Journal Description
Actuators
Actuators
is an international, peer-reviewed, open access journal on the science and technology of actuators and control systems, published monthly online by MDPI.
- Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
- High Visibility: indexed within SCIE (Web of Science), Scopus, Inspec, and other databases.
- Journal Rank: JCR - Q2 (Engineering, Mechanical) / CiteScore - Q1 (Control and Optimization)
- Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 16.6 days after submission; acceptance to publication is undertaken in 3.7 days (median values for papers published in this journal in the first half of 2026).
- Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.
- Journal Cluster of Instruments and Instrumentation: Actuators, AI Sensors, Instruments, Metrology, Micromachines and Sensors.
Impact Factor:
2.4 (2025);
5-Year Impact Factor:
2.5 (2025)
Latest Articles
An Intelligent Bearing Fault Diagnosis Model with Physics-Information Fusion: Design and Interpretability Mechanism Research
Actuators 2026, 15(9), 481; https://doi.org/10.3390/act15090481 - 7 Sep 2026
Abstract
To address the issue of limited interpretability in current deep learning-based bearing fault diagnosis methods, this study proposes a convolutional neural network model incorporating spectral physical constraints. The model integrates data-driven learning with physical constraints by embedding the spectral features of bearing faults
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To address the issue of limited interpretability in current deep learning-based bearing fault diagnosis methods, this study proposes a convolutional neural network model incorporating spectral physical constraints. The model integrates data-driven learning with physical constraints by embedding the spectral features of bearing faults as prior knowledge into the network architecture during training. This guides the model to adaptively learn spectral features closely associated with fault mechanisms. Experimental results on both public datasets and self-collected data show that the proposed model not only maintains high diagnostic accuracy but also provides intuitive and credible justification for fault classification through the visualization of spectral responses at the network output layer. This enhances the spectral interpretability of the model’s decisions, achieving a transition from a “black box” to a “white box” and effectively improving the reliability of deep diagnostic models.
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(This article belongs to the Section Actuators for Manufacturing Systems)
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Open AccessReview
Pneumatic Soft Actuation in Elbow Rehabilitation Devices: Actuator Architectures, Sensing Modalities, and Control Strategies—Scoping Review
by
Attila Mészáros and József Sárosi
Actuators 2026, 15(9), 480; https://doi.org/10.3390/act15090480 - 7 Sep 2026
Abstract
Soft and compliant rehabilitation devices may provide improved anatomical adaptability, reduced distal mass, and more flexible human–robot interaction compared with conventional rigid exoskeletons. This scoping review examines elbow rehabilitation technologies across three interconnected domains: (1) the broader landscape of soft and compliant actuation,
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Soft and compliant rehabilitation devices may provide improved anatomical adaptability, reduced distal mass, and more flexible human–robot interaction compared with conventional rigid exoskeletons. This scoping review examines elbow rehabilitation technologies across three interconnected domains: (1) the broader landscape of soft and compliant actuation, (2) the structural, material, and operating architectures of pneumatic soft actuators, and (3) the sensing, intention-detection, and closed-loop control methods used in pneumatic systems. The review included 109 peer-reviewed reports. Four main actuation families were identified: pneumatic soft actuators, motor-driven cable and tendon systems, series-elastic or variable-stiffness actuators, and shape-memory-alloy-based devices. Pneumatic architectures were primarily organized around linear artificial muscles and chamber-based bending or rotary actuators, complemented by rigid–soft integrated, cable-transmitted, modular, antagonistic, self-sensing, and variable-stiffness configurations. Feedback most relied on pressure, kinematic, force, and electromyographic signals. Control architectures combined position, force, torque, impedance, and pressure regulation, while nonlinearities and uncertainties were addressed using model-based, adaptive, sliding-mode, fuzzy, neural, and hybrid methods.
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(This article belongs to the Special Issue Recent Advances in the Design and Applications for Pneumatic Actuators)
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Open AccessArticle
Cascaded Dual-Observer-Based Decoupled Estimation of Mass and Track Gradient for Permanent-Magnet-Driven Electric Monorail Cranes
by
Qijing Qin, Ziming Kou, Shaokai Kou, Guijun Gao and Lei Xu
Actuators 2026, 15(9), 479; https://doi.org/10.3390/act15090479 - 5 Sep 2026
Abstract
Precise data regarding the overall mass of the machinery and the gradient of the track are crucial for optimizing the control of monorail cranes and enhancing energy efficiency. Within the context of electric monorail cranes (EMCs), accurately estimating the total mass of the
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Precise data regarding the overall mass of the machinery and the gradient of the track are crucial for optimizing the control of monorail cranes and enhancing energy efficiency. Within the context of electric monorail cranes (EMCs), accurately estimating the total mass of the machinery and the track gradient poses a formidable challenge. This challenge arises from the strong coupling between the overall mass of the machine and the track gradient, the robustness of parameter estimation methods under varying operational conditions, and the generalizability of the algorithm to real-world operations and rail scenarios of EMCs. To address these challenges, this paper proposes a novel parameter estimation scheme that comprehensively considers the impact of parameter coupling relationships and multiple influencing factors in the transportation scenarios of EMCs under actual working conditions. First, to overcome measurement difficulties induced by strong coupling between the EMC mass and track gradient, a decoupling estimation method based on cascaded dual observers is proposed to jointly estimate the two states. Secondly, to mitigate track slope estimation errors under complex track types and diverse operating conditions, an enhanced immune optimization algorithm, integrating a Weibull function and Levy flight mechanism, in conjunction with an unscented Kalman filter (UKF), is developed. Furthermore, to achieve high-precision and stable parameter identification results, a Weibull dynamic forgetting factor is incorporated into the RLS algorithm, leading to the design of a WDFF-RLS estimator. Finally, real vehicle experiments were conducted on complex tracks at the test site to validate the accuracy and robustness of the proposed estimation method.
