Machines

29 pages, 28063 KB

Open AccessArticle

Braking Energy Recovery Control Strategy Based on Instantaneous Response and Dynamic Weight Optimization

by Lulu Cai, Pengxiang Yan, Xiaopeng Yang, Liyu Yang, Yi Liu, Guanfu Huang, Shida Liu and Jingjing Fan

Machines 2026, 14(1), 10; https://doi.org/10.3390/machines14010010 - 19 Dec 2025

Abstract

Multi-axle electric heavy-duty trucks face significant challenges in maintaining braking stability and achieving real-time control during regenerative braking due to their large mass and complex inter-axle coupling dynamics. To address these issues, this paper proposes an improved model predictive control (IMPC) strategy that [...] Read more.

Multi-axle electric heavy-duty trucks face significant challenges in maintaining braking stability and achieving real-time control during regenerative braking due to their large mass and complex inter-axle coupling dynamics. To address these issues, this paper proposes an improved model predictive control (IMPC) strategy that enhances computational efficiency and control responsiveness through an instantaneous response mechanism. The approach integrates a first-order error attenuation term within the MPC framework and employs an extended Kalman filter to estimate tire–road friction in real time, enabling adaptive adjustment between energy recovery and stability objectives under varying road conditions. A control barrier function constraint is further introduced to ensure smooth and safe regenerative braking. Simulation results demonstrate improved energy recovery efficiency and faster convergence, while real-vehicle tests confirm that the IMPC maintains superior real-time performance and adaptability under complex operating conditions, reducing average computation time by approximately 14% compared with conventional MPC and showing strong potential for practical deployment. Full article

(This article belongs to the Special Issue Active and Passive Safety and Noise, Vibration, and Harshness (NVH) of Intelligent Vehicles)

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29 pages, 26080 KB

Open AccessArticle

A Machine Learning Vibration-Based Methodology for Robust Detection and Severity Characterization of Gear Incipient Faults Under Variable Working Speed and Load

by Dimitrios M. Bourdalos and John S. Sakellariou

Machines 2026, 14(1), 9; https://doi.org/10.3390/machines14010009 - 19 Dec 2025

Abstract

A machine learning (ML) methodology for the robust detection and severity characterization of incipient gear faults under variable speed and load is postulated. The methodology is trained using vibration signals from a single accelerometer mounted on the gearbox, simultaneously acquired with tachometer signals [...] Read more.

A machine learning (ML) methodology for the robust detection and severity characterization of incipient gear faults under variable speed and load is postulated. The methodology is trained using vibration signals from a single accelerometer mounted on the gearbox, simultaneously acquired with tachometer signals at a sample of working conditions (WCs) from the range of interest. A special parametric identification procedure of gearbox dynamics that may account for the continuous range of WCs is introduced through `clouds’ of advanced stochastic data-driven Functionally Pooled models, estimated from angularly resampled vibration signals. Each cloud represents the gearbox dynamics at a specific fault severity level, while the pseudo-static effects of the WCs on the dynamics are accounted for through data pooling. Fault detection and severity characterization are achieved by testing the consistency of a vibration signal with each model cloud within a hypothesis testing framework in which the unknown load is also estimated. The methodology is assessed through 18,300 experiments on a single-stage spur gearbox including four incipient single-tooth pinion faults, 61 speeds, and four load levels. The faults produce no significant changes in the time-domain signals, while their frequency-domain effects overlap with the variations caused by the WCs, rendering the diagnosis problem highly challenging. The comparison with a state-of-the-art deep Stacked Autoencoder (SAE) demonstrates the ML method’s superior performance, achieving 95.4% and 91.6% accuracy in fault detection and characterization, respectively. Full article

(This article belongs to the Special Issue Intelligent Vibration Control and Condition Monitoring in Smart Structures and Electromechanical Systems)

25 pages, 4758 KB

Open AccessArticle

Quantitative Evaluation of an Industrial Robot Tool Trajectory Deviation Using a High-Speed Camera

by Mantas Makulavičius, Sigitas Petkevičius, Vytautas Bučinskas and Andrius Dzedzickis

Machines 2026, 14(1), 8; https://doi.org/10.3390/machines14010008 - 19 Dec 2025

Abstract

One of the primary applications of industrial robots is in various manufacturing processes, such as milling, grinding, and additive manufacturing. To achieve the desired precision in tool trajectory performance when machining specific parts, it is necessary to calibrate the tool centre point (TCP) [...] Read more.

