Actuators

28 pages, 3006 KiB

Open AccessArticle

Research on Sensorless Control Strategy of High-Speed Submersible Permanent Magnet Synchronous Motor

by Liang Xiong, Xiaolian Zhang, Lieyu Tian, Yang Lv, Jinsong Lu, Ailiyaer Ahemaiti, Qi Shi and Junguo Cui

Actuators 2025, 14(6), 282; https://doi.org/10.3390/act14060282 - 9 Jun 2025

Abstract

The application fields of high-speed submersible permanent magnet synchronous motors (PMSM) are constantly expanding. Especially in high-risk and complex environments such as oil exploration, offshore oil exploitation, and deep well operation, the reliability, stability, and efficiency of motor drive systems are more and [...] Read more.

The application fields of high-speed submersible permanent magnet synchronous motors (PMSM) are constantly expanding. Especially in high-risk and complex environments such as oil exploration, offshore oil exploitation, and deep well operation, the reliability, stability, and efficiency of motor drive systems are more and more prominent. The submersible motor is greatly affected by load disturbance, pressure change, and external oil flow, and the traditional method may not perform well in complex disturbance problems. Therefore, a three-order adaptive nonlinear extended state observer is proposed to collect the input and output information of the system in real time, and estimate the motor speed, position, and total disturbance. A linear feedback control law is designed to eliminate the disturbance. The superiority of the proposed algorithm under complex operating conditions is verified by the Simulink model and experiments, which provide a theoretical basis for the control of submersible motors. Full article

(This article belongs to the Section Control Systems)

16 pages, 1220 KiB

Open AccessArticle

A Servo Control Algorithm Based on an Explicit Model Predictive Control and Extended State Observer with a Differential Compensator

by Zhuobo Dong, Shuai Chen, Zheng Sun, Benyi Tang and Wenjun Wang

Actuators 2025, 14(6), 281; https://doi.org/10.3390/act14060281 - 8 Jun 2025

Abstract

Positioning servo systems utilizing permanent magnet synchronous linear motors (PMSLMs) are conventionally governed by cascaded P-PI controllers, which, despite their simplicity and robustness, suffer from limited tracking and anti-disturbance performance due to their single-degree-of-freedom (1-DOF) structure. This paper introduces a novel two-degree-of-freedom (2-DOF) [...] Read more.

Positioning servo systems utilizing permanent magnet synchronous linear motors (PMSLMs) are conventionally governed by cascaded P-PI controllers, which, despite their simplicity and robustness, suffer from limited tracking and anti-disturbance performance due to their single-degree-of-freedom (1-DOF) structure. This paper introduces a novel two-degree-of-freedom (2-DOF) control algorithm that integrates explicit model predictive control (EMPC) with a differential-compensated extended state observer (DCESO). The EMPC framework leverages position and velocity as state variables, eliminating the need for integral terms and thereby enhancing dynamic response. By employing an offline optimization approach, a control law is explicitly formulated to handle system constraints while minimizing online computational overhead. Additionally, a velocity feedforward term derived from the MPC framework is incorporated to further reduce tracking errors. To bolster disturbance rejection, the proposed DCESO introduces a differential compensator that mitigates the low-pass effects inherent in traditional ESOs, thereby improving estimation dynamics. Experimental results demonstrate that the proposed method significantly outperforms the conventional P-PI controller, increasing the position loop bandwidth from 147 Hz to 208 Hz and markedly enhancing anti-disturbance performance. The algorithm’s low online computational demand makes it highly suitable for industrial applications. Full article

(This article belongs to the Section Control Systems)

22 pages, 6676 KiB

Open AccessArticle

Design of a Longitudinal-Bending Elliptical Vibration Ultrasonic Transducer with a Bent Horn

by Zhiyong Huang, Mingshuo Zhang, Jiteng Li, Xinggang Jiang, Daxi Geng and Deyuan Zhang

Actuators 2025, 14(6), 280; https://doi.org/10.3390/act14060280 - 8 Jun 2025

Abstract

The thin and straight horn of the ultrasonic transducer is located in the center of the thick transducer, so that the tool tip of the ultrasonic vibration turning tool holder cannot be located on the outermost side of the entire tool holder, which [...] Read more.