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(This article belongs to the Section Actuators for Robotics)
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Open AccessArticle
Constraint-Based Multi-Pole EL Map Screening for Pole and Slot Selection in Axial Flux Motors of Collaborative Robot Joints
by
Min-Ki Hong and Won-Ho Kim
Actuators 2026, 15(9), 478; https://doi.org/10.3390/act15090478 - 5 Sep 2026
Abstract
This paper proposes an inverter constraint-based EL map screening method for selecting pole–slot combinations of an axial flux permanent magnet motor (AFPM) for collaborative robot joints according to the requirements of the actual drive system. First, an initial set of candidates is identified
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This paper proposes an inverter constraint-based EL map screening method for selecting pole–slot combinations of an axial flux permanent magnet motor (AFPM) for collaborative robot joints according to the requirements of the actual drive system. First, an initial set of candidates is identified based on the winding factor and pole and slot characteristics. The inductance and no-load back-EMF of each candidate are then represented on a common EL map, enabling different pole and slot topologies to be compared within the same electromagnetic parameter space. Subsequently, the required current and voltage for generating the target torque are calculated and evaluated against the inverter voltage and current limits to assess the system-level drive suitability of each candidate. Among the candidates satisfying both the voltage and current constraints, the current margin is used as the primary selection criterion, while the harmonic characteristics of the no-load back-EMF are additionally considered. Based on this evaluation, the 22-pole and 24-slot combination is selected for detailed design. For the selected AFPM, a detailed 3D finite element method (FEM) design is performed considering the number of turns, permanent magnet length, magnet spacing, and tooth spacing as design variables. Under the same motor volume constraint as the conventional radial flux permanent magnet motor (RFPM), the final AFPM increases the load torque from 0.737 N·m to 0.907 N·m and the output power from 263.6 W to 332.4 W, corresponding to improvements of 23.1% in torque density and 26.1% in power density, respectively.
Full article
(This article belongs to the Special Issue Advanced Design and Control of Electrical Machines)
Open AccessArticle
Development, Dynamic Characterization, and Response Prediction of an Energy-Dissipating Magnetorheological Fluid Elastomeric Damper
by
Lili Fan, Haimin Zhu, Guolin Guo, Zhichao Li, Wenmin Ou, Lin Zou, Wangwei Li and Shenglong Zhang
Actuators 2026, 15(9), 477; https://doi.org/10.3390/act15090477 - 4 Sep 2026
Abstract
In helicopter rotor systems, effective suppression of lead–lag vibration requires dampers with reliable load transfer, appropriate stiffness matching, tunable damping, and efficient energy dissipation. However, conventional lead–lag dampers often suffer from limited stiffness–damping adjustability and sealing-related constraints. Here, we developed a magnetorheological fluid
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In helicopter rotor systems, effective suppression of lead–lag vibration requires dampers with reliable load transfer, appropriate stiffness matching, tunable damping, and efficient energy dissipation. However, conventional lead–lag dampers often suffer from limited stiffness–damping adjustability and sealing-related constraints. Here, we developed a magnetorheological fluid elastomeric (MRFE) damper by integrating magnetorheological fluid with a rubber elastomer. An elastomer system with a target shear modulus of 0.72 MPa was obtained through systematic design of the rubber formulation, rubber–metal bonding, and vulcanization process. Dynamic characterization showed that the dissipated energy increased markedly with amplitude but only slightly with frequency, whereas applied current exerted the strongest influence on the MRFE response. As the current increased from 0 to 1.5 A, the dissipated energy, effective stiffness, and equivalent damping coefficient increased by 1901.5%, 491.0%, and 961.1%, respectively. The zero-current effective stiffness of 0.443 kN/mm closely matched the required baseline stiffness of 0.44 kN/mm. For inverse current prediction, the improved Transformer model with hyperparameters optimized using PSO achieved a 72.04% lower RMSE than the differential evolution-assisted one-dimensional long short-term memory (DE-1DLSTM) model. These results suggest the potential of the MRFE for stiffness-matched support, controllable energy dissipation, and data-driven current prediction in rotor lead–lag vibration mitigation.
