022
Cited by 1 | Viewed by 1777
Abstract
In this paper, we consider the robust stabilization control problem of underactuated translational oscillator with a rotating actuator (TORA) system in the presence of unknown matched disturbances by employing continuous control inputs. A nonlinear continuous robust control approach is proposed by integrating the [...] Read more.
In this paper, we consider the robust stabilization control problem of underactuated translational oscillator with a rotating actuator (TORA) system in the presence of unknown matched disturbances by employing continuous control inputs. A nonlinear continuous robust control approach is proposed by integrating the techniques of backstepping and linear extended state observer (LESO). Specifically, based on the backstepping design methodology, a hyperbolic tangent virtual control law is designed for the first subsystem of the cascaded TORA model, via which an integral chain error subsystem is subsequently constructed and the well-known LESO technique is easy to implement. Then, an LEO is designed to estimate the lumped matched disturbances in real-time, and the influence of the disturbances is compensated by augmenting the feedback controller with the disturbance estimation. The convergence and stability of the entire control system are rigorously proved by utilizing Lyapunov theory and LaSalle’s invariance principle. Unlike some existing methods, the proposed controller is capable of generating robust and continuous control inputs, which guarantee that both the rotation and translation of TORA systems are stabilized at the origin simultaneously and smoothly, attenuating the influence of disturbances. Comparative simulation results are presented to demonstrate the effectiveness and superior control performance of the proposed method. Full article
(This article belongs to the Special Issue Advance Control Research for Underactuated Robot Systems)
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14 pages, 3165 KiB  
Article
Analysis of Pneumatic Artificial Muscles and the Inelastic Braid Assumption
by Jonathan M. Chambers and Norman M. Wereley
Actuators 2022, 11(8), 219; https://doi.org/10.3390/act11080219 - 4 Aug 2022
Cited by 1 | Viewed by 1690
Abstract
Pneumatic artificial muscles (PAMs) are becoming an increasingly popular form of soft actuator due to their unique actuation characteristics. The creation of accurate PAM actuation models is important for their successful implementation. However, PAM studies often employ actuation models that use simplifying assumptions [...] Read more.
Pneumatic artificial muscles (PAMs) are becoming an increasingly popular form of soft actuator due to their unique actuation characteristics. The creation of accurate PAM actuation models is important for their successful implementation. However, PAM studies often employ actuation models that use simplifying assumptions which make the models easier to formulate and use, but at the cost of reduced accuracy. One of the most commonly used assumptions, the inelastic braid assumption, suggests that the braid does not stretch, and therefore would not affect its geometry or actuation force. Although this assumption has often been cited as a likely source of model error, its use has persevered for decades due to researchers’ inability to directly measure the effects of braid elasticity. The recent development of a photogrammetric method to accurately measure PAM geometry now enables this analysis. This study seeks to assess the current default adoption of the inelastic braid assumption in PAM models by attempting to quantify the braid elasticity effects. This research finds that current models that use the inelastic braid assumption can underestimate PAM diameter by as much as 30%, and overestimate actuation force by as much as 70%. These results show that braid elasticity can have a substantial effect on the geometry and actuation force of PAMs, and demonstrates that the inelastic braid assumption may not be a suitable universal assumption for PAM modeling and analyses, especially when low-stiffness braid materials are used. Full article
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13 pages, 24958 KiB  
Article
Achieving Full Forward Flow of Valveless Piezoelectric Micropump Used for Micro Analysis System
by Kai Li, Xianxin Zhou, Haoyuan Zheng, Biao Liu, Shuo Chen, Weishan Chen and Junkao Liu
Actuators 2022, 11(8), 218; https://doi.org/10.3390/act11080218 - 4 Aug 2022
Cited by 2 | Viewed by 2153
Abstract
The valveless piezoelectric micropump has the advantages of simple structure, high precision and low cost, which can realize the directional transport of micro-fluid and wildly be applied in a micro analysis system. However, backflow at the outlet cannot be avoided due to the [...] Read more.
The valveless piezoelectric micropump has the advantages of simple structure, high precision and low cost, which can realize the directional transport of micro-fluid and wildly be applied in a micro analysis system. However, backflow at the outlet cannot be avoided due to the limitation of its working mechanism. Large reflux rate can increase the volume control accuracy per cycle, but reduces the stability of the micro analysis system. In order to achieve a full forward flow, which reduce the influence of backflow on the system’s stability, the reflux characteristics of the designed valveless piezoelectric micropump were studied. The condition proposed, which should be satisfied for obtaining full forward flow, is that the reflux rate should be less than 50%. The influence of relations between the size of the key structures and pumping characteristics are established, and the references for structural parameter selection to reduce backflow and achieve full forward flow are given. This paper highlights the methods of controlling the pumping performance and achieving full forward flow, based on structural parameter selection analysis and adjusting excitation. The reflux rate can be reduced to 5% when the inlet angle is increased to 9°. The experimental results verify the validity of the obtained results and the proposed methods of control. This work provides important references for applying valveless piezoelectric micropumps in micro analysis and precision-driven systems. Full article
(This article belongs to the Special Issue Piezoelectric Ultrasonic Actuators and Motors)
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26 pages, 7728 KiB  
Article
Application of Least-Squares Support-Vector Machine Based on Hysteresis Operators and Particle Swarm Optimization for Modeling and Control of Hysteresis in Piezoelectric Actuators
by Ayad G. Baziyad, Adnan S. Nouh, Irfan Ahmad and Abdulaziz Alkuhayli
Actuators 2022, 11(8), 217; https://doi.org/10.3390/act11080217 - 2 Aug 2022
Cited by 8 | Viewed by 2147
Abstract
Nanopositioning systems driven by piezoelectric actuators are widely used in different fields. However, the hysteresis phenomenon is a major factor in reducing the positioning accuracy of piezoelectric actuators. This effect makes the task of accurate modeling and position control of piezoelectric actuators challenging. [...] Read more.
