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Volume 14
Issue 6
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Actuators, Volume 14, Issue 6 (June 2025) – 46 articles

Cover Story (view full-size image): This review explores the role of electroactive polymers (EAPs) in developing self-powered actuators and biosensors for biomedical diagnostics. It highlights how EAPs utilize energy harvesting mechanisms such as piezoelectricity and triboelectricity to enable real-time, autonomous operations without external power sources. This paper also discusses material advances, device integration, and future clinical potential in smart healthcare and bioelectronics. View this paper
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20 pages, 2287 KiB  
Article
The Design of a Turning Tool Based on a Self-Sensing Giant Magnetostrictive Actuator
by Dongjian Xie, Qibo Wu, Yahui Zhang, Yikun Yang, Bintang Yang and Cheng Zhang
Actuators 2025, 14(6), 302; https://doi.org/10.3390/act14060302 - 19 Jun 2025
Viewed by 139
Abstract
Smart tools are limited by actuation–sensing integration and structural redundancy, making it difficult to achieve compactness, ultra-precision feed, and immediate feedback. This paper proposes a self-sensing giant magnetostrictive actuator-based turning tool (SSGMT), which enables simultaneous actuation and output sensing without external sensors. A [...] Read more.
Smart tools are limited by actuation–sensing integration and structural redundancy, making it difficult to achieve compactness, ultra-precision feed, and immediate feedback. This paper proposes a self-sensing giant magnetostrictive actuator-based turning tool (SSGMT), which enables simultaneous actuation and output sensing without external sensors. A multi-objective optimization model is first established to determine the key design parameters of the SSGMT to improve magnetic transfer efficiency, system compactness, and sensing signal quality. Then, a dynamic hysteresis model with a Hammerstein structure is developed to capture its nonlinear characteristics. To ensure accurate positioning and a robust response, a hybrid control strategy combining feedforward compensation and adaptive feedback is implemented. The SSGMT is experimentally validated through a series of tests including self-sensing displacement accuracy and trajectory tracking under various frequencies and temperatures. The prototype achieves nanometer-level resolution, stable output, and precise tracking across different operating conditions. These results confirm the feasibility and effectiveness of integrating actuation and sensing in one structure, providing a promising solution for the application of smart turning tools. Full article
(This article belongs to the Special Issue Recent Developments in Precision Actuation Technologies)
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20 pages, 19693 KiB  
Article
Design and Optimization of a Large-Air-Gap Voice Coil Motor with Enhanced Thermal Management for Magnetic Levitation Vibration Isolation in a Vacuum
by Junren Mu and He Zhang
Actuators 2025, 14(6), 301; https://doi.org/10.3390/act14060301 - 19 Jun 2025
Viewed by 175
Abstract
This study presents the design, optimization, and experimental validation of a large-air-gap voice coil motor (LAG-VCM) for high-precision magnetic levitation vibration isolation in vacuum environments. Key challenges arising from a large air gap, including pronounced leakage flux and a reduced flux density, were [...] Read more.
This study presents the design, optimization, and experimental validation of a large-air-gap voice coil motor (LAG-VCM) for high-precision magnetic levitation vibration isolation in vacuum environments. Key challenges arising from a large air gap, including pronounced leakage flux and a reduced flux density, were addressed by employing the equivalent magnetic charge method and the image method for the modeling of permanent magnets. Finite element analysis was applied to refine the motor geometry and obtain high thrust, low ripple, and strong linearity. To mitigate the severe thermal conditions of a vacuum, a heat pipe-based cooling strategy was introduced to efficiently dissipate heat from the coil windings. The experimental results demonstrate that the optimized LAG-VCM delivers a thrust of 277 N with low ripple while effectively maintaining coil temperatures below critical limits for prolonged operation. These findings confirm the suitability of the proposed LAG-VCM for vacuum applications with stringent requirements for both a large travel range and stable, high-force output. Full article
(This article belongs to the Special Issue Advanced Theory and Application of Magnetic Actuators—2nd Edition)
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14 pages, 1274 KiB  
Article
State Observer-Based Sampled-Data Control for Path Tracking of Autonomous Agricultural Tractor
by Haozhe Li, Keqi Mei, Li Ma, Shihong Ding and Chen Ding
Actuators 2025, 14(6), 300; https://doi.org/10.3390/act14060300 - 19 Jun 2025
Viewed by 160
Abstract
This study develops a sampled-data controller for the path tracking system of an autonomous agricultural tractor (AAT) on the basis of a state observer. First of all, to solve the cost of the whole system, the state observer is constructed for estimating the [...] Read more.