The thin and straight horn of the ultrasonic transducer is located in the center of the thick transducer, so that the tool tip of the ultrasonic vibration turning tool holder cannot be located on the outermost side of the entire tool holder, which leads to the structural interference between the tool holder and the part during turning. In order to solve this problem, this paper proposes a longitudinal-bending elliptical vibration ultrasonic transducer with a bending horn for ultrasonic vibration-assisted cutting (UVAC). The designed transducer can be used for the partial separation continuous high-speed elliptic ultrasonic vibration cutting (HEUVC) of external surface and internal cavity. The ultrasonic vibration amplitude of the transducer can meet the needs of HEUVC. When using an ultrasonic transducer with a bending horn for HEUVC, compared with conventional cutting (CC), HEUVC can improve the tool life by about 50%. Full article

(This article belongs to the Section Actuators for Manufacturing Systems)

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18 pages, 3385 KiB

Open AccessArticle

Optimal Realtime Toolpath Planning for Industrial Robots with Sparse Sensing

by Enkhsaikhan Boldsaikhan and Cole Birney

Actuators 2025, 14(6), 279; https://doi.org/10.3390/act14060279 - 7 Jun 2025

Abstract

Non-contact surface processing does not involve direct contact between the tool and a worksurface. An industrial robot mostly uses preplanned toolpaths to perform non-contact surface processing. A preplanned toolpath may work well in repetitive conditions but may easily become inaccurate and unsafe if [...] Read more.

Non-contact surface processing does not involve direct contact between the tool and a worksurface. An industrial robot mostly uses preplanned toolpaths to perform non-contact surface processing. A preplanned toolpath may work well in repetitive conditions but may easily become inaccurate and unsafe if the tool needs to follow unknown worksurface variations. Many industrial processes, e.g., painting, coating, and sandblasting, typically involve worksurfaces with unknown variations. This study proposes an optimal toolpath planning method for an industrial robot equipped with end-of-arm distance sensors to automatically guide its tool motion along unknown worksurface variations. The distance sensors facilitate sparse sensing to acquire sparse data that is just enough for the quick and adequate perception of unknown worksurfaces by requiring fewer measurements and less computing. Optimization facilitates the optimality of multi-objective toolpath planning with a customizable value function, where the multiple objectives comprise adapting to unknown worksurface variations and traveling between known tool targets. To validate the proposed toolpath planning method, this study conducts a simulation experiment on a virtual robot with four end-of-arm distance sensors and a workpiece with unknown surface variations. The experimental results indicate that the proposed method is accurate and near-optimal even in the presence of sensor noises. Full article

(This article belongs to the Special Issue Actuator Technologies and Control: Materials, Devices and Applications)

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17 pages, 6777 KiB

Open AccessArticle

The Design and Control of a Proprioceptive Modular Actuator for Tendon-Driven Robots

by Di Zhao, Xinbo Wang, Fanbo Wei, Lei Ren, Kunyang Wang and Luquan Ren

Actuators 2025, 14(6), 278; https://doi.org/10.3390/act14060278 - 6 Jun 2025

Abstract

Tendon-driven robots offer advantages in terms of their compliance, lightweight design, and remote actuation, making them ideal for applications requiring dexterity and safety. However, existing tendon-driven actuators often suffer from low integration and inaccurate proprioceptive sensing due to their complex pulley-based tension sensors [...] Read more.

Tendon-driven robots offer advantages in terms of their compliance, lightweight design, and remote actuation, making them ideal for applications requiring dexterity and safety. However, existing tendon-driven actuators often suffer from low integration and inaccurate proprioceptive sensing due to their complex pulley-based tension sensors and bulky angle sensors. This paper presents the design and control of a compact and proprioceptive modular tendon-driven actuator. The actuator features a simplified single-pulley tension sensing mechanism and a novel maze-slot fixation method, minimizing friction and maximizing the structural integrity. A 3D Hall effect sensor is employed for accurate estimation of the tendon length with minimal space usage. A feedforward PID controller and a model-based tendon length observer are proposed to enhance the dynamic performance and sensing accuracy. Bench tests demonstrate that the actuator achieves a high power density (0.441 W/g), accurate closed-loop tension control, and reliable tendon length estimations. The proposed design provides a practical and high-performance solution for tendon-driven robots, enabling more agile, compact, and robust robotic systems. Full article