One of the primary applications of industrial robots is in various manufacturing processes, such as milling, grinding, and additive manufacturing. To achieve the desired precision in tool trajectory performance when machining specific parts, it is necessary to calibrate the tool centre point (TCP) of the robot for each manufacturing process. The development of industrial robot tool trajectories is a multipurpose task. It encompasses issues related to robot geometry, path interpolation type, and trajectory waypoints approximation. The primary objective of this study is to establish a camera-based methodology for evaluating trajectory-following accuracy in industrial robots. The present paper proposes the use of a high-speed motion camera system for non-contact tracking of TCP trajectories. By capturing the robot’s end-effector motion in real-time and under actual trajectory tracking conditions, this technique enables a clearer understanding of how trajectory execution accuracy varies with velocity, trajectory geometry, trajectory interpolation, and robot kinematics. Provided analysis of two industrial robot types opened interesting findings related to the dependencies between the implementation of first- and second-degree interpolations. To illustrate this point, the implementation of second-degree interpolation ensures a more consistent velocity in the trajectory. This contrasts with first-degree interpolation, which is more challenging to achieve and is susceptible to variations in curvature. Conversely, the utilization of first-degree interpolation facilitates enhanced performance accuracy for smaller curvatures. The results of the experimental research confirm the initial hypothesis regarding the influence of interpolation mode and pave the way for future uses of this information for machine learning algorithms. Full article

(This article belongs to the Section Robotics, Mechatronics and Intelligent Machines)

30 pages, 4538 KB

Open AccessArticle

Operator-Based Direct Nonlinear Control Using Self-Powered TENGs for Rectifier Bridge Energy Harvesting

by Chengyao Liu and Mingcong Deng

Machines 2026, 14(1), 7; https://doi.org/10.3390/machines14010007 - 19 Dec 2025

Abstract

Triboelectric nanogenerators (TENGs) offer intrinsically high open-circuit voltages in the kilovolt range; however, conventional diode rectifier interfaces clamp the voltage prematurely, restricting access to the high-energy portion of the mechanical cycle and preventing delivery-centric control. This work develops a unified physical basis for [...] Read more.

Triboelectric nanogenerators (TENGs) offer intrinsically high open-circuit voltages in the kilovolt range; however, conventional diode rectifier interfaces clamp the voltage prematurely, restricting access to the high-energy portion of the mechanical cycle and preventing delivery-centric control. This work develops a unified physical basis for contact–separation (CS) TENGs by confirming the consistency of the canonical

V_{o c}

–

C_{s}

relation with a dual-capacitor energy model and analytically establishing that both terminal voltage and storable electrostatic energy peak near maximum plate separation. Leveraging this insight, a self-powered gas-discharge-tube (GDT) rectifier bridge is devised to replace two diodes and autonomously trigger conduction exclusively in the high-voltage window without auxiliary bias. An inductive buffer regulates the current slew rate and reduces

I^{2} R

loss, while the proposed topology realizes two decoupled power rails from a single CS-TENG, enabling simultaneous sensing/processing and actuation. A low-power microcontroller is powered from one rail through an energy-harvesting module and executes an operator-based nonlinear controller to regulate the actuator-side rail via a MOSFET–resistor path. Experimental results demonstrate earlier and higher-efficiency energy transfer compared with a diode-bridge baseline, robust dual-rail decoupling under dynamic loading, and accurate closed-loop voltage tracking with negligible computational and energy overhead. These findings confirm the practicality of the proposed self-powered architecture and highlight the feasibility of integrating operator-theoretic control into TENG-driven rectifier interfaces, advancing delivery-oriented power extraction from high-voltage TENG sources. Full article

(This article belongs to the Special Issue Advances in Dynamics and Vibration Control in Mechanical Engineering)

16 pages, 1259 KB

Open AccessArticle

Impact and Detection of Coil Asymmetries in a Permanent Magnet Synchronous Generator with Parallel Connected Stator Coils

by Nikolaos Gkiolekas, Alexandros Sergakis, Marios Salinas, Markus Mueller and Konstantinos N. Gyftakis

Machines 2026, 14(1), 6; https://doi.org/10.3390/machines14010006 - 19 Dec 2025

Abstract

Permanent magnet synchronous generators (PMSGs) are suitable for offshore applications due to their high efficiency and power density. Inter-turn short circuits (ITSCs) stand as one of the most critical faults in these machines due to their rapid evolution in phase or ground short [...] Read more.