Full article
(This article belongs to the Special Issue Magnetic Materials for Novel Actuators)
Open AccessArticle
Soft Disagreement-Based Adaptive Uncertainty Regulation for Fuzzy Servo Control
by
Dosti Kheder Abbas and Sadegh Abdollah Aminifar
Actuators 2026, 15(9), 476; https://doi.org/10.3390/act15090476 - 3 Sep 2026
Abstract
This paper proposes a supervisory soft disagreement framework for adaptive uncertainty regulation in Interval Type-2 (IT2) fuzzy servo control and validates its performance through embedded implementation on an industrial servo platform. The proposed framework introduces a supervisory learning layer that combines supervised classification
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This paper proposes a supervisory soft disagreement framework for adaptive uncertainty regulation in Interval Type-2 (IT2) fuzzy servo control and validates its performance through embedded implementation on an industrial servo platform. The proposed framework introduces a supervisory learning layer that combines supervised classification and unsupervised fuzzy clustering to characterize servo operating conditions using experimentally extracted performance indicators, including rise time, settling time, overshoot, steady-state error, Integral Absolute Error (IAE), control-effort energy, tracking-error standard deviation, and maximum control effort. Operating condition confidence is quantified by measuring the soft disagreement between the posterior class probabilities of a Support Vector Machine (SVM) classifier and the normalized membership degrees of a Fuzzy C-Means (FCM) clustering algorithm using the Bhattacharyya coefficient. The resulting disagreement index adaptively regulates the Footprint of Uncertainty (FOU) of the antecedent membership functions in IT2 fuzzy controller. A closed-form Uncertainty Avoider Defuzzification (UAD) strategy enables computationally efficient uncertainty-aware type reduction for real-time embedded implementation without iterative procedures. The framework was trained using experimental data collected from a Delta ASDA-B2 400 W industrial servo drive under diverse operating conditions. The complete controller was implemented on a Raspberry Pi and experimentally compared with conventional Proportional–Integral–Derivative (PID), Type-1, and fixed-FOU IT2 fuzzy controllers. Experimental results show that the proposed controller achieved an average IAE of 1.08, representing improvements of 55.6% and 27.5% over the PID and fixed-FOU IT2 controllers, respectively. Overshoot was reduced to 2.2% and settling time to 0.24 s, while the supervisory computation required only 4.55 ms, confirming real-time feasibility. The scientific significance of this work lies in introducing a new disagreement-driven supervisory paradigm that links probabilistic machine learning confidence with adaptive fuzzy uncertainty regulation. By establishing a principled connection among supervised learning, unsupervised learning, and Interval Type-2 fuzzy control, the proposed framework provides a general foundation for confidence-aware adaptive uncertainty management in intelligent control systems operating under uncertain and time-varying conditions.
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(This article belongs to the Section Control Systems)
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Open AccessArticle
Underwater Gravity-Matching Navigation Algorithm Based on Adaptive-Scale Feature Descriptor
by
Hui Liu, Rui Jiang, Han Cheng and Yuhang Liu
Actuators 2026, 15(9), 475; https://doi.org/10.3390/act15090475 - 3 Sep 2026
Abstract
Gravity matching provides an absolute position reference for correcting the accumulated errors of an inertial navigation system (INS) during long-endurance underwater navigation. Its performance, however, can deteriorate when the available sampling data are limited, the gravity field is weakly distinctive, or the measurements
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Gravity matching provides an absolute position reference for correcting the accumulated errors of an inertial navigation system (INS) during long-endurance underwater navigation. Its performance, however, can deteriorate when the available sampling data are limited, the gravity field is weakly distinctive, or the measurements are contaminated by noise. To improve matching accuracy and robustness under these conditions, this paper proposes a gravity-matching navigation method based on an adaptive-scale feature descriptor (ASFD). A coarse-to-fine framework is first established by introducing the feature extraction mechanism of SURF into gravity sequence matching. An adaptive multi-scale descriptor is then constructed to screen candidate positions efficiently. During fine matching, the matching position estimates obtained using phase correlation, random sample consensus, and least squares are integrated through a reliability-aware adaptive fusion strategy. Simulation experiments evaluate the effects of measurement length, measurement accuracy, and regional gravity-field characteristics, followed by validation using three independent shipborne gravity survey trajectories acquired in different matching areas with two marine gravimeters. Across the three trajectories, the ASFD achieves APEs of 0.80–1.13 n miles, representing reductions of approximately 23.1–50.9% relative to the best-performing traditional methods, with MSRs of 89–99% at the 2 n mile threshold. These results indicate that the ASFD maintains relatively high and consistent gravity-matching accuracy under different simulated and measured-data conditions.
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(This article belongs to the Special Issue Advanced Underwater Robotics)
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Open AccessArticle
FEA-Based Nonlinear Modeling and Fuzzy-PI Speed Control of Doubly Salient Permanent-Magnet Motor
by
Tianyu Yang, Wenxin Huang, Lei Mei and Feifei Bu
Actuators 2026, 15(9), 474; https://doi.org/10.3390/act15090474 - 3 Sep 2026
Abstract
Standard modeling methodologies and classic PI control strategies are poorly suited for doubly salient permanent-magnet (DSPM) motors because of their nonlinear magnetic characteristics and commutation-dependent operating behavior. This study establishes a control-oriented nonlinear model for a 12/8-pole DSPM with an internal radial permanent-magnet
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Standard modeling methodologies and classic PI control strategies are poorly suited for doubly salient permanent-magnet (DSPM) motors because of their nonlinear magnetic characteristics and commutation-dependent operating behavior. This study establishes a control-oriented nonlinear model for a 12/8-pole DSPM with an internal radial permanent-magnet arrangement. Current- and position-dependent finite-element flux-linkage Jacobians, rotor-position derivatives, and total electromagnetic torque are organized as three-dimensional lookup tables in the stationary αβ frame, thereby retaining the effects of saturation, armature reaction, interphase coupling, and simultaneous nonzero phase currents. Fuzzy-PI control, implemented as a low-complexity nonlinear gain-scheduling approach, provides a practical alternative to computationally intensive advanced algorithms. To optimize the operational performance, a closed-loop control system is introduced, which utilizes an outer fuzzy-PI loop and an inner current hysteresis loop. This fuzzy-PI speed controller is then compared with a conventionally tuned PI controller under the same conditions. The results demonstrate the usefulness of the FEA-derived model for control evaluation and the favorable transient performance of the fuzzy-PI controller.