This study develops a sampled-data controller for the path tracking system of an autonomous agricultural tractor (AAT) on the basis of a state observer. First of all, to solve the cost of the whole system, the state observer is constructed for estimating the heading offset and for accelerating the convergence process. Built on the observer, an advanced output feedback sampled-data controller is formulated, which tackles the problem of slow data freshness caused by the low signal frequency of the GPS-RTK system. Subsequently, a Lyapunov stability analysis is conducted to guarantee that the AAT system can be stabilized under the proposed control strategy. Finally, comparative simulation results are provided to illustrate the efficacy of the control strategy. Full article
(This article belongs to the Section Actuators for Surface Vehicles)
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14 pages, 4313 KiB  
Article
Metal Thickness Measurement Using an Ultrasonic Probe with a Linear Actuator for a Magnet-Type Climbing Robot: Design and Development
by Yuki Nishimura, Cheng Wang and Wei Song
Actuators 2025, 14(6), 299; https://doi.org/10.3390/act14060299 - 18 Jun 2025
Viewed by 178
Abstract
The inspection of oil storage tanks is a critical measure to prevent the risk of oil leakage. Therefore, research has focused on magnet-type climbing robots for automated tank inspections. While existing magnet-type climbing robots have demonstrated significant improvements in climbing steel structures, their [...] Read more.
The inspection of oil storage tanks is a critical measure to prevent the risk of oil leakage. Therefore, research has focused on magnet-type climbing robots for automated tank inspections. While existing magnet-type climbing robots have demonstrated significant improvements in climbing steel structures, their capability in terms of metal thickness measurement has not been previously evaluated. During thickness inspections, ultrasonic thickness sensors require a probe to be pressed against target surfaces. To automate metal thickness measurements, this pressing motion of the probe needs to be performed by the robot. This study introduces a novel metal thickness measurement device comprising an ultrasonic probe, a linear actuator, a gel pump, and a pressure sensor designed for a magnet-type climbing robot. The linear actuator moves the probe to its initial position, the gel pump injects a coupling gel, and then the actuator moves the probe to the surface and back. Finally, our prototype of an ultrasonic probe with a linear actuator was installed on a magnet-type climbing robot to demonstrate its functionality in a practical application regarding an oil storage tank inspection system. The prototype achieved a measurement success rate of 65.9% and an average error of 0.7% compared to a reference thickness. This article details the design and development of the ultrasonic probe with a linear actuator to enable the probe to make contact with the surface. It then details the experimental results and evaluation of metal thickness measurement performed using the prototype and the climbing robot. Full article
(This article belongs to the Special Issue Advanced Robots: Design, Control and Application—3rd Edition)
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24 pages, 10609 KiB  
Article
Computational Fluid Dynamics Analysis of Draft Tube Flow Characteristics in a Kaplan Turbine
by Qinwen Yan, Zhiqiang Xiong, Yuan Zheng, Chen Feng, Zhen Li, Lin Hu and Lianchen Xu
Actuators 2025, 14(6), 298; https://doi.org/10.3390/act14060298 - 18 Jun 2025
Viewed by 112
Abstract
This study presents a numerical investigation of the internal flow characteristics within the draft tube of a Kaplan turbine using computational fluid dynamics (CFD). The distribution and evolution of vortical structures, particularly the formation and development of vortex ropes under various operating conditions, [...] Read more.
This study presents a numerical investigation of the internal flow characteristics within the draft tube of a Kaplan turbine using computational fluid dynamics (CFD). The distribution and evolution of vortical structures, particularly the formation and development of vortex ropes under various operating conditions, are systematically analyzed. The study aims to explore the effects of blade angle and guide vane opening on the internal flow characteristics of the unit, thereby providing guidance for flow control strategies. The influence of guide vane opening and turbine head on vortex dynamics and flow stability is examined, with a focus on the pressure pulsations induced by vortex ropes through frequency-domain analysis. The results indicate that increased guide vane openings and higher heads lead to the expansion and downstream extension of the vortex rope into the elbow section, causing significant low-frequency pressure pulsations and enhancing flow instability. These findings contribute to a deeper understanding of unsteady flow behavior in Kaplan turbine draft tubes and provide a theoretical foundation for improving hydraulic stability and optimizing operational performance. Full article
(This article belongs to the Section High Torque/Power Density Actuators)
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16 pages, 22381 KiB  
Article
Control Strategy of Dual-Disc Electromagnetic–EMB Composite Braking System Based on Hybrid Systems
by Zhen Shi, Yunbing Yan and Sen Zhang
Actuators 2025, 14(6), 297; https://doi.org/10.3390/act14060297 - 18 Jun 2025
Viewed by 107
Abstract
In this study, to address the problems of the redundant safety and mass production of electro-mechanical braking (EMB) structures that are widely used in distributed drive electric vehicles (DDEV), we designed a compact dual-disc electromagnetic–EMB composite brake. The composite brake embeds an electromagnetic [...] Read more.