Permanent magnet synchronous generators (PMSGs) are suitable for offshore applications due to their high efficiency and power density. Inter-turn short circuits (ITSCs) stand as one of the most critical faults in these machines due to their rapid evolution in phase or ground short circuits. It is therefore necessary to detect ITSCs at an early stage. In the literature, ITSC detection is often based on current signal processing methods. One of the challenges that these methods face is the presence of imperfections in the stator coils, which also affects the three-phase symmetry. Moreover, when the stator coils are connected in parallel, this type of fault becomes important, as circulating currents will flow between the parallel windings. This, in turn, increases the thermal stress on the insulation and the permanent magnets, while also exacerbating the vibrations of the generator. In this study, a finite-element analysis (FEA) model has been developed to simulate a dual-rotor PMSG under conditions of coil asymmetry. To further investigate the impact of this asymmetry, mathematical modeling has been conducted. For fault detection, negative-sequence current (NSC) analysis and torque monitoring have been used to distinguish coil asymmetry from ITSCs. While both methods demonstrate potential for fault identification, NSC induced small amplitudes and the torque analysis was unable to detect ITSCs under low-severity conditions, thereby underscoring the importance of developing advanced strategies for early-stage ITSC detection. The innovative aspect of this work is that, despite these limitations, the combined use of NSC phase-angle tracking and torque harmonic analysis provides, for the first time in a core-less PMSG with parallel-connected coils, a practical way to distinguish ITSC from coil asymmetry, even though both faults produce almost identical signatures in conventional current-based indices. Full article

(This article belongs to the Special Issue Fault Diagnostics and Fault Tolerance of Synchronous Electric Drives)

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19 pages, 4518 KB

Open AccessArticle

Dynamic Damage Behavior Analysis of Hail Impact on Composite Radome Structure Using Peridynamic Bond-Based Theory

by Feng Zhang, Yuxiao Xu, Xiayu Xu, Lingwei Bai, Xiaoxiao Liu and Yazhou Guo

Machines 2026, 14(1), 5; https://doi.org/10.3390/machines14010005 - 19 Dec 2025

Abstract

This paper studies the progressive damage process and final damage form of composite laminate aircraft radome under high-speed hail impact A simulation method based on Peridynamic bond-based theory is proposed to study the progressive damage process and final damage form of composite laminate [...] Read more.

This paper studies the progressive damage process and final damage form of composite laminate aircraft radome under high-speed hail impact A simulation method based on Peridynamic bond-based theory is proposed to study the progressive damage process and final damage form of composite laminate aircraft radome under high-speed hail impact. Using the Peridynamic theory, the dynamic damage behavior of hailstone impact on a composite laminate plate is analyzed, and an impact model of hailstone impact is established to study the damage initiation, expansion, and failure behavior of the composite laminate. The dynamic mechanical constitutive and failure criteria that characterize the macromechanical behavior of both hailstone and composite laminate during impact are established. Additionally, equations describing the interaction forces between these two materials are proposed to develop a numerical simulation method for the laminate failure process. The dynamic damage evolution and failure mechanisms are subsequently investigated to provide a theoretical foundation for the optimum design of composite structures, such as aircraft radomes, subjected to hail impact. To describe the interaction force equations between two materials, a new method based on Peridynamics (PD) is proposed to establish a numerical simulation method for the damage process of laminated plates. This method provides a theoretical basis for optimizing the design of composite structures (such as aircraft radome) after being impacted by hail. Full article

(This article belongs to the Special Issue Advanced Aircraft Aerodynamics, Flight Stability, Stabilization and Control of Flying Vehicles)

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13 pages, 2449 KB

Open AccessArticle

Dynamic System Analysis of Vent and Recycle Configurations in Centrifugal Compressors

by Andrea Betti, Leonardo Cappelli, Andrea Fusi, Fulvio Palmieri and Luigi Tundo

Machines 2026, 14(1), 4; https://doi.org/10.3390/machines14010004 - 19 Dec 2025

Abstract

Centrifugal compressors are vital components in industrial applications, but they are prone to a disruptive phenomenon known as surge, which can lead to mechanical stress and temperature increase. Surge occurrence is influenced by machine design, plant layout, and geometry. Engineers often deploy long [...] Read more.

