Actuators

30 pages, 2603 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

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)

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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22 pages, 33852 KiB

Open AccessArticle

Research on Actuator Control System Based on Improved MPC

by Qingjian Zhao, Qinghai Zhang, Shuang Zhao, Xiaoqian Zhang, Shilei Lu, Yang Guo, Liqiang Song and Zhengxu Zhao

Actuators 2025, 14(6), 263; https://doi.org/10.3390/act14060263 - 27 May 2025

Abstract

To improve the control accuracy and interference resistance of actuator control systems in complex environments, a complete actuator control system solution has been designed. The system uses an STM32 controller as the core processing unit, integrating high-precision position sensors to build a multi-level [...] Read more.

To improve the control accuracy and interference resistance of actuator control systems in complex environments, a complete actuator control system solution has been designed. The system uses an STM32 controller as the core processing unit, integrating high-precision position sensors to build a multi-level control architecture. An improved model predictive control algorithm is proposed, which introduces extended state observers and multi-objective optimization strategies to estimate system states and external disturbances in real-time, achieving precise disturbance compensation. Experimental and test results show that, under electromagnetic interference and mechanical vibration conditions, the system’s stability and robustness are significantly enhanced, with error fluctuations of less than 0.03 mm, dynamic response time of 4.82 s, overshoot of 1.5%, steady-state error of 0.14 mm, and energy consumption reduced by 15%, all better than MPC, fuzzy control, and PID control methods under similar conditions. This research provides a comprehensive solution for hardware design and algorithm optimization in actuator control for industrial automation and precision manufacturing. Full article

(This article belongs to the Section Control Systems)

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11 pages, 1374 KiB

Open AccessArticle

A Preemptive Scan Speed Control Strategy Based on Topographic Data for Optimized Atomic Force Microscopy Imaging

by Thi Thu Nguyen, Oyoo Michael Juma, Luke Oduor Otieno, Thi Ngoc Nguyen and Yong Joong Lee

Actuators 2025, 14(6), 262; https://doi.org/10.3390/act14060262 - 26 May 2025

Abstract

Rapid advancement in the nanotechnology and semiconductor industries has driven the demand for fast, precise measurement systems. Atomic force microscopy (AFM) is a standout metrology technique due to its high precision and wide applicability. However, when operated at high speeds, the quality of [...] Read more.

Rapid advancement in the nanotechnology and semiconductor industries has driven the demand for fast, precise measurement systems. Atomic force microscopy (AFM) is a standout metrology technique due to its high precision and wide applicability. However, when operated at high speeds, the quality of AFM images often deteriorates, especially in areas where sharp topographic features are present. This occurs because the feedback speed of the Z-scanner cannot keep up with the sample height changes during raster scanning. This study presents a simple variable scan speed control strategy for improving AFM imaging speed while maintaining the image quality obtained at low scan speeds. The proposed strategy aims to leverage the similarity in the height profiles between successive scan lines. The topographic information collected from the previous line scan is used to assess the surface complexity and to adjust the scan speed for the following line scan. The AFM system with this variable speed control algorithm was found to reduce the scan time needed for one AFM image by over 50% compared to the fixed-speed scanning while maintaining the similar level of accuracy. The calculated mean square errors (MSEs) show that the combination of speed adjustments and preemptive surface topography prediction has successfully allowed us to suppress the potential oscillations during the speed adjustment process, thereby enhancing the stability of the adaptive AFM system as well. Full article

(This article belongs to the Section Precision Actuators)

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27 pages, 10903 KiB

Open AccessArticle

Pressure Control in the Pump-Controlled Hydraulic Die Cushion Pressure-Building Phase Using Enhanced Model Predictive Control with Extended State Observer-Genetic Algorithm Optimization

by Zhikui Dong, Song He, Yi Liao, Heng Wang, Mingxing Song, Jinpei Jiang and Gexin Chen

Actuators 2025, 14(6), 261; https://doi.org/10.3390/act14060261 - 25 May 2025

Abstract

With the enhancement of safety performance requirements in the car manufacturing field, the quality standards for the sheet molding process have imposed higher demands. However, during the pressure-building phase of pump-controlled hydraulic die cushion systems, the combined effects of high-order dynamics, system uncertainties, [...] Read more.