(This article belongs to the Section Actuators for Robotics)

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24 pages, 9811 KiB

Open AccessArticle

A Robust Strategy for Sensor Fault Reconstruction of Lower Limb Rehabilitation Exoskeleton Robots

by Zhe Sun, Zhuguang Li, Jinchuan Zheng and Zhihong Man

Actuators 2025, 14(6), 277; https://doi.org/10.3390/act14060277 - 6 Jun 2025

Abstract

Ensuring the reliability and stability of lower limb rehabilitation exoskeleton robots during rehabilitation training is of paramount importance. Sensor faults in such systems can degrade overall performance and may even pose significant safety hazards. Consequently, the effective reconstruction of sensor faults has become [...] Read more.

Ensuring the reliability and stability of lower limb rehabilitation exoskeleton robots during rehabilitation training is of paramount importance. Sensor faults in such systems can degrade overall performance and may even pose significant safety hazards. Consequently, the effective reconstruction of sensor faults has become a critical challenge in ensuring the safe and dependable operation of lower limb rehabilitation exoskeleton robots. This paper presents a novel sensor fault reconstruction method for systems subject to unknown external disturbances. Initially, an equivalent input disturbance (EID) approach based on an improved sliding mode observer is developed to mitigate the adverse effects of disturbances on the fault reconstruction process. Subsequently, a novel high-order sliding mode observer (NHSMO) is proposed to accurately reconstruct sensor faults. In contrast to conventional sliding mode observers, the proposed NHSMO guarantees finite-time convergence of the observation error, thereby enhancing both estimation accuracy and robustness. The effectiveness of this method is validated through both simulation and experimental results, demonstrating its superior fault reconstruction capabilities and strong resilience to external disturbances. Full article

(This article belongs to the Special Issue Advanced Perception and Control of Intelligent Equipment)

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19 pages, 5820 KiB

Open AccessArticle

Angle-Based RGN-Enhanced ADRC for PMSM Compressor Speed Regulation Considering Aperiodic and Periodic Disturbances

by Chenchen Zhang, Yang Yang, Yimin Gong, Yibo Guo, Hongda Song and Jiannan Zhang

Actuators 2025, 14(6), 276; https://doi.org/10.3390/act14060276 - 4 Jun 2025

Abstract

Achieving excellent speed control in permanent magnet synchronous motors (PMSMs) relies on the simultaneous suppression of both aperiodic and periodic disturbances. This paper presents an enhanced Active Disturbance Rejection Control (ADRC) strategy specifically designed to address these disturbances in single-rotor compressors (SRCs). To [...] Read more.

Achieving excellent speed control in permanent magnet synchronous motors (PMSMs) relies on the simultaneous suppression of both aperiodic and periodic disturbances. This paper presents an enhanced Active Disturbance Rejection Control (ADRC) strategy specifically designed to address these disturbances in single-rotor compressors (SRCs). To achieve simultaneous suppression, a Recursive Gauss–Newton (RGN) algorithm is implemented in parallel with the conventional extended state observer (ESO) to enhance the ADRC framework. The RGN algorithm iteratively estimates the amplitude and phase information of periodic disturbances, while the ESO primarily observes the system’s aperiodic disturbances. In contrast to existing methods, the proposed angle-based approach demonstrates superior performance during speed transients. Detailed convergence and decoupling analyses are provided to facilitate parameter tuning. The effectiveness of the proposed method is validated through simulations and experiments conducted on a 650 W SRC, demonstrating its superiority over proportional–integral (PI) control, conventional ADRC, and quasi-resonant controller-based ADRC (QRC-ADRC) under both steady-state and dynamic conditions. Full article

(This article belongs to the Section Control Systems)

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16 pages, 8112 KiB

Open AccessArticle

Identification and Compensation of Detection Gain Asymmetry Errors for Hemispherical Resonant Gyroscopes in Whole-Angle Mode

by Ruizhao Cheng, Gongliu Yang, Qingzhong Cai, Xiaodi Yi and Yongqiang Tu

Actuators 2025, 14(6), 275; https://doi.org/10.3390/act14060275 - 3 Jun 2025

Abstract

Detection gain asymmetry error is one of the primary errors of the hemispherical resonator gyroscope (HRG) in whole-angle (WA) mode. This paper analyzes the influence of detection gain asymmetry error and its coupling error with damping and stiffness asymmetry on the performance of [...] Read more.