Centrifugal compressors are vital components in industrial applications, but they are prone to a disruptive phenomenon known as surge, which can lead to mechanical stress and temperature increase. Surge occurrence is influenced by machine design, plant layout, and geometry. Engineers often deploy long (cold) and short (hot) recycle valves to address this issue. To ensure surge prevention, a fluid dynamic model is indispensable. In this study, a 1D Computational Fluid Dynamics (1D-CFD) model was developed using Amesim for a two-section centrifugal compressor. The main objective was to investigate the impact of various parameters on surge occurrence and compare different plant layouts to determine the most suitable solution for the specific study case. Here, the focus is on the influence of vent valves over the plant performance. To achieve this comparison, transient simulations of emergency shutdown (ESD) operations were performed. This study contributes to a better understanding of how machine design and operational factors affect surge behavior. By systematically evaluating different plant layouts, we identified the most effective strategies for preventing surge and enhancing compressor performance. This research provides valuable insights for engineers and operators striving to optimize industrial processes and improve the reliability and efficiency of centrifugal compressor systems. Full article

(This article belongs to the Section Turbomachinery)

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17 pages, 6041 KB

Open AccessArticle

Design and Performance Evaluation of a Hybrid Flux-Path Limited-Angle Torque Motor

by Ho-Young Lee, Soon-O Kwon and Min-Ro Park

Machines 2026, 14(1), 3; https://doi.org/10.3390/machines14010003 - 19 Dec 2025

Abstract

Torque motors are typically operated within a limited angular range and are widely used in high-precision control applications due to their ability to provide uniform torque throughout the operating region. In this paper, a new torque motor structure is proposed that enhances torque [...] Read more.

Torque motors are typically operated within a limited angular range and are widely used in high-precision control applications due to their ability to provide uniform torque throughout the operating region. In this paper, a new torque motor structure is proposed that enhances torque density while maintaining the inherent torque uniformity. The proposed motor employs an optimized stator pole geometry that enables the magnetic flux generated by both the armature and the permanent magnet to contribute more effectively to torque production. To clarify the torque generation mechanism, the flux distributions of the field and armature were analyzed and validated through finite element analysis. Key design parameters were then defined, and an optimal design was performed to maximize the average torque. The performance of the proposed structure was evaluated through a comparative analysis with a conventional torque motor, confirming its superiority. Finally, a prototype of the proposed torque motor was fabricated, and its torque performance was verified through load testing. Full article

(This article belongs to the Special Issue Electromagnetic and Multi-Physics Analysis and Design of Electric Machines)

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43 pages, 5472 KB

Open AccessReview

A Review of Configurations and Control Strategies for Linear Motor-Based Electromagnetic Suspension

by Renkai Ding, Xuwen Chen, Ruochen Wang and Dong Jiang

Machines 2026, 14(1), 2; https://doi.org/10.3390/machines14010002 - 19 Dec 2025

Abstract

This paper presents a systematic review of linear motor-based electromagnetic suspension, a key technology for reconciling vehicle comfort, handling stability, and energy consumption. The review focuses on two core areas: actuator configuration and control strategy. In configuration design, a comparison of moving-coil, permanent [...] Read more.

This paper presents a systematic review of linear motor-based electromagnetic suspension, a key technology for reconciling vehicle comfort, handling stability, and energy consumption. The review focuses on two core areas: actuator configuration and control strategy. In configuration design, a comparison of moving-coil, permanent magnet synchronous (PMSLM), and switched-reluctance linear motors identifies the PMSLM as the mainstream approach due to its high-power density and performance. Key design challenges for meeting stringent vehicle operating conditions, such as mass-volume optimization, thermal management, and high reliability, are also analyzed. Regarding control strategy, the review outlines the evolutionary path from classical to advanced and intelligent control. It also examines the energy-efficiency trade-off between vibration suppression and energy recovery. Furthermore, the paper summarizes three core challenges for industrialization: nonlinear issues like thrust fluctuation and friction, the coupling of electromagnetic–mechanical–thermal multi-physical fields, and bottlenecks related to high costs and reliability verification. Finally, future research directions are envisioned, including new materials, sensorless control, and active safety integration for autonomous driving. Full article