In this study, to address the problems of the redundant safety and mass production of electro-mechanical braking (EMB) structures that are widely used in distributed drive electric vehicles (DDEV), we designed a compact dual-disc electromagnetic–EMB composite brake. The composite brake embeds an electromagnetic brake into the original friction disc, which realizes an organic combination of the friction and electromagnetic brakes. Electromagnetic braking has the advantages of no friction, a rapid response, and a high-speed braking effect, which can effectively improve the reliability and mechanical redundancy of composite braking systems. The braking system comprises regenerative, electromagnetic, and friction braking, which are typical hybrid systems. We designed a mode-switching control strategy for a composite braking system based on the hybrid control theory. MATLAB/Simulink were used to model each system and set different simulation conditions. The simulation results showed that, under different working conditions, the hybrid automata control strategy had a fast response speed, small overshoot error, and adapted to different road conditions. The feasibility of the redundant design of the electromagnetic–friction–regenerative composite braking structure and the rationality of the hybrid automata control strategy design were verified. Full article
(This article belongs to the Section Actuators for Surface Vehicles)
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29 pages, 8368 KiB  
Article
Research on the Development of an Abdominal Massage Robot: Diversified Manipulation Strategies and Improved Force Interaction Performance
by Xinyi Tang, Ping Shi, Hongliu Yu, Sujiao Li, Xin Xing, Zhenjie Luo and Junjie Fu
Actuators 2025, 14(6), 296; https://doi.org/10.3390/act14060296 - 18 Jun 2025
Viewed by 208
Abstract
Abdominal massage for constipation has problems such as high labor costs, insufficient standardization, and large differences in efficacy. This study aims to develop a new type of abdominal massage robot to break through the bottlenecks of manual abdominal massage. This paper constructs a [...] Read more.
Abdominal massage for constipation has problems such as high labor costs, insufficient standardization, and large differences in efficacy. This study aims to develop a new type of abdominal massage robot to break through the bottlenecks of manual abdominal massage. This paper constructs a new six-degree-of-freedom multi-functional abdominal massage robot system, improves and designs a new series-parallel hybrid mechanical structure, and based on this, establishes an abdominal interaction force control strategy that uses a variable-stiffness physical model to represent the biomechanical properties of the abdomen. Verified by simulation and human experiments, this robot can accurately reproduce a variety of massage techniques, and demonstrate stable force control performance in prosthesis experiments and human abdominal tests, with the interaction force error controlled within 0.8 N, providing an innovative path for the intelligentization and standardization of clinical abdominal massage. Full article
(This article belongs to the Section Actuators for Robotics)
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18 pages, 2517 KiB  
Article
Development of a Novel Digital Pressure Control Valve Applied to Emulsion Pump Station Control and Research on the Performance of Its Dynamic Characteristics
by Peng Xu, Ziming Kou and Jun Zhang
Actuators 2025, 14(6), 295; https://doi.org/10.3390/act14060295 - 17 Jun 2025
Viewed by 180
Abstract
To advance the construction of intelligent mining, electro-hydraulic digital control technology has emerged as a critical direction for the digital transformation of mining machinery. This study proposes a digital control scheme based on the pressure state of the system and the operating state [...] Read more.
To advance the construction of intelligent mining, electro-hydraulic digital control technology has emerged as a critical direction for the digital transformation of mining machinery. This study proposes a digital control scheme based on the pressure state of the system and the operating state of the actuator. The scheme utilises a novel convergence rate sliding film position control method to regulate the system pressure in real time by controlling the pilot valve, which is driven by a permanent magnet synchronous motor (PMSM). Moreover, a prototype of an incremental digital pressure control valve was developed for high-pressure, high water-based working conditions. A simulation model of the valve was established using AMESim/Simulink, and dynamic characteristics under various operating conditions were analyzed. The relative error between simulated and experimental pressure results remained within ±4.7%. Finally, a multi-parameter optimization was conducted using a genetic algorithm. The results demonstrate that the optimized digital pressure control valve achieved a stabilized inlet pressure within 44.8 ms, with a pressure overshoot of 4.1% and a response time of 20.1 ms, exhibiting excellent real-time dynamic pressure regulation capabilities. This study provides a theoretical foundation and practical reference for comprehensive research on pressure control in underground emulsion pump stations. Full article
(This article belongs to the Section Control Systems)
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20 pages, 2957 KiB  
Article
Magnetic Field Analytical Calculation of No-Load Electromagnetic Performance of Line-Start Explosion-Proof Permanent Magnet Synchronous Motors Considering Saturation Effect
by Jinhui Liu, Yunbo Shi, Yang Zheng and Minghui Wang
Actuators 2025, 14(6), 294; https://doi.org/10.3390/act14060294 - 17 Jun 2025
Viewed by 93
Abstract
This paper proposes an improved analytical model for a line-start explosion-proof magnet synchronous motor that considers the effect of magnetic bridge saturation. Under the condition of maintaining the air-gap magnetic field unchanged, and taking into account the topological structures of embedded magnets, squirrel [...] Read more.