Detection gain asymmetry error is one of the primary errors of the hemispherical resonator gyroscope (HRG) in whole-angle (WA) mode. This paper analyzes the influence of detection gain asymmetry error and its coupling error with damping and stiffness asymmetry on the performance of HRG and proposes a novel compensation method for detection gain asymmetry error. Firstly, the nonlinear error model of HRG considering the detection gain asymmetry error and its coupling error is established by using the average method. The influence of the angle-dependent scale factor error (ADS) and angle-dependent bias error (ADB) caused by the detection gain asymmetry error is analyzed by numerical simulation. Secondly, a parameter estimation algorithm based on force-to-rebalance (FTR) mode is proposed to decouple and identify the detection gain asymmetry error and damping asymmetry error. The identified parameters are used for the calibration of the HRG. Finally, the method is applied to the HRG operating in WA mode. The effectiveness of the proposed method is verified by experiments. After compensation, the bias instability is reduced from 3.6°/h to 0.6°/h, the scale factor nonlinearity is reduced from 646.57 ppm to 207.43 ppm, and the maximum pattern angle deviation is reduced from 0.6° to 0.05°. Full article

(This article belongs to the Section Precision Actuators)

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23 pages, 10598 KiB

Open AccessArticle

Robotic Wound Closure: Detection and Control of Patient Motion

by Edward H. Currie, Yimin Zhao, Louis Kavoussi and Sina Y. Rabbany

Actuators 2025, 14(6), 274; https://doi.org/10.3390/act14060274 - 31 May 2025

Abstract

Physiological organ motion, such as breathing movement, presents a challenge in the development of medical robots for autonomous wound closure. The robot’s task is to determine the wound’s pose and relay magnetic fixtures near the wound edge with pre-specified accuracy. To address this [...] Read more.

Physiological organ motion, such as breathing movement, presents a challenge in the development of medical robots for autonomous wound closure. The robot’s task is to determine the wound’s pose and relay magnetic fixtures near the wound edge with pre-specified accuracy. To address this problem, a visual motion detection system (VMDS) is designed to determine the pose of a wound. To ensure precise tracking of the wound, a varying target sliding mode control (VT-SMC) scheme was developed to follow the wound movement. Experiments demonstrate excellent agreement, with less than 0.67 mm variance between the VMDS measurements, real motion for three translations, and 0.26 degrees for three rotations. The relay error is 0.86 mm under the patient motion (position: 15 mm, orientation: 5 deg) in the autonomous robotic wound closure system. The developed robot successfully achieves the necessary motion tracking, which proves sufficient for the accuracy of wound closure in clinical applicability. Full article

(This article belongs to the Special Issue Actuators in Robotic Control—3rd Edition)

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26 pages, 6044 KiB

Open AccessArticle

Drill-String Vibration Suppression Using Hybrid Magnetorheological Elastomer-Fluid Absorbers

by Jasem M. Kamel, Asan G. A. Muthalif and Abdulazim H. Falah

Actuators 2025, 14(6), 273; https://doi.org/10.3390/act14060273 - 30 May 2025

Abstract

Rotary drilling systems with PDC bits, commonly used for drilling deep wells in the production and exploration of oil and natural gas, frequently encounter severe vibrations. These vibrations can cause significant damage to the drilling system, particularly its downhole components, leading to drilling [...] Read more.