Full article
(This article belongs to the Section High Torque/Power Density Actuators)
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Open AccessArticle
Direct Yaw Moment Control of Distributed-Drive Electric Vehicles via Multi-Agent Full-Order Terminal Sliding Mode
by
Qingbo Guo, Guangzu Gui, Minghao Zhou, Niaona Zhang, Longbin Jiang, Feng Qiu and Zhe Wu
Actuators 2026, 15(9), 473; https://doi.org/10.3390/act15090473 - 3 Sep 2026
Abstract
To improve the yaw-stability tracking accuracy and torque smoothness of distributed-drive electric vehicles (DDEVs) under high-speed double-lane-change maneuvers and crosswind disturbances, this paper proposes a multi-agent-system (MAS)-based direct yaw moment control (DYC) method using full-order terminal sliding mode (FOTSM) control. First, based on
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To improve the yaw-stability tracking accuracy and torque smoothness of distributed-drive electric vehicles (DDEVs) under high-speed double-lane-change maneuvers and crosswind disturbances, this paper proposes a multi-agent-system (MAS)-based direct yaw moment control (DYC) method using full-order terminal sliding mode (FOTSM) control. First, based on the vehicle yaw dynamics model and the vector superposition principle, the whole-vehicle yaw-rate and sideslip-angle responses are decomposed into the local contributions of four wheel agents. A leader–follower MAS tracking framework is then established, in which the yaw-stability reference model acts as the virtual leader, and the four wheel agents act as followers. Second, the yaw-rate error and sideslip-angle error are combined into an aggregated tracking error, thereby transforming yaw-stability control into a second-order nonlinear MAS tracking problem. A FOTSM DYC law is designed, and Lyapunov analysis proves that the closed-loop error system reaches the sliding surface and converges within finite time. Finally, hardware-in-the-loop experiments are conducted under double-lane-change maneuvers with and without crosswind disturbance. Compared with the uncontrolled case and a conventional MAS-based linear sliding mode controller, the proposed method reduces yaw-rate and sideslip-angle deviations, improves trajectory-tracking performance, maintains yaw stability under crosswind disturbance, and suppresses wheel-driving-torque chattering.
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(This article belongs to the Section Actuators for Surface Vehicles)
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Open AccessArticle
Integrated Yaw and Roll Stability Control of Distributed-Drive Electric Vehicles Based on the Phase Plane Method
by
Jinwen Yang, Yang Zhang, Lei Xiao, Yiming Hu, Weidong Liu, Zhiqiang Jiang, Xiaoliang Wang and Giuseppe Carbone
Actuators 2026, 15(9), 472; https://doi.org/10.3390/act15090472 - 2 Sep 2026
Abstract
Aiming at the potential simultaneous occurrence of spin-out and rollover during high-speed cornering on road surfaces, this paper takes distributed-drive electric vehicles as the research object and designs a yaw and roll integrated control (YRIC) strategy based on the vehicle’s stability state. Firstly,
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Aiming at the potential simultaneous occurrence of spin-out and rollover during high-speed cornering on road surfaces, this paper takes distributed-drive electric vehicles as the research object and designs a yaw and roll integrated control (YRIC) strategy based on the vehicle’s stability state. Firstly, the phase plane and phase plane are respectively employed to define the stability control regions and serve as the stability criteria for the vehicle. Secondly, according to the vehicle states within the prediction horizon, the corresponding control mode is selected and the control weighting factors are provided to the upper-level controller. The upper-level controller, based on Model Predictive Control (MPC) theory, computes the optimal control outputs. From the derived desired tire longitudinal forces, the desired additional yaw moment is calculated. The lower-level controller allocates this desired additional yaw moment to the optimal driving torque for each wheel. Finally, co-simulation results using MATLAB/Simulink2021b and Carsim2020 demonstrate that the proposed integrated control strategy possesses strong body attitude correction capability under high-speed cornering conditions and can significantly improve vehicle stability.
