Subjects -> OCCUPATIONS AND CAREERS (Total: 33 journals)
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Advances in Developing Human Resources     Hybrid Journal   (Followers: 26)
American Journal of Pastoral Counseling     Hybrid Journal  
BMC Palliative Care     Open Access   (Followers: 33)
British Journal of Guidance & Counselling     Hybrid Journal   (Followers: 14)
Career Development and Transition for Exceptional Individuals     Hybrid Journal   (Followers: 9)
Career Development International     Hybrid Journal   (Followers: 18)
Career Development Quarterly     Hybrid Journal   (Followers: 5)
Community Development     Hybrid Journal   (Followers: 21)
Education + Training     Hybrid Journal   (Followers: 23)
Equality, Diversity and Inclusion : An International Journal     Hybrid Journal   (Followers: 20)
Field Actions Science Reports     Open Access  
Formation emploi     Open Access  
Health Care Analysis     Hybrid Journal   (Followers: 13)
Human Resource Development Review     Hybrid Journal   (Followers: 27)
Industrial and Organizational Psychology     Hybrid Journal   (Followers: 25)
International Journal for Educational and Vocational Guidance     Hybrid Journal   (Followers: 7)
International Journal for Quality in Health Care     Hybrid Journal   (Followers: 40)
International Journal of Health Care Quality Assurance     Hybrid Journal   (Followers: 14)
International Journal of Work Innovation     Hybrid Journal   (Followers: 2)
Journal of Career Assessment     Hybrid Journal   (Followers: 6)
Journal of Career Development     Hybrid Journal   (Followers: 10)
Journal of Human Capital     Full-text available via subscription   (Followers: 11)
Journal of Human Development and Capabilities : A Multi-Disciplinary Journal for People-Centered Development     Hybrid Journal   (Followers: 22)
Journal of Multicultural Counseling and Development     Hybrid Journal   (Followers: 7)
Journal of Psychological Issues in Organizational Culture     Hybrid Journal   (Followers: 8)
Journal of Vocational Behavior     Hybrid Journal   (Followers: 28)
Neurocritical Care     Hybrid Journal   (Followers: 17)
Palliative & Supportive Care     Hybrid Journal   (Followers: 33)
Performance Improvement Quarterly     Hybrid Journal   (Followers: 4)
Recherches & éducations     Open Access  
Rehabilitation Counseling Bulletin     Hybrid Journal   (Followers: 3)
Research on Economic Inequality     Hybrid Journal   (Followers: 9)
Vocations and Learning     Hybrid Journal   (Followers: 7)
Work and Occupations     Hybrid Journal   (Followers: 57)
Work, Employment & Society     Hybrid Journal   (Followers: 51)
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Trabajo : Revista de la Asociación Estatal de Centros Universitarios de Relaciones Laborales y Ciencias del Trabajo
Number of Followers: 0  

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ISSN (Print) 1136-3819 - ISSN (Online) 1136-3819
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  • Actuators, Vol. 11, Pages 64: Novel SPECTA Actuator to Improve Energy
           Recuperation and Efficiency

    • Authors: Elias Saerens, Raphaël Guy Furnémont, Julie Legrand, Stein Crispel, Pablo Lopez Garcia, Tom Verstraten, Bram Vanderborght, Dirk Lefeber
      First page: 64
      Abstract: The current state of the art in compliant actuation has already good performance, but this is still insufficient to provide a decent autonomy for the next generation of robots. In this paper, a next step is taken to improve the efficiency of actuators by tackling and enhancing the Series-Parallel Elastic Constant Torque Actuation (SPECTA) concept, which has previously been analyzed in simulations. In this work, the efficiency is increased further by decoupling the springs and their driving parts through the use of locking mechanisms, such that the motors are not always loaded and the springs can easily store energy from both input or output. Simulations have been performed to confirm this and they also showed that, in the SPECTA concept, it is always better to use high-speed motors instead of high-torque motors, even with non-efficient gearing. In this paper, the SPECTA concept is also validated experimentally with the use of a newly built test setup. In light of the obtained results, showing an increase in efficiency for almost all working points, it can be stated that SPECTA is a promising new actuation technology that allows for an increase in energy recuperation, efficiency, and autonomy.
      Citation: Actuators
      PubDate: 2022-02-22
      DOI: 10.3390/act11030064
      Issue No: Vol. 11, No. 3 (2022)
  • Actuators, Vol. 11, Pages 65: Modeling-Based EMG Signal (MBES) Classifier
           for Robotic Remote-Control Purposes

    • Authors: Michele Gabrio Antonelli, Pierluigi Beomonte Zobel, Francesco Durante, Mohammad Zeer
      First page: 65
      Abstract: The fast-growing human–robot collaboration predicts that a human operator could command a robot without mechanical interface if effective communication channels are established. In noisy, vibrating and light sensitive environments, some sensors for detecting the human intention could find critical issues to be adopted. On the contrary, biological signals, as electromyographic (EMG) signals, seem to be more effective. In order to command a laboratory collaborative robot powered by McKibben pneumatic muscles, promising actuators for human–robot collaboration due to their inherent compliance and safety features have been researched, a novel modeling-based electromyographic signal (MBES) classifier has been developed. It is based on one EMG sensor, a Myotrac one, an Arduino Uno and a proper code, developed in the Matlab environment, that performs the EMG signal recognition. The classifier can recognize the EMG signals generated by three hand-finger movements, regardless of the amplitude and time duration of the signal and the muscular effort, relying on three mathematical models: exponential, fractional and Gaussian. These mathematical models have been selected so that they are the best fitting with the EMG signal curves. Each of them can be assigned a consent signal for performing the wanted pick-and-place task by the robot. An experimental activity was carried out to test and achieve the best performance of the classifier. The validated classifier was applied for controlling three pressure levels of a McKibben-type pneumatic muscle. Encouraging results suggest that the developed classifier can be a valid command interface for robotic purposes.
      Citation: Actuators
      PubDate: 2022-02-22
      DOI: 10.3390/act11030065
      Issue No: Vol. 11, No. 3 (2022)
  • Actuators, Vol. 11, Pages 66: A Fault Diagnosis Approach for
           Electromechanical Actuators with Simulating Model under Small Experimental
           Data Sample Condition

    • Authors: Zhaoqin Peng, Zhengyi Sun, Juan Chen, Zilong Ping, Kunyu Dong, Jia Li, Yongling Fu, Enrico Zio
      First page: 66
      Abstract: Electromechanical actuators (EMAs) have shown a high efficiency in flight surface control with the development of more electric aircraft. In order to identify the abnormalities and potential failures of EMA, a methodology for fault diagnosis is developed. A simulating model of EMA is first built to perform different working states. Based on the modeling of EMA, the corresponding faults are then simulated to re-generate the fault data. Afterwards, a gated recurrent unit (GRU) and co-attention-based fault diagnosis approach is proposed to classify the working states of EMA. Experiments are conducted and a satisfying classification accuracy on simulated data is obtained. Furthermore, fault diagnosis on an actual working system is performed. The experimental results demonstrate that the proposed method has a high efficiency.
      Citation: Actuators
      PubDate: 2022-02-22
      DOI: 10.3390/act11030066
      Issue No: Vol. 11, No. 3 (2022)
  • Actuators, Vol. 11, Pages 67: Remaining Useful Life Prediction of an
           Aircraft Turbofan Engine Using Deep Layer Recurrent Neural Networks

    • Authors: Unnati Thakkar, Hicham Chaoui
      First page: 67
      Abstract: The turbofan engine is a pivotal component of the aircraft. Engine components are susceptible to degradation over the life of their operation, which affects the reliability and performance of an engine. In order to direct the necessary maintenance behavior, remaining useful life prediction is the key. This research uses machine learning to provide a prediction framework for an aircraft’s remaining useful life (RUL) based on the entire life cycle data and deterioration parameter data (ML). For the engine’s lifetime assessment, a Deep Layer Recurrent Neural Network (DL-RNN) model is presented. The suggested method is compared to Multilayer Perceptron (MLP), Nonlinear Auto Regressive Network with Exogenous Inputs (NARX), and Cascade Forward Neural Network (CFNN), as well as the Prognostics and Health Management (PHM) conference Challenge dataset and NASA’s C-MAPSS dataset. Mean Absolute Error (MAE) and Root Mean Square Error (RMSE) are calculated for both the datasets, and the values are in the range of 0.15% to 0.203% for DL-RNN, whereas for the other three topologies, they are in the range of 0.2% to 4.8%. Comparative results show a better predictive accuracy with respect to other ML algorithms.
      Citation: Actuators
      PubDate: 2022-02-22
      DOI: 10.3390/act11030067
      Issue No: Vol. 11, No. 3 (2022)
  • Actuators, Vol. 11, Pages 68: Design and Control of a Nonlinear Series
           Elastic Cable Actuator Based on the Hill Muscle Model

    • Authors: Yingbing Su, Huaiwu Zou, Hongrun Lu, Bingshan Hu, Hongliu Yu
      First page: 68
      Abstract: The bionic design of muscles is a research hotspot at present. Many researchers have designed bionic elastic actuators based on the Hill muscle model, and most of them include an active contraction element, passive contraction element and series elastic element, but they need more parametric design of mechanical structure and control under the guidance of Hill muscle model. In this research, a nonlinear series elastic cable actuating mechanism is designed in which the parameters of the elastic mechanism are optimized based on the Hill muscle model to fit the nonlinear passive elasticity of a muscle. Through the force–position relationship determined by the Hill muscle model, the output force and position of a nonlinear series elastic cable actuator are controlled to simulate the active contraction performance of a muscle. The experiments show that the proposed design and control method can make the nonlinear cable actuator have good muscle-like output force–displacement characteristics.
      Citation: Actuators
      PubDate: 2022-02-22
      DOI: 10.3390/act11030068
      Issue No: Vol. 11, No. 3 (2022)
  • Actuators, Vol. 11, Pages 69: Research on an Intelligent Driving Algorithm
           Based on the Double Super-Resolution Network

    • Authors: Taoyang Hang, Bo Li, Qixian Zhao, Shaoyi Bei, Xiao Han, Dan Zhou, Xinye Zhou
      First page: 69
      Abstract: Semantic segmentation plays a very important role in image processing, and has been widely used in intelligent driving, medicine, and other fields. With the development of semantic segmentation, the model has become more and more complex and the resolution of training pictures is higher and higher, so the requirements for required hardware facilities have become higher and higher. Many high-precision networks are difficult to apply in intelligent driving vehicles with limited hardware conditions, and will bring delay to recognition, which is not allowed in practical application. Based on the Dual Super-Resolution Learning (DSRL) network, this paper proposes a network model for training high-resolution pictures, adding a high-resolution convolution module which improves segmentation accuracy and speed while reducing computation. In a CamVid dataset, taking the road category as an example, IOU is 95.23%, which is 4% higher than DSRL, the real-time segmentation time of the same video is reduced by 46% from 120 s to 65 s, and the segmentation effect is better and faster, which greatly alleviates the recognition delay caused by high-resolution input.
      Citation: Actuators
      PubDate: 2022-02-23
      DOI: 10.3390/act11030069
      Issue No: Vol. 11, No. 3 (2022)
  • Actuators, Vol. 11, Pages 70: A 2-DOF Impact Actuator for Haptic

    • Authors: Sangyoon Kim, Woochan Lee, Jaeyoung Park
      First page: 70
      Abstract: The demand for realistic haptic feedback actuators has increased as mobile devices have increased in popularity. However, most current haptic actuators provide limited 1-DOF tactile sensations, such as vibrations. This paper presents a 2-DOF haptic impact actuator that can provide planar directional (e.g., x and y directional) and magnitude tactile cues to a user. We built an impact actuator that was designed to be of such a size that a user can grasp it with one hand. Multiple electromagnets of the actuator drive a permanent magnet to hit the actuator housing, creating an impact. For the control of the impact direction, we assumed the direction of a magnetic field vector at the centre of the actuator would follow that of a reference vector formed by voltage heading into the electromagnet array. The results of magnetic field measurements support our assumption by showing that the trend of the magnetic field vector coincided with that of the reference voltage vector. Furthermore, the measurement of the impact acceleration showed the trend that the impact direction follows the reference voltage vector.
      Citation: Actuators
      PubDate: 2022-02-24
      DOI: 10.3390/act11030070
      Issue No: Vol. 11, No. 3 (2022)
  • Actuators, Vol. 11, Pages 71: Downsizing Effects on Micro and Nano Comb

    • Authors: Alessio Buzzin, Andrea Rossi, Ennio Giovine, Giampiero de Cesare, Nicola Pio Belfiore
      First page: 71
      Abstract: Downscaling has been a focal task of Electronics and Electromechanics in the last few decades, and a great engine for technological progress as well. Nevertheless, a scaling operation affects device physics, functioning and performance. The present paper investigates about the impact of scaling on a test case compliant electrostatic micro or nano actuator that is under development with two preferred micro fabrication methods, namely, thick SOI and thin amorphous silicon. A series of numerical trials on materials strength, electro-mechanical characteristics, sensitivity and overall actuation performance have been carried out at different grades of down-scaling and of aspect ratio. This gave rise to new design charts that we propose here as a predictive and friendly guide to select the most appropriate micro fabrication method.
      Citation: Actuators
      PubDate: 2022-02-25
      DOI: 10.3390/act11030071
      Issue No: Vol. 11, No. 3 (2022)
  • Actuators, Vol. 11, Pages 72: Fault-Tolerant Control of Skid Steering
           Vehicles Based on Meta-Reinforcement Learning with Situation Embedding

    • Authors: Huatong Dai, Pengzhan Chen, Hui Yang
      First page: 72
      Abstract: Meta-reinforcement learning (meta-RL), used in the fault-tolerant control (FTC) problem, learns a meta-trained model from a set of fault situations that have a high-level similarity. However, in the real world, skid-steering vehicles might experience different types of fault situations. The use of a single initial meta-trained model limits the ability to learn different types of fault situations that do not possess a strong similarity. In this paper, we propose a novel FTC method to mitigate this limitation, by meta-training multiple initial meta-trained models and selecting the most suitable model to adapt to the fault situation. The proposed FTC method is based on the meta deep deterministic policy gradient (meta-DDPG) algorithm, which includes an offline stage and an online stage. In the offline stage, we first train multiple meta-trained models corresponding to different types of fault situations, and then a situation embedding model is trained with the state-transition data generated from meta-trained models. In the online stage, the most suitable meta-trained model is selected to adapt to the current fault situation. The simulation results demonstrate that the proposed FTC method allows skid-steering vehicles to adapt to different types of fault situations stably, while requiring significantly fewer fine-tuning steps than the baseline.
      Citation: Actuators
      PubDate: 2022-02-25
      DOI: 10.3390/act11030072
      Issue No: Vol. 11, No. 3 (2022)
  • Actuators, Vol. 11, Pages 73: Motion Trajectories Prediction of Lower Limb
           Exoskeleton Based on Long Short-Term Memory (LSTM) Networks

    • Authors: Bin Ren, Zhiqiang Zhang, Chi Zhang, Silu Chen
      First page: 73
      Abstract: A typical man–machine coupling system could provide the wearer a coordinated and assisted movement by the lower limb exoskeleton. The process of cooperative movement relies on the accurate perception of the wearer’s human movement information and the accurate planning and control of the joint movement of the lower limb exoskeleton. In this paper, a neural network and a Long-Short Term Memory (LSTM) machine learning model method is proposed to predict the actual movement trajectory of the human body’s lower limbs. Then a wearable joint angle measurement device was designed for gait trajectory prediction, which can be used for predictive control through machine learning methods. The experimental results show that the LSTM model can accurately predict the gait trajectory with an average mean square error. This method has practical significance for prediction the trajectory of the lower limb exoskeleton.
      Citation: Actuators
      PubDate: 2022-02-26
      DOI: 10.3390/act11030073
      Issue No: Vol. 11, No. 3 (2022)
  • Actuators, Vol. 11, Pages 74: A Soft Electro-Hydraulic Pneumatic Actuator
           with Self-Sensing Capability toward Multi-Modal Haptic Feedback

    • Authors: Haoyu Wang, Xiang Cheng, Pei Huang, Meng Yu, Jiaqi Ma, Shigang Peng, Yue Cheng, Yuan Yu, Weimin Yang, Pengfei Wang, Zhiwei Jiao
      First page: 74
      Abstract: Haptic feedback is appealing for achieving the realistic perception of environmental changes for human bodies in human–computer interaction fields. However, existing haptic actuators have some hurdles such as single mode, poor compatibility, or incomplete tactile information. In this study, we proposed a novel way to generate haptic feedback by designing a soft electro-hydraulic pneumatic actuator (SEHPA) with dual drive modes. The SEHPA was structured with silicone films, a silicone air chamber, flexible electrodes, and an insulating liquid dielectric for good human–machine compatibility. The SEHPA had the advantages of high output force (1.5 N at 10 kPa) and displacement (4.5 mm at 5 kPa), as well as various haptic notifications (0~400 Hz vibration). The electro-hydraulic drive method realized smooth output force changes at the millinewton level (0~40 mN) and output displacement changes at the micron level (0~800 μm), which further enriched the details of the tactile experience. In addition, the self-sensing capability of the SEHPA can be dedicated to monitoring and ensuring precise output. The SEHPAs can be potentially mounted on the fingertips to provide accurate tactile sensation once the manipulator touches an object through teleoperation. More invisible information can also be obtained by customizing various haptic notifications. The excellent response behavior and accurate tactile haptic feedback demonstrate the candidate for teleoperation fields.
      Citation: Actuators
      PubDate: 2022-03-02
      DOI: 10.3390/act11030074
      Issue No: Vol. 11, No. 3 (2022)
  • Actuators, Vol. 11, Pages 75: Leg Configuration Analysis and Prototype
           Design of Biped Robot Based on Spring Mass Model