(This article belongs to the Special Issue Smart Vibration Control and Suspension Systems in Automotive Engineering)

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28 pages, 99906 KB

Open AccessArticle

Design and Implementation of an Automated Thermal Imaging Device for Lower Limb Prosthetic Applications

by Daniel Pizarro, Joel C. Huegel, Elias Diaz, Beatriz Alemon, Hugh Herr and Luis C. Felix-Herran

Machines 2026, 14(1), 1; https://doi.org/10.3390/machines14010001 - 19 Dec 2025

Abstract

Since elevated temperature and humidity may occur at the prosthetic socket–skin interface, it is essential to collect thermal data from the residual limb, as this information serves as an indicator of adverse effects such as irritation, postural problems, and significant damage to health. [...] Read more.

Since elevated temperature and humidity may occur at the prosthetic socket–skin interface, it is essential to collect thermal data from the residual limb, as this information serves as an indicator of adverse effects such as irritation, postural problems, and significant damage to health. These data are obtained non-invasively through the execution of a thermal imaging (TI) procedure. However, the precision and repeatability of a TI procedure rely significantly on its execution technique. This work presents the design and implementation of a mechatronic device that automates a thermal imaging technique. The application of the device is in lower-limb prosthetics evaluation. The proposed system improves data acquisition consistency by reducing execution time and minimizing human error, thereby enhancing the reproducibility and reliability of thermal measurements. The introduced device, Thermal Imaging Booth, proposes an automated solution for TI standardization in clinical and research settings. By minimizing inconsistencies, this system improves the diagnostic potential of thermography, facilitating its adoption in biomedical applications. Full article

(This article belongs to the Special Issue Advances in Medical and Rehabilitation Robots)

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21 pages, 1774 KB

Open AccessArticle

Title Discrete-Time Fast Terminal Sliding Mode Control Based on Generalized Implicit Reaching Law for Electronic Throttle

by Wenjiang Zhu, Jie Zhang, Yinhui Yu and Wenqian Liu

Machines 2025, 13(12), 1153; https://doi.org/10.3390/machines13121153 - 18 Dec 2025

Abstract

To achieve precise tracking control under the hardware of electronic throttle digital control, this paper proposes a novel implicit discrete-time fast terminal sliding mode control method for electronic throttles. Specifically, a recursive discrete-time fast terminal sliding surface is adopted, which can ensure that [...] Read more.

To achieve precise tracking control under the hardware of electronic throttle digital control, this paper proposes a novel implicit discrete-time fast terminal sliding mode control method for electronic throttles. Specifically, a recursive discrete-time fast terminal sliding surface is adopted, which can ensure that the system error converges to a smaller error bandwidth. To further eliminate the chattering problem in actual systems, a new generalized implicit discrete reaching law is designed. Compared with the traditional explicit Euler reaching law, the proposed implicit reaching law can effectively suppress the chattering caused by discretization through backward discretization (implicit discretization). Meanwhile, compared with existing implicit discrete reaching laws, the proposed reaching law has an explicit recursive equation, avoiding the problems of high computational complexity and difficult engineering implementation. Subsequently, strict theoretical analysis proves the existence of the quasi-sliding mode (QSM) and the convergence of the system tracking error. Moreover, experimental results demonstrate that the proposed controller achieves faster transient response, smaller steady-state tracking error, and significantly reduced chattering compared with DFSM, DSTWISTING, and DLSMC, highlighting its clear performance advantages over existing sliding mode methods. Full article

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19 pages, 21965 KB

Open AccessArticle

A Hybrid Strategy for the Design and Optimization of Coaxial Magnetic Gears

by Xinyan Zhang, Renato Galluzzi and Nicola Amati

Machines 2025, 13(12), 1152; https://doi.org/10.3390/machines13121152 - 18 Dec 2025

Abstract

Magnetic gear transmissions are promising alternatives to mechanical ones due to their contactless power transfer, reduced acoustic noise and vibration, inherent overload protection, and improved reliability. However, their design requires fast but accurate tools. While three-dimensional finite-element models offer good accuracy, their complexity [...] Read more.