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(This article belongs to the Section Actuators for Surface Vehicles)
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Open AccessArticle
Four-Wheel Independent Steering Stability Control Based on VSR-ANMPC
by
Yuxing Bai, Weixin Zhang, Weiyi Kong, Song Cui and Liguo Zang
Actuators 2026, 15(9), 471; https://doi.org/10.3390/act15090471 - 2 Sep 2026
Abstract
To address the problems of poor steering smoothness and handling stability for four-wheel independent steering (4WIS) vehicles, this paper presents an adaptive nonlinear model predictive control (ANMPC) strategy based on variable steering ratio (VSR). First, a two-degree-of-freedom (2-DOF) vehicle and reference model are
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To address the problems of poor steering smoothness and handling stability for four-wheel independent steering (4WIS) vehicles, this paper presents an adaptive nonlinear model predictive control (ANMPC) strategy based on variable steering ratio (VSR). First, a two-degree-of-freedom (2-DOF) vehicle and reference model are established to provide a theoretical basis for controller design. Second, the Hermite interpolation polynomial is used to achieve a smooth transition design of the four-stage VSR. By optimizing the steering ratio curve, the steering smoothness and flexibility across the entire speed range are significantly improved. Furthermore, innovatively, the hyperbolic tangent function (tanh) is employed in combination with the μ-V adaptive weight optimization method to construct an adaptive weight adjustment mechanism for the ANMPC controller. To assess the efficacy of the control strategy, co-simulation experiments are performed using CarSim/Simulink. Simulation results demonstrate that versus conventional MPC, the developed algorithm achieves a 37.75% reduction in yaw rate dynamic response RMSE and a 4.61% decrease in lateral velocity RMSE during low-adhesion double lane-change maneuvers, significantly boosting handling stability and steering smoothness in 4WIS vehicles. The VSR-ANMPC control strategy enhances steering performance substantially while demonstrating exceptional handling stability control across diverse speed and adhesion conditions.
Full article
(This article belongs to the Special Issue Integrated Intelligent Vehicle Dynamics and Control—2nd Edition)
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Open AccessArticle
Ultra-Local Model-Based Finite-Time Sliding Mode Control Using Neural Network Observer for Quadrotor Position and Attitude
by
Chengcheng Song, Xingyu Ma, Yuang Luo, Chongsheng Yuan, Fangzheng Gao and Jiacai Huang
Actuators 2026, 15(9), 470; https://doi.org/10.3390/act15090470 - 2 Sep 2026
Abstract
In this paper, an ultra-local model-based finite-time sliding mode control (ULM-FTSMC) method is developed for tracking quadrotor position and attitude in the presence of uncertainties and external disturbances. Based on an ultra-local model technique, the proposed ULM-FTSMC scheme consists of an adaptive neural
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In this paper, an ultra-local model-based finite-time sliding mode control (ULM-FTSMC) method is developed for tracking quadrotor position and attitude in the presence of uncertainties and external disturbances. Based on an ultra-local model technique, the proposed ULM-FTSMC scheme consists of an adaptive neural network observer (ANNO) and a non-singular fast terminal sliding mode controller (NFTSMC). The ultra-local model is employed to approximate complex quadrotor dynamics, thereby reducing the complexity of controller design. The ANNO is designed to estimate the state variables required for subsequent control design and compensate for the lumped disturbances. Furthermore, an improved reaching law incorporating a variable exponent and multiple power terms is developed for the nonsingular fast terminal sliding surface, based on which an NFTSMC is constructed to achieve accurate trajectory tracking within finite time. The stability of the closed-loop system and the finite-time convergence of the tracking errors are rigorously established using Lyapunov theory. Finally, comparative numerical simulations with several existing controllers are conducted to demonstrate the effectiveness and superiority of the proposed method.
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(This article belongs to the Section Aerospace Actuators)
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Open AccessArticle
A 3D-Printed Stretchable Planar Mesh Shape Memory Alloy Actuator with Tailorable Load-Stroke Behavior
by
Dongsu Shin, Young Jin Gong, Youchan Choi and Hyouk Ryeol Choi
Actuators 2026, 15(9), 469; https://doi.org/10.3390/act15090469 - 2 Sep 2026
Abstract
Soft robotic and wearable systems increasingly require actuators that conform to curved surfaces and stretch with the structures they are mounted on, yet conventional shape memory alloy (SMA) form factors—wires, springs, and sheets—remain limited to one-dimensional contraction or out-of-plane bending. This paper presents
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Soft robotic and wearable systems increasingly require actuators that conform to curved surfaces and stretch with the structures they are mounted on, yet conventional shape memory alloy (SMA) form factors—wires, springs, and sheets—remain limited to one-dimensional contraction or out-of-plane bending. This paper presents the Mesh-Structured Shape Memory Alloy (MeSMA) actuator, a thin, planar, and stretchable actuator in which flat SMA wire spans form a periodic mesh clamped by 3D-printed insulating beads; the beads are fabricated by a print–pause–insert process and define the effective beam length ( ) of each span. Isotonic characterization over = 3–7 mm shows that the peak contraction stroke (30–81 mm) and the corresponding optimal payload (7.8–3.9 N) are well approximated by linear functions of over the tested range, consistent with a constant critical bending moment at the span level, establishing a single-parameter design rule for tailoring the actuator operating point. Isothermal tests show that temperature tunes the passive secant stiffness approximately threefold. Separately fabricated specimens exhibit a stroke coefficient of variation of about 1% over 30 thermal cycles with matching degradation trajectories. A tubular compression sleeve demonstrates conformal donning and spatially selective compression enabled by the planar, stretchable form factor.