    • Authors: Junjie Che, Yang Pan, Wei Yan, Jiexian Yu
      First page: 75
      Abstract: The leg structure with high dynamic stability can make the bionic biped robot have the inherent conditions to perform elastic and highly dynamic motion. Compared with the quadruped robot, the leg structure of the biped robot is more complex and has more degrees of freedom. This also complicates kinematic and dynamic modeling. In this paper, the kinematics model of a bionic biped robot is established. The leg configuration of the robot is a series parallel hybrid mechanism with five active joints and six passive joints. The mechanism is a spring mass model that interacts organically with the environment and mimics the characteristics of human walking well. By analyzing the topological configuration of leg mechanism, we use the screw theory to establish the forward and inverse kinematics models. Then, we build the prototype, and use a step gait to test the model and prototype. The research of this paper has obvious application significance for the design and iteration of biped robot prototype.
      Citation: Actuators
      PubDate: 2022-03-02
      DOI: 10.3390/act11030075
      Issue No: Vol. 11, No. 3 (2022)
  • Actuators, Vol. 11, Pages 76: Power-Efficient Soft Pneumatic Actuator
           Using Spring-Frame Collateral Compression Mechanism

    • Authors: Sungjun Kim, Seung Ryeol Lee, Sinyoung Lee, Dongun Lee, Dongjun Shin
      First page: 76
      Abstract: With the ongoing research on soft robots, the performance of soft actuators needs to be enhanced for more wide robotic applications. Currently, most soft robots based on pneumatic actuation are capable of assisting small systems, but they are not fully suited for supporting joints requiring large force and range of motion. This is due to the actuation characteristics of the pneumatic artificial muscle (PAM); they are relatively slow, inefficient, and experience a significant force reduction when the PAM contracts. Hence, we propose a novel PAM based on a spring-frame collateral compression mechanism. With only a single compressed air source, the external mesh-covered and inner spring-frame actuators of the proposed PAM operate simultaneously to generate considerable force. Additionally, the design of the internal actuator within the void space of PAM reduces the air consumption and consequently improves the actuator’s operating speed and efficiency. We experimentally confirmed that the proposed PAM exhibited 31.2% greater force, was 25.6% faster, and consumed 21.5% lower air compared to the conventional McKibben muscles. The performance enhancement of the proposed PAM improves the performance of soft robots, allowing the development of more compact robots with greater assistive range.
      Citation: Actuators
      PubDate: 2022-03-02
      DOI: 10.3390/act11030076
      Issue No: Vol. 11, No. 3 (2022)
  • Actuators, Vol. 11, Pages 77: Design and Testing of a New
           Piezoelectric-Actuated Symmetric Compliant Microgripper

    • Authors: Zekui Lyu, Qingsong Xu
      First page: 77
      Abstract: Precise and stable operations in micromanipulation and microassembly require a high-performance microgripper. To improve the predominant static and dynamic characteristics, a novel piezoelectric-actuated compliant microgripper is designed, analyzed, and tested in this paper. The microgripper realizes a large gripping stroke by integrating a compliant bridge mechanism, an L-shaped mechanism, and a levered parallelogram mechanism. Optimization technology based on response surface analysis is applied to demonstrate the influence of structural parameters on the microgripper performance. Simulation results of finite element analysis reveal the superior performance of the designed microgripper in terms of gripping displacement, mechanism stiffness, equivalent stress, and natural frequency. A gripper prototype has been fabricated, and experimental studies have been conducted to test the microgripper’s physical properties. Experimental results show that the microgripper can grasp micro-objects with a maximum jaw motion stroke of 312.8 μm, natural frequency of 786 Hz, motion resolution of ±0.6 μm, and force resolution of ±1.69 mN. The gripping tests of an optical fiber with a diameter of 200 μm and a metal sheet with a thickness of 100 μm have been performed to demonstrate its gripping capability with position and force control.
      Citation: Actuators
      PubDate: 2022-03-03
      DOI: 10.3390/act11030077
      Issue No: Vol. 11, No. 3 (2022)
  • Actuators, Vol. 11, Pages 78: Robust Adaptive Control of Knee
           Exoskeleton-Assistant System Based on Nonlinear Disturbance Observer

    • Authors: Anwer S. Aljuboury, Akram Hashim Hameed, Ahmed R. Ajel, Amjad J. Humaidi, Ahmed Alkhayyat, Ammar K. Al Mhdawi
      First page: 78
      Abstract: This study presents a control design of an angular position for the exoskeleton knee assistance system based on a model reference adaptive control (MRAC) strategy. Three schemes of the MRAC design have been proposed: the classical MRAC, MRAC with an adaptive disturbance observer, and MRAC with a nonlinear observer. The stability analysis for each scheme has been conducted and developed based on the Lyapunov theorem to prove the uniform ultimate bound of tracking and estimation errors. In addition, the adaptive laws have been developed for the proposed schemes according to the stability analysis. The effectiveness of the proposed state and output feedback controllers has been verified via computer simulation. The results based on numerical simulation have shown that the MRAC with a nonlinear observer could give better robustness characteristics and better performance in terms of tracking and estimation errors as compared to the other controllers.
      Citation: Actuators
      PubDate: 2022-03-04
      DOI: 10.3390/act11030078
      Issue No: Vol. 11, No. 3 (2022)
  • Actuators, Vol. 11, Pages 79: Discussion on the Stiffness of the Drive
           Chain in the Legs of Biped Robots

    • Authors: Ruilong Du, Sumian Song, Haihui Yuan, Daming Nie, Jason Gu
      First page: 79
      Abstract: Biped robots’ locomotion is realized by driving the joint motion via a drive chain. Therefore, the stiffness of the drive chain is an important factor that affects the drive performance and can influence the locomotion behavior of the biped robot. This work focused on the influence of the stiffness of the leg’s drive chain using a mass-spring model based on the biped robot AIRO built in Zhejiang Lab. Methods for determination of the parameters in the proposed model were presented, including the use of ANSYS Workbench to determine the stiffness parameters and the determination of the inertia parameters by dynamic modelling of the biped robot. Simulation results show that special attention should be paid to the stiffness of the drive train of the leg when designing a biped robot to ensure the walking capability of the robot. Using the model proposed in this work, relations between the executed accuracy of the joint trajectories and the stiffness can be analyzed; after that, the stiffness parameters can be optimized. In addition, simulation results also showed that attention should be paid to manufacturing tolerances to ensure the symmetry of the legs of the bipedal robot in order to reduce the vibration of the robot body. Experiments were conducted on AIRO for validating the proposed model and the simulation analysis.
      Citation: Actuators
      PubDate: 2022-03-04
      DOI: 10.3390/act11030079
      Issue No: Vol. 11, No. 3 (2022)
  • Actuators, Vol. 11, Pages 80: Review of Brake-by-Wire System and Control

    • Authors: Dexiang Li, Cao Tan, Wenqing Ge, Jin Cui, Chaofan Gu, Xuwen Chi
      First page: 80
      Abstract: In accordance with the developing trend of “safety, comfort and low-carbon” technology, the market for intelligent X-by-wire chassis is huge. A new requirement of the X-by-wire system, including the response, accuracy, energy consumption and fault-tolerance, is put forward. Based on the analysis of the structure and design flow of the brake-by-wire (BBW) system, this paper analyzes the research status and development trend of the control methods of braking force, coordination control strategies and fault-tolerant control of the BBW system. The application possibilities of direct-driving technology in the BBW system are analyzed. At present, the key points of research focus on considering the influence of the multi-field coupling effect in the design, observing and compensating various nonlinear factors, and having a higher requirement for fault-tolerant control. Finally, an intelligent direct-driving BBW system is proposed as a research direction, which takes high efficiency and energy saving as a foothold and aims at breakthroughs in dynamic response, control accuracy and fault-tolerant abilities.
      Citation: Actuators
      PubDate: 2022-03-04
      DOI: 10.3390/act11030080
      Issue No: Vol. 11, No. 3 (2022)
  • Actuators, Vol. 11, Pages 81: Understanding Shape Memory Alloy Torsional
           Actuators: From the Conceptual to the Preliminary Design

    • Authors: Mario Sansone, Salvatore Ameduri, Antonio Concilio, Enrico Cestino
      First page: 81
      Abstract: Shape memory alloy actuators have been studied for more than thirty years. Many experimental tests have been performed, and several patents have been registered. However, designing such devices is still a challenging task. On the one hand, models are not yet able to provide the accuracy required to replace a substantial portion of the experimental tests; on the other hand, it seems that a gap exists in the literature between the main ideas behind SMA torsional actuators and their actual implementation. This work is a systematic effort to fill this gap, helping researchers and designers in developing SMA torsional actuators with a particular focus on aeronautical applications. This paper reports all the steps toward the preliminary design of such devices, using a state-of-the-art, commercially available FEM software. Moreover, the SMA rods’ behaviour under mechanical and thermal loading is thoroughly examined, looking at monitoring stress, temperature, torque and martensite evolution simultaneously, and thus providing a holistic vision of the macroscopic phenomena involved during phase transformations. Simple aerodynamic load predictions are also performed, using Xfoil for three classes of aircraft (medium size UAV, Four-Seat Aircraft and Regional Transport Aircraft).
      Citation: Actuators
      PubDate: 2022-03-06
      DOI: 10.3390/act11030081
      Issue No: Vol. 11, No. 3 (2022)
  • Actuators, Vol. 11, Pages 82: Implications of Spatially Constrained
           Bipennate Topology on Fluidic Artificial Muscle Bundle Actuation

    • Authors: Emily Duan, Matthew Bryant
      First page: 82
      Abstract: In this paper, we investigate the design of pennate topology fluidic artificial muscle bundles under spatial constraints. Soft fluidic actuators are of great interest to roboticists and engineers, due to their potential for inherent compliance and safe human–robot interaction. McKibben fluidic artificial muscles are an especially attractive type of soft fluidic actuator, due to their high force-to-weight ratio, inherent flexibility, inexpensive construction, and muscle-like force-contraction behavior. The examination of natural muscles has shown that those with pennate fiber topology can achieve higher output force per geometric cross-sectional area. Yet, this is not universally true for fluidic artificial muscle bundles, because the contraction and rotation behavior of individual actuator units (fibers) are both key factors contributing to situations where bipennate muscle topologies are advantageous, as compared to parallel muscle topologies. This paper analytically explores the implications of pennation angle on pennate fluidic artificial muscle bundle performance with spatial bounds. A method for muscle bundle parameterization as a function of desired bundle spatial envelope dimensions has been developed. An analysis of actuation performance metrics for bipennate and parallel topologies shows that bipennate artificial muscle bundles can be designed to amplify the muscle contraction, output force, stiffness, or work output capacity, as compared to a parallel bundle with the same envelope dimensions. In addition to quantifying the performance trade space associated with different pennate topologies, analyzing bundles with different fiber boundary conditions reveals how bipennate fluidic artificial muscle bundles can be designed for extensile motion and negative stiffness behaviors. This study, therefore, enables tailoring the muscle bundle parameters for custom compliant actuation applications.
      Citation: Actuators
      PubDate: 2022-03-09
      DOI: 10.3390/act11030082
      Issue No: Vol. 11, No. 3 (2022)
  • Actuators, Vol. 11, Pages 83: Cutting Mechanism Rotor System Dynamic
           Characteristics of Cantilever Roadheader under Random Hard Rock Load

    • Authors: Zhonghai Zhang, Shiqi Chen, Yutao Liu, Hao Wang, Chao Cao
      First page: 83
      Abstract: Accurately mastering the power transmission characteristics of the cutting arm transmission shaft system is key to improving the reliability and working capacity of the cantilever roadheader. Based on the rigid–flexible coupling vibration characteristic modeling of the roadheader cutting arm, the vibration characteristics of different substructures in the transmission shaft system of the roadheader cutting arm were considered, the dynamic characteristic model was comprehensively constructed, and the numerical analysis was carried out with the parameters of the XTR260 tunnel hard rock roadheader to compare the vibration characteristics of the cutting head under different cutting conditions. The experiment was carried out by using an artificial concrete wall, and the measurement results verify the established dynamic model that lays the foundation for the dynamic design of a high-performance roadheader.
      Citation: Actuators
      PubDate: 2022-03-09
      DOI: 10.3390/act11030083
      Issue No: Vol. 11, No. 3 (2022)
  • Actuators, Vol. 11, Pages 84: Evaluation of Fiber-Reinforced Modular Soft
           Actuators for Individualized Soft Rehabilitation Gloves

    • Authors: Shota Kokubu, Yuanyuan Wang, Pablo E. Tortós Vinocour, Yuxi Lu, Shaoying Huang, Reiji Nishimura, Ya-Hsin Hsueh, Wenwei Yu
      First page: 84
      Abstract: Applying soft actuators to hand motion assist for rehabilitation has been receiving increasing interest in recent years. Pioneering research efforts have shown the feasibility of soft rehabilitation gloves (SRGs). However, one important and practical issue, the effects of users’ individual differences in finger size and joint stiffness on both bending performance (e.g., Range of motion (ROM) and torque) and the mechanical loads applied to finger joints when the actuators are placed on a patient’s hand, has not been well investigated. Moreover, the design considerations of SRGs for individual users, considering individual differences, have not been addressed. These, along with the inherent safety of soft actuators, should be investigated carefully before the practical use of SRGs. This work aimed to clarify the effects of individual differences on the actuator’s performance through a series of experiments using dummy fingers designed with individualized parameters. Two types of fiber-reinforced soft actuators, the modular type for assisting each joint and conventional (whole-finger assist) type, were designed and compared. It was found that the modular soft actuators respond better to individual differences set in the experiment and exhibit a superior performance to the conventional ones. By suitable connectors and air pressure, the modular soft actuators could cope with the individual differences with minimal effort. The effects of the individualized parameters are discussed, and design considerations are extracted and summarized. This study will play an important role in pushing forward the SRGs to real rehabilitation practice.
      Citation: Actuators
      PubDate: 2022-03-09
      DOI: 10.3390/act11030084
      Issue No: Vol. 11, No. 3 (2022)
  • Actuators, Vol. 11, Pages 85: Distributed Drive Electric Bus Handling
           Stability Control Based on Lyapunov Theory and Sliding Mode Control

    • Authors: Feng Zhang, Hongchao Xiao, Yong Zhang, Gang Gong
      First page: 85
      Abstract: To improve the handling stability of distributed drive electric buses, a vehicle stability control system based on direct yaw moment control (DYC) with a hierarchical control structure was designed. Considering that the vehicle dynamics system is highly nonlinear, a nonlinear controller based on Lyapunov stability theory was designed to calculate the required additional yaw moment of the vehicle in the upper controller. In the lower controller, the additional yaw moment is distributed to four wheel-side motors according to the equal proportion torque distribution method, and the direction of wheel-side motor output torque is determined based on the steering state of the vehicle. A co-simulation based on Simulink and Trucksim was conducted to verify the designed controller under two extreme conditions. Simulation results indicate that the proposed method performs feasibly and effectively in the handling stability of vehicles. Compared with traditional sliding mode control (SMC), the proposed control strategy can significantly reduce the chattering of the system, which provides a theoretical basis for the application of this yaw stability control method in engineering practice.
      Citation: Actuators
      PubDate: 2022-03-10
      DOI: 10.3390/act11030085
      Issue No: Vol. 11, No. 3 (2022)
  • Actuators, Vol. 11, Pages 86: A Bi-State Shape Memory Material Composite
           Soft Actuator

    • Authors: Ramprasad Rajagopalan, Andrew J. Petruska, David Howard
      First page: 86
      Abstract: Shape memory materials have been widely used as programmable soft matter for developing multifunctional hybrid actuators. Several challenges of fabrication and effective modelling of these soft actuating systems can be addressed by implementing novel 3D printing techniques and simulations to aid the designer. In this study, the temperature-dependent recovery of an embedded U-shaped Shape Memory Alloy (SMA) and the shape fixity of a 3D-printed Shape Memory Polymer (SMP) matrix were exploited to create a bi-state Shape Memory Composite (SMC) soft actuator. Electrical heating allowed the SMA to achieve the bi-state condition, undergoing phase transformation to a U shape in the rubbery phase and a flat shape in the glassy phase of the SMP. A COMSOL Multiphysics model was developed to predict the deformation and recovery of the SMC by leveraging the in-built SMA constitutive relations and user-defined material subroutine for the SMP. The bi-state actuation model was validated by capturing the mid-point displacement of the 80 mm length × 10 mm width × 2 mm-thick 3D-printed SMC. The viability of the SMC as a periodic actuator in terms of shape recovery was addressed through modelling and simulation. Results indicated that the proposed COMSOL model was in good agreement with the experiment. In addition, the effect of varying the volume ratio of the SMA wire in the SMC on the maximum and recovered deflection was also obtained. Our model can be used to design SMC actuators with various performance profiles to facilitate future designs in soft robotics and wearable technology applications.
      Citation: Actuators
      PubDate: 2022-03-11
      DOI: 10.3390/act11030086
      Issue No: Vol. 11, No. 3 (2022)
  • Actuators, Vol. 11, Pages 87: Evaluation Method of Soil Surface Roughness
           after Ditching Operation Based on Wavelet Transform