Rotary drilling systems with PDC bits, commonly used for drilling deep wells in the production and exploration of oil and natural gas, frequently encounter severe vibrations. These vibrations can cause significant damage to the drilling system, particularly its downhole components, leading to drilling performance inefficiencies, notably reducing the rate of penetration and incurring high costs. This paper presents a parametric study on a proposed new axial semi-active tool designed to mitigate these unwanted vibrations. The tool, an axial absorber with tunable stiffness and damping coefficients over a wide range, composed of a hybrid magnetorheological elastomer-fluid (MRE-F), is installed above the PDC bit. In this study, the lumped parameter model considering axial and torsional vibrations is followed to assess the effectiveness of including the proposed absorber in the drill-string system’s behavior and to estimate the optimal coefficient values for achieving high-efficiency drilling. The drilling system response shown in this study indicates that, with optimal axial absorber coefficient values, the bit dynamically stabilizes, and unwanted vibrations are minimized, effectively eliminating the occurrence of bit-bounce and stick–slip, even when operating at critical frequencies. The proposed semi-active control tool has been proven to significantly reduce maintenance time, reduce the costs associated with severe vibrations, extend the lifespan of bottom-hole assembly components, and achieve smoother drilling with a simple addition to the drilling system. Full article

(This article belongs to the Section High Torque/Power Density Actuators)

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30 pages, 6654 KiB

Open AccessArticle

Time-Jerk Optimal Robotic Trajectory Planning Under Jerk and Continuity Constraints via Convex Optimization

by Chen Qian, Jianjun Yao and Yikun Zhang

Actuators 2025, 14(6), 272; https://doi.org/10.3390/act14060272 - 29 May 2025

Abstract

This paper proposes a robot trajectory planning method focused on time and jerk optimization under compound constraints. First, the robot path-tracking task is parameterized by incorporating both kinematic and dynamic constraints in joint and Cartesian spaces, establishing a time-optimal trajectory optimization model. To [...] Read more.

This paper proposes a robot trajectory planning method focused on time and jerk optimization under compound constraints. First, the robot path-tracking task is parameterized by incorporating both kinematic and dynamic constraints in joint and Cartesian spaces, establishing a time-optimal trajectory optimization model. To achieve C³ continuity in joint motion, joint-motion continuity conditions are analyzed, and optimization variables are reconstructed using piecewise cubic splines with corresponding continuity constraints. Considering the nonlinear and nonconvex characteristics of jerk constraints, the time-optimal planning model is decomposed into two second-order cone programming (SOCP) subproblems, achieving linear convexification of the original problem. Additionally, the objective function is improved to optimize both time and joint jerk simultaneously. Experimental results confirm that the proposed method effectively improves robot efficiency and trajectory smoothness. Full article

(This article belongs to the Special Issue Motion Planning, Trajectory Prediction, and Control for Robotics)

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12 pages, 3776 KiB

Open AccessArticle

Design and Test of a Magnetorheological Damper of a Multi-Layered Permanent Magnet

by Fang Chen, Qinkui Guo, Yuchen Liu, Yuan Dong, Yangjie Xiao, Ningqiang Zhang and Wangxu Li

Actuators 2025, 14(6), 271; https://doi.org/10.3390/act14060271 - 29 May 2025

Abstract

To effectively suppress spindle vibrations in rotating machinery, magnetorheological (MR) dampers, as an ideal vibration control device, have attracted attention. To enhance the vibration damping effect, in the paper, a MR damper vibration with a multi-layered permanent magnet as the magnetic source is [...] Read more.

To effectively suppress spindle vibrations in rotating machinery, magnetorheological (MR) dampers, as an ideal vibration control device, have attracted attention. To enhance the vibration damping effect, in the paper, a MR damper vibration with a multi-layered permanent magnet as the magnetic source is designed, and the self-made magnetorheological fluid is used as the damping medium. The mechanical properties of the MR damper were obtained through testing and calculation. On this base, both simulation and experimental methods are used to demonstrate the effectiveness of the multi-layered permanent-magnet MR damper. The simulation results show that the critical speed increases greatly for the first four modes. The experimental results show that the Y-direction displacement decreases greatly, especially at 1800 rpm and at 3400 rpm, after applying the MR damper. The vibration displacement at 1× frequency shows a 69.74% reduction at 2600 rpm and a 65.69% reduction at 3200 rpm in the Y-direction after applying the MR damper. The effectiveness of the multi-layered permanent magnet MR damper in rotor vibration suppression was confirmed. Full article

(This article belongs to the Special Issue Advanced Actuators and Magnetic Fluid Systems: Design, Control, and Applications)