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(This article belongs to the Section Actuators for Robotics)
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Open AccessSystematic Review
Digital Twins for Metal-Cutting Machine Tools: A Systematic Review
by
Oleksandr Sokolov, Vitalii Ivanov, Serhii Sokolov and Andrii Panych
Actuators 2026, 15(9), 468; https://doi.org/10.3390/act15090468 - 1 Sep 2026
Abstract
Digital twin (DT) technology has become a transformative engineering paradigm for metal-cutting machine tool systems and materials-processing equipment, enabling real-time synchronisation, predictive analytics, and intelligent decision-making throughout the entire production cycle. This systematic review summarises the latest advances in the engineering-oriented implementation of
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Digital twin (DT) technology has become a transformative engineering paradigm for metal-cutting machine tool systems and materials-processing equipment, enabling real-time synchronisation, predictive analytics, and intelligent decision-making throughout the entire production cycle. This systematic review summarises the latest advances in the engineering-oriented implementation of digital twins, with a focus on their modelling frameworks, tool condition monitoring, compensation for geometric, kinematic, thermal and dynamic errors, fault diagnosis and adaptive control, and on the application of this technology to lathes, milling machines and grinding machines. The search for and selection of literature were carried out in accordance with the PRISMA 2020 guidelines. In total, 680 records were identified in Google Scholar in May 2026, of which 197 studies met the inclusion criteria and were synthesised narratively within six thematic sections. The analysis demonstrates that modern digital twin architectures integrate multiphysics modelling, multi-sensor data fusion, and machine learning to create high-precision virtual replicas of physical assets. Predictive maintenance and fault diagnosis systems use machine learning and deep learning to detect incipient faults in feed systems, spindles, and other critical components before failure. The review also analyses existing challenges and outlines future research directions for reliable industrial digital twins.
Full article
(This article belongs to the Special Issue AI, Designing, Sensing, Instrumentation, Diagnosis, Controlling, and Integration of Actuators in Digital Manufacturing—3rd Edition)
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Open AccessArticle
Evidence-Guided Attention Neural Network for Structural Crack Identification with Multi-Source Sensors
by
Yifei Wang and Xiaojun Wang
Actuators 2026, 15(9), 467; https://doi.org/10.3390/act15090467 - 1 Sep 2026
Abstract
The integration of complementary sensing modalities provides a basis for accurate crack identification in advanced aircraft structures. In this context, PZT transducers are sensitive to incipient damage through guided-wave interrogation, whereas strain gauges capture quasi-static deformation. Prevailing fusion paradigms, however, encounter an interpretability–adaptability
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The integration of complementary sensing modalities provides a basis for accurate crack identification in advanced aircraft structures. In this context, PZT transducers are sensitive to incipient damage through guided-wave interrogation, whereas strain gauges capture quasi-static deformation. Prevailing fusion paradigms, however, encounter an interpretability–adaptability dilemma. Model-based approaches lack robustness to sensor degradation, while data-driven attention methods sacrifice transparency. To resolve this trade-off, an Evidence-guided Attention Neural Network (EANN) is proposed. Its central methodological contribution lies in repositioning Dempster–Shafer (D-S) evidence theory from a terminal fusion operator to an upstream credibility feature extraction module. Evidence-derived credibility features, comprising belief entropy, inter-source similarity, and Kalman-filtered residuals, drive the attention weight optimization and endow the learned channel weights with physically interpretable evidential meaning. Ablation experiments confirm that the observed improvement arises from the interaction between the evidence-guided credibility representation and adaptive attention weighting, with neither component sufficient on its own. The framework fuses quasi-static strain measurements with active piezoelectric guided-wave interrogation, which offers high sensitivity to incipient damage but remains vulnerable to channel degradation. Experiments on aluminum tensile plates and trapezoidal wing skin specimens show that EANN maintains identification accuracy under simulated sensor anomalies and partial failures by attenuating compromised channels without explicit fault detection, providing an uncertainty-aware fusion framework for online structural health monitoring of aerospace structures.
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(This article belongs to the Section Aerospace Actuators)
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Open AccessArticle
Graph-Enhanced Proximal Policy Optimization for Simulation-Based Point Cloud Coverage Planning on Curved Surfaces
by
Zhongxiang Chen, Zeng Feng, Zewu Li, Xingni Jiang and Biju Yin
Actuators 2026, 15(9), 466; https://doi.org/10.3390/act15090466 - 1 Sep 2026
Abstract
This study examines the effects of graph aggregation and candidate-level scoring on PPO-based coverage planning for simulated curved point clouds. In a static uniform-coverage benchmark, a parameter-matched global MLP reaches 22.13% overall coverage, GCN-PPO reaches 76.97%, and Graph-Enhanced PPO reaches 88.37%; DFS remains
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This study examines the effects of graph aggregation and candidate-level scoring on PPO-based coverage planning for simulated curved point clouds. In a static uniform-coverage benchmark, a parameter-matched global MLP reaches 22.13% overall coverage, GCN-PPO reaches 76.97%, and Graph-Enhanced PPO reaches 88.37%; DFS remains the strongest at 95.80%. A separate 50-decision task introduces nonuniform priorities and motion costs. In that setting, GCN-PPO and Graph-Enhanced PPO obtain nearly identical weighted coverage (0.812 and 0.811, respectively), and no statistically reliable difference is detected. On a separate 1000-node scan-derived Stanford Bunny surface with retained holes and mesh-geodesic connectivity, GCN-PPO and Graph-Enhanced PPO again show comparable weighted coverage (0.450 and 0.445, respectively) and task utility (0.321 and 0.315, respectively), with no statistically reliable difference. Across the physically normalized zero-shot density and area tests, the direction of the small mean differences varies by condition, and none remain significant after multiplicity correction; both policies lose performance as the sampling density or workspace size changes. Direct adaptation on the known fivefold-area target graphs raises Graph-Enhanced PPO coverage from 0.631 to 0.753 for held-out starts. Because adaptation and evaluation use the same target graph instances, unseen large-graph generalization is not tested. Across the experiments, graph aggregation provides the clearest learned improvement. The auxiliary scorer improves the static benchmark result, but the added parameters prevent assigning that gain solely to a separate scoring mechanism; no consistent benefit appears in the other tests. Systematic traversal remains preferable when exhaustive uniform coverage is feasible. The study remains simulation-based: scan-derived geometry is evaluated, but validation on physical hardware is still required.