With the enhancement of safety performance requirements in the car manufacturing field, the quality standards for the sheet molding process have imposed higher demands. However, during the pressure-building phase of pump-controlled hydraulic die cushion systems, the combined effects of high-order dynamics, system uncertainties, and strong nonlinearities pose significant challenges to maintaining precise control and dynamic response performance of the blank holder force (BHF). To address these challenges, we propose an intelligent model predictive control (MPC) strategy that synergistically integrates an extended state observer (ESO) for disturbance compensation with parameters optimized by a genetic algorithm (GA). The mathematical model and state-space model of the system are established. Subsequently, the ESO is integrated with MPC to enable active compensation for internal and external disturbances. The GA is employed to optimize the controller parameters within the MPC framework. Finally, a simulation testbed for the pump-controlled hydraulic die cushion experimentally validates the process. Experimental results demonstrate that compared to MPC and conventional PID control, the proposed strategy achieves significant reductions in pressure overshoot (0.87% and 1.8% at 100 bar; 3.3% and 5.9% at 200 bar), pressure-building time (13.9% and 31.4% at 100 bar; 6.7% and 11.5% at 200 bar), and stroke length (10.5% and 32% at 100 bar; 11.5% and 28.1% at 200 bar). This validates its effectiveness in enhancing both control precision and dynamic response performance, providing a reliable solution for large-scale applications of pump-controlled hydraulic die cushions in high-dynamic stamping scenarios. Full article

(This article belongs to the Section Control Systems)

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17 pages, 5574 KiB

Open AccessArticle

Improving Tandem Fluency Through Utilization of Deep Learning to Predict Human Motion in Exoskeleton

by Bon HoKoo, Ho Chit Siu, Luke Apostolides, Sangbae Kim and Lonnie G. Petersen

Actuators 2025, 14(6), 260; https://doi.org/10.3390/act14060260 - 23 May 2025

Abstract

Today’s exoskeletons face challenges with low fluency (a quantifiable alternative to “seamlessness”), hypothesized to be caused by a lag in active control innate in many leader–follower paradigms seen in contemporary systems, leading to inefficiencies and discomfort. Furthermore, tandem fluency, a variation of fluency [...] Read more.

Today’s exoskeletons face challenges with low fluency (a quantifiable alternative to “seamlessness”), hypothesized to be caused by a lag in active control innate in many leader–follower paradigms seen in contemporary systems, leading to inefficiencies and discomfort. Furthermore, tandem fluency, a variation of fluency specific for tandem robots systems as exoskeletons, is yet to be rigorously tested in practice. This study aims to utilize metrics of tandem fluency in order to demonstrate improved human–robot interaction (HRI) in exoskeletons through human subject testing of a prototype 1 degree of freedom (DoF) exoskeleton using a motion prediction bidirectional long short-term memory (bi-LSTM) deep learning network. Subjects were recruited to conduct various upper body exercises about the elbow joint, and the collected sEMG, goniometer, and gas exchange data was used to design, test, optimize, and assess the performance of the 1 DoF exoskeleton using tandem fluency metrics. We found that the correlation between I-ACT, a metric of tandem fluency, the subjective survey responses, and metabolic data suggest that the use of a predictive bi-LSTM network to control a 1 DoF exoskeleton about the elbow results in an overall positive trend, which may correlate to high tandem fluency. Full article

(This article belongs to the Special Issue Recent Advances in Soft Actuators, Robotics and Intelligence)

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23 pages, 12272 KiB

Open AccessArticle

Optimized Design and Deep Vision-Based Operation Control of a Multi-Functional Robotic Gripper for an Automatic Loading System

by Yaohui Wang, Sheng Guo, Jinliang Zhang, Hongbo Ding, Bo Zhang, Ao Cao, Xiaohu Sun, Guangxin Zhang, Shihe Tian, Yongxu Chen, Jixuan Ma and Guangrong Chen

Actuators 2025, 14(6), 259; https://doi.org/10.3390/act14060259 - 23 May 2025

Abstract

This study presents an optimized design and vision-guided control strategy for a multi-functional robotic gripper integrated into an automatic loading system for warehouse environments. The system adopts a modular architecture, including standardized platforms, transport containers, four collaborative 6-DOF robotic arms, and a multi-sensor [...] Read more.