This paper proposes an improved analytical model for a line-start explosion-proof magnet synchronous motor that considers the effect of magnetic bridge saturation. Under the condition of maintaining the air-gap magnetic field unchanged, and taking into account the topological structures of embedded magnets, squirrel cages, and rotor slot openings, a subdomain model partitioning method is systematically investigated. Considering the saturation effect of the magnetic bridge of the rotor, the equivalent magnetic circuit method was utilized to calculate the permeance of the saturated region. It not only facilitates the establishment of subdomain equations and corresponding subdomain boundary conditions, but also ensures the maximum accuracy of the equivalence by maintaining the topology of the rotor. The motor was partitioned into subdomains, and in conjunction with the boundary conditions, the Poisson equation and Laplace equation are solved to obtain the electromagnetic performance of the motor. The accuracy of the analytical model is verified through finite element analysis. The accuracy of the analytical model is verified through finite element analysis (FEA). Compared to the FEA, the improved model maintains high precision while reducing computational time and exhibiting better generality, making it suitable for the initial design and optimization of industrial motors. Full article
(This article belongs to the Section Actuators for Manufacturing Systems)
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21 pages, 4453 KiB  
Article
Accuracy Analysis and Synthesis of Planar Mechanism for Antenna Based on Screw Theory and Geometric Coordination
by Qiying Li, Jing Zhang, Miao Yu, Chuang Shi, Yaliang Dou, Hongwei Guo and Rongqiang Liu
Actuators 2025, 14(6), 293; https://doi.org/10.3390/act14060293 - 16 Jun 2025
Viewed by 97
Abstract
To address the deployment accuracy issues of multi-frequency band reflector antennas, this study takes a hexagonal prism modular deployable antenna as an example and proposes an accuracy design method. This paper proposes a screw-theory-based sub-chain precision analysis method. This method constructs a virtual [...] Read more.
To address the deployment accuracy issues of multi-frequency band reflector antennas, this study takes a hexagonal prism modular deployable antenna as an example and proposes an accuracy design method. This paper proposes a screw-theory-based sub-chain precision analysis method. This method constructs a virtual screw model of rod length errors and hinge gap errors. Based on geometric relationships, a multi-loop point position error model is established, and accuracy surfaces considering rod length errors and hinge gap are output using MATLAB R2024b. By outputting the relationship curves of single-rod errors relative to point errors, the linearized influence law of individual rods on precision is further elucidated. Simulation results demonstrate the reliability of the error modeling theory. Based on the established cost-effective precision model and the minimum point error, which is obtained by using the numerical iterative method, the optimal solution for error parameters is obtained. Full article
(This article belongs to the Section Aerospace Actuators)
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18 pages, 6092 KiB  
Article
Dynamic Response Analysis of Tooth Root Crack Failure in Helical Idler Gear System Under Different Working Flank Conditions
by Hengzhe Shi, Wei Li and Wanlin Zhou
Actuators 2025, 14(6), 292; https://doi.org/10.3390/act14060292 - 14 Jun 2025
Viewed by 202
Abstract
Helical idler gear transmission systems can adapt to high-speed, heavy-load working environments and are thus widely used in aerospace, shipbuilding, and other heavy industry sectors. Root crack is one of the common fault types. Prior studies generally only considered cracks at a single [...] Read more.