Full article
(This article belongs to the Section Actuators for Robotics)
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Open AccessArticle
A Fault Diagnosis Method for Roadheader Cutting Head Based on GADF and Attention-Enhanced Transfer Learning AlexNet
by
Changpeng Li and Zhenyu Dai
Actuators 2026, 15(9), 465; https://doi.org/10.3390/act15090465 - 1 Sep 2026
Abstract
The cutting head is the primary cutting load device of the roadheader. The harsh, complex excavation environment often leads to a scarcity of labelled fault samples, significantly hindering the development of accurate fault diagnosis models. This paper proposes a novel fault diagnosis method
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The cutting head is the primary cutting load device of the roadheader. The harsh, complex excavation environment often leads to a scarcity of labelled fault samples, significantly hindering the development of accurate fault diagnosis models. This paper proposes a novel fault diagnosis method based on the Gramian angular difference field (GADF) and an attention-enhanced transfer-learning AlexNet. The collected one-dimensional vibration signals are transformed into two-dimensional image data using GADF to capture transient impact gradients and preserve absolute temporal correlations. To overcome data limitations, the method retains the base convolutional feature extractor of an AlexNet model pre-trained on ImageNet, whilst discarding the original fully connected and classification layers. A novel classification head incorporating a multihead self-attention (MSA) mechanism is constructed to fine-tune the network specifically for the fault diagnosis task. This structural modification adaptively assigns higher weights to fault-sensitive spatial regions, significantly enhancing the model’s feature extraction focus and generalisation capability even under intense background noise. Experimental validation was conducted on a scaled cutting head fault diagnosis test bench. The results demonstrate that the proposed method outperforms other baselines across evaluation metrics, exhibiting robust recognition accuracy and stability. This effectively identifies the cutting head’s operating condition, offering a novel and practical approach for future underground fault diagnosis in coal mines.
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(This article belongs to the Special Issue Fault Diagnosis and Prognosis in Actuators)
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Open AccessArticle
Analysis and Experimental Determination of Fluid Dynamics Within a Sphere for the Development of Multi Degree of Freedom Attitude Control Actuator
by
Huu Quan Vu and Enrico Stoll
Actuators 2026, 15(9), 464; https://doi.org/10.3390/act15090464 - 31 Aug 2026
Abstract
In the contemporary landscape of spacecraft engineering, reaction wheels, control moment gyros, and momentum wheels are standard tools for precise attitude control, functioning by exchanging angular momentum through the rotation of a solid mass around its major axis. The VEKTOR-FDA (Vector Fluid Dynamic
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In the contemporary landscape of spacecraft engineering, reaction wheels, control moment gyros, and momentum wheels are standard tools for precise attitude control, functioning by exchanging angular momentum through the rotation of a solid mass around its major axis. The VEKTOR-FDA (Vector Fluid Dynamic Actuator) proposed in this paper offers an alternative by utilizing the principle of rotating liquid to generate angular momentum instead of relying on a solid body. Electromagnetic pumps drive and circulate the fluid, connecting to a hollow sphere via inlet and outlet channels. The fluid within the sphere is drawn into the pump through the outlet channel and reintroduced through the inlet channel. This circulation, combined with the spherical shape, generates a rotational fluid flow inside the hollow sphere, creating a rotating fluid volume and an angular momentum vector aligned with the rotation axis. By utilizing at least three pumps arranged orthogonally, simultaneous operation allows flow mixing, which can be precisely controlled by adjusting the individual flow velocities of each pump. This setup enables the rotation axis of the fluid flow to be directed in any desired orientation, allowing the rotating fluid volume and its angular momentum vector to be spatially aligned as needed. As a result, a single VEKTOR-FDA can manage attitude control across all three axes of the spacecraft, effectively functioning as a multiple-degree-of-freedom (MDOF) actuator. The electromagnetic pump drive in the VEKTOR-FDA actuator provides self-lubrication and eliminates the need for moving mechanical parts, minimizing potential damage from mechanical loads like shocks during launch. Its simple design also enables the use of commercial off-the-shelf components, ensuring cost-effective implementation. This paper provides a comprehensive overview of the motivation and concept behind the VEKTOR-FDA actuator. Additionally, this paper presents analyses and experimental results that investigate how rotating fluid flow can be generated within the sphere and examines its behavior. The study evaluates various factors influencing fluid flow inside the sphere, including configurations with variable cross-sectional shapes of the inlet and outlet channels. Furthermore, it determines the optimal positioning and arrangement of these channels to achieve efficient fluid flow volume, which is essential for maximizing angular momentum output.