Magnetic gear transmissions are promising alternatives to mechanical ones due to their contactless power transfer, reduced acoustic noise and vibration, inherent overload protection, and improved reliability. However, their design requires fast but accurate tools. While three-dimensional finite-element models offer good accuracy, their complexity hinders their use for design purposes. Two-dimensional representations, on the other hand, tend to overestimate performance due to the lack of end effects in the axial direction. This paper proposes a hybrid design and optimization framework for coaxial magnetic gears that couples a two-dimensional optimizer based on a genetic algorithm with a three-dimensional parametric model. The former model helps identify promising combinations in the design variable space. Then, specific selections are refined through the three-dimensional model. Numerical results show that both approaches exhibit consistent parameter trends, with a resulting prototype yielding a torque density of 213 Nm/L in an envelope contained within 90 mm of diameter and 16.57 mm of active length. Full article

(This article belongs to the Section Electrical Machines and Drives)

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21 pages, 2476 KB

Open AccessArticle

Energy-Model-Based Global Path Planning for Pure Electric Commercial Vehicles Toward 3D Environments

by Kexue Lai, Dongye Sun, Binhao Xu, Feiya Li, Yunfei Liu, Guangliang Liao and Junhang Jian

Machines 2025, 13(12), 1151; https://doi.org/10.3390/machines13121151 - 17 Dec 2025

Abstract

Traditional path planning methods primarily optimize distance or time, without fully considering the impact of slope gradients in park road networks, variations in vehicle load capacity, and braking energy recovery characteristics on the energy consumption of pure electric commercial vehicles. To address these [...] Read more.

Traditional path planning methods primarily optimize distance or time, without fully considering the impact of slope gradients in park road networks, variations in vehicle load capacity, and braking energy recovery characteristics on the energy consumption of pure electric commercial vehicles. To address these issues, this paper proposes a globally optimized path planning method based on energy consumption minimization. The proposed method introduces a multi-factor coupled energy consumption model for pure electric commercial vehicles, integrating slope gradients, load capacity, motor efficiency, and energy recovery. Using this vehicle energy consumption model and the park road network topology map, an energy consumption topology map representing energy consumption between any two nodes is constructed. An energy-optimized improved ant colony optimization algorithm (E-IACO) is proposed. By introducing an exponential energy consumption heuristic factor and an enhanced pheromone update mechanism, it prioritizes energy-saving path exploration, thereby effectively identifying the optimal energy consumption path within the constructed energy consumption topology map. Simulation results demonstrate that in typical three-dimensional industrial park scenarios, the proposed energy-optimized path planning method achieves maximum reductions of 10.57% and 4.90% compared to the A* algorithm and ant colony optimization (ACO), respectively, with average reductions of 5.14% and 1.97%. It exhibits excellent stability and effectiveness across varying load capacities. This research provides a reliable theoretical framework and technical support for reducing logistics operational costs in industrial parks and enhancing the economic efficiency of pure electric commercial vehicles. Full article

(This article belongs to the Section Vehicle Engineering)

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18 pages, 3770 KB

Open AccessArticle

Fractional-Order Nonlinear PI Control for Tracking Wind Direction in Large Wind Energy Converters

by Adrian Gambier

Machines 2025, 13(12), 1150; https://doi.org/10.3390/machines13121150 - 17 Dec 2025

Abstract

In this work, the yaw control of large wind turbines is studied. The objective is to analyse how to maximise energy conversion by yawing the rotor in response to wind direction while minimising yaw activity. In order to improve the control performance, three [...] Read more.

In this work, the yaw control of large wind turbines is studied. The objective is to analyse how to maximise energy conversion by yawing the rotor in response to wind direction while minimising yaw activity. In order to improve the control performance, three algorithms are used and compared: the classic PI controller, the nonlinear PI controller, and the fractional-order nonlinear PI controller. An adaptive dead-zone and anti-windup procedure for amplitude- and rate-limited actuators are also considered, which helps to reach the main objective. Simulation experiments are carried out on a 20 MW reference wind turbine. The results are very promising, showing clear performance improvements. Full article

(This article belongs to the Section Automation and Control Systems)

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23 pages, 7009 KB

Open AccessArticle

Design and Anti-Impact Performance Study of a Parallel Vector Thruster

by Liangxiong Dong and Jubao Li

Machines 2025, 13(12), 1149; https://doi.org/10.3390/machines13121149 - 17 Dec 2025

Abstract

With the rapid development of unmanned surface vessels (USVs), a vector thruster was designed in this paper to meet their evolving operational demands. The anti-impact capability of the vector thruster, in which the universal joint plays a critical role in attenuating impact loads, [...] Read more.