Helical idler gear transmission systems can adapt to high-speed, heavy-load working environments and are thus widely used in aerospace, shipbuilding, and other heavy industry sectors. Root crack is one of the common fault types. Prior studies generally only considered cracks at a single working flank, lacking comparative analysis between the crack at the working flank and the non-working flank. This paper examines the dynamic response of helical idler gears with root cracks at different working flanks, comparing dynamic response differences between working and non-working flank cracks. First, a comprehensive dynamics model of the helical idler gear system is established. Second, the influence of root crack location (the working flank or the non-working flank) on time-varying meshing stiffness is considered based on potential energy method, and a flexible model is established by finite element method for the faulty gear. Finally, solution results of the rigid-flexible coupling dynamics model are analyzed. The dynamic response signal characteristics of root cracks at the working flank and the non-working flank are analyzed in time domain, frequency domain and time frequency domain, respectively. Corresponding experiments are designed based on the FZG experimental platform, and the experimental results are in good agreement with the simulation results, which verified the accuracy of the model. Full article
(This article belongs to the Section Actuators for Manufacturing Systems)
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27 pages, 3222 KiB  
Article
DNN-Augmented Kinematically Decoupled Three-DoF Origami Parallel Robot for High-Precision Heave and Tilt Control
by Gaokun Shi, Hassen Nigatu, Zhijian Wang and Yongsheng Huang
Actuators 2025, 14(6), 291; https://doi.org/10.3390/act14060291 - 13 Jun 2025
Viewed by 156
Abstract
This paper presents a three-degrees-of-freedom origami parallel robot that is free from parasitic motion. This robot is designed to achieve one translational and two rotational motions within its workspace, enabling precise orientation about a fixed point—a capability unattainable for parallel robots with parasitic [...] Read more.
This paper presents a three-degrees-of-freedom origami parallel robot that is free from parasitic motion. This robot is designed to achieve one translational and two rotational motions within its workspace, enabling precise orientation about a fixed point—a capability unattainable for parallel robots with parasitic motion. The elimination of parasitic motion is critical, allowing the use of this device in applications requiring high precision. The robot’s key kinematic features include a parasitic motion-free workspace, large orientational capability, compactness, decoupled motion, simplicity in manufacturing and control, mechanically pivoted rotation of the moving platform, and scalability. These characteristics make the robot particularly well-suited for micromanipulation tasks in both manufacturing and medical applications. In manufacturing, it can enable high-precision operations such as micro-assembly, optical fiber alignment, and semiconductor packaging. In medicine, it can support delicate procedures such as microsurgery and cell injection, where sub-micron accuracy, high stability, and precise motion decoupling are critical requirements. The use of nearly identical limbs simplifies the architecture, facilitating easier design, manufacture, and control. The kinematics of the robot is analyzed using reciprocal screw theory for an analytic constraint-embedded Jacobian. To further enhance operational accuracy and robustness, particularly in the presence of uncertainties or disturbances, a deep neural network (DNN)-based state estimation method is integrated, providing accurate forward kinematic predictions. The construction of the robot utilizes origami-inspired limbs and joints, enhancing miniaturization, manufacturing simplicity, and foldability. Although capable of being scaled up or further miniaturized, its current size is 66 mm × 68 mm × 100 mm. The robot’s moving platform is theoretically and experimentally proven to be free of parasitic motion and possesses a large orientation capability. Its unique features are demonstrated, and its potential for high-precision applications is thoroughly discussed. Full article
(This article belongs to the Section Actuators for Robotics)
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21 pages, 3324 KiB  
Article
The Influence of Axial-Bearing Position of Active Magnetic Suspension Flywheel Energy Storage System on Vibration Characteristics of Flywheel Rotor
by Lei Wang, Tielei Li and Zhengyi Ren
Actuators 2025, 14(6), 290; https://doi.org/10.3390/act14060290 - 13 Jun 2025
Viewed by 237
Abstract
This study introduces a flywheel rotor support structure for an active magnetic suspension flywheel energy storage system. In this structure, there is an axial offset between the axial-bearing position and the mass-center of the flywheel rotor, which affects the tilting rotation of the [...] Read more.
This study introduces a flywheel rotor support structure for an active magnetic suspension flywheel energy storage system. In this structure, there is an axial offset between the axial-bearing position and the mass-center of the flywheel rotor, which affects the tilting rotation of the flywheel rotor and which causes the coupling between its tilting rotation and radial motion. Therefore, the influence of the bearing position on the vibration characteristics of the flywheel rotor is explored in this paper. The tilting rotation constraint of the flywheel rotor by axial active magnetic bearing (AAMB) is analyzed, and the radial active magnetic bearing (RAMB) is equivalently treated with dynamic stiffness and dynamic damping. Based on this, a dynamic model of the active magnetic suspension rigid flywheel rotor, considering the position parameter of the axial bearing, is established. To quantify the axial offset between the position of the AAMB and the mass-center of the flywheel rotor, the axial-bearing position offset ratio γ is defined. The variation trend of the vibration characteristics of flywheel rotor with γ is discussed, and its correctness is validated through experiments. It is indicated that, with the increase of γ, the second-order positive precession frequency of the flywheel rotor decreases obviously, and the influence of the gyroscope torque gradually weakens. Meanwhile, its second-order critical speed ω2c decreases significantly (when γ is 0.5, ω2c decreases by about 62%); ω2c corresponds to the inclined mode, revealing that the offset ratio γ has a prominent influence on the critical speed under this mode. In addition, as γ increases, the mass unbalance response amplitude of the flywheel rotor under the speed of ω2c decreases significantly. The reasonable design of the axial-bearing position parameter can effectively improve the operational stability of the active magnetic suspension flywheel energy storage system. Full article
(This article belongs to the Special Issue Actuators in Magnetic Levitation Technology and Vibration Control)
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16 pages, 3276 KiB  
Article
Actuation and Control of Railcar-Mounted Sensor Systems
by Caroline Craig and Mehdi Ahmadian
Actuators 2025, 14(6), 289; https://doi.org/10.3390/act14060289 - 13 Jun 2025
Viewed by 153
Abstract
This study provides the design, analysis, and prototype fabrication of a remotely controlled actuation system for railcar-mounted sensors. Frequent railway inspections are essential for detecting and preventing major defects that could lead to train derailments or accidents. Integrating supplemental automated inspection systems into [...] Read more.