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(This article belongs to the Special Issue Flow Control and Beyond: Enhancing Performance and Energy Efficiency in Complex Fluid Systems—2nd Edition)
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Open AccessArticle
Adaptive Front and Rear Braking Force Distribution Strategy for Electric Commercial Vehicles: Modeling, Control, and Experimental Validation
by
Abdallah Yousef Aldaher, Ebaa Khaled Mohammed Matar, Jamshid Valiev Fayzullayevich, Yuxiao Zhang, Mohammed A. Hassan and Gangfeng Tan
Actuators 2026, 15(9), 463; https://doi.org/10.3390/act15090463 - 28 Aug 2026
Abstract
The dynamic distribution of braking forces between front and rear axles in electric commercial vehicles represents a critical multi-objective optimization challenge requiring simultaneous satisfaction of regulatory safety compliance, regenerative energy recovery, thermal stability, and actuator coordination under varying load and road conditions. This
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The dynamic distribution of braking forces between front and rear axles in electric commercial vehicles represents a critical multi-objective optimization challenge requiring simultaneous satisfaction of regulatory safety compliance, regenerative energy recovery, thermal stability, and actuator coordination under varying load and road conditions. This paper addresses this challenge through the development and experimental validation of an integrated adaptive brake force distribution strategy combining model predictive control (MPC) with Particle Swarm Optimization (PSO) within a unified framework that ensures compliance with ECE Regulation No. 13. A comprehensive experimental test bench was designed and instrumented, integrating three independent braking mechanisms: magnetic brakes with front and rear torque coefficients of 4.73 N·m/A and 3.65 N·m/A, respectively; an eddy current retarder with coefficient 2.220 × 10−4 N·m·s/(A2·rad), producing braking torque that is quadratic in excitation current and linear in rotor speed; a regenerative braking system with 82–90% efficiency; and a switchable magnetic clutch for FWD/4WD operation. The MPC controller was formulated with a prediction horizon = 20, control horizon = 5, and sampling time = 20 ms. PSO was employed for systematic tuning of MPC weights using 30 particles over 50 iterations with cognitive and social coefficients = = 2.0 and linearly decreasing inertia from 0.8 to 0.4. A vehicle state estimation module using Kalman Filtering was developed for real-time estimation of vehicle mass (<3% error), road slope (<0.3% error), and road friction coefficient (<5% error). Experimental validation across eight comprehensive test scenarios demonstrates that the PSO-optimized MPC controller achieves 43% reduction in front RMSE (from 2.65 Nm to 1.52 Nm), 44% reduction in rear RMSE (from 0.78 Nm to 0.44 Nm), 100% ECE R13 compliance (improved from 67.5%), 57% settling time improvement (from 4.2 s to 1.8 s), 92% overshoot reduction (from 67% to 5%), and average recovered energy improvement from 3.51 kJ to 4.04 kJ. The proposed framework provides a comprehensive solution for next-generation electric commercial vehicle brake management systems.
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(This article belongs to the Section Actuators for Surface Vehicles)
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Open AccessArticle
Comparative Analysis of Y- and Delta-Connected Windings in Line-Start Permanent Magnet Motors with Different Rotor Configurations
by
Seung-Heon Lee, In-Jun Yang and Si-Woo Song
Actuators 2026, 15(9), 462; https://doi.org/10.3390/act15090462 - 28 Aug 2026
Abstract
A line-start permanent-magnet motor (LSPM) combines the direct-on-line starting capability of a squirrel-cage induction motor (IM) with permanent-magnet-assisted synchronous operation. Previous studies on LSPM winding connections have mainly focused on load-dependent efficiency and the power factor, while their effects on harmonics, torque ripple,
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A line-start permanent-magnet motor (LSPM) combines the direct-on-line starting capability of a squirrel-cage induction motor (IM) with permanent-magnet-assisted synchronous operation. Previous studies on LSPM winding connections have mainly focused on load-dependent efficiency and the power factor, while their effects on harmonics, torque ripple, and synchronization across different rotor configurations remain unclear. This study compares Y- and delta-connected windings in two 5.5 kW, four-pole LSPM models using transient finite-element analysis. Current and voltage harmonics, losses, efficiency, torque ripple, and synchronization response were evaluated. The Y-connected cases exhibited lower current harmonic distortion and stator copper loss, whereas the delta-connected cases reduced torque ripple and maximum speed overshoot but required slightly longer settling times. For LSPM-B, the Y connection achieved the highest efficiency of 92.92% with a stator copper loss of 137.81 W, while the delta connection reduced the torque ripple ratio from 43.8% to 39.5%. These results demonstrate that winding-connection effects depend on the rotor magnetic circuit and cage-assisted starting characteristics, requiring a trade-off among efficiency, harmonic loss, torque ripple, and synchronization response.
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(This article belongs to the Special Issue Advanced Design and Control of Electrical Machines)
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