    • Authors: Lichao Liu, Quanpeng Bi, Qianwei Zhang, Junjie Tang, Dawei Bi, Liqing Chen
      First page: 87
      Abstract: Soil surface roughness (SSR) is an important parameter affecting surface hydrology, erosion, gas exchange and other processes. The surface roughness of the farmland environment is directly related to the tillage process. In order to accurately characterize the random roughness (RR) parameters of the surface after ditching, a three-dimensional (3D) digital model of the surface was obtained by laser scanning under the conditions of an indoor ditching test, and the influence of oriented roughness components formed by removing ridge characteristics on the RR of the surface was analyzed by introducing the wavelet processing method. For this reason, four groups of ditching depths and two types of surface conditions (whether the surface was agglomerated or not) were designed in this paper. By comparing the root mean squared height (RMSH) and correlation length (CL) data calculated before and after wavelet processing under each group of tests, it was concluded that the RMSH values of the four groups before and after wavelet processing all change more than 200%, the change amplitude reached 271.02% under the treatment of 12 cm ditching depth, meanwhile, the average CL value of five cross-sections under each group of ditching depths decreased by 1.43–2.28 times, which proves that the oriented roughness component formed by furrows and ridges has a significant influence on the calculation of RR. By further analyzing the roughness value differences of clods and pits in different directions and local areas before and after wavelet transform, it was shown that the wavelet transform can effectively remove the surface anisotropy characteristics formed in the tillage direction and provide a uniform treatment method for the evaluation of surface RR at different ditching depths.
      Citation: Actuators
      PubDate: 2022-03-12
      DOI: 10.3390/act11030087
      Issue No: Vol. 11, No. 3 (2022)
  • Actuators, Vol. 11, Pages 88: Study on Buckling Characteristics of a
           Convex Tape-Shaped Ti-Ni Shape Memory Alloy Element for Application to
           Passive Vibration Isolator Devices and Force Limit Devices

    • Authors: Hiroki Cho, Sho Nagamatsu, Takumi Sasaki
      First page: 88
      Abstract: The tape-shaped Ti-Ni shape memory alloy (SMA) shows negative or quasi-zero stiffness during post-buckling deformation, and this characteristic can be applied to passive vibration isolator devices and force limit devices. Design calculation of the buckling load and the negative stiffness gradient after buckling of tape-shaped SMA element are required to apply the SMA element to these devices. When the cross-section of the SMA element is convex tape shaped, an improvement in buckling properties is expected. In this study, the effects of the curvature of the cross-section on the buckling characteristics of convex tape-shaped SMA elements were investigated by the 3D finite element method (3D-FEM) and material testing. The results of the study indicate that the buckling load and negative stiffness gradient of convex tape-shaped SMA elements tend to increase with increasing curvature of the cross-section. Furthermore, when the convex tape-shaped SMA elements buckled in the convex direction of the cross-section, the loading stress was approximately equivalent to that of buckling a flat tape-shaped SMA elements. Therefore, the convex tape-shaped SMA element is considered to be more suitable for device application compared to the flat tape-shaped SMA element, because the buckling characteristics of convex tape-shaped SMA elements can be controlled by adjusting the curvature of the cross-section without changing the dimensions.
      Citation: Actuators
      PubDate: 2022-03-14
      DOI: 10.3390/act11030088
      Issue No: Vol. 11, No. 3 (2022)
  • Actuators, Vol. 11, Pages 89: Development of Variable Viscoelastic Joint
           Module Performance Evaluation and Proposal of Application Examples

    • Authors: Tetsuhito Fujita, Yusuke Shimoda, Katsuki Machida, Manabu Okui, Rie Nishihama, Taro Nakamura
      First page: 89
      Abstract: With the diversification of robots, modularization of robots has been attracting attention. In our previous study, we developed a robot that mimics the principle of human joint drive using a straight-fiber-type pneumatic rubber artificial muscle (“artificial muscle”) and a magnetorheological fluid brake (“MR brake”). The variable viscoelastic joints have been modularized. Therefore, this paper evaluates the basic characteristics of the developed Joint Module, characterizes the variable viscoelastic joint, and compares it with existing modules. As basic characteristics, we confirmed that the Joint Module has a variable viscoelastic element by experimentally verifying the joint angle, stiffness, viscosity, and tracking performance of the generated torque to the command value. As a characteristic evaluation, we verified the change in motion and response to external disturbances due to differences in driving methods through simulations and experiments and proved the strength of the variable viscoelastic joint against external disturbances, which is a characteristic of variable viscoelastic joints. Based on the results of the basic characterization and the characterization of the variable viscoelastic drive joint, we discussed what kind of device the Joint Module is suitable to be applied to and clarified the position of the variable viscoelastic joint as an actuator system.
      Citation: Actuators
      PubDate: 2022-03-14
      DOI: 10.3390/act11030089
      Issue No: Vol. 11, No. 3 (2022)
  • Actuators, Vol. 11, Pages 90: Modeling and Control Design of a
           Contact-Based, Electrostatically Actuated Rotating Sphere

    • Authors: Michael Olbrich, Mario Farny, Martin Hoffmann, Christoph Ament
      First page: 90
      Abstract: The performance of micromirrors in terms of their maximum deflection is often limited due to mechanical constraints in the design. To increase the range of achievable deflection angles, we present a novel concept in which a free-lying sphere with a flat side as reflector can be rotated. Due to the large forces needed to move the sphere, multiple electrostatic actuators are used to cooperatively rotate the sphere in iterative steps by impacts and friction. A parameterized system-level model of the configuration is derived, which considers arbitrary multi-contact scenarios and can be used for simulation, analysis, and control design purposes. Due to the complex, indirect relation between the actuator voltages and the sphere motion, model-based numerical optimization is applied to obtain suitable system inputs. This results in rotation sequences, which can be understood as a sequence of motion primitives, thus transforming the continuous time model into an abstract discrete time model. Based on this, we propose a feedback control strategy for trajectory following, considering model uncertainties by a learning scheme. High precision is achieved by an extension controlling the angular change of each rotation step. The suitability of the overall approach is demonstrated in simulation for maximum angles of 40°, achieving angular velocities of approximately 10°/s.
      Citation: Actuators
      PubDate: 2022-03-15
      DOI: 10.3390/act11030090
      Issue No: Vol. 11, No. 3 (2022)
  • Actuators, Vol. 11, Pages 91: Control Strategies for Highly Gyroscopic
           Outer Rotors with Diametral Enlargement in Active Magnetic Bearings

    • Authors: Timo Hopf, Michael Richter, Benedikt Schüßler, Stephan Rinderknecht
      First page: 91
      Abstract: Flywheels are used for peak shaving or load smoothing to generate a higher efficiency and a more stable power supply. Therefore, this paper investigates highly integrated outer rotor flywheels levitated by active magnetic bearings (AMB). Due to the highly gyroscopic behavior and the diametrical enlargement under rotation, the system behavior changes with the speed, leading to a significant decrease in the maximum force and maximum force slew rate of the AMB. Thus, the speed range in which a decentralized feedback control stabilizes the system is reduced. In the literature, there are numerous approaches for coping with gyroscopic behavior. However, there are far fewer investigations for explicit consideration of the change in the air gap in the control structure. Therefore, the goal of this work is to find a control strategy to reduce the effect of the gyroscopic behavior as well as the change of the air gap. The authors propose a control strategy combining a cross feedback control with a decentralized variable feedback control. With this combination, the drawbacks of the previously described effects are compensated, leading to a higher operating range of the system and a reduced utilization of the amplifier without overcompensation at lower rotational speeds.
      Citation: Actuators
      PubDate: 2022-03-15
      DOI: 10.3390/act11030091
      Issue No: Vol. 11, No. 3 (2022)
  • Actuators, Vol. 11, Pages 92: Pneumatic Soft Robots: Challenges and

    • Authors: Hang Su, Xu Hou, Xin Zhang, Wen Qi, Shuting Cai, Xiaoming Xiong, Jing Guo
      First page: 92
      Abstract: In the field of robotics, soft robots have been showing great potential in the areas of medical care, education, service, rescue, exploration, detection, and wearable devices due to their inherently high flexibility, good compliance, excellent adaptability, and natural and safe interactivity. Pneumatic soft robots occupy an essential position among soft robots because of their features such as lightweight, high efficiency, non-pollution, and environmental adaptability. Thanks to its mentioned benefits, increasing research interests have been attracted to the development of novel types of pneumatic soft robots in the last decades. This article aims to investigate the solutions to develop and research the pneumatic soft robot. This paper reviews the status and the main progress of the recent research on pneumatic soft robots. Furthermore, a discussion about the challenges and benefits of the recent advancement of the pneumatic soft robot is provided.
      Citation: Actuators
      PubDate: 2022-03-16
      DOI: 10.3390/act11030092
      Issue No: Vol. 11, No. 3 (2022)
  • Actuators, Vol. 11, Pages 93: A Compound Scheme Based on Improved ADRC and
           Nonlinear Compensation for Electromechanical Actuator

    • Authors: Mingyue Zhang, Qingdang Li
      First page: 93
      Abstract: A compound scheme, based on an improved active disturbance rejection controller (ADRC) and nonlinear compensation, is developed for the electromechanical actuator (EMA) system in this paper. First, considering the influences of backlash, friction on the EMA system, a model for the EMA system is presented. The LuGre model and Hysteresis inverse model are used to compensate for the friction and backlash phenomenon. Then, the method of improved ADRC, based on the Fal function filter and a Linear extended state observer (LESO), is investigated. Simultaneously, since the controller parameters of the improved ADRC are complicated, the non-dominated sorting genetic algorithm II (NSGA-II) is presented to optimize the controller parameters, to achieve the best dynamic response. Finally, simulation and experiment are presented to validate the effectiveness of the proposed method. Under the nonlinear compensation, the performance of the proposed compound scheme is compared with the conventional proportional integral (PI) controller, in terms of step response analysis and sine wave response analysis. Simulation and experiments show that the proposed controller provides high-performance dynamic characteristics.
      Citation: Actuators
      PubDate: 2022-03-17
      DOI: 10.3390/act11030093
      Issue No: Vol. 11, No. 3 (2022)
  • Actuators, Vol. 11, Pages 94: A Paper-Based Cantilever Beam Mini Actuator
           Using Hygro-Thermal Response

    • Authors: Laura Alejandra Ireta-Muñoz, Isaias Cueva-Perez, Juan Jose Saucedo-Dorantes, Angel Pérez-Cruz
      First page: 94
      Abstract: New technological and scientific advances in the development of sensors and actuators demand the development of new devices to deal with recent problems and challenges in these new and emerging processes. Moreover, paper-based devices have tremendous potential for developing actuators as paper exhibits capillary transport and hygroexpansion due to swelling of the fibers when absorbing water. Therefore, this paper proposes a mini actuator that is based on a hygro-thermal-paper-based cantilever beam that is activated by means of a droplet of an aqueous solution in combination with a circulating electrical current to analyze its response. The contribution of this proposal includes the analysis of the flexural response of the mini actuator when it is tested by using two different solutions: distilled water and a water/alcohol solution. Additionally, four cases related to the droplet volume are studied and a statistical analysis of the bending responses is presented. The results achieved show that that water-alcohol solutions have a lower deviation in comparison with water only. Moreover, it is demonstrated that a specific change in the maximum displacement is obtained according to the volume and the type of solution. Thus, it is suggested that the response of the mini actuator can be tuned using different aqueous solutions.
      Citation: Actuators
      PubDate: 2022-03-17
      DOI: 10.3390/act11030094
      Issue No: Vol. 11, No. 3 (2022)
  • Actuators, Vol. 11, Pages 95: High-Precision Anti-Interference Control of
           Direct Drive Components

    • Authors: Jieji Zheng, Xianliang Jiang, Guangan Ren, Xin Xie, Dapeng Fan
      First page: 95
      Abstract: This study presents a compound control algorithm that enhances the servo accuracy and disturbance suppression capability of direct drive components (DDCs). The servo performance of DDCs is easily affected by external disturbance and the deterioration of assembly characteristics due to a lack of deceleration device. The purpose of this study is to compensate for the impact of external and internal disturbances on the system. First, a linear state space model of the system is established. Second, we analyzed the main factors restricting the performance of DDCs which includes sensor noise, friction and external disturbance. Then, a fractional-order proportional integral (FOPI) controller was used to eliminate the steady-state error caused by the time-invariable disturbance which can also improve the system’s anti-interference capability. A state-augmented Kalman filter (SAKF) was proposed to suppress the quantization noise and compensate for the time-varying disturbances simultaneously. The effectiveness of the proposed compound algorithm was demonstrated by comparative experiments, demonstrating a maximum 89.34% improvement. The experimental results show that, compared with the traditional PI controller, the FOPISAKF controller can not only improve the tracking accuracy of the system, but also enhance the disturbance suppression ability.
      Citation: Actuators
      PubDate: 2022-03-19
      DOI: 10.3390/act11030095
      Issue No: Vol. 11, No. 3 (2022)
  • Actuators, Vol. 11, Pages 28: Study on Properties of Potassium Sodium
           Niobate Coating Prepared by High Efficiency Supersonic Plasma Spraying

    • Authors: Longlong Zhou, Xuewu Li, Dongyu He, Weiling Guo, Yanfei Huang, Gengchao He, Zhiguo Xing, Haidou Wang
      First page: 28
      Abstract: In order to realize the construction of environmentally friendly potassium sodium niobate ceramic coating on metal surface, potassium sodium niobate ceramic coating was prepared by supersonic plasma spraying technology. The morphology, element extension and phase structure of such coating were investigated. The dielectric and ferroelectric properties were also analyzed. The results show that the coating has good quality and tetragonal phase structure. When test frequency ≥ 2 MHz, the dielectric constant is stable at about 300, and also dielectric loss is stable at about 0.05. The coating exhibits good hysteresis loops under different applied electric fields. When the applied electric field is 16 KV/cm, residual polarization value of as-prepared coating reaches 17.02 μC·cm−2.
      Citation: Actuators
      PubDate: 2022-01-18
      DOI: 10.3390/act11020028
      Issue No: Vol. 11, No. 2 (2022)
  • Actuators, Vol. 11, Pages 29: Spall Fault Quantification Method for Flight
           Control Electromechanical Actuator

    • Authors: Mohamed A. A. Ismail, Edward Balaban, Jens Windelberg
      First page: 29
      Abstract: Flight control electro-mechanical actuators (EMAs) are among the primary onboard systems that significantly influence the reliability and safety of unmanned aerial vehicles. Recent reliability studies have shown that the ball-screw element of a flight control EMA is subject to oscillating operating conditions that may initiate rapid degradation, such as fatigue spall defects. Accordingly, detecting and quantifying such faults are crucial for developing efficient fault prognostic and remaining useful life estimation capabilities. In this study, a vibration-based fault quantification method is developed to quantify the fatigue faults of a ball-screw mechanism of an EMA. The method is based on identifying the ball passing instants through a localized surface defect on the vibrational jerk rather than the vibrational acceleration measurement. The jerk is numerically determined from conventional accelerometers using a Savitzky–Golay differentiator. This method was successfully tested for ball bearings and it is adjusted in this paper for ball-screw faults. The experimental validation is investigated on a set of fault-seeded samples on NASA’s Ames Research Center Flyable Electro-Mechanical Actuator test stand.
      Citation: Actuators
      PubDate: 2022-01-20
      DOI: 10.3390/act11020029
      Issue No: Vol. 11, No. 2 (2022)
  • Actuators, Vol. 11, Pages 30: Drop-Downs of an Outer Rotor Flywheel in
           Different Planetary Touch-Down Bearing Designs

    • Authors: Benedikt Schüßler, Timo Hopf, Stephan Rinderknecht
      First page: 30
      Abstract: With an increase in renewable energy in the electricity grid, more storage capacity for grid stabilization and energy flexibilization is necessary. Dynamic grid stabilization is one possible application for flywheels. To increase the energy density of flywheels, they can be built as highly integrated outer rotor systems. The losses of the flywheel are reduced by magnetic levitation and operation under vacuum conditions. In the case of the failure or overload of the active magnetic bearings, the system needs touch-down bearings to prevent system destruction. Planetary touch-down bearings consisting of several small bearing units circumferentially distributed around the stator are especially suited for these systems. In the literature, these planetary touch-down bearings are rarely investigated, especially the number of bearing units. Therefore, this paper investigates the influence of the number of touch-down bearing elements in simulations and experiments for an 8-element and a 6-element touch-down bearing arrangement. For the investigation, drop-downs at four different speeds were performed. Simulation and experimental results showed that, for the 6-element touch-down bearing, in contrast to the 8-element touch-down bearing, maximal velocity did not increase with the drop-down speed. Therefore, the touch-down bearing arrangement with fewer elements is preferrable.
      Citation: Actuators
      PubDate: 2022-01-21
      DOI: 10.3390/act11020030
      Issue No: Vol. 11, No. 2 (2022)
  • Actuators, Vol. 11, Pages 31: Model-Free Parallel Predictive Torque
           Control Based on Ultra-Local Model of Permanent Magnet Synchronous Machine

    • Authors: Manping Lv, Siyu Gao, Yanjun Wei, Di Zhang, Hanhong Qi, Yao Wei
      First page: 31
      Abstract: The finite control set model predictive torque control (FCS-MPTC) selects the optimal voltage vector (VV) by the composite cost function composed of torque and flux error, which makes it have a faster dynamic response than conventional control methods. However, the prediction state error caused by machine parameter mismatch and the difficulty in setting the weight factor in the composite cost function seriously restrict the popularization and application of FCS-MPTC. In this paper, a model-free parallel predictive torque control (MF-PPTC) based on an ultra-local (UL) model is proposed to solve above problems. The UL model replaces the machine mathematical model without any machine parameters and only uses the input and output of the system, which greatly improves the robustness of the control system. The nonlinear extended state observer proposed for the unknown part of the system has fast convergence and improves the dynamic performance of the system. In addition, the conventional parallel predictive control structure is optimized to reduce the dynamic adjustment process during the selection of optimal voltage vector. Simulation and experimental comparison between the conventional PPTC and the proposed MF-PPTC verified the superiority of the proposed method.
      Citation: Actuators
      PubDate: 2022-01-21
      DOI: 10.3390/act11020031
      Issue No: Vol. 11, No. 2 (2022)
  • Actuators, Vol. 11, Pages 32: Design, Computational Modelling and
           Experimental Characterization of Bistable Hybrid Soft Actuators for a
           Controllable-Compliance Joint of an Exoskeleton Rehabilitation Robot