With the rapid development of unmanned surface vessels (USVs), a vector thruster was designed in this paper to meet their evolving operational demands. The anti-impact capability of the vector thruster, in which the universal joint plays a critical role in attenuating impact loads, directly governs the stability and security of power transmission in USVs. A mechanical model of the vector thruster with a universal joint was established, incorporating length and stiffness ratio coefficients to characterize its key dynamics. Based on this model, numerical simulation using the Newmark method was conducted to systematically evaluate the thruster’s mechanical characteristics, particularly the dynamic variation of the inclination angle, under various working conditions and impact loads. The results indicate that an increase in stiffness ratio amplifies the angular displacement amplitude of the driven shaft but shortens the vibration stabilization time. During the operation of the vector thruster, an increase in the inclination angle leads to greater vibration amplitude. Furthermore, systems with a higher, longer ratio exhibit a more pronounced tendency for amplitude growth as the inclination angle increases. Finally, the theoretical model was validated through a test bench, and the variation pattern of dynamic thrust under impact load was revealed. These results emphasize that the stiffness and dimensional parameters must be carefully considered in the design and control optimization of vector thrusters to ensure reliable performance under demanding operational conditions. Full article

(This article belongs to the Section Machine Design and Theory)

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67 pages, 4380 KB

Open AccessArticle

Adaptive Multi-Objective Reinforcement Learning for Real-Time Manufacturing Robot Control

by Claudio Urrea

Machines 2025, 13(12), 1148; https://doi.org/10.3390/machines13121148 - 17 Dec 2025

Abstract

Modern manufacturing robots must dynamically balance multiple conflicting objectives amid rapidly evolving production demands. Traditional control approaches lack the adaptability required for real-time decision-making in Industry 4.0 environments. This study presents an adaptive multi-objective reinforcement learning (MORL) framework integrating dynamic preference weighting with [...] Read more.

Modern manufacturing robots must dynamically balance multiple conflicting objectives amid rapidly evolving production demands. Traditional control approaches lack the adaptability required for real-time decision-making in Industry 4.0 environments. This study presents an adaptive multi-objective reinforcement learning (MORL) framework integrating dynamic preference weighting with Pareto-optimal policy discovery for real-time adaptation without manual reconfiguration. Experimental validation employed a UR5 manipulator with RG2 gripper performing quality-aware object sorting in CoppeliaSim with realistic physics (friction μ = 0.4, Bullet engine), manipulating 12 objects across four geometric types on a dynamic conveyor. Thirty independent runs per algorithm (seven baselines, 30,000+ manipulation cycles) demonstrated +24.59% to +34.75% improvements (p < 0.001, d = 0.89–1.52), achieving hypervolume 0.076 ± 0.015 (19.7% coefficient of variation—lowest among all methods) and 95% optimal performance within 180 episodes—five times faster than evolutionary baselines. Four independent verification methods (WFG, PyMOO, Monte Carlo, HSO) confirmed measurement reliability (<0.26% variance). The framework maintains edge computing compatibility (<2 GB RAM, <50 ms latency) and seamless integration with Manufacturing Execution Systems and digital twins. This research establishes new benchmarks for adaptive robotic control in sustainable Industry 4.0/5.0 manufacturing. Full article

(This article belongs to the Section Advanced Manufacturing)

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16 pages, 11763 KB

Open AccessArticle

Prescribed Performance Trajectory Tracking Control for Electro-Hydraulic Servo Pump-Controlled Systems with Input and State Delays

by Gengting Qiu, Yujie Hao, Gexin Chen, Guishan Yan and Yao Chen

Machines 2025, 13(12), 1147; https://doi.org/10.3390/machines13121147 - 17 Dec 2025

Abstract

Electro-hydraulic servo pump-controlled systems have advantages such as energy saving and high integration and are widely applied in aerospace, engineering machinery, and other fields. However, the input and state delays introduced by drive circuit, control period, and oil leakage result in lower dynamic [...] Read more.