This study presents an optimized design and vision-guided control strategy for a multi-functional robotic gripper integrated into an automatic loading system for warehouse environments. The system adopts a modular architecture, including standardized platforms, transport containers, four collaborative 6-DOF robotic arms, and a multi-sensor vision module. Methodologically, we first developed three gripper prototypes, selecting the optimal design (30° angle between the gripper and container side) through workspace and interference analysis. A deep vision-based recognition system, enhanced by an improved YOLOv5 algorithm and multi-feature fusion, was employed for real-time object detection and pose estimation. Kinematic modeling and seventh-order polynomial trajectory planning ensured smooth and precise robotic arm movements. Key results from simulations and experiments demonstrated a 95.72% success rate in twist lock operations, with a positioning accuracy of 1.2 mm. The system achieved a control cycle of 35 ms, ensuring efficiency compared with non-vision-based methods. Practical implications include enabling fully autonomous container handling in logistics, reducing labor costs, and enhancing operational safety. Limitations include dependency on fixed camera setups and sensitivity to extreme lighting conditions. Full article

(This article belongs to the Special Issue Advancement in the Design and Control of Robotic Grippers—Second Edition)

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20 pages, 2425 KiB

Open AccessReview

A Review of Electroactive Polymers in Sensing and Actuator Applications

by Diana Narvaez and Brittany Newell

Actuators 2025, 14(6), 258; https://doi.org/10.3390/act14060258 - 23 May 2025

Abstract

Electroactive polymers (EAPs) represent a versatile class of smart materials capable of converting electrical stimuli into mechanical motion and vice versa, positioning them as key components in the next generation of actuators and sensors. This review summarizes recent developments in both electronic and [...] Read more.

Electroactive polymers (EAPs) represent a versatile class of smart materials capable of converting electrical stimuli into mechanical motion and vice versa, positioning them as key components in the next generation of actuators and sensors. This review summarizes recent developments in both electronic and ionic EAPs, highlighting their activation mechanisms, material architectures, and multifunctional capabilities. Representative systems include dielectric elastomers, ferroelectric and conducting polymers, liquid crystal elastomers, and ionic gels. Advances in fabrication methods, such as additive manufacturing, nanocomposite engineering, and patternable electrode deposition, are discussed with emphasis on miniaturization, stretchability, and integration into soft systems. Applications span biomedical devices, wearable electronics, soft robotics, and environmental monitoring, with growing interest in platforms that combine actuation and sensing within a single structure. Finally, the review addresses critical challenges such as long-term material stability and scalability, and outlines future directions toward self-powered, AI-integrated, and sustainable EAP technologies. Full article

(This article belongs to the Special Issue Electroactive Polymer (EAP) for Actuators and Sensors Applications)

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38 pages, 2989 KiB

Open AccessReview

Electroactive Polymers for Self-Powered Actuators and Biosensors: Advancing Biomedical Diagnostics Through Energy Harvesting Mechanisms

by Nargish Parvin, Sang Woo Joo, Jae Hak Jung and Tapas Kumar Mandal

Actuators 2025, 14(6), 257; https://doi.org/10.3390/act14060257 - 23 May 2025

Abstract

Electroactive polymers (EAPs) have emerged as versatile materials for self-powered actuators and biosensors, revolutionizing biomedical diagnostics and healthcare technologies. These materials harness various energy harvesting mechanisms, including piezoelectricity, triboelectricity, and ionic conductivity, to enable real-time, energy-efficient, and autonomous sensing and actuation without external [...] Read more.

Electroactive polymers (EAPs) have emerged as versatile materials for self-powered actuators and biosensors, revolutionizing biomedical diagnostics and healthcare technologies. These materials harness various energy harvesting mechanisms, including piezoelectricity, triboelectricity, and ionic conductivity, to enable real-time, energy-efficient, and autonomous sensing and actuation without external power sources. This review explores recent advancements in EAP-based self-powered systems, focusing on their applications in biosensing, soft robotics, and biomedical actuation. The integration of nanomaterials, flexible electronics, and wireless communication technologies has significantly enhanced their sensitivity, durability, and multifunctionality, making them ideal for next-generation wearable and implantable medical devices. Additionally, this review discusses key challenges, including material stability, biocompatibility, and optimization strategies for enhanced performance. Future perspectives on the clinical translation of EAP-based actuators and biosensors are also highlighted, emphasizing their potential to transform smart healthcare and bioelectronic applications. Full article

(This article belongs to the Special Issue Electroactive Polymer (EAP) for Actuators and Sensors Applications)

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22 pages, 7903 KiB

Open AccessArticle

Gear Pump Versus Variable Axial Piston Pump in Electro-Hydrostatic Servoactuators

by Alexandru Dumitrache, Liviu Dinca, Jenica-Ileana Corcau, Adriana Ionescu and Mihai Negru

Actuators 2025, 14(5), 256; https://doi.org/10.3390/act14050256 - 21 May 2025

Abstract

This paper presents a comparison of some different configurations of electro-hydrostatic actuators (EHA). The gear pump EHA has a simpler mechanical configuration, but the electronic power command circuits and the electric motor are in high demand due to the very frequent speed variations. [...] Read more.