    • Authors: Donatella Dragone, Luigi Randazzini, Alessia Capace, Francesca Nesci, Carlo Cosentino, Francesco Amato, Elena De Momi, Roberto Colao, Lorenzo Masia, Alessio Merola
      First page: 32
      Abstract: This paper presents the mechatronic design of a biorobotic joint with controllable compliance, for innovative applications of “assist-as-needed” robotic rehabilitation mediated by a wearable and soft exoskeleton. The soft actuation of robotic exoskeletons can provide some relevant advantages in terms of controllable compliance, adaptivity and intrinsic safety of the control performance of the robot during the interaction with the patient. Pneumatic Artificial Muscles (PAMs), which belong to the class of soft actuators, can be arranged in antagonistic configuration in order to exploit the variability of their mechanical compliance for the optimal adaptation of the robot performance during therapy. The coupling of an antagonistic configuration of PAMs with a regulation mechanism can achieve, under a customized control strategy, the optimal tuning of the mechanical compliance of the exoskeleton joint over full ranges of actuation pressure and joint rotation. This work presents a novel mechanism, for the optimal regulation of the compliance of the biorobotic joint, which is characterized by a soft and hybrid actuation exploiting the storage/release of the elastic energy by bistable Von Mises elastic trusses. The contribution from elastic Von Mises structure can improve both the mechanical response of the soft pneumatic bellows actuating the regulation mechanism and the intrinsic safety of the whole mechanism. A comprehensive set of design steps is presented here, including the optimization of the geometry of the pneumatic bellows, the fabrication process through 3D printing of the mechanism and some experimental tests devoted to the characterization of the hybrid soft actuation. The experimental tests replicated the main operating conditions of the regulation mechanism; the advantages arising from the bistable hybrid soft actuation were evaluated in terms of static and dynamic performance, e.g., pressure and force transition thresholds of the bistable mechanism, linearity and hysteresis of the actuator response.
      Citation: Actuators
      PubDate: 2022-01-22
      DOI: 10.3390/act11020032
      Issue No: Vol. 11, No. 2 (2022)
  • Actuators, Vol. 11, Pages 33: Redundancy Exploitation of an 8-DoF Robotic
           Assistant for Doppler Sonography

    • Authors: Elie Gautreau, Juan Sandoval, Aurélien Thomas, Jean-Michel Guilhem, Giuseppe Carbone, Saïd Zeghloul, Med Amine Laribi
      First page: 33
      Abstract: The design of a teleoperated 8-DoF redundant robot for Doppler sonography is detailed in this paper. The proposed robot is composed of a 7-DoF robotic arm mounted on a 1-DoF linear axis. This solution has been conceived to allow Doppler ultrasound examination of the entire patient’s body. This paper details the design of the platform and proposes two alternative control modes to deal with its redundancy at the torque level. The first control mode considers the robot as a full 8-DoF kinematics chain, synchronizing the action of the eight joints and improving the global robot manipulability. The second control mode decouples the 7-DoF arm and the linear axis controllers and proposes a switching strategy to activate the linear axis motion when the robot arm approaches the workspace limits. Moreover, a new adaptive Joint-Limit Avoidance (JLA) strategy is proposed with the aim of exploiting the redundancy of the 7-DoF anthropomorphic arm. Unlike classical JLA approaches, a weighting matrix is actively adapted to prioritize those joints that are approaching the mechanical limits. Simulations and experimental results are presented to verify the effectiveness of the proposed control modes.
      Citation: Actuators
      PubDate: 2022-01-24
      DOI: 10.3390/act11020033
      Issue No: Vol. 11, No. 2 (2022)
  • Actuators, Vol. 11, Pages 34: Research on Trajectory Tracking of Sliding
           Mode Control Based on Adaptive Preview Time

    • Authors: Hongzhen Hu, Shaoyi Bei, Qixian Zhao, Xiao Han, Dan Zhou, Xinye Zhou, Bo Li
      First page: 34
      Abstract: The preview model is one of the common methods used in trajectory tracking. The traditional fixed preview time is not adaptable to most speeds and road conditions, which not only reduces the tracking accuracy but also reduces the vehicle stability. Therefore, a controller can be designed to determine the adaptive preview time based on an optimization function of the lateral deviation, the road boundary, and the road boundary of the whole vehicle motion response characteristics. Traditional optimal preview control theory predicts the next state of the vehicle by the assumption of constant transverse pendulum angular velocity. In this paper, an expectation-based approach is used to find the ideal steering wheel turning angle based on the adaptive preview time, and a single-point preview model is established. Based on the two-degree-of-freedom dynamics model, a sliding mode controller is designed for control, and the low-pass filters are designed to suppress jitter in the sliding mode controller. Simulation results with different preview times, different speeds and different road adhesion coefficients prove that the controller has a good control effect and has good effectiveness and adaptability to speed and adhesion coefficient.
      Citation: Actuators
      PubDate: 2022-01-24
      DOI: 10.3390/act11020034
      Issue No: Vol. 11, No. 2 (2022)
  • Actuators, Vol. 11, Pages 35: Exploiting Cyclic Angle-Dependency in a
           Kalman Filter-Based Torque Estimation on a Mechatronic Drivetrain

    • Authors: Thijs Van der Veken, Jan Croes, Matteo Kirchner, Jonathan Baake, Wim Desmet, Frank Naets
      First page: 35
      Abstract: Torsional vibrations play a critical role in the design and operation of a mechanical or mechatronic drivetrain due to their impact on lifetime, performance, and cost. A magnetic spring allows one to reduce these vibrations and improve the actuator performance yet introduces additional challenges on the identification. As a direct torque measurement is generally not favourable because of its intrusive nature, this paper proposes a nonintrusive approach to identify torsional load profiles. The approach combines a physics-based lumped parameter model of the torsional dynamics of the drivetrain with measurements coming from a motor encoder and two MEMS accelerometers in a combined state/input estimation, using an augmented extended Kalman filter (A-EKF). In order to allow a generic magnetic spring torque estimation, a random walk input model is used, where additionally the angle-dependent behaviour is exploited by constructing an angle-dependent estimate and variance map. Experimental validation leads to a significant reduction in bias in the load torque estimation for this approach, compared to conventional estimators. Moreover, this newly proposed approach significantly reduces the variance on the estimated states by exploiting the angle dependency. The proposed approach provides knowledge of the torsional vibrations in a nonintrusive way, without the need for an extensive magnetic spring torque identification. Further, the approach is applicable on any drivetrain with angle-dependent input torques.
      Citation: Actuators
      PubDate: 2022-01-24
      DOI: 10.3390/act11020035
      Issue No: Vol. 11, No. 2 (2022)
  • Actuators, Vol. 11, Pages 36: Optimal Design of the Electroadhesion Pad
           with a Dual-Insulating Layer for Climbing Robots

    • Authors: Yong-Jin Jeong, Tae-Hwa Hong, Hak-Jun Lee, Kihyun Kim
      First page: 36
      Abstract: The electroadhesion pad is mainly studied for applications, such as climbing robots and grippers. In this paper, we present our study with the confirmation of the adhesion properties of the electroadhesion pad with a double-insulating layer, pad modeling, and optimal design. Modeling and analysis consider the air layer generated during the manufacturing of both conventional single-insulated structures and dual-insulated structures. Through the finite element analysis simulation, the characteristics of the electroadhesion were verified, and modeling verification was performed, based on the variables that had a large influence as follows: applied voltage, electrode area, dielectric thickness, and permittivity. The electrode is made of aluminum, the substrate is made of silicon, and the dielectric is made of polyimide film. An error of up to 8.3% was found between the modeling and simulation. The optimization results were validated based on a pad applied to a climbing robot measuring 320×480mm² and weighing 2.8 kg. As a result, the optimal pad design resulted in an error of 7.3% between the modeling and simulation.
      Citation: Actuators
      PubDate: 2022-01-25
      DOI: 10.3390/act11020036
      Issue No: Vol. 11, No. 2 (2022)
  • Actuators, Vol. 11, Pages 37: Methodology for Shape Optimization of
           Magnetic Designs: Magnetic Spring Characteristic Tailored to Application

    • Authors: Branimir Mrak, Bianca Wex, Hubert Mitterhofer
      First page: 37
      Abstract: Topology and shape optimization are still rarely applied to problems in electromagnetic design due to the computational complexity and limited commercial tooling, even though components such as electrical motors, magnetic springs or magnetic bearings could benefit from it, either to improve performance (reducing torque ripple and losses through shaping harmonic content in back electromotive force) or reduce the use of rare-earth materials. Magnetic springs are a fatigue free alternative to mechanical springs, where shape optimization can be exploited to a great degree—allowing for advanced non-linear stiffness characteristic shaping. We present the optimization methodology relying on a combination of several approaches for characteristic shaping of magnetic springs through either a modular design approach based on: (i) Fourier order decomposition; (ii) breaking conventional design symmetry; or (iii) free shaping of magnets through deviation from a nominal design using problem formulations such as spline and polynomials for material boundary definitions. Each of the parametrizations is formulated into a multi-objective optimization problem with both performance and material cost, and solved using gradient free optimization techniques (direct search, genetic algorithm). The methodology is employed on several benchmark problems—both academic and application inspired magnetic spring torque characteristic requirements. The resulting designs fit well with the requirements, with a relatively low computational cost. As such, the methodology presented is a promising candidate for other design problems in 2D shape optimization in electrical motor research and development.
      Citation: Actuators
      PubDate: 2022-01-25
      DOI: 10.3390/act11020037
      Issue No: Vol. 11, No. 2 (2022)
  • Actuators, Vol. 11, Pages 38: Visualization of the Electrohydrodynamic and
           Thermal Effects of AC-DBD Plasma Actuators of Plate- and Wire-Exposed

    • Authors: Yutaka Kaneko, Hiroyuki Nishida, Yoshiyuki Tagawa
      First page: 38
      Abstract: The dielectric barrier discharge plasma actuator is a promising flow control device that uses surface discharge. The actuator generates an electrohydrodynamic force and Joule heating that contribute to the flow control. Thus, it is important to investigate the electrohydrodynamic and thermal effects on the air flow. To this end, the flow velocity field, density field, and surface temperature distribution induced by an alternating current dielectric barrier discharge plasma actuator were experimentally examined, adopting particle image velocimetry, the background oriented schlieren technique, and an infrared camera. These experiments were conducted for plate- and wire-exposed electrode plasma actuators to investigate the effect of the shape of the exposed electrode. It was confirmed that the topology of the discharge is different between the two types of plasma actuators. This results in a difference in the spatial distributions of the velocity and density fields between the two actuators. In particular, we clarified that there is an obvious difference in the peak position of the density and temperature distribution between the two actuators. We also confirmed that the difference in the spatial distribution of the vertical velocity makes the above difference.
      Citation: Actuators
      PubDate: 2022-01-25
      DOI: 10.3390/act11020038
      Issue No: Vol. 11, No. 2 (2022)
  • Actuators, Vol. 11, Pages 39: Electrical Properties of Li+-Doped Potassium
           Sodium Niobate Coating Prepared by Supersonic Plasma Spraying

    • Authors: Yaya Song, Yanfei Huang, Weiling Guo, Xinyuan Zhou, Zhiguo Xing, Dongyu He, Zhenlin Lv
      First page: 39
      Abstract: The current work aims to compare the effects of systematic A-site substitutions on the electrical properties of potassium sodium niobate (KNN)-based coating. The A-site elements were replaced by Li+ to form (K0.4675Na0.4675Li0.065) NbO3 (KNLN). The pure KNN coating and the Li+-doped potassium sodium niobate (KNLN) coating with dense morphology and single perovskite structure were successfully prepared by supersonic plasma spraying, and the phase composition, microscopic morphology and electrical properties of the two coatings were compared and analyzed in detail by XRD, XPS, three-dimensional morphology and SEM on an Agilent 4294A (Santa Clara, CA, USA) and FE-5000 wide-range ferroelectric performance tester. The results show that: as the polarization voltage increases, the pure KNN coating is flatter and fuller, but the leakage current is large. The KNLN coating has a relatively long hysteresis loop and is easily polarized. The domain deflection responds faster to the external electric field, and the resistance of the domain wall motion to the external electric field is small. The dielectric constant of KNLN coating is 375, which is much higher than that of the pure KNN coating with 125, and the dielectric loss is stable at 0.01, which is lower than that of pure KNN coating at 0.1–0.35. This is because Li+ doping has successfully constructed a polycrystalline phase boundary in which O-T phases coexist, and has higher dielectric properties, piezoelectric properties and ferroelectric properties. At the same time, due to the high-temperature acceleration process in supersonic plasma spraying, the violent volatilization of the alkaline elements Li+, Na+ and K+ leads to the presence of oxygen vacancies and part of Nb4+ in the coating, which seriously affects the electrical properties of the coating.
      Citation: Actuators
      PubDate: 2022-01-26
      DOI: 10.3390/act11020039
      Issue No: Vol. 11, No. 2 (2022)
  • Actuators, Vol. 11, Pages 40: Acknowledgment to Reviewers of Actuators in

    • Authors: Actuators Editorial Office Actuators Editorial Office
      First page: 40
      Abstract: Rigorous peer-reviews are the basis of high-quality academic publishing [...]
      Citation: Actuators
      PubDate: 2022-01-26
      DOI: 10.3390/act11020040
      Issue No: Vol. 11, No. 2 (2022)
  • Actuators, Vol. 11, Pages 41: A Variable Parameter Method Based on Linear
           Extended State Observer for Position Tracking

    • Authors: Ying Zheng, Wei Jiang, Xinguo Qiu
      First page: 41
      Abstract: This paper presents a control strategy with a linear extended state observer (LESO) and Kalman filter to achieve a high performance of the motion control system. The moment of inertia of the system, which is variable with the robotic joint motion, is estimated in the established model. A LESO with variable gain is designed, which could estimate the states and the total disturbance of the plant without a precision mathematical model. The disturbance caused by variable load and unknown dynamics can be compensated based on the LESO, while the moment of inertia is variable. In order to restrain the process noise and measure the noise of the system, the Kalman filter was applied. Tracking differentiator was utilized to avoid the overshoot of the system for the step signal. The designed control strategy with the LESO and the Kalman filter could improve the tracking performance for the servo system with parametric uncertainties, unknown dynamics, and disturbances. The effectiveness of the proposed method is implemented and validated in the experiment of the robotic joint, for which desired servo tracking performance is achieved with the conditions of load variation and sudden disturbance.
      Citation: Actuators
      PubDate: 2022-01-27
      DOI: 10.3390/act11020041
      Issue No: Vol. 11, No. 2 (2022)
  • Actuators, Vol. 11, Pages 42: Servo Robust Control of Uncertain Mechanical
           Systems: Application in a Compressor/PMSM System

    • Authors: Qiang Zhang, Rongrong Yu, Chenming Li, Ye-Hwa Chen, Jieying Gu
      First page: 42
      Abstract: High-speed Permanent Magnet Synchronous Motor (PMSM) systems have been widely used in industry and other fields for their advantages of having a simple structure, low processing cost and high efficiency. At present, the control precision of PMSM is required to be higher and higher, but it faces two major challenges. The first is that the PMSM system possesses (possibly fast) time-varying uncertainty. The second is that there exist nonlinear portions in the PMSM system, such as nonlinear elasticity, etc. To resolve these challenges, a novel performance measure β^ is introduced as a dynamic depiction of the constraint-following error, and a new robust control design is proposed based on β^. While this control renders guaranteed performance regardless of uncertainty, an optimal design of a control parameter is further pursued. This inquiry is summed up as a semi-infinite constrained optimization problem. After the induction of the necessary condition, the candidate solutions can be identified. These are further screened by a sufficient condition, which results in the actual solution. To verify the effectiveness of the control design, the compressor powered by a super high-speed PMSM system is simulated, and its performance is discussed.
      Citation: Actuators
      PubDate: 2022-01-28
      DOI: 10.3390/act11020042
      Issue No: Vol. 11, No. 2 (2022)
  • Actuators, Vol. 11, Pages 43: H-Infinity Observer for Vehicle Steering
           System with Uncertain Parameters and Actuator Fault

    • Authors: Hongwei Wang, Qianyu Wang, Haotian Zhang, Jie Han
      First page: 43
      Abstract: In this paper, an actuator fault diagnosis and reconfiguration problem is discussed for an uncertain vehicle steering system with external disturbances. Aiming at the factors affecting the control performance, a fault reconstruction strategy based on H-infinity observer is designed to improve the vehicle stability under complex conditions when the actuator fails. Firstly, aiming at the uncertain part caused by the road condition transformation, a mathematical model of dual input and dual output four-wheel steering system is established. Secondly, an augmented system is constructed in which the augmented state vector consists of the original state and actuator faults. Thirdly, the H-infinity observer is designed, and the gain of the observer is obtained by the Lyapunov function and linear matrix inequality. Finally, the effectiveness of the proposed strategy is verified by MATLAB/Simulink and Carsim co-simulation.
      Citation: Actuators
      PubDate: 2022-01-28
      DOI: 10.3390/act11020043
      Issue No: Vol. 11, No. 2 (2022)
  • Actuators, Vol. 11, Pages 44: Applications of Magnetorheological Fluid
           Actuator to Multi-DOF Systems: State-of-the-Art from 2015 to 2021