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19 pages, 15213 KiB

Open AccessArticle

Derivation and Experimental Validation of Multi-Parameter Performance Optimization of Magnetic Adhesion Unit of Wall-Climbing Robot

by Helei Zhu, Haifeng Ji, Peixing Li and Leijie Lai

Actuators 2025, 14(6), 270; https://doi.org/10.3390/act14060270 - 29 May 2025

Abstract

Wall-climbing robots have broad application potential in industrial equipment inspection, chemical storage tank maintenance, and high-altitude operations. However, their practical implementation is challenged by the robots’ adhesion requirements in complex wall environments. This study uses a systematic methodology integrating computational simulation and experimental [...] Read more.

Wall-climbing robots have broad application potential in industrial equipment inspection, chemical storage tank maintenance, and high-altitude operations. However, their practical implementation is challenged by the robots’ adhesion requirements in complex wall environments. This study uses a systematic methodology integrating computational simulation and experimental validation to design and optimize a magnetic adsorption system for wall-climbing robots. Firstly, an adjustable suspended magnetic adhesion unit is designed to achieve intelligent control of a wall-climbing robot’s adhesion force on a wall surface. The Maxwell software (AnsysEM21.1) is used to simulate and analyze the critical parameters of the magnetic adsorption unit, including the thickness of the magnet and yoke, as well as the distance and angle between the magnet and the wall surface. Then, a magnetic wheel is designed for the wall-climbing robot based on the optimization of the structure and parameters of the magnetic adhesion unit. The absorption and demagnetization of the magnetic wheels are achieved by rotating the magnetic absorption unit. Subsequently, the simulation results are verified on the experimental platform, and adhesion performance tests are conducted on both standard flat surfaces and inclined walls. The results show that the optimized single magnetic adhesion unit gives the wall-climbing robot an adhesion force of 2767 N under normal working conditions, with a simulation experiment error margin as low as 8.3%. These results both provide theoretical guidance and highlight practical methodologies for developing high-performance magnetic adsorption systems in complex operational environments. Full article

(This article belongs to the Section Actuators for Robotics)

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25 pages, 3990 KiB

Open AccessArticle

Study on Trajectory Planning for Polishing Free-Form Surfaces of XY-3-RPS Hybrid Robot

by Xiaozong Song, Junfeng An and Xingwu Ma

Actuators 2025, 14(6), 269; https://doi.org/10.3390/act14060269 - 29 May 2025

Abstract

Free-form surface polishing is a key process in precision machining within high-end manufacturing, where optimizing the polishing trajectory directly influences both processing quality and efficiency. Traditional trajectory planning methods for free-form surface polishing in high-curvature regions suffer from issues such as a lack [...] Read more.

Free-form surface polishing is a key process in precision machining within high-end manufacturing, where optimizing the polishing trajectory directly influences both processing quality and efficiency. Traditional trajectory planning methods for free-form surface polishing in high-curvature regions suffer from issues such as a lack of precision, low trajectory continuity, and inefficiency. This paper proposes an improved trajectory planning method based on curvature characteristics, incorporating dynamic partitioning and boundary smoothing algorithms. These methods dynamically adjust according to surface curvature, enhancing processing efficiency and surface quality. Additionally, a hybrid optimization framework combining a genetic algorithm (GA) and local search (LS) is proposed to address the challenges of balancing global optimization with local fine-tuning in traditional trajectory planning methods. These challenges often result in large errors, low machining efficiency, and unstable surface quality. The method optimizes the overall trajectory distribution through a global search using GA while locally refining the high-curvature regions with LS. This combination improves trajectory uniformity and smoothness, and the results demonstrate significant increases in machining efficiency and accuracy. Finally, the feasibility of the trajectory planning method was verified through motion simulation. This paper also provides a detailed description of the mathematical modeling, algorithm implementation, and simulation analysis of the XY-3-RPS hybrid robot for trajectory optimization, offering both a theoretical foundation and engineering support for its application in free-form surface polishing. Full article

(This article belongs to the Section Actuators for Robotics)

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25 pages, 9816 KiB

Open AccessArticle

Design and Basic Performance Analysis of a Bionic Finger Soft Actuator with a Dual-Chamber Composite Structure

by Yu Cai, Sheng Liu, Dazhong Wang, Shuai Huang, Dong Zhang, Mengyao Shi, Wenqing Dai and Shang Wang

Actuators 2025, 14(6), 268; https://doi.org/10.3390/act14060268 - 28 May 2025

Abstract

Pneumatic soft manipulators are one of the current development trends in the field of manipulators. The soft manipulator that has been developed at present still has problems with single function and poor load-bearing capacity. This paper designs a composite soft finger inspired by [...] Read more.