This paper presents a comparison of some different configurations of electro-hydrostatic actuators (EHA). The gear pump EHA has a simpler mechanical configuration, but the electronic power command circuits and the electric motor are in high demand due to the very frequent speed variations. The variable piston pump EHA has a more complicated mechanical configuration, but the electronic power command circuits and the main electric motor are less loaded due to the constant speed of the electric motor. The variable displacement pump control can be made either using an electric motor and mechanical transmission, or an additional hydraulic circuit, to modify the swash plate angle. In total, four EHA configurations are studied in this paper (one with a gear pump and three with variable axial piston pumps). The paper aims to advantages and disadvantages of each type of EHA, using numerical simulations. Full article

(This article belongs to the Special Issue Recent Advances in the Design Solutions of Electro-Hydraulic Actuators for Mechatronic Systems)

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25 pages, 7986 KiB

Open AccessArticle

A Long-Tail Fault Diagnosis Method Based on a Coupled Time–Frequency Attention Transformer

by Li Zhang, Ying Zhang, Hao Luo, Tongli Ren and Hongsheng Li

Actuators 2025, 14(5), 255; https://doi.org/10.3390/act14050255 - 20 May 2025

Abstract

Bearings are essential rotational components that enable mechanical equipment to operate effectively. In real-world industrial environments, bearings are subjected to high temperatures and loads, making failure prediction and health management critical for ensuring stable equipment operations and safeguarding both personnel and property. To [...] Read more.

Bearings are essential rotational components that enable mechanical equipment to operate effectively. In real-world industrial environments, bearings are subjected to high temperatures and loads, making failure prediction and health management critical for ensuring stable equipment operations and safeguarding both personnel and property. To address long-tail defect identification, we propose a coupled time–frequency attention model that accounts for the long-tail distribution and pervasive noise present in production environments. The model efficiently learns amplitude and phase information by first converting the time-domain signal into the frequency domain with the Fast Fourier Transform (FFT) and then processing the data using a real–imaginary attention mechanism. To capture dependencies in long sequences, a multi-head self-attention mechanism is then implemented in the time domain. Furthermore, the model’s ability to fully learn features is enhanced through the linear coupling of time–frequency domain attention, which effectively mitigates noise interference and corrects imbalances in data distribution. The performance of the proposed model is compared with that of advanced models under the conditions of imbalanced label distribution, cross-load, and noise interference, proving its superiority. The model is evaluated using the Case Western Reserve University (CWRU) and laboratory bearing datasets. Full article

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

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24 pages, 6850 KiB

Open AccessArticle

Comparative Study of Analytical Model Predictive Control and State Feedback Control for Active Vibration Suppression of Two-Mass Drive

by Adam Gorla and Piotr Serkies

Actuators 2025, 14(5), 254; https://doi.org/10.3390/act14050254 - 20 May 2025

Abstract

This article discusses speed control methods for electric motor drives with elastic mechanical coupling causing torsional vibrations, which negatively affect the operation of the system. Model Predictive Control (MPC) is often presented as an effective solution; however, it is notoriously difficult to implement [...] Read more.

This article discusses speed control methods for electric motor drives with elastic mechanical coupling causing torsional vibrations, which negatively affect the operation of the system. Model Predictive Control (MPC) is often presented as an effective solution; however, it is notoriously difficult to implement in real-time due to the high computational complexity of the controller. In this paper, a simplified predictive control approach in the form of Analytical MPC (aMPC) is proposed for the speed control of a two-mass motor drive. In contrast to conventional MPC, which requires complex online optimisation, aMPC derives an explicit control law analytically under simplifying assumptions, greatly reducing the computational load. The effect of the controller parameters on the drive performance is investigated and a multi-objective performance function for automatic tuning is proposed. The aMPC structure is compared with conventional State Feedback Control (SFC), including a system robustness test of both approaches. Based on simulation studies and experimental verification, the proposed structure is shown to ensure high dynamics in drive control, with smoother torque control and superior robustness for higher-load inertia ratios than SFC. Full article

(This article belongs to the Section Control Systems)

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