Nanopositioning systems driven by piezoelectric actuators are widely used in different fields. However, the hysteresis phenomenon is a major factor in reducing the positioning accuracy of piezoelectric actuators. This effect makes the task of accurate modeling and position control of piezoelectric actuators challenging. In this paper, the learning and generalization capabilities of the model are efficiently enhanced to describe and compensate for the rate-independent and rate-dependent hysteresis using a kernel-based learning method. The proposed model is inspired by the classical Preisach hysteresis model, in which a set of hysteresis operators is used to address the problem of mapping, and then least-squares support-vector machines (LSSVM) combined with a particle swarm optimization (PSO) algorithm are used for identification. Two control schemes are proposed for hysteresis compensation, and their performance is evaluated through real-time experiments on a nanopositioning platform. First, an inverse model-based feedforward controller is designed based on the LSSVM model, and then a combined feedback/feedforward control scheme is designed using a classical control strategy (PID) to further enhance the tracking performance. For performance evaluation, different datasets with a variety of hysteresis loops are used during the simulation and experimental procedures. The results show that the proposed method is successful in enhancing the generalization capabilities of LSSVM training and achieving the best tracking performance based on the combination of feedforward control and PID feedback control. The proposed control scheme outperformed the inverse Preisach model-based control scheme in terms of both positioning accuracy and execution time. The control scheme that uses the LSSVM based on nonlinear autoregressive exogenous (NARX) models has significantly less computational complexity compared to our control scheme but at the expense of accuracy. Full article
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11 pages, 2850 KiB  
Article
Characterization of LCR Parallel-Type Electromagnetic Shunt Damper for Superconducting Magnetic Levitation
by Kentaro Fujita and Toshihiko Sugiura
Actuators 2022, 11(8), 216; https://doi.org/10.3390/act11080216 - 2 Aug 2022
Cited by 2 | Viewed by 1907
Abstract
This study investigated the effect of electromagnetic shunt dampers on the resonance amplitude reduction in a superconducting magnetic levitation system. There are two types of electromagnetic shunt dampers, series type and parallel type, depending on the configuration of the electric circuit, and their [...] Read more.
This study investigated the effect of electromagnetic shunt dampers on the resonance amplitude reduction in a superconducting magnetic levitation system. There are two types of electromagnetic shunt dampers, series type and parallel type, depending on the configuration of the electric circuit, and their damping characteristics may differ depending on the external resistance value in the circuit. In this study, after discussing the vibration-suppression effects of both types according to the governing equations, vibration experiments were conducted using both dampers with different resistance values. As a result, it was confirmed that, for the larger resistance value, the amplitude reduction effect is smaller in the series-type damper, while it remained high in the parallel type. We also performed numerical integrations, including the nonlinearity of magnetic force in the superconducting magnetic levitation system. As a result, it was numerically confirmed that the parallel-type damper can also be expected to reduce amplitude at a resonance caused by nonlinearity. Full article
(This article belongs to the Special Issue Advanced Technologies in Superconducting Actuators)
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12 pages, 8251 KiB  
Article
Suspension-Type of Flywheel Energy Storage System Using High Tc Superconducting Magnetic Bearing (SMB)
by Mochimitsu Komori, Hirohisa Kato and Ken-ichi Asami
Actuators 2022, 11(8), 215; https://doi.org/10.3390/act11080215 - 1 Aug 2022
Cited by 2 | Viewed by 1999
Abstract
In this paper, a new superconducting flywheel energy storage system is proposed, whose concept is different from other systems. The superconducting flywheel energy storage system is composed of a radial-type superconducting magnetic bearing (SMB), an induction motor, and some positioning actuators. The SMB [...] Read more.