This study provides the design, analysis, and prototype fabrication of a remotely controlled actuation system for railcar-mounted sensors. Frequent railway inspections are essential for detecting and preventing major defects that could lead to train derailments or accidents. Integrating supplemental automated inspection systems into existing trains can aid inspection crews without interfering with standard railway operations. However, many sensors and cameras require protection during transit, motivating the need for a deployable mounting assembly. The feasibility of a deployable sensor system was successfully assessed by creating and demonstrating a functional prototype mounting assembly that can be used with future automated inspection systems. Typical loads and accelerations experienced by a train were used to design a lead screw and stepper motor system capable of working within desired tolerances. Optimized inputs controlling this motion with an Arduino Uno were found through the iterative testing of digital signals and direct port manipulation. Further research testing in a field-like environment is suggested. Full article
(This article belongs to the Special Issue Actuator Technologies and Control: Materials, Devices and Applications)
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17 pages, 939 KiB  
Article
Adaptive Parameter Identification Based Tracking Control of Servo Systems with Unknown Actuator Backlash Compensation
by Hailan Du, Liang Tao, Xiongfeng Deng and Binzi Xu
Actuators 2025, 14(6), 288; https://doi.org/10.3390/act14060288 - 11 Jun 2025
Viewed by 641
Abstract
This paper presents a robust tracking control strategy for servo systems with unknown backlash, employing adaptive parameter identification to address performance degradation caused by backlash nonlinearities. In high-precision positioning and rapid-response applications, backlash significantly compromises system performance. To address this challenge, a servo [...] Read more.
This paper presents a robust tracking control strategy for servo systems with unknown backlash, employing adaptive parameter identification to address performance degradation caused by backlash nonlinearities. In high-precision positioning and rapid-response applications, backlash significantly compromises system performance. To address this challenge, a servo system model incorporating backlash nonlinearities is developed, and a novel adaptive inverse function is introduced for backlash compensation. The estimation error of unidentified parameters is indirectly obtained through the design of a state observer. Minimizing the estimation error facilitates the accurate identification of model parameters, encompassing those associated with backlash. Additionally, an adaptive law is designed to estimate the unknown upper bounds of disturbance dynamics. Then, a robust tracking controller is proposed, which dynamically adjusts control inputs in real time based on identified backlash parameters to counteract backlash-induced adverse effects. Theoretical analysis and simulation results demonstrate that the proposed strategy significantly improves tracking performance in servo systems with unknown backlash. Full article
(This article belongs to the Section Control Systems)
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16 pages, 8564 KiB  
Article
Robotic Tack Welding Path and Trajectory Optimization Using an LF-IWOA
by Bingqi Jia, Haihong Pan, Lei Zhang, Yifan Yang, Huaxin Chen and Lin Chen
Actuators 2025, 14(6), 287; https://doi.org/10.3390/act14060287 - 10 Jun 2025
Viewed by 481
Abstract
Robotic tack welding poses challenges in path optimization due to local optimum entrapment, limited adaptability, and high-dimensional complexity. To overcome these challenges, a Lévy flight-enhanced improved whale optimization algorithm (LF-IWOA) was developed. The algorithm combines elite opposition-based learning (EOBL), differential evolution (DE), and [...] Read more.