    • Authors: Jong-Seok Oh, Jung Woo Sohn, Seung-Bok Choi
      First page: 44
      Abstract: This review article presents various multi-DOF application systems that utilize smart magnetorheological (MR) fluid. It is well known that MR fluid has been actively studied and applied in many practical systems such as vehicle suspension dampers. The design requirements for the effective applications of MR fluid include geometry optimization, working principles, and control schemes. The geometry optimization is mostly related to the size minimization with high damping force, while the working principles are classified into the shear mode, the flow mode, and the squeeze mode depending on the dominant dynamic motion of the application system. The control schemes are crucial to achieve final targets such as robust vibration control against disturbances. It should be addressed that advanced output performances of MR application systems heavily depends on these three requirements. This review article presents numerous application systems such as sandwich structures, dampers, mounts, brakes, and clutches, which have been developed considering the three design requirements. In addition, in this article some merits and demerits of each application system are discussed to enable potential researchers to develop more effective and practical MR application systems featuring the multi-DOF dynamic motions.
      Citation: Actuators
      PubDate: 2022-02-01
      DOI: 10.3390/act11020044
      Issue No: Vol. 11, No. 2 (2022)
  • Actuators, Vol. 11, Pages 45: Application of the Half-Order Derivative to
           Impedance Control of the 3-PUU Parallel Robot

    • Authors: Luca Bruzzone, Pietro Fanghella, Davide Basso
      First page: 45
      Abstract: This paper presents an extension of impedance control of robots based on fractional calculus. In classical impedance control, the end-effector reactions are proportional to the end-effector position errors through the stiffness matrix K, while damping is proportional to the first-order time-derivative of the end-effector coordinate errors through the damping matrix D. In the proposed approach, a half-derivative damping is added, proportional to the half-order time-derivative of the end-effector coordinate errors through the half-derivative damping matrix HD. The discrete-time digital implementation of the half-order derivative alters the steady-state behavior, in which only the stiffness term should be present. Consequently, a compensation method is proposed, and its effectiveness is validated by multibody simulation on a 3-PUU parallel robot. The proposed approach can be considered the extension to MIMO robotic systems of the PDD1/2 control scheme for SISO mechatronic systems, with potential benefits in the transient response performance.
      Citation: Actuators
      PubDate: 2022-02-01
      DOI: 10.3390/act11020045
      Issue No: Vol. 11, No. 2 (2022)
  • Actuators, Vol. 11, Pages 46: Experimental Study of Dynamical Airfoil and
           Aerodynamic Prediction

    • Authors: Zheyu Shi, Kaiwen Zhou, Chen Qin, Xin Wen
      First page: 46
      Abstract: Dynamic stall is a critical limiting factor for airfoil aerodynamics and a challenging problem for active flow control. In this experimental study, dynamic stall was measured by high-frequency surface pressure tapes and pressure-sensitive paint (PSP). The influence of the oscillation frequency was examined. Dynamic mode decomposition (DMD) with time-delay embedding was proposed to predict the pressure field on the oscillating airfoil based on scattered pressure measurements. DMD with time-delay embedding was able to reconstruct and predict the dynamic stall based on scattered measurements with much higher accuracy than standard DMD. The reconstruction accuracy of this method increased with the number of delay steps, but this also prolonged the computation time. In summary, using the Koopman operator obtained by DMD with time-delay embedding, the future dynamic pressure on an oscillating airfoil can be accurately predicted. This method provides powerful support for active flow control of dynamic stall.
      Citation: Actuators
      PubDate: 2022-02-02
      DOI: 10.3390/act11020046
      Issue No: Vol. 11, No. 2 (2022)
  • Actuators, Vol. 11, Pages 47: Development, Optimization, Biological
           Assays, and In Situ Field Immersion of a Transparent Piezoelectric
           Vibrating System for Antifouling Applications

    • Authors: Lucas Grilli, Fabrice Casset, Christine Bressy, Hugues Brisset, Jean-François Briand, Raphaëlle Barry-Martinet, Mikael Colin
      First page: 47
      Abstract: This paper presents the development and experimentations of transparent vibrating piezoelectric micromembranes dedicated to protecting immersed measurement instruments from marine biofouling. As any surface immersed is subject to the adhesion and settlement of organisms, especially in seawater, transparent materials quickly become opaque, resulting in deteriorated accuracy for optical sensors. According to this, we developed a transparent vibrating membrane to promote biofouling detachment in order to reduce the data quality drift and the frequency of maintenance operations on deployed optical sensors. In the first part, the design, the materials, and the steps to manufacture demonstrators are described. Then, the electromechanical characterizations of the demonstrators are carried out and interpreted with the support of FEM simulations. The last part describes the laboratory bioassays and the field immersion tests. Laboratory bioassays assess the antifouling potential of the vibrating piezoelectric membranes by exposing their surface to a suspended bacterial solution. In situ assays allow the membrane to perform in the Mediterranean Sea to assess their effectiveness in real conditions. Laboratory bioassays showed a great potential against the adhesion and settlement of a bacterial solution, while in situ tests confirmed the antifouling effect of piezoelectric vibrating micromembrane. Nevertheless, in situ experimentations revealed troubles with the piezo driver actuating the vibrating membranes, and tests should be carried out again with an improved piezo driver to reveal the full potential of the vibrating membranes. These are the first steps to set up an efficient antifouling vibrating system for immersed optical sensors.
      Citation: Actuators
      PubDate: 2022-02-02
      DOI: 10.3390/act11020047
      Issue No: Vol. 11, No. 2 (2022)
  • Actuators, Vol. 11, Pages 48: Magnetic Suspension System with Large
           Distance of 82 mm Using Persistent Current in Superconducting Coil

    • Authors: Mochimitsu Komori, Shun Imada, Kaoru Nemoto, Ken-ichi Asami
      First page: 48
      Abstract: Superconducting techniques are applied to a superconducting magnetic suspension system. A superconducting coil, copper coils, a magnetically suspended object, a photo sensor, a PID controller, and power amplifiers are the main components of the suspension system. A persistent current in the superconducting coil and a control current in the copper coils are used for suspending the object and controlling the object, respectively. This paper discusses a large gap trial for the suspension system, and the static and dynamic characteristics of the suspension system are studied. As a result, it is found that the magnetically suspended object continues to be suspended at a distance of 82 mm for more than 60 s. Since a superconducting persistent current has a maximum limit for the suspension system, a persistent current of 50 A is adopted. The details of the superconducting persistent current are studied for the performance of the suspension system. There are few reports about such a suspension system with a large gap of more than 80 mm using a superconducting persistent current.
      Citation: Actuators
      PubDate: 2022-02-05
      DOI: 10.3390/act11020048
      Issue No: Vol. 11, No. 2 (2022)
  • Actuators, Vol. 11, Pages 49: Optimization Design for the Planetary Gear
           Train of an Electric Vehicle under Uncertainties

    • Authors: Xiang Xu, Jiawei Chen, Zhongyan Lin, Yiran Qiao, Xinbo Chen, Yong Zhang, Yanan Xu, Yan Li
      First page: 49
      Abstract: The planetary gear train is often used as the main device for decelerating and increasing the torque of the drive motor of electric vehicles. Considering the lightweight requirement and existing uncertainty in structural design, a multi-objective uncertainty optimization design (MUOD) framework is developed for the planetary gear train of the electric vehicle in this study. The volume and transmission efficiency of the planetary gear train are taken into consideration as optimization objectives. The manufacturing size, material, and load input of the planetary gear train are considered as uncertainties. An approximate direct decoupling model, based on subinterval Taylor expansion, is applied to evaluate the propagation of uncertainties. To improve the convergence ability of the multi-objective evolutionary algorithm, the improved non-dominated sorting genetic algorithm II (NSGA-II) is designed by using chaotic and adaptive strategies. The improved NSGA-II has better convergence efficiency than classical NSGA-II and multi-objective particle swarm optimization (MOPSO). In addition, the multi-criteria decision making (MCDM) method is applied to choose the most satisfactory solution in Pareto sets from the multi-objective evolutionary algorithm. Compared with the multi-objective deterministic optimization design (MDOD), the proposed MUOD framework has better reliability than MDOD under different uncertainty cases. This MUOD method enables further guidance pertaining to the uncertainty optimization design of transportation equipment, containing gear reduction mechanisms, in order to reduce the failure risk.
      Citation: Actuators
      PubDate: 2022-02-05
      DOI: 10.3390/act11020049
      Issue No: Vol. 11, No. 2 (2022)
  • Actuators, Vol. 11, Pages 50: Establishment and Experimental Verification
           of a Nonlinear Position Servo System Model for a Magnetically Coupled
           Rodless Cylinder

    • Authors: Yeming Zhang, Kaimin Li, Maolin Cai, Feng Wei, Sanpeng Gong, Shuping Li, Baozhan Lv
      First page: 50
      Abstract: The nonlinear characteristics of the pneumatic servo system are the main factors limiting its control accuracy. A new mathematical model of the nonlinear system of the valve control cylinder is proposed in order to improve the control accuracy of the pneumatic servo system. Firstly, the mass flow equation of the gas flowing through each port is established by analyzing the physical structure of the proportional directional control valve. Then, the dynamic equation of the system is set up by applying the Stribeck friction model for the friction model of the valve control cylinder and building a pneumatic circuit experiment to identify the friction model parameters. Finally, the correctness of the mathematical model is verified by the inflation and deflation experiment of the fixed capacitive chamber and the servo controls experiment based on PID position. The Simulink simulation of the mathematical model better reflects the characteristics of the pneumatic position servo system.
      Citation: Actuators
      PubDate: 2022-02-07
      DOI: 10.3390/act11020050
      Issue No: Vol. 11, No. 2 (2022)
  • Actuators, Vol. 11, Pages 51: High-Precision Displacement and Force Hybrid
           Modeling of Pneumatic Artificial Muscle Using 3D PI-NARMAX Model

    • Authors: Yanding Qin, Yuankai Xu, Chenyu Shen, Jianda Han
      First page: 51
      Abstract: Pneumatic artificial muscle (PAM) is attractive in rehabilitation and biomimetic robots due to its flexibility. However, there exists a strong hysteretic nonlinearity in PAMs and strong coupling between the output displacement and the output force. At present, most commonly used hysteresis models can be treated as two-dimensional models, which only consider the nonlinearity between the input and the output displacement of the PAM without considering the coupling of the output force. As a result, high-precision modeling and estimation of the PAM’s behavior is difficult, especially when the external load of the system varies significantly. In this paper, the influence of the output force on the displacement is experimentally investigated. A three-dimensional model based on the modified Prandtl–Ishlinskii (MPI) model and the Nonlinear AutoRegressive Moving Average with eXogenous inputs (NARMAX) model is proposed to describe the relationship and couplings among the input, the output displacement, and the output force of the PAM. Experiments are conducted to verify the modeling accuracy of the proposed model when the external load of the PAM varies across a wide range. The experimental results show that the proposed model captures well the hysteresis and couplings of the PAM and can precisely predict the PAM’s behavior.
      Citation: Actuators
      PubDate: 2022-02-08
      DOI: 10.3390/act11020051
      Issue No: Vol. 11, No. 2 (2022)
  • Actuators, Vol. 11, Pages 52: Autonomous Vehicle Path Planning Based on
           Driver Characteristics Identification and Improved Artificial Potential

    • Authors: Shaobo Wang, Fen Lin, Tiancheng Wang, Youqun Zhao, Liguo Zang, Yaoji Deng
      First page: 52
      Abstract: Different driving styles should be considered in path planning for autonomous vehicles that are travelling alongside other traditional vehicles in the same traffic scene. Based on the drivers’ characteristics and artificial potential field (APF), an improved local path planning algorithm is proposed in this paper. A large amount of driver data are collected through tests and classified by the K-means algorithm. A Keras neural network model is trained by using the above data. APF is combined with driver characteristic identification. The distances between the vehicle and obstacle are normalized. The repulsive potential field functions are designed according to different driver characteristics and road boundaries. The designed local path planning method can adapt to different surrounding manual driving vehicles. The proposed human-like decision path planning method is compared with the traditional APF planning method. Simulation tests of an individual driver and various drivers with different characteristics in overtaking scenes are carried out. The simulation results show that the curves of human-like decision-making path planning method are more reasonable than those of the traditional APF path planning method; the proposed method can carry out more effective path planning for autonomous vehicles according to the different driving styles of surrounding manual vehicles.
      Citation: Actuators
      PubDate: 2022-02-08
      DOI: 10.3390/act11020052
      Issue No: Vol. 11, No. 2 (2022)
  • Actuators, Vol. 11, Pages 53: Manufacturing and Testing of a Variable
           Chord Extension for Helicopter Rotor Blades

    • Authors: Christoph Balzarek, Steffen Kalow, Johannes Riemenschneider, Andres Rivero
      First page: 53
      Abstract: Helicopters are still an indispensable addition to aviation in this day and age. They are characterized by their ability to master both forward flight and hover. These characteristics result in a wide range of possible operations. Key for the design of the rotor blades is a blade design that always represents a compromise between the different flight conditions, which enables safe and efficient flight in the various flight conditions. In order to operate the rotor blade even more efficiently in all flight conditions, a new morphing concept, the so-called linear variable chord extension, has been developed. Here, the blade chord length in the root area is changed with the help of an elastic skin to adapt it to the respective flight condition. The simulations performed for this concept showed a promising increase in overall helicopter performance. The fabrication of the resulting demonstrator as well as the tests in the whirl-tower and wind tunnel are presented in this paper. The results of the tests show that the concept of linear variable chord extension has a positive influence and a great potential for hovering flight.
      Citation: Actuators
      PubDate: 2022-02-09
      DOI: 10.3390/act11020053
      Issue No: Vol. 11, No. 2 (2022)
  • Actuators, Vol. 11, Pages 54: Vehicle Positioning and Navigation in
           Asynchronous Navigation System

    • Authors: Xinyang Zhao, Bocheng Zhu
      First page: 54
      Abstract: A Pseudo-satellite system that transmits signals similar to GNSS can provide positioning services in places where GNSS signals are not captured and have enormous potential for indoor machine system and airports. Different paths of the device have different carrier phase initial solution positioning accuracy. Existing methods rely on measuring instruments or use many coordinate points for solving ambiguity resolution (AR), which creates inconvenience for real-time ground positioning. This study aims to find a new on-the-fly (OTF) method to achieve high accuracy and convenient positioning. A new method is proposed based on a two-difference observation model for ground-based high-precision point positioning. We used an adaptive particle swarm algorithm to solve the initial solution, followed by a nonlinear least-squares method to optimize the localization solution. It is free of priori information or measuring instruments. We designed several different paths, such as circular trajectory and square trajectory, to study the positioning accuracy of the solution. Simulation experiments with different trajectories showed that geometric changes significantly impact solutions. In addition, it does not require precise time synchronization of the base stations, making the whole system much easier to deploy. We built a real-world pseudo-satellite system and used a multi-sensor crewless vehicle as a receiver. Real-world experiments showed that our approach could achieve centimeter-level positioning accuracy in applications.
      Citation: Actuators
      PubDate: 2022-02-10
      DOI: 10.3390/act11020054
      Issue No: Vol. 11, No. 2 (2022)
  • Actuators, Vol. 11, Pages 55: Influence of the Dynamic Effects and
           Grasping Location on the Performance of an Adaptive Vacuum Gripper

    • Authors: Matteo Maggi, Giacomo Mantriota, Giulio Reina
      First page: 55
      Abstract: A rigid in-plane matrix of suction cups is widely used in robotic end-effectors to grasp objects with flat surfaces. However, this grasping strategy fails with objects having different geometry e.g., spherical and cylindrical. Articulated rigid grippers equipped with suction cups are an underinvestigated solution to extend the ability of vacuum grippers to grasp heavy objects with various shapes. This paper extends previous work by the authors in the development of a novel underactuated vacuum gripper named Polypus by analyzing the impact of dynamic effects and grasping location on the vacuum force required during a manipulation cycle. An articulated gripper with suction cups, such as Polypus, can grasp objects by adhering to two adjacent faces, resulting in a decrease of the required suction action. Moreover, in the case of irregular objects, many possible grasping locations exist. The model explained in this work contributes to the choice of the most convenient grasping location that ensures the minimum vacuum force required to manipulate the object. Results obtained from an extensive set of simulations are included to support the validity of the proposed analytical approach.
      Citation: Actuators
      PubDate: 2022-02-12
      DOI: 10.3390/act11020055
      Issue No: Vol. 11, No. 2 (2022)
  • Actuators, Vol. 11, Pages 56: Simulation and Model-Based Verification of
           an Emergency Strategy for Cable Failure in Cable Robots

    • Authors: Roland Boumann, Tobias Bruckmann
      First page: 56
      Abstract: Cable failure is an extremely critical situation in the operation of cable-driven parallel robots (CDPR), as the robot might be instantly outside of its predefined workspace. Therefore, the calculation of a cable force distribution might fail and, thus, the controller might not be able to master the guidance of the system anymore. However, as long as there is a remaining set of cables, the dynamic behavior of the system can be influenced to prevent further damage, such as collisions with the ground. The paper presents a feasible algorithm, introduces the models for dynamical multi-body simulation and verifies the algorithm within control loop closure.
      Citation: Actuators
      PubDate: 2022-02-14
      DOI: 10.3390/act11020056
      Issue No: Vol. 11, No. 2 (2022)
  • Actuators, Vol. 11, Pages 57: Internal Rotor Actuation and Magnetic
           Bearings for the Active Control of Rotating Machines