In this paper, a new superconducting flywheel energy storage system is proposed, whose concept is different from other systems. The superconducting flywheel energy storage system is composed of a radial-type superconducting magnetic bearing (SMB), an induction motor, and some positioning actuators. The SMB is composed of a superconducting stator and a flywheel rotor. The flywheel rotor is suspended by the superconducting stator, whose one end is fixed to a stable and heavy base. Free-run experiments in the case of the unfixed stator are performed. The natural rotation decay curve, displacement at the upper position of the rotor and displacement at a lower position of the rotor are measured. Moreover, free-run experiments in the case of the fixed stator are performed, and the same dynamic characteristics of the unfixed stator are measured. Especially, impulse responses for the rotor in the case of an unfixed stator are very different from those in the case of a fixed stator. The experimental results discuss some important characteristics of the superconducting flywheel energy storage system, whose rotor is suspended by the superconducting stator. Full article
(This article belongs to the Special Issue Advanced Technologies in Superconducting Actuators)
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16 pages, 5556 KiB  
Review
Short Review of EMB Systems Related to Safety Concepts
by Simon Schrade, Xi Nowak, Armin Verhagen and Dieter Schramm
Actuators 2022, 11(8), 214; https://doi.org/10.3390/act11080214 - 31 Jul 2022
Cited by 8 | Viewed by 4084
Abstract
A growing interest in Electromechanical Brakes (EMBs) is discernible in the automotive industry. Nevertheless, no EMBs have ever been deployed for series production, although countless publications have been made, and patents have been filed. One reason for this is the need for the [...] Read more.
A growing interest in Electromechanical Brakes (EMBs) is discernible in the automotive industry. Nevertheless, no EMBs have ever been deployed for series production, although countless publications have been made, and patents have been filed. One reason for this is the need for the optimization of functional safety. Due to the missing mechanical/hydraulic link between the driver and the actuator, sophisticated concepts need to be elaborated upon. This paper presents the current state of the art of safety concepts for EMB systems (only publicly available publications are reviewed). An analysis of current regulatory and safety requirements is conducted to provide a base for design options. These design options are explored on the basis of an extensive patent and literature research. The various discovered designs are summarized and analyzed according to their (a) EMB actuators; (b) control topology; (c) energy supply; and (d) communication architecture. This paper concludes by revealing the weak points of the current systems. Full article
(This article belongs to the Section Actuators for Land Transport)
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21 pages, 6411 KiB  
Article
Flying State Sensing and Estimation Method of Large-Scale Bionic Flapping Wing Flying Robot
by Guangze Liu, Song Wang and Wenfu Xu
Actuators 2022, 11(8), 213; https://doi.org/10.3390/act11080213 - 31 Jul 2022
Cited by 4 | Viewed by 1895
Abstract
A large bionic flapping wing robot has unique advantages in flight efficiency. However, the fluctuation of fuselage centroid during flight makes it difficult for traditional state sensing and estimation methods to provide stable and accurate data. In order to provide stable and accurate [...] Read more.
A large bionic flapping wing robot has unique advantages in flight efficiency. However, the fluctuation of fuselage centroid during flight makes it difficult for traditional state sensing and estimation methods to provide stable and accurate data. In order to provide stable and accurate positioning and attitude information for a flapping wing robot, this paper proposes a flight state sensing and estimation method integrating multiple sensors. Combined with the motion characteristics of a large flapping wing robot, the autonomous flight, including the whole process of takeoff, cruise and landing, is realized. An explicit complementary filtering algorithm is designed to fuse the data of inertial sensor and magnetometer, which solves the problem of attitude divergence. The Kalman filter algorithm is designed to estimate the spatial position and speed of a flapping wing robot by integrating inertial navigation with GPS (global positioning system) and barometer measurement data. The state sensing and estimation accuracy of the flapping wing robot are improved. Finally, the flying state sensing and estimation method is integrated with the flapping wing robot, and the flight experiments are carried out. The results verify the effectiveness of the proposed method, which can provide a guarantee for the flapping wing robot to achieve autonomous flight beyond the visual range. Full article
(This article belongs to the Special Issue Mechanism Design and Control for Robotics)
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15 pages, 4258 KiB  
Article
Research on the Influence of Friction Pairs on the Output Characteristics of the Piezoelectric Ultrasonic Actuator
by Jie Deng, Jianfei Cheng, Yuntian Guan, He Li, Fei Lu and Weishan Chen
Actuators 2022, 11(8), 212; https://doi.org/10.3390/act11080212 - 30 Jul 2022
Cited by 1 | Viewed by 1701
Abstract
The piezoelectric ultrasonic actuator is driven by the friction coupling between the stator and mover. Its friction pairs are very important, but there are few studies on the long-term output stability. Therefore, zirconia (ZrO2) is selected as a stator material to [...] Read more.
The piezoelectric ultrasonic actuator is driven by the friction coupling between the stator and mover. Its friction pairs are very important, but there are few studies on the long-term output stability. Therefore, zirconia (ZrO2) is selected as a stator material to form friction pairs with four different wear-resistant materials: silicon nitride (Si3N4), ZrO2, bearing steel (GCr15) and polyether ether ketone (PEEK). Experiments show that the friction pair composed of ZrO2-Si3N4 is the best, and the attenuation percentage of the speed from the initial state to the end state in the speed rising stage of 50 m is 3.66%. A linear piezoelectric platform is developed based on the best friction pair; a maximum speed of 426.2 mm/s and a resolution of 85 nm are achieved. Full article
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