Electro-hydraulic servo pump-controlled systems have advantages such as energy saving and high integration and are widely applied in aerospace, engineering machinery, and other fields. However, the input and state delays introduced by drive circuit, control period, and oil leakage result in lower dynamic response speed compared to traditional valve control systems, which restricts the promotion of the system. In this paper, a prescribed performance trajectory tracking control method is proposed to improve the transient and steady-state performance of the system. A performance function is designed to constrain the range of trajectory tracking errors. The constrained space is mapped to an unconstrained space via a homeomorphic transformation, and the control laws are designed by integrating it with the backstepping method. In the final step of the backstepping design, the input and state delays are processed using Lyapunov–Krasovskii functionals. The simulation and experimental results show that under the condition of fixed input delay and state delay, the trajectory tracking errors converge within the preset range, and all states of the system are uniformly bounded. The results demonstrate the effectiveness of the proposed method in this paper. Full article

(This article belongs to the Special Issue Advances in the Control of Electro-Hydraulic Servo Systems)

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22 pages, 1721 KB

Open AccessArticle

ADP-Based Event-Triggered Optimal Control of Grid-Connected Voltage Source Inverters

by Zemeng Mi, Jiawei Wang, Hanguang Su, Dongyuan Zhang, Wencheng Yan and Yuanyuan Bai

Machines 2025, 13(12), 1146; https://doi.org/10.3390/machines13121146 - 17 Dec 2025

Abstract

In this paper, an event-triggered optimal control strategy is proposed for three-phase grid-connected voltage source inverters (VSIs) based on the voltage-modulated direct power control (VM-DPC) principle. The optimization control problem of VSIs is addressed in the framework of nonzero sum (NZS) games to [...] Read more.

In this paper, an event-triggered optimal control strategy is proposed for three-phase grid-connected voltage source inverters (VSIs) based on the voltage-modulated direct power control (VM-DPC) principle. The optimization control problem of VSIs is addressed in the framework of nonzero sum (NZS) games to ensure mutual cooperation between active power and reactive power. To achieve optimal performance, the power components are driven to track their desired references while minimizing the individual performance index function. Accurate tracking of active and reactive powers not only stabilizes the grid but also guarantees compliant renewable integration. An adaptive dynamic programming (ADP) approach is adopted, where the critic neural network (NN) approximates the value function and provides optimal control policies. Moreover, an event-triggered mechanism with a dead-zone operation is incorporated to reduce redundant updates, thereby saving computational and communication resources. The stability of the closed-loop system and a strictly positive minimum inter-event interval are guaranteed. Simulation results verify that the proposed method achieves accurate power tracking, improved dynamic performance, and efficient implementation. Full article

(This article belongs to the Special Issue Advances in Condition Monitoring of Distributed Energy Equipment and Systems)

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23 pages, 14105 KB

Open AccessArticle

A Comprehensive Study on Meshing Performances Compensation for Face-Hobbed Hypoid Gears: Coupled Analysis of Spatial Installation Errors and Manufactured Tooth Flank Characteristics

by Chengcheng Liang, Yihao Zhang, Longhua Liu, Chaosheng Song and Siyuan Liu

Machines 2025, 13(12), 1145; https://doi.org/10.3390/machines13121145 - 16 Dec 2025

Abstract

In manufacturing face-hobbing hypoid gears, the coupling between tooth flank errors and installation errors has a significant impact on dynamic meshing behavior, yet quantitative models for their synergistic effects remain scarce. This study elucidates the combined effects of three-dimensional (3D) installation errors and [...] Read more.

In manufacturing face-hobbing hypoid gears, the coupling between tooth flank errors and installation errors has a significant impact on dynamic meshing behavior, yet quantitative models for their synergistic effects remain scarce. This study elucidates the combined effects of three-dimensional (3D) installation errors and real tooth flank deviations on transmission error. First, a geometric model of the real tooth flank, incorporating midpoint pitch deviation, is established based on theoretical flank equations and coordinate transformations. Then, a finite element model integrating 3D installation errors is developed. Finally, the combined effects of installation errors and real tooth flanks on meshing performance are analyzed. Results reveal a dual role of installation errors: when compensating for midpoint pitch deviation, the peak-to-peak transmission error (PPTE) decreases by 3.78%, while the contact pattern length and area increase. Under certain conditions, despite a 26.28% increase in PPTE, the contact pattern length grows by 2.29%, accompanied by a notable reduction in maximum contact stress on the tooth flanks. Full article

(This article belongs to the Section Advanced Manufacturing)

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