Pneumatic soft manipulators are one of the current development trends in the field of manipulators. The soft manipulator that has been developed at present still has problems with single function and poor load-bearing capacity. This paper designs a composite soft finger inspired by the human middle finger, featuring a dual-chamber pneumatic drive and embedded steel sheet structure. Utilizing the principles of moment equilibrium and virtual work, a theoretical model for the bending behavior of the soft finger is developed, and the correlation between the bending angle and driving air pressure is derived. The determination process of key parameters and their influence on bending deformation are explained in detail through simulation. The bending experiment confirmed the reliability of the theoretical model. The fingertip force test indicates that the composite finger exerts a greater force than the ordinary one, with the extra force equivalent to 42.57% of the composite finger’s own fingertip force. Subsequent tests on the soft robotic hand measured the hooking quality, gripping diameter, and gripping force. The hooking experiment confirmed that composite fingers have a stronger load-bearing capacity than ordinary fingers, with an extra capacity equivalent to 31.25% of the composite finger’s own load-bearing capacity. Finally, the grasping experiment demonstrates that the soft manipulator can grasp objects of varying shapes and weights, indicating its strong adaptability and promising applications. Full article

(This article belongs to the Section Actuators for Robotics)

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18 pages, 738 KiB

Open AccessArticle

PD-like Consensus Tracking Algorithm for Discrete Multi-Agent Systems with Time-Varying Reference State Under Binary-Valued Communication

by Yuqi Wu, Xu Sun, Ting Wang and Jie Wang

Actuators 2025, 14(6), 267; https://doi.org/10.3390/act14060267 - 28 May 2025

Abstract

In this paper, a new consensus tracking control algorithm is proposed for discrete multi-agent systems under binary communication with noise and a time-varying reference state. Unlike previous studies, the leader’s reference state is time-varying and convergent. Each agent estimates its neighbors’ states using [...] Read more.

In this paper, a new consensus tracking control algorithm is proposed for discrete multi-agent systems under binary communication with noise and a time-varying reference state. Unlike previous studies, the leader’s reference state is time-varying and convergent. Each agent estimates its neighbors’ states using a recursive projection algorithm based on noisy binary-valued information. The controller design incorporates both the error between the current and estimated states and the rate of change of the estimated state, resulting in a proportional–derivative-like algorithm (PD-like algorithm). The algorithm achieves consensus tracking with a convergence rate of

O (1 / t^{ε})

under certain conditions. Finally, numerical simulations demonstrate the algorithm’s effectiveness and validate the theoretical results. Full article

(This article belongs to the Special Issue Advances in Intelligent Control of Actuator Systems)

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28 pages, 19774 KiB

Open AccessArticle

Design and Performance Evaluation of a μ-Synthesis-Based Robust Impedance Controller for Robotic Joints

by Nianfeng Shao, Yuancan Huang, Da Hong and Weiheng Zhong

Actuators 2025, 14(6), 266; https://doi.org/10.3390/act14060266 - 28 May 2025

Abstract

This paper proposes a robust impedance controller to address the performance limitations of mechanical impedance rendering in robotic joints, enabling stable interaction with passive environments. Considering structured uncertainties, such as dynamic parameter perturbations, sensor noise, disturbances, and unmodeled dynamics in actuator models, the [...] Read more.