Robotic tack welding poses challenges in path optimization due to local optimum entrapment, limited adaptability, and high-dimensional complexity. To overcome these challenges, a Lévy flight-enhanced improved whale optimization algorithm (LF-IWOA) was developed. The algorithm combines elite opposition-based learning (EOBL), differential evolution (DE), and Lévy flight (LF) to improve global exploration capability, increase population diversity, and improve convergence. Additionally, a dynamic trajectory optimization model is designed to consider joint-level constraints, including velocity, acceleration, and jerk. The performance of LF-IWOA was evaluated using two industrial workpieces with varying welding point distributions. Comparative experiments with metaheuristic algorithms, such as the genetic algorithm (GA), WOA and other recent nature-inspired methods, show that LF-IWOA consistently achieves shorter paths and faster convergence. For Workpiece 1, the algorithm reduces the welding path by up to 25.53% compared to the genetic algorithm, with an average reduction of 14.82% across benchmarks. For Workpiece 2, the optimized path is 18.41% shorter than the baseline. Moreover, the dynamic trajectory optimization strategy decreases execution time by 26.83% and reduces mechanical energy consumption by 15.40% while maintaining smooth and stable joint motion. Experimental results demonstrated the effectiveness and practical applicability of the LF-IWOA in robotic welding tasks. Full article
(This article belongs to the Section Actuators for Robotics)
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26 pages, 13125 KiB  
Article
A Novel Double-Sided Electromagnetic Dog Clutch with an Integrated Synchronizer Function
by Bogdan Miroschnitschenko, Florian Poltschak and Wolfgang Amrhein
Actuators 2025, 14(6), 286; https://doi.org/10.3390/act14060286 - 10 Jun 2025
Viewed by 759
Abstract
Dog clutches are superior to synchromesh units due to much less wear caused by friction but require an external torque source to synchronize the rotation speeds. The current trend in e-mobility to use the driving motor of an electric vehicle as this source [...] Read more.
Dog clutches are superior to synchromesh units due to much less wear caused by friction but require an external torque source to synchronize the rotation speeds. The current trend in e-mobility to use the driving motor of an electric vehicle as this source just creates another problem, which is known as torque holes. In this work, we propose a novel double-sided dog clutch that synchronizes the speeds electromagnetically by itself avoiding mechanical contact between the parts. A shift sleeve, two coils placed coaxially in their stators, and two complementary rings form an electromagnetic reluctance actuator, which is integrated inside the gearbox between two gearwheels and represents the double-sided clutch. Thus, intermediate parts between the shift sleeve and the actuator are not required. Both actuator sides can produce axial force and electromagnetic torque. However, torques and forces are generated simultaneously on both sides. Therefore, a special control algorithm is developed to keep the resulting axial force approximately equal to zero while the torque is generated in the neutral gear position. After the synchronization, the axial force is applied on the corresponding side to shift the required gear engaging the shift sleeve teeth directly with the slots of the complementary ring mounted on the gearwheel. So, an axial contact of the teeth at an unaligned state, which can lead to unsuccessful shifting, is avoided. A testrig, which includes a clutch prototype and a testing two-speed gearbox, has been designed and built. The developed theoretical ideas have been verified during the experiments under different conditions. The experiments confirm that the actuator can reduce positive and negative speed differences on both sides and subsequently shift the gear without a shift sleeve collision at misaligned angular positions. Full article
(This article belongs to the Section High Torque/Power Density Actuators)
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16 pages, 3025 KiB  
Article
A Permanent Magnet Hybrid Levitation Based on High-Temperature Superconducting Magnetic Levitation
by Tianyu Xing, Lingfeng Gao, Peiyu Yin, Can Peng and Zigang Deng
Actuators 2025, 14(6), 285; https://doi.org/10.3390/act14060285 - 10 Jun 2025
Viewed by 241
Abstract
This paper proposes an A-shape hybrid levitation system combining high-temperature superconducting (HTS) maglev and permanent magnet levitation (PML) technologies to address the lateral instability of the PML system. By tilting the PM arrays and HTS bulks on both sides at a specific angle, [...] Read more.
This paper proposes an A-shape hybrid levitation system combining high-temperature superconducting (HTS) maglev and permanent magnet levitation (PML) technologies to address the lateral instability of the PML system. By tilting the PM arrays and HTS bulks on both sides at a specific angle, the system’s cross-section forms an “A” shape. This configuration offers dual advantages: the A-shape PML significantly mitigates unstable lateral deflection forces while preserving levitation capacity, whereas the A-shape HTS maglev enhances guidance force. Through systematic analysis, the effects of the tilt angle and the magnetization direction of the PM arrays on levitation performance are investigated and optimized. The simulation results demonstrate that, at the lateral movement of 5 mm, for the PML system, a tilt angle of 45° reduces lateral deflection force by 94.4%, and synergistic optimization of the tilt angle of 40° and magnetization direction of 38° achieves an 84.6% reduction. The HTS maglev system enhances guidance force, with a 45.3% improvement at a 60° tilt angle and a 30° magnetization direction. This study presents a promising solution for developing a stable, high-load-capacity hybrid levitation system. Full article
(This article belongs to the Special Issue Actuators in Magnetic Levitation Technology and Vibration Control)
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19 pages, 6633 KiB  
Article
The Design and Testing of a Cross-Scale Compliant Rotary Actuator with Minimum Actuation Redundancy and Sub-Microradian Resolution
by Yingjie Jia, Jinyuan Cao, Zhishen Liao, Wei Wu, Hui Tang, Yanling Tian and Yuzhang Wei
Actuators 2025, 14(6), 284; https://doi.org/10.3390/act14060284 - 10 Jun 2025
Viewed by 525
Abstract
Solving the common paradoxical problem between sub-micro-arc level resolution and a wide range of rotation angles in rotary actuators, this paper designs a single-drive compliant rotary mechanism (CRM) and develops a cross-scale compliant rotary actuator (CCRA). Specially, the proposed CRM employs a single-input–four-output [...] Read more.