    • Authors: Gauthier A. Fieux, Nicola Y. Bailey, Patrick S. Keogh
      First page: 57
      Abstract: Passive rotors are often limited in rotational speed due to bearing constraints, stability and excessive vibration levels. To address the vibration issue, Active Magnetic Bearings (AMBs) levitating the rotor with a magnetic field can be used. They offer a clearance and variable stiffness and damping to the rotor support, which help to mitigate greatly the vibration issue. However, they are also limited at large rotational speed because of the high frequency control force required to levitate the rotor safely. To overcome the frequency limitation, a dual AMBs/internal bending control concept is investigated with associated modelling and control algorithms. This approach is examined in simulation with a 19 kg rotor running up to 10,000 RPM, where three resonance frequencies are present at 2700, 5300, and 9300 RPM, with the first resonant frequency being the most strongly excited. Using internal rotor bending control, a maximum radial displacement of 15 μm for the rotor mid-point is achieved, which gives a reduction in vibration amplitude of 45% compared to the case of no control. Variations of the algorithm are presented and discussed, showing the potential of the proposed approach.
      Citation: Actuators
      PubDate: 2022-02-16
      DOI: 10.3390/act11020057
      Issue No: Vol. 11, No. 2 (2022)
  • Actuators, Vol. 11, Pages 58: Data-Driven Kinematic Model of PneuNets
           Bending Actuators for Soft Grasping Tasks

    • Authors: Ciprian Rad, Olimpiu Hancu, Ciprian Lapusan
      First page: 58
      Abstract: The paper proposes a novel data-driven approximation kinematic (DAK) model to estimate the shape and opening level of a PneuNets soft gripper in relation to the applied pressure signal. The model offers suitable capabilities for implementing in real-time applications involving soft grasping planning and size recognition of fragile objects with different sizes and shapes. The proposed DAK model estimates the free bending behavior of a PneuNets actuator (soft gripper finger) based on a set of approximation functions derived from experimental data and an equivalent serial mechanism that mimics the shape of the actuator. The model was tested for a commercial PneuNets actuator with decreasing chamber height, produced by SoftGripping Co. (Hamburg, Germany). The model validation is accomplished through a set of experiments, where the shape and elementary displacements were measured using a digital image processing technique. The experimental data and the estimated data from the DAK model were compared and analyzed, respectively. The proposed approach has applicability in sensorless/self-sensing bending control algorithms of PneuNets actuators and in soft grasping applications where the robotic system must estimate the opening level of the gripper in order to be able to accomplish its task.
      Citation: Actuators
      PubDate: 2022-02-16
      DOI: 10.3390/act11020058
      Issue No: Vol. 11, No. 2 (2022)
  • Actuators, Vol. 11, Pages 59: Research on the Identification of Tyre-Road
           Peak Friction Coefficient under Full Slip Rate Range Based on Normalized
           Tyre Model

    • Authors: Yinfeng Han, Yongjie Lu, Na Chen, Hongwei Wang
      First page: 59
      Abstract: The accurate estimation of the tyre-road peak friction coefficient is the key basis for the normal operation of the vehicle active safety control system. The estimation algorithm needs to be able to adapt to various conditions encountered in the actual driving process of the vehicle and obtain the estimation results timely and accurately. Therefore, a new normalized strategy is proposed in this paper. The core is the equal ratio between the peak friction coefficient and the utilization friction coefficient between adjacent typical roads. This strategy can establish the direct connection (normalization) between tyre force and tyre-road peak friction coefficient through most tyre models in the field of vehicle dynamics and accomplish estimation by combining with the filtering algorithm. In addition, most of the vehicle dynamic estimation algorithms are limited by road excitation, and it is difficult to obtain satisfactory estimation results. This strategy can greatly reduce the system error caused by insufficient road excitation (slip rate is not 0.15–0.20) and improve the applicability of the estimation algorithm to the actual driving process of the vehicle. Finally, the magic formula (MF) tyre model is selected to describe the tyre characteristics after treatment of the normalized strategy; the tyre-road peak friction coefficient is estimated by combining the extended Kalman filter and vehicle dynamics model. Satisfactory estimation results are obtained in both simulation and real vehicle tests, which verifies the effectiveness of the proposed normalized strategy.
      Citation: Actuators
      PubDate: 2022-02-17
      DOI: 10.3390/act11020059
      Issue No: Vol. 11, No. 2 (2022)
  • Actuators, Vol. 11, Pages 60: Mechanism Design of a Transformable Crawling
           Robot and Feasibility Analysis for the Unstructured Environment

    • Authors: Jiwei Yuan, Zhouyi Wang, Zhourong Zhang, Yuhang Xing, Aihong Ji
      First page: 60
      Abstract: The better application of crawl robots depends on their ability to adapt to unstructured environments with significant variations in their structural shape and size. This paper presents the design and analysis of a novel robot with different locomotion configurations to move through varying environments. The leg of the robot, inspired by insects, was designed as a multi-link structure, including the Hoekens linkage and multiple parallel four-link mechanisms. The end trajectory was a symmetrical closed curve composed of an approximate straight line and a shell curve with a downward opening. The special trajectory allowed the robot to share drives and components to achieve structural deformation and locomotion. The structural characteristics of the crawl robot on the inner and outer arcs were obtained based on the working space. The constraint relationship between the structure size, the radius of the arc, and the coefficient of static friction with which the robot could crawl on the arc were established. The feasible support posture and support position of the robot under different arc radii were obtained. The simulation tested the locomotion of the robot on the plane, arc, and restricted space. The robot can be used for detection, search, and rescue missions in unstructured environments.
      Citation: Actuators
      PubDate: 2022-02-17
      DOI: 10.3390/act11020060
      Issue No: Vol. 11, No. 2 (2022)
  • Actuators, Vol. 11, Pages 61: Optimal Control Method of Path Tracking for
           Four-Wheel Steering Vehicles

    • Authors: Xiaojun Tan, Deliang Liu, Huiyuan Xiong
      First page: 61
      Abstract: Path tracking is a key technique for intelligent electric vehicles, while four-wheel steering (4WS) technology is of great significance to improve its accuracy and flexibility. However, the control methods commonly used in path tracking for a 4WS vehicle cannot take full advantage of the additional steering freedom of the 4WS vehicle, because of restricting the relationship between the front and rear wheels steering angle. To address this issue, we derive a kinematic model without the restriction based on the small-angle assumption. Then, the objective function and constraints of system control quantity optimization are designed based on the tracking error model. After the optimization problem is solved in the form of quadratic programming with constraints, the control sequence with the smallest performance index is obtained through rolling optimization. The proposed method is tested on a high-fidelity Carsim/Simulink co-simulation platform and an experimental vehicle. The results show that the standard deviation of the lateral error and the yaw angle error of the algorithm is less than 0.1 m and 3.0°, respectively. Compared with the other two algorithms, the control of the front and rear wheels angle of this method is more flexible and the tracking accuracy is higher.
      Citation: Actuators
      PubDate: 2022-02-18
      DOI: 10.3390/act11020061
      Issue No: Vol. 11, No. 2 (2022)
  • Actuators, Vol. 11, Pages 62: Robotic Sponge and Watercolor Painting Based
           on Image-Processing and Contour-Filling Algorithms

    • Authors: Lorenzo Scalera, Giona Canever, Stefano Seriani, Alessandro Gasparetto, Paolo Gallina
      First page: 62
      Abstract: In this paper, the implementation of a robotic painting system using a sponge and the watercolor painting technique is presented. A collection of tools for calibration and sponge support operations was designed and built. A contour-filling algorithm was developed, which defines the sponge positions and orientations in order to color the contour of a generic image. Finally, the proposed robotic system was employed to realize a painting combining etching and watercolor techniques. To the best of our knowledge, this is the first example of robotic painting that uses the watercolor technique and a sponge as the painting media.
      Citation: Actuators
      PubDate: 2022-02-19
      DOI: 10.3390/act11020062
      Issue No: Vol. 11, No. 2 (2022)
  • Actuators, Vol. 11, Pages 63: Control Design for CABLEankle, a Cable
           Driven Manipulator for Ankle Motion Assistance

    • Authors: Idumudi Venkata Sai Prathyush, Marco Ceccarelli, Matteo Russo
      First page: 63
      Abstract: A control design is presented for a cable driven parallel manipulator for performing a controlled motion assistance of a human ankle. Requirements are discussed for a portable, comfortable, and light-weight solution of a wearable device with an overall design with low-cost features and user-oriented operation. The control system utilizes various operational and monitoring sensors to drive the system and also obtain continuous feedback during motion to ensure an effective recovery. This control system for CABLEankle device is designed for both active and passive rehabilitation to facilitate the improvement in both joint mobility and surrounding muscle strength.
      Citation: Actuators
      PubDate: 2022-02-21
      DOI: 10.3390/act11020063
      Issue No: Vol. 11, No. 2 (2022)
  • Actuators, Vol. 11, Pages 11: Characteristics of Hydraulic and Electric
           Servo Motors

    • Authors: Sayako Sakama, Yutaka Tanaka, Akiya Kamimura
      First page: 11
      Abstract: Until the 1970s, hydraulic actuators were widely used in many mechanical systems; however, recently, electric motors have become mainstream by virtue of their improved performance, and hydraulic motors have largely been replaced by electric motors in many applications. Although this trend is expected to continue into the future, it is important to comprehensively evaluate which motor is most suitable when designing mechanical systems. This paper presents the results of a survey of the performance of electric and hydraulic servo motors and aims to provide quantitative data that can be used as a reference for selecting appropriate motors. We surveyed AC, AC direct, brushless DC, and brushed DC electric motors and swash plate-type axial piston, bent axis-type axial piston, crank-type radial piston, and multistroke-type radial piston hydraulic motors. Performance data were collected from catalogs and nonpublic data. We compared and evaluated the characteristics of these diverse servo motors using indexes such as torque, rotating speed, output power, power density, and power rate.
      Citation: Actuators
      PubDate: 2022-01-05
      DOI: 10.3390/act11010011
      Issue No: Vol. 11, No. 1 (2022)
  • Actuators, Vol. 11, Pages 12: Evaluation of Dynamic Load Reduction for a
           Tractor Semi-Trailer Using the Air Suspension System at all Axles of the

    • Authors: Dang Viet Ha, Vu Van Tan, Vu Thanh Niem, Olivier Sename
      First page: 12
      Abstract: The air suspension system has become more and more popular in heavy vehicles and buses to improve ride comfort and road holding. This paper focuses on the evaluation of the dynamic load reduction at all axles of a semi-trailer with an air suspension system, in comparison with the one using a leaf spring suspension system on variable speed and road types. First, a full vertical dynamic model is proposed for a tractor semi-trailer (full model) with two types of suspension systems (leaf spring and air spring) for three axles at the semi-trailer, while the tractor’s axles use leaf spring suspension systems. The air suspension systems are built based on the GENSYS model; meanwhile, the remaining structural parameters are considered equally. The full model has been validated by experimental results, and closely follows the dynamical characteristics of the real tractor semi-trailer, with the percent error of the highest value being 6.23% and Pearson correlation coefficient being higher than 0.8, corresponding to different speeds. The survey results showed that the semi-trailer with the air suspension system can reduce the dynamic load of the entire field of speed from 20 to 100 km/h, given random road types from A to F according to the ISO 8608:2016 standard. The dynamic load coefficient (DLC) with the semi-trailer using the air spring suspension system can be reduced on average from 14.8% to 29.3%, in comparison with the semi-trailer using the leaf spring suspension system.
      Citation: Actuators
      PubDate: 2022-01-05
      DOI: 10.3390/act11010012
      Issue No: Vol. 11, No. 1 (2022)
  • Actuators, Vol. 11, Pages 13: 3D Object Recognition and Localization with
           a Dense LiDAR Scanner

    • Authors: Hao Geng, Zhiyuan Gao, Guorun Fang, Yangmin Xie
      First page: 13
      Abstract: Dense scanning is an effective solution for refined geometrical modeling applications. The previous studies in dense environment modeling mostly focused on data acquisition techniques without emphasizing autonomous target recognition and accurate 3D localization. Therefore, they lacked the capability to output semantic information in the scenes. This article aims to make complementation in this aspect. The critical problems we solved are mainly in two aspects: (1) system calibration to ensure detail-fidelity for the 3D objects with fine structures, (2) fast outlier exclusion to improve 3D boxing accuracy. A lightweight fuzzy neural network is proposed to remove most background outliers, which was proven in experiments to be effective for various objects in different situations. With precise and clean data ensured by the two abovementioned techniques, our system can extract target objects from the original point clouds, and more importantly, accurately estimate their center locations and orientations.
      Citation: Actuators
      PubDate: 2022-01-05
      DOI: 10.3390/act11010013
      Issue No: Vol. 11, No. 1 (2022)
  • Actuators, Vol. 11, Pages 14: Development of a Mechatronic System for the
           Mirror Therapy

    • Authors: Maurizio Ruggiu, Pierluigi Rea
      First page: 14
      Abstract: This paper fits into the field of research concerning robotic systems for rehabilitation. Robotic systems are going to be increasingly used to assist fragile persons and to perform rehabilitation tasks for persons affected by motion injuries. Among the recovery therapies, the mirror therapy was shown to be effective for the functional recovery of an arm after stroke. In this paper we present a master/slave robotic device based on the mirror therapy paradigm for wrist rehabilitation. The device is designed to orient the affected wrist in real time according to the imposed motion of the healthy wrist. The paper shows the kinematic analysis of the system, the numerical simulations, an experimental mechatronic set-up, and a built 3D-printed prototype.
      Citation: Actuators
      PubDate: 2022-01-05
      DOI: 10.3390/act11010014
      Issue No: Vol. 11, No. 1 (2022)
  • Actuators, Vol. 11, Pages 15: Intermediate-Variable-Based Distributed
           Fusion Estimation for Wind Turbine Systems

    • Authors: Shengwei Yang, Rusheng Wang, Jing Zhou, Bo Chen
      First page: 15
      Abstract: In wind turbine systems, the state of the generator is always disturbed by various unknown perturbances, which leads to system instability and inaccurate state estimation. In this paper, an intermediate-variable-based distributed fusion estimation method is proposed for the state estimation problem in wind turbine systems. By constructing an augmented state error system and using the idea of bounded recursive optimization, the local estimators and distributed fusion criterion are designed, which can be used to estimate the disturbance signals and system states. Then, the local estimator gains and the distributed weighting fusion matrices are obtained by solving the established convex optimization problems. Furthermore, a compensation strategy is designed by using the estimated disturbance signals, which can potentially reduce the influence of the disturbance signals on the system state. Finally, a numerical simulation is provided to show that the proposed method can effectively improve the accuracy of the estimation of the wind turbine state and disturbance, and the superiority of the proposed method is illustrated as a comparison to the Kalman fusion method.
      Citation: Actuators
      PubDate: 2022-01-06
      DOI: 10.3390/act11010015
      Issue No: Vol. 11, No. 1 (2022)
  • Actuators, Vol. 11, Pages 16: Development of Sliding Mode Controller Based
           on Internal Model Controller for Higher Precision Electro-Optical Tracking

    • Authors: Bing Zhang, Kang Nie, Xinglong Chen, Yao Mao
      First page: 16
      Abstract: The electro-optical tracking system (ETS) on moving platforms is affected by the vibration of the moving carrier, the wind resistance torque in motion, the uncertainty of mechanisms and the nonlinear friction between frames and other disturbances, which may lead to the instability of the electro-optical tracking platform. Sliding mode control (SMC) has strong robustness to system disturbances and unknown dynamic external signals, which can enhance the disturbance suppression ability of ETSs. However, the strong robustness of SMC requires greater switching gain, which causes serious chattering. At the same time, the tracking accuracy of SMC has room for further improvement. Therefore, in order to solve the chattering problem of SMC and improve the tracking accuracy of SMC, an SMC controller based on internal model control (IMC) is proposed. Compared with traditional SMC, the proposed method can be used to suppress the strongest disturbance with the smallest switching gain, effectively solving the chattering problem of the SMC, while improving the tracking accuracy of the system. In addition, to reduce the adverse influence of sensor noise on the control effect, lifting wavelet threshold de-noising is introduced into the control structure to further improve the tracking accuracy of the system. The simulation and experimental results verify the superiority of the proposed control method.
      Citation: Actuators
      PubDate: 2022-01-07
      DOI: 10.3390/act11010016
      Issue No: Vol. 11, No. 1 (2022)
  • Actuators, Vol. 11, Pages 17: Real-Time Numerical Simulation for Accurate
           Soft Tissues Modeling during Haptic Interaction

    • Authors: Paolo Tripicchio, Salvatore D’Avella, Emanuele Ruffaldi
      First page: 17
      Abstract: The simulation of fabrics physics and its interaction with the human body has been largely studied in recent years to provide realistic-looking garments and wears specifically in the entertainment business. When the purpose of the simulation is to obtain scientific measures and detailed mechanical properties of the interaction, the underlying physical models should be enhanced to obtain better simulation accuracy increasing the modeling complexity and relaxing the simulation timing constraints to properly solve the set of equations under analysis. However, in the specific field of haptic interaction, the desiderata are to have both physical consistency and high frame rate to display stable and coherent stimuli as feedback to the user requiring a tradeoff between accuracy and real-time interaction. This work introduces a haptic system for the evaluation of the fabric hand of specific garments either existing or yet to be produced in a virtual reality simulation. The modeling is based on the co-rotational Finite Element approach that allows for large displacements but the small deformation of the elements. The proposed system can be beneficial for the fabrics industry both in the design phase or in the presentation phase, where a virtual fabric portfolio can be shown to customers around the world. Results exhibit the feasibility of high-frequency real-time simulation for haptic interaction with virtual garments employing realistic mechanical properties of the fabric materials.
      Citation: Actuators
      PubDate: 2022-01-08
      DOI: 10.3390/act11010017
      Issue No: Vol. 11, No. 1 (2022)
  • Actuators, Vol. 11, Pages 18: An Enhanced Sliding Mode Speed Control for
           Induction Motor Drives