This paper proposes a robust impedance controller to address the performance limitations of mechanical impedance rendering in robotic joints, enabling stable interaction with passive environments. Considering structured uncertainties, such as dynamic parameter perturbations, sensor noise, disturbances, and unmodeled dynamics in actuator models, the

μ

-synthesis method is employed to optimize closed-loop robustness performance. This approach minimizes impedance-matching errors in the frequency domain, thereby enhancing the regulation of the systems’s inherent impedance characteristics. Key performance metrics are analyzed, and the impedance-rendering accuracy is evaluated. Furthermore, the limiting factors affecting impedance-matching bandwidth are investigated to inform the selection of impedance parameters and ensure safe physical interaction. The proposed controller is validated through simulations and hardware experiments on a one-DoF modular robotic joint. Frequency domain impedance matching comparisons show that relative to

H_{\infty}

control, the

μ

-synthesis approach reduces impedance matching errors by up to 94.6% and 97.5% under 5% and 30% inertia uncertainties, respectively. Furthermore, experimental results demonstrate that compared to classical impedance control, the proposed method reduces impedance rendering errors by an average of 85.71% across all tested configurations while maintaining superior passivity and interaction stability under diverse impedance conditions. These results validate the effectiveness of

μ

-synthesis in achieving safe and high-fidelity physical interaction behavior. Full article

(This article belongs to the Section Actuators for Robotics)

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13 pages, 3176 KiB

Open AccessCommunication

The Design of a Closed-Loop Piezoelectric Friction–Inertia XY Positioning Platform with a Centimeter Travel Range

by Zheng-Rong Guo, Hong-Sheng Tan, Chin-Shun Chang, Ing-Shouh Hwang, En-Te Hwu and Hsien-Shun Liao

Actuators 2025, 14(6), 265; https://doi.org/10.3390/act14060265 - 28 May 2025

Abstract

Friction–inertia piezoelectric actuators can perform long-range positioning with nanometer resolution. However, friction and inertia are not easy to control and can influence the actuator’s performance. The present study proposes a friction–inertia-type piezoelectric XY positioning platform with a simple structure, which uses magnets to [...] Read more.

Friction–inertia piezoelectric actuators can perform long-range positioning with nanometer resolution. However, friction and inertia are not easy to control and can influence the actuator’s performance. The present study proposes a friction–inertia-type piezoelectric XY positioning platform with a simple structure, which uses magnets to provide stable normal force and friction. Sliders and rails were used to provide long travel ranges of 80 mm and 70 mm in the X and Y directions, respectively. Compact optical encoders were installed on the platform to enhance the positioning accuracy. With a three-phase positioning strategy involving both stepping and closed-loop methods, the system achieved a positioning accuracy of 3 µm (0.03%) and a repeatability of 325 nm (0.0033%) over a 10 mm long travel range. The positioning resolution was 4.7 nm, which was primarily limited by optical encoder noise under the closed-loop control mode. An astigmatic optical profilometer was used for the wide-range and high-resolution surface imaging of the XY positioning platform. Full article

(This article belongs to the Section Precision Actuators)

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26 pages, 8452 KiB

Open AccessArticle

Synchronised Control of Multiple Actuators of Wind Turbines

by Adrian Gambier

Actuators 2025, 14(6), 264; https://doi.org/10.3390/act14060264 - 27 May 2025

Abstract

Wind turbines align with the wind direction and adjust to wind speed by rotating their nacelle and blades using electromechanical or hydraulic actuators. Due to the fact that the rated capacity of wind turbines is increasing and that the actuators are reaching some [...] Read more.

Wind turbines align with the wind direction and adjust to wind speed by rotating their nacelle and blades using electromechanical or hydraulic actuators. Due to the fact that the rated capacity of wind turbines is increasing and that the actuators are reaching some size limits, the current solution is to install several actuators at each joint until the required torque is reached. The problem with this approach is that, despite the fact the actuators can be selected from the same type and series, they typically have distinct parameters, resulting in different behaviours. The synchronisation of actuators of wind turbines has still not been studied in the specialised literature. Therefore, a control approach for the synchronisation of the pitch actuators is proposed in this work. Two cases are considered: the synchronisation of torque outputs and the synchronisation of position angle. The simulation results indicate that the proposed solution is effective for synchronising actuators, either when they are placed together on the same blade or when they are on separate blades while simultaneously following the collective pitch control command. Full article

(This article belongs to the Special Issue New Control Schemes for Actuators—2nd Edition)

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