Solving the common paradoxical problem between sub-micro-arc level resolution and a wide range of rotation angles in rotary actuators, this paper designs a single-drive compliant rotary mechanism (CRM) and develops a cross-scale compliant rotary actuator (CCRA). Specially, the proposed CRM employs a single-input–four-output divergent parallel configuration to transform a unidirectional input force into a rotational moment around the rotational center, effectively avoiding asynchronous motion and rotational center shift caused by the multiple actuation. Moreover, the CCRA is developed based on the CRM and a direct-drive rotary (DDR) motor, and adaptive switching between the macro- and micro-combination can simultaneously achieve large rotary range and sub-µrad resolution. After a series of modeling, mechanism optimization, and simulation, a prototype experimental system was built to further test the performance of proposed CCRA. The open-loop and closed-loop characterization experiments showed that the CRM can achieve a rotational resolution of 0.05 μrad and a driving force of 0.78 N·m. In addition, the cross-scale switching experimental results show that the CCRA is able to achieve a static positioning accuracy of 3.5 μrad within a ±5∘ rotational range. Full article
(This article belongs to the Section Miniaturized and Micro Actuators)
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22 pages, 6108 KiB  
Article
Torsional Vibration Suppression in Multi-Condition Electric Propulsion Systems Through Harmonic Current Modulation
by Hanjie Jia, Guanghong Hu, Xiangyang Xu, Dong Liang and Changzhao Liu
Actuators 2025, 14(6), 283; https://doi.org/10.3390/act14060283 - 9 Jun 2025
Viewed by 380
Abstract
Electric helicopters represent a pivotal component in the advancement of urban air mobility (UAM), with considerable potential for future development. The electric propulsion system (EPS) is the core component of these systems. However, the inherent complexities of electromechanical coupling can induce excessive torsional [...] Read more.
Electric helicopters represent a pivotal component in the advancement of urban air mobility (UAM), with considerable potential for future development. The electric propulsion system (EPS) is the core component of these systems. However, the inherent complexities of electromechanical coupling can induce excessive torsional vibrations, potentially compromising operational comfort and even threatening flight safety. This study proposes an active torsional vibration suppression method for EPS that explicitly incorporates electromechanical coupling characteristics. A nonlinear dynamic model has been developed, accounting for time-varying meshing stiffness, meshing errors, and multi-harmonic motor excitation. The motor and transmission system models are coupled using torsional angular displacement. A harmonic current command generation algorithm is then formulated, based on the analysis of harmonic torque-to-current transmission characteristics. To achieve dynamic tracking and the real-time compensation of high-order harmonic currents under non-steady-state conditions, a high-order resonant controller with frequency-domain decoupling characteristics was designed. The efficacy of the proposed harmonic current modulation is verified through simulations, showing an effective reduction of torsional vibrations in the EPS under both steady-state and non-steady-state conditions. It decreases the peak dynamic meshing force by 4.17% and the sixth harmonic amplitude by 88.15%, while mitigating overshoot and accelerating vibration attenuation during speed regulation. The proposed harmonic current modulation method provides a practical solution for mitigating torsional vibrations in electric propulsion systems, enhancing the comfort, reliability, and safety of electric helicopters. Full article
(This article belongs to the Section Aerospace Actuators)
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28 pages, 5445 KiB  
Article
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
Viewed by 223
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)
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16 pages, 1842 KiB  
Article
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
Viewed by 284
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)
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22 pages, 6676 KiB  
Article
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
Viewed by 566
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  
Article
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
Viewed by 649
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  
Article
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
Viewed by 629
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  
Article
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
Viewed by 787
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  
Article
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
Viewed by 573
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  
Article
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
Viewed by 467
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  
Article
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
Viewed by 649
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  
Article
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
Viewed by 754
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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