    • Authors: Fahimeh Shiravani, Patxi Alkorta, Jose Antonio Cortajarena, Oscar Barambones
      First page: 18
      Abstract: In this paper, an enhanced Integral Sliding Mode Control (ISMC) for mechanical speed of an Induction Motor (IM) is presented and experimentally validated. The design of the proposed controller has been done in the d-q synchronous reference frame and indirect Field Oriented Control (FOC). Global asymptotic speed tracking in the presence of model uncertainties and load torque variations has been guaranteed by using an enhanced ISMC surface. Moreover, this controller provides a faster speed convergence rate compared to the conventional ISMC and the Proportional Integral methods, and it eliminates the steady-state error. Furthermore, the chattering phenomenon is reduced by using a switching sigmoid function. The stability of the proposed controller under parameter uncertainties and load disturbances has been provided by using the Lyapunov stability theory. Finally, the performance of this control method is verified through numerical simulations and experimental tests, getting fast dynamics and good robustness for IM drives.
      Citation: Actuators
      PubDate: 2022-01-10
      DOI: 10.3390/act11010018
      Issue No: Vol. 11, No. 1 (2022)
  • Actuators, Vol. 11, Pages 19: Modeling and Experiments of an Annular
           Multi-Channel Magnetorheological Valve

    • Authors: Xiaolong Yang, Yingjie Chen, Yuting Liu, Ruibo Zhang
      First page: 19
      Abstract: With the increasing number of cars, the demand for vehicle maintenance lifts is also increasing. The hydraulic valve is one of its core components, but there are problems with it such as inaccurate positioning and failure. In order to improve the service performance of vehicle maintenance elevators, a novel annular multi-channel magnetorheological (MR) valve structure was creatively proposed based on intelligent material MR fluid (MRF), and its magnetic circuit was designed. The influence of current, damping gap and coil turns on the pressure drop performance of the annular multi-channel MR valve was numerically studied and compared with ordinary type magnetorheological valve pressure drop performance through contrast and analysis. The influence of different loads and currents on the pressure drop performance of annular multi-channel magnetorheological valve was verified by experiments, and the reliability of numerical analysis results was verified. The results show that the single winding excitation coil is 321 to meet the demand. The pressure drop performance of the annular multi-channel magnetorheological valve is 5.6 times that of the ordinary magnetorheological valve. The load has little influence on the regulating range and performance of pressure drop of the MR valve. Compared with the common type, the pressure drop performance of the annular multi-channel MR Valve is improved by 3.7 times, which is basically consistent with the simulation results.
      Citation: Actuators
      PubDate: 2022-01-10
      DOI: 10.3390/act11010019
      Issue No: Vol. 11, No. 1 (2022)
  • Actuators, Vol. 11, Pages 20: Design and Experimental Analysis of Charge
           Recovery for Piezoelectric Fan

    • Authors: Zhenwei Chen, Wei Tang, Ze Li, Jiaqi Lan
      First page: 20
      Abstract: The piezoelectric (PE) fan is widely adopted in the field of microelectronics cooling due to its advantages of high reliability and good heat dissipation characteristics. However, PE fans driven by conventional circuits suffer from plenty of energy loss. To save energy, we propose an inductor-based charge recovery method and apply it to the driving circuit for the PE fan. Two inductor-based driving circuits, a single inductor-based driving (SID) circuit and a double inductor-based driving (DID) circuit are compared. The SID circuit has a simple structure and a slightly higher energy-saving rate, while the DID circuit introduces no additional oscillations and is more stable. The experimental results show that when the supply voltage changes, both circuits have a relatively stable energy-saving rate, which is about 30% for the SID circuit and 28% for the DID circuit. Moreover, the proposed circuits enjoy the same driving capacity as the conventional circuit, and the driven fan has the same cooling performance.
      Citation: Actuators
      PubDate: 2022-01-10
      DOI: 10.3390/act11010020
      Issue No: Vol. 11, No. 1 (2022)
  • Actuators, Vol. 11, Pages 21: Novel Strategy of Adaptive Predictive
           Control Based on a MIMO-ARX Model

    • Authors: Alejandro Piñón, Antonio Favela-Contreras, Francisco Beltran-Carbajal, Camilo Lozoya, Graciano Dieck-Assad
      First page: 21
      Abstract: Many industrial processes include MIMO (multiple-input, multiple-output) systems that are difficult to control by standard commercial controllers. This paper describes a MIMO case of a class of SISO-APC (single-input, single-output adaptive predictive controller) based upon an ARX (autoregressive with exogenous variable) model. This class of SISO-APC based on ARX models has been successfully and extensively used in many industrial applications. This approach aims to minimize the barriers between the theory of predictive adaptive control and its application in the industrial environment. The proposed MIMO-APC (MIMO adaptive predictive controller) performance is validated with two simulated processes: a quadrotor drone and the quadruple tank process. In the first experiment the proposed MIMO APC shows ISE-IAE-ITAE performance indices improvements of up to 25%, 25.4% and 38.9%, respectively. For the quadruple tank process the water levels in the lower tanks follow closely the set points, with the exception of a 13% overshoot in tank 1 for the minimum phase behavior response. The controller responses show significant performance improvements when compared with previously published MIMO control strategies.
      Citation: Actuators
      PubDate: 2022-01-10
      DOI: 10.3390/act11010021
      Issue No: Vol. 11, No. 1 (2022)
  • Actuators, Vol. 11, Pages 22: Path Tracking Control of an Autonomous
           Tractor Using Improved Stanley Controller Optimized with
           Multiple-Population Genetic Algorithm

    • Authors: Liang Wang, Zhiqiang Zhai, Zhongxiang Zhu, Enrong Mao
      First page: 22
      Abstract: To improve the path tracking accuracy of autonomous tractors in operation, an improved Stanley controller (IMP-ST) is proposed in this paper. The controller was applied to a two-wheel tractor dynamics model. The parameters of the IMP-ST were optimized by multiple-population genetic algorithm (MPGA) to obtain better tracking performance. The main purpose of this paper is to implement path tracking control on an autonomous tractor. Thus, it is significant to study this field because of smart agricultural development. According to the turning strategy of tractors in field operations, five working routes for tractors were designed, including straight, U, Ω, acute-angle and obtuse-angle routes. Simulation tests were conducted to verify the effectiveness of the proposed IMP-ST in tractor path tracking for all routes. The lateral root-mean-square (RMS) error of the IMP-ST was reduced by up to 36.84% and 48.61% compared to the extended Stanley controller and the original Stanley controller, respectively. The simulation results indicate that the IMP-ST performed well in guiding the tractor to follow all planned working routes. In particular, for the U and Ω routes, the two most common turning methods in tractor field operations, the path tracking performance of the IMP-ST was improved by 41.72% and 48.61% compared to the ST, respectively. Comparing and analyzing the e-Ψ and β-γ phase plane of the three controllers, the results indicate that the IMP-ST has the best control stability.
      Citation: Actuators
      PubDate: 2022-01-11
      DOI: 10.3390/act11010022
      Issue No: Vol. 11, No. 1 (2022)
  • Actuators, Vol. 11, Pages 23: Lodged Sugarcane/Crop Dividers Interaction:
           Analysis of Robotic Sugarcane Harvester in Agriculture via a
           Rigid-Flexible Coupled Simulation Method

    • Authors: Qingqing Wang, Qianwei Zhang, Yin Zhang, Guoan Zhou, Zhiqiang Li, Liqing Chen
      First page: 23
      Abstract: As a critical component of the sugarcane harvester, the primary function of the crop dividers is to lift the lodged sugarcane (LS) and reduce the loss rate of the sugarcane harvest. In this study, a rigid-flexible coupling simulation method is proposed to improve the lifting efficiency of the crop dividers on severely LS and analyze the nature of interaction between the sugarcane stalk and the crop dividers. The model’s accuracy was verified using field experiments, and the operational performance of the crop dividers on sugarcane in different lodging postures was investigated. The results showed that the curve of the vertical height of the center (VHC) fluctuated more and slipped with highest frequency during the lifting process of side and forward LS. The speed of VHC was fastest during the lifting operation of side LS. The effect of side angle on the lifting effect of sugarcane was significant; the qualified values of the VHC of sugarcane being lifted in different lodged postures were: side and reverse lodged > side lodged > side and forward lodged. The coupling method and experimental results described in this paper can provide guidance for the optimal design and field operation of the crop dividers.
      Citation: Actuators
      PubDate: 2022-01-13
      DOI: 10.3390/act11010023
      Issue No: Vol. 11, No. 1 (2022)
  • Actuators, Vol. 11, Pages 24: Experimental Evaluation on Haptic Feedback
           Accuracy by Using Two Self-Made Haptic Devices and One Additional
           Interface in Robotic Teleoperation

    • Authors: Guan-Yang Liu, Yi Wang, Chao Huang, Chen Guan, Dong-Tao Ma, Zhiming Wei, Xinan Qiu
      First page: 24
      Abstract: The goal of haptic feedback in robotic teleoperation is to enable users to accurately feel the interaction force measured at the slave side and precisely understand what is happening in the slave environment. The accuracy of the feedback force describing the error between the actual feedback force felt by a user at the master side and the measured interaction force at the slave side is the key performance indicator for haptic display in robotic teleoperation. In this paper, we evaluate the haptic feedback accuracy in robotic teleoperation via experimental method. A special interface iHandle and two haptic devices, iGrasp-T and iGrasp-R, designed for robotic teleoperation are developed for experimental evaluation. The device iHandle integrates a high-performance force sensor and a micro attitude and heading reference system which can be used to identify human upper limb motor abilities, such as posture maintenance and force application. When a user is asked to grasp the iHandle and maintain a fixed position and posture, the fluctuation value of hand posture is measured to be between 2 and 8 degrees. Based on the experimental results, human hand tremble as input noise sensed by the haptic device is found to be a major reason that results in the noise of output force from haptic device if the spring-damping model is used to render feedback force. Therefore, haptic rendering algorithms should be independent of hand motion information to avoid input noise from human hand to the haptic control loop in teleoperation. Moreover, the iHandle can be fixed at the end effector of haptic devices; iGrasp-T or iGrasp-R, to measure the output force/torque from iGrasp-T or iGrasp-Rand to the user. Experimental results show that the accuracy of the output force from haptic device iGrasp-T is approximately 0.92 N, and using the force sensor in the iHandle can compensate for the output force inaccuracy of device iGrasp-T to 0.1 N. Using a force sensor as the feedback link to form a closed-loop feedback force control system is an effective way to improve the accuracy of feedback force and guarantee high-fidelity of feedback forces at the master side in robotic teleoperation.
      Citation: Actuators
      PubDate: 2022-01-14
      DOI: 10.3390/act11010024
      Issue No: Vol. 11, No. 1 (2022)
  • Actuators, Vol. 11, Pages 25: Equivalent Rope Length-Based Trajectory

    • Authors: Qingxiang Wu, Ning Sun, Xiaokai Wang
      First page: 25
      Abstract: The hoisting form in which the payload is hung on the hook by two rigging ropes is widely used in the industry, but it also results in the complex double pendulum dynamic of the bridge crane, making the anti-swing trajectory planning full of challenges. In this paper, based on the concept of the equivalent rope length, an equivalent single pendulum model of the double pendulum bridge crane with the distributed mass payload is established. On this basis, the particle swarm optimization algorithm is adopted to solve the equivalent rope length and calculate the parameters of the anti-swing velocity trajectory based on the phase plane method. To evaluate the effectiveness of the proposed method, experiments with a laboratory double pendulum bridge crane are conducted. Experimental results demonstrate that the residual oscillation angle of the payload of the proposed method is smaller than those of the existing methods, such as the trajectory planning without the equivalent rope length, input shaping and command smoothing.
      Citation: Actuators
      PubDate: 2022-01-17
      DOI: 10.3390/act11010025
      Issue No: Vol. 11, No. 1 (2022)
  • Actuators, Vol. 11, Pages 26: A Portable Non-Contact Tremor Vibration
           Measurement and Classification Apparatus

    • Authors: Mohd Zarhamdy Md Zain, Ali Zolfagharian, Moslem Mohammadi, Mahdi Bodaghi, Abd Rahim Abu Bakar, Abbas Z. Kouzani
      First page: 26
      Abstract: Tremors are the most common type of movement disorder and affect the lives of those experiencing them. The efficacy of tremor therapies varies according to the aetiology of the tremor and its correct diagnosis. This study develops a portable measurement device capable of non-contact measurement of the tremor, which could assist in tremor diagnosis and classification. The performance of this device was assessed through a validation process using a shaker at a controlled frequency to measure human tremors, and the device was able to measure vibrations of 50 Hz accurately, which is more than twice the frequency of tremors produced by humans. Then, the device is tested to measure the tremors for two different activation conditions: rest and postural, for both hand and leg. The measured non-contact tremor vibration data successfully led to tremor classification in the subjects already diagnosed using a contact accelerometer.
      Citation: Actuators
      PubDate: 2022-01-17
      DOI: 10.3390/act11010026
      Issue No: Vol. 11, No. 1 (2022)
  • Actuators, Vol. 11, Pages 27: Study on Multidegree-of-Freedom Ultrasonic
           Motor Using Vibration Mode Rotation of Metal Spherical Stator

    • Authors: Ai Mizuno, Hidekazu Kajiwara, Hideki Tamura, Manabu Aoyagi
      First page: 27
      Abstract: Most of the multidegree-of-freedom ultrasonic motors (MDOF-USMs) use a spherical rotor, and the design of the stator is restricted due to the use of the resonance mode. (1) Therefore, there is almost impossible to freely design the overall shape, resulting in a complicated structure. (2) To solve such an inconvenience, an MDOF-USM using a metal spherical stator was proposed. The vibration mode rotation on the stator was designed by theoretical analysis of spherical vibration and finite element method analysis. Multilayer piezoelectric actuators (MPAs) were embedded in the sphere to excite the vibration mode. Cylindrical projections were attached to the surface of the stator to magnify the vibration displacement and worked as the driving part. Their effects were evaluated using an electronic circuit simulator method of performance analysis. (3) As a result, two types of vibration mode rotation methods for the 3-DOF rotation were confirmed. It was also confirmed that the rotor covering the outside stator rotates around three axes. However, tiny torque, low power factor, and slow speed were obtained. (4) An MDOF-USM using a spherical stator was realized according to the operating principle. However, since the cause of such a low performance is the excitation method of the sphere and the rotor structure, research for improvement is required in the future.
      Citation: Actuators
      PubDate: 2022-01-17
      DOI: 10.3390/act11010027
      Issue No: Vol. 11, No. 1 (2022)
  • Actuators, Vol. 11, Pages 1: Estimation of the Dynamic Parameters of the
           Bearings in a Flexible Rotor System Utilizing Electromagnetic Excitation
           by a Built-In Motor

    • Authors: Yinsi Chen, Ren Yang, Naohiro Sugita, Jianpeng Zhong, Junhong Mao, Tadahiko Shinshi
      First page: 1
      Abstract: Estimation of the dynamic parameters of bearings is essential in order to be able to interpret the performance of rotating machinery. In this paper, we propose a method to estimate the dynamic parameters of the bearings in a flexible rotor system. By utilizing the electromagnetic excitation generated by a built-in PM motor and finite element (FE) modeling of the rotor, safe, low-cost, and real-time monitoring of the bearing dynamics can be achieved. The radial excitation force is generated by injecting an alternating d-axis current into the motor windings. The FE model of the rotor and the measured frequency responses at the motor and bearing locations are used to estimate the dynamic parameters of the bearings. To evaluate the feasibility of the proposed method, numerical simulation and experiments were carried out on a flexible rotor system combined with a bearingless motor (BELM) having both motor windings and suspension windings. The numerical simulation results show that the proposed algorithm can accurately estimate the dynamic parameters of the bearings. In the experiment, the estimates made when utilizing the excitation force generated by the motor windings are compared with the estimates made when utilizing the excitation force generated by the suspension windings. The results show that most of the stiffness and damping coefficients for the two experiments are in good agreement, within a maximum error of 8.92%. The errors for some coefficients are large because the base values of these coefficients are small in our test rig, so these coefficients are sensitive to deviations. The natural frequencies calculated from the dynamic parameters estimated from the two experiments are also in good agreement, within a maximum relative error of 3.04%. The proposed method is effective and feasible for turbomachines directly connected to motors, which is highly significant for field tests.
      Citation: Actuators
      PubDate: 2021-12-23
      DOI: 10.3390/act11010001
      Issue No: Vol. 11, No. 1 (2021)
  • Actuators, Vol. 11, Pages 2: A New Method for Identifying Kinetic
           Parameters of Industrial Robots

    • Authors: Bin Kou, Shijie Guo, Dongcheng Ren
      First page: 2
      Abstract: Identifying the kinetic parameters of an industrial robot is the basis for designing a controller for it. To solve the problems of the poor accuracy and easy premature convergence of common bionic algorithms for identifying the dynamic parameters of such robots, this study proposed simulated annealing with similar exponential changes based on the beetle swarm optimization (SEDSABSO) algorithm. Expressions for the dynamics of the industrial robot were first obtained through the SymPyBotics toolkit in Python, and the required trajectories of excitation were then designed to identify its dynamic parameters. Following this, the search pattern of the global optimal solution for the beetle swarm optimization algorithm was improved in the context of solving for these parameters. The global convergence of the algorithm was improved by improving the iterative form of the number N of skinks in it by considering random perturbations and the simulated annealing algorithm, whereas its accuracy of convergence was improved through the class exponential change model. The improved beetle swarm optimization algorithm was used to identify the kinetic parameters of the Zhichang Kawasaki RS010N industrial robot. The results of experiments showed that the proposed algorithm was fast and highly accurate in identifying the kinetic parameters of the industrial robot.
      Citation: Actuators
      PubDate: 2021-12-23
      DOI: 10.3390/act11010002
      Issue No: Vol. 11, No. 1 (2021)
  • Actuators, Vol. 11, Pages 3: A Pneumatic Novel Combined Soft Robotic
           Gripper with High Load Capacity and Large Grasping Range

    • Authors: Dan Wang, Xiaojun Wu, Jinhua Zhang, Yangyang Du
      First page: 3
      Abstract: Pneumatic soft grippers have been widely studied. However, the structures and material properties of existing pneumatic soft grippers limit their load capacity and manipulation range. In this article, inspired by sea lampreys, we present a pneumatic novel combined soft gripper to achieve a high load capacity and a large grasping range. This soft gripper consists of a cylindrical soft actuator and a detachable sucker. Three internal air chambers of the cylindrical soft actuator are inflated, which enables them to hold objects. Under vacuum pressure, the cylindrical soft actuator and the detachable sucker can both adsorb objects. A finite element model was constructed to simulate three inflation chambers for predicting the grasping range of the cylindrical soft actuator. The validity of the finite element model was established by an experiment. The mechanism of holding force and adsorption force were analyzed. Several groups of experiments were conducted to determine adsorption range, holding force, and adsorption force. In addition, practical applications further indicated that the novel combined soft gripper has a high load capacity (10.85 kg) at a low pressure (16 kPa) and a large grasping range (minimum diameter of the object: d = 6 mm), being able to lift a variety of objects with different weights, material properties, and shapes.
      Citation: Actuators
      PubDate: 2021-12-27
      DOI: 10.3390/act11010003
      Issue No: Vol. 11, No. 1 (2021)
  • Actuators, Vol. 11, Pages 4: Multi-UAV Optimal Mission Assignment and Path
           Planning for Disaster Rescue Using Adaptive Genetic Algorithm and Improved
           Artificial Bee Colony Method

    • Authors: Haoting Liu, Jianyue Ge, Yuan Wang, Jiacheng Li, Kai Ding, Zhiqiang Zhang, Zhenhui Guo, Wei Li, Jinhui Lan
      First page: 4
      Abstract: An optimal mission assignment and path planning method of multiple unmanned aerial vehicles (UAVs) for disaster rescue is proposed. In this application, the UAVs include the drug delivery UAV, image collection UAV, and communication relay UAV. When implementing the modeling and simulation, first, three threat sources are built: the weather threat source, transmission tower threat source, and upland threat source. Second, a cost-revenue function is constructed. The flight distance, oil consumption, function descriptions of UAV, and threat source factors above are considered. The analytic hierarchy process (AHP) method is utilized to estimate the weights of cost-revenue function. Third, an adaptive genetic algorithm (AGA) is designed to solve the mission allocation task. A fitness function which considers the current and maximum iteration numbers is proposed to improve the AGA convergence performance. Finally, an optimal path plan between the neighboring mission points is computed by an improved artificial bee colony (IABC) method. A balanced searching strategy is developed to modify the IABC computational effect. Extensive simulation experiments have shown the effectiveness of our method.
      Citation: Actuators
      PubDate: 2021-12-28
      DOI: 10.3390/act11010004
      Issue No: Vol. 11, No. 1 (2021)
  • Actuators, Vol. 11, Pages 5: An IDA-PBC Design with Integral Action for
           Output Voltage Regulation in an Interleaved Boost Converter for DC
           Microgrid Applications

    • Authors: Oscar Danilo Montoya, Federico Martin Serra, Walter Gil-González, Eduardo Maximiliano Asensio, Jonathan Emmanuel Bosso
      First page: 5
      Abstract: This paper describes the output voltage regulation control for an interleaved connected to a direct current (DC) microgrid considering bidirectional current flows. The proposed controller is based on an interconnection and damping passivity-based control (IDA-PBC) approach with integral action that regulates the output voltage profile at its assigned reference. This approach designs a control law via nonlinear feedback that ensures asymptotic stability in a closed-loop in the sense of Lyapunov. Moreover, the IDA-PBC design adds an integral gain to eliminate the possible tracking errors in steady-state conditions. Numerical simulations in the Piecewise Linear Electrical Circuit Simulation (PLECS) package for MATLAB/Simulink demonstrate that the effectiveness of the proposed controller is assessed and compared with a conventional proportional-integral controller under different scenarios considering strong variations in the current injected/absorbed by the DC microgrid.
      Citation: Actuators
      PubDate: 2021-12-29
      DOI: 10.3390/act11010005
      Issue No: Vol. 11, No. 1 (2021)
  • Actuators, Vol. 11, Pages 6: Design and Analysis of a Novel Composited
           Electromagnetic Linear Actuator

    • Authors: Xinyu Fan, Jie Yin, Qinfen Lu
      First page: 6
      Abstract: Electromagnetic linear actuators, as key executive components, have a vital impact on the performance of fully flexible variable valve trains. Considering that the conventional moving coil electromagnetic linear actuator (MCELA) has the disadvantages of low force density and a lack of end-passive self-holding ability, a novel composited electromagnetic linear actuator (CELA) is proposed by combining the performance advantages of MCELA and moving iron electromagnetic linear actuator (MIELA) in this work. Firstly, the structure and magnetic circuit design scheme of the proposed actuator are introduced and the finite element simulation model is established. The magnetic field distribution and force characteristics of the actuators are assessed by finite element simulation. Secondly, the construction of the prototype of the actuator is outlined, based on which the feasibility of the design scheme and the steady-state performance of the actuator are verified. Finally, the coordinated control strategy is proposed to realize the multi motion coordination control of the actuator. The research results show that the maximum starting force of the CELA with the end-passive self-holding ability is 574.92 N while the holding force can approach 229.25 N. Moreover, the CELA is proven to have excellent dynamic characteristics and control precision under different motion modes and to have an improved adaptability to the complex working conditions of internal combustion engines.
      Citation: Actuators
      PubDate: 2021-12-29
      DOI: 10.3390/act11010006
      Issue No: Vol. 11, No. 1 (2021)
  • Actuators, Vol. 11, Pages 7: A Dynamic Modeling Method for the
           Bi-Directional Pneumatic Actuator Using Dynamic Equilibrium Equation

    • Authors: Yiqing Li, Wen Zhou, Junwu Wu, Guoxu Hu
      First page: 7
      Abstract: Dynamic modeling of soft pneumatic actuators are a challenging research field. In this paper, a dynamic modeling method used for a bi-directionaly soft pneumatic actuator with symmetrical chambers is proposed. In this dynamic model, the effect of uninflated rubber block on bending deformation is considered. The errors resulting from the proposed dynamic equilibrium equation are analyzed, and a compensation method for the dynamic equilibrium equation is proposed. The equation can be solved quickly after simplification. The results show that the proposed dynamic model can describe the motion process of the bi-directional pneumatic actuator effectively.
      Citation: Actuators
      PubDate: 2021-12-30
      DOI: 10.3390/act11010007
      Issue No: Vol. 11, No. 1 (2021)
  • Actuators, Vol. 11, Pages 8: Modeling and Experimental Research of One
           Kind of New Planar Vortex Actuator Based on Shape Memory Alloy

    • Authors: Xiangsen Kong, Yilei Gu, Jiajun Wu, Yang Yang, Xing Shen
      First page: 8
      Abstract: In order to alleviate the problems of complex structure and low reliability of traditional Shape Memory Alloy (SMA) rotary actuator, a planar vortex actuator (PVA) based on SMA material was proposed to directly output torque and angular displacement. Based on the calculation method of PVA and the constitutive model of the phase transition equation of SMA, the mechanical model is established, and the pre-tightening torque, temperature, output torque, and rotation angle are obtained. The relationship expression between the tests has verified the mechanical model. The results show that the relationship between the excitation temperature and the output torque, the coefficient of determination between the calculated value and the tested value, is 0.938, the minimum error is 0.46%, and the maximum error is 49.8%. In the relationship between angular displacement and torque, the coefficient of determination between the calculated value and the test value is 0.939, the maximum error is 58.5%, and the minimum error is 28.0%. The test results show that the calculated values of mechanical model and experimental data have similar representation form.
      Citation: Actuators
      PubDate: 2021-12-31
      DOI: 10.3390/act11010008
      Issue No: Vol. 11, No. 1 (2021)
  • Actuators, Vol. 11, Pages 9: An Intelligent Process to Estimate the
           Nonlinear Behaviors of an Elasto-Plastic Steel Coil Damper Using
           Artificial Neural Networks

    • Authors: Seongkyu Chang, Sung Gook Cho
      First page: 9
      Abstract: This study developed a nonlinear behavior prediction model for elasto-plastic steel coil dampers (SCDs) using artificial neural networks (ANN). To train the ANN, first, the input and output data of the behavior of the elasto-plastic SCD was prepared. This study utilized the design parameters and load–displacement curves of the SCD to train the ANN. The elasto-plastic load–displacement curve of the SCD was obtained from simulation results using an ANSYS workbench. The design parameters (wire diameter, internal diameter, number of active windings, yield strength) of the SCD were defined as the input patterns, while the yield deformation, first stiffness, and second stiffness were output patterns. During learning of the neural network model, 60 datasets of the SCD were used as the learning pattern, and the remaining 21 were used to verify the model. Although this study used a small number of learning patterns, the ANN predicted accurate results for yield displacement, first stiffness, and second stiffness. In this study, the ANN was found to perform very well, predicting the nonlinear response of the SCD, compared with the values obtained from a finite element analysis program.
      Citation: Actuators
      PubDate: 2021-12-31
      DOI: 10.3390/act11010009
      Issue No: Vol. 11, No. 1 (2021)
  • Actuators, Vol. 11, Pages 10: Analysis of a Low-Speed Drive System Using
           Intelligent Materials

    • Authors: Vasile Eusebiu Toader, Laurențiu Dan Milici, Constantin Ungureanu, Ciprian Bejenar, Oana Vasilica Grosu
      First page: 10
      Abstract: This paper presents a low speed drive system with a simple and reliable construction, which can be used in an area where there is no power supply (isolated areas, forests, agricultural fields, etc.) and which operates on the basis of two heat sources, one from solar radiation and one provided by water. Alternatively, this system can be used to recover energy from wastewater from industry. The operation and role of the parameters that can influence the value of the rotation speed of the drive system are analyzed through a simulation, maintaining a constant speed in the case of the prototype is achieved through the control system because in real situations the temperature of heat sources can vary within certain limits. The models and tests performed highlight the parameters of the analyzed drive system and the limits of the range in which its speed can vary.
      Citation: Actuators
      PubDate: 2021-12-31
      DOI: 10.3390/act11010010
      Issue No: Vol. 11, No. 1 (2021)
  • Actuators, Vol. 10, Pages 331: High Precision Motion Control of
           Electro-Mechanical Launching Platform with Modeling Uncertainties: A New
           Integrated Error Constraint Asymptotic Design

    • Authors: Zhenle Dong, Yinghao Yang, Geqiang Li, Zheng Zhang
      First page: 331
      Abstract: For the demands of a high precision motion control of an uncertain electro-mechanical launching platform, a novel integrated error constraint asymptotic control in the presence of parametric uncertainties and uncertain disturbance is proposed, of which the barrier function method and a continuous asymptotic control design are integrated for the first time. The former technique can effectively avoid excessive tracking errors at the transient phase, which is caused by the disturbance and the large uncertain system parameters’ deviation between the initial estimated value and the actual value, by selecting a proper barrier threshold, while the latter technique can handle the uncertain disturbance to achieve asymptotic tracking. A rigorous stability analysis is given to illustrate the theoretical performance. In addition, as a supplementary measure, repetitive control is employed to estimate and compensate the possible periodic-like disturbance under certain conditions. Two experimental cases on a prototype of a launching platform demonstrate the effectiveness of the proposed controller.
      Citation: Actuators
      PubDate: 2021-12-15
      DOI: 10.3390/act10120331
      Issue No: Vol. 10, No. 12 (2021)
  • Actuators, Vol. 10, Pages 332: An Active Fault-Tolerant Control for
           Robotic Manipulators Using Adaptive Non-Singular Fast Terminal Sliding
           Mode Control and Disturbance Observer

    • Authors: Van-Cuong Nguyen, Phu-Nguyen Le, Hee-Jun Kang
      First page: 332
      Abstract: In this study, a fault-tolerant control (FTC) tactic using a sliding mode controller–observer method for uncertain and faulty robotic manipulators is proposed. First, a finite-time disturbance observer (DO) is proposed based on the sliding mode observer to approximate the lumped uncertainties and faults (LUaF). The observer offers high precision, quick convergence, low chattering, and finite-time convergence estimating information. Then, the estimated signal is employed to construct an adaptive non-singular fast terminal sliding mode control law, in which an adaptive law is employed to approximate the switching gain. This estimation helps the controller automatically adapt to the LUaF. Consequently, the combination of the proposed controller–observer approach delivers better qualities such as increased position tracking accuracy, reducing chattering effect, providing finite-time convergence, and robustness against the effect of the LUaF. The Lyapunov theory is employed to illustrate the robotic system’s stability and finite-time convergence. Finally, simulations using a 2-DOF serial robotic manipulator verify the efficacy of the proposed method.
      Citation: Actuators
      PubDate: 2021-12-15
      DOI: 10.3390/act10120332
      Issue No: Vol. 10, No. 12 (2021)
  • Actuators, Vol. 10, Pages 333: Guided Wave Transducer for the Locating
           Defect of the Steel Pipe Based on the Weidemann Effect

    • Authors: Jin Xu, Guang Chen, Jiang Xu, Qing Zhang
      First page: 333
      Abstract: The electromagnetic guided wave transducer has been widely used in pipeline detection in recent years due to its non-contact energy conversion characteristics. Based on the Weidemann effect, an electromagnetic guided wave transducer that can realize the locating defect of the steel pipe was provided. Firstly, the principle of the transducer was analyzed based on the Weidemann effect. The basic structure of the transducer and the basic functions of each part were given. Secondly, the key structural parameters of the transducer were studied. Based on the size of the magnets and the coils, a protype electromagnetic guided wave transducer based on Wiedemann effect was developed. Finally, the experiments were carried out on the steel pipe with a defect using the developed transducer. The results show that the transducer can actuate and receive the T(0,1) and T(1,1) modes in the steel pipe. The axial positioning of the defect is located by moving the transducer axially. The circumferential positioning of the defect is located by rotating the transducer. Additionally, missed detection can be effectively avoided by rotating the transducer.
      Citation: Actuators
      PubDate: 2021-12-16
      DOI: 10.3390/act10120333
      Issue No: Vol. 10, No. 12 (2021)
  • Actuators, Vol. 10, Pages 334: Wheel Deflection Control of Agricultural
           Vehicles with Four-Wheel Independent Omnidirectional Steering

    • Authors: Qimeng Xu, Hongwen Li, Quanyu Wang, Chunlei Wang
      First page: 334
      Abstract: Due to the harsh working environment of wheeled agricultural vehicles in the field, it is difficult to ensure that all wheels make contact with the ground at the same time, which is easy to unequally distribute the yaw moments of each independent wheel. The commonly used vehicle lateral control methods are mostly controlled by coordinating the individual torque between different wheels. Obviously, this control method is not suitable for agricultural four-wheeled vehicles. The goal of this study was to provide a wheel steering angle control method that uses electric push rods as actuators that can cope with this problem. The design of a four-wheel steering controller generally adopts the linear PID control method, but the research object of this paper is difficult to establish an accurate and linear mathematical model due to the complex working environment. Therefore, fuzzy adjustment is added on the basis of PID control, which can meet the requirements of model difficulty and control accuracy at the same time. In order to verify the feasibility and rationality of the designed wheel steering mechanism, the model dynamics simulation based on ADAMS software and the response analysis of the electric linear actuator thrust were completed. Based on the kinematics model of the controlled object, the rotation angle of the actuator motor is used as the control target, the lateral deviation e and deviation variation ec are taken as input variables and the parameters KP, KI and KD are taken as output variables, thereby establishing a fuzzy PID controller. Then, this controller is constructed in the Matlab/ Simulink simulation environment to analyze the lateral deviation and response stability during the process of vehicle path tracking. From the verification results of the linear path walking test under the fuzzy PID control method, the maximum lateral deviation of vehicle chassis is 2.7 cm when the driving speed is set as 1 m/s, and the deviation adjustment stable time of the system is 0.15 s. It can be seen that the proposed steering control strategy has good response performance and effectively increases the steering stability.
      Citation: Actuators
      PubDate: 2021-12-16
      DOI: 10.3390/act10120334
      Issue No: Vol. 10, No. 12 (2021)
  • Actuators, Vol. 10, Pages 335: 3D-Printed Miniature Robots with
           Piezoelectric Actuation for Locomotion and Steering Maneuverability

    • Authors: Víctor Ruiz-Díez, José Luis García-Caraballo, Jorge Hernando-García, José Luis Sánchez-Rojas
      First page: 335
      Abstract: The miniaturization of robots with locomotion abilities is a challenge of significant technological impact in many applications where large-scale robots have physical or cost restrictions. Access to hostile environments, improving microfabrication processes, or advanced instrumentation are examples of their potential use. Here, we propose a miniature 20 mm long sub-gram robot with piezoelectric actuation whose direction of motion can be controlled. A differential drive approach was implemented in an H-shaped 3D-printed motor platform featuring two plate resonators linked at their center, with built-in legs. The locomotion was driven by the generation of standing waves on each plate by means of piezoelectric patches excited with burst signals. The control of the motion trajectory of the robot, either translation or rotation, was attained by adjusting the parameters of the actuation signals such as the applied voltage, the number of applied cycles, or the driving frequency. The robot demonstrated locomotion in bidirectional straight paths as long as 65 mm at 2 mm/s speed with a voltage amplitude of only 10 V, and forward and backward precise steps as low as 1 µm. The spinning of the robot could be controlled with turns as low as 0.013 deg. and angular speeds as high as 3 deg./s under the same conditions. The proposed device was able to describe complex trajectories of more than 160 mm, while carrying 70 times its own weight.
      Citation: Actuators
      PubDate: 2021-12-20
      DOI: 10.3390/act10120335
      Issue No: Vol. 10, No. 12 (2021)
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