Machines

19 pages, 3467 KB

Open AccessArticle

Lubrication Mechanism and Establishment of a Three-Phase Lubrication Model for SCCO₂-MQL Ultrasonic Vibration Milling of SiCp/Al Composites

by Bowen Wang and Huiping Zhang

Machines 2025, 13(9), 879; https://doi.org/10.3390/machines13090879 - 22 Sep 2025

Abstract

SiCp/Al composites (Silicon Carbide Particle-Reinforced Aluminum Matrix Composites), due to their light weight, high strength, and superior wear resistance, are extensively utilized in aerospace and other sectors; nonetheless, they are susceptible to tool wear and surface imperfections during machining, which negatively impact overall [...] Read more.

SiCp/Al composites (Silicon Carbide Particle-Reinforced Aluminum Matrix Composites), due to their light weight, high strength, and superior wear resistance, are extensively utilized in aerospace and other sectors; nonetheless, they are susceptible to tool wear and surface imperfections during machining, which negatively impact overall machining performance. Supercritical carbon dioxide minimal quantity lubrication (SCCO₂-MQL) is an environmentally friendly and efficient lubrication method that significantly improves interfacial lubricity and thermal stability. Nonetheless, current lubrication models are predominantly constrained to gas–liquid two-phase scenarios, hindering the characterization of the three-phase lubrication mechanism influenced by the combined impacts of SCCO₂ phase transition and ultrasonic vibration. This study formulates a lubricant film thickness model that incorporates droplet atomization, capillary permeation, shear spreading, and three-phase modulation while introducing a pseudophase enhancement factor β_ps(p,T) to characterize the phase fluctuation effect of CO₂ in the critical region. Simulation analysis indicates that, with an ultrasonic vibration factor Af = 1200 μm·kHz, a lubricant flow rate Q_f = 16 mL/h, and a pressure gradient Δp_tot = 6.0 × 10⁵ Pa/m, the lubricant film thickness attains its optimal value, with Δp_tot having the most pronounced effect on the film thickness (normalized sensitivity S = 0.488). The model results align with the experimental trends, validating its accuracy and further elucidating the nonlinear regulation of the film-forming process by various parameters within the three-phase synergistic lubrication mechanism. This research offers theoretical backing for the enhancement of performance and the expansion of modeling in SCCO₂-MQL lubrication systems. Full article

(This article belongs to the Special Issue Machine Tools for Precision Machining: Design, Control and Prospects)

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19 pages, 6922 KB

Open AccessArticle

Mechanical Insertion Force and Electrical Contact Resistance of By-Pass Switches with Axially Canted Coil Springs

by Chao Zhang, Ming Li, Wanbin Ren and Jian Liu

Machines 2025, 13(9), 878; https://doi.org/10.3390/machines13090878 - 21 Sep 2025

Viewed by 73

Abstract

By-pass switches play a crucial role in high-power electrical equipment, where reliable mechanical insertion and stable electrical contact are essential for safety and performance. However, few computational models have been developed to characterize the coupled mechanical–electrical behavior of by-pass switches with axially canted [...] Read more.

By-pass switches play a crucial role in high-power electrical equipment, where reliable mechanical insertion and stable electrical contact are essential for safety and performance. However, few computational models have been developed to characterize the coupled mechanical–electrical behavior of by-pass switches with axially canted coil springs, which limits the understanding of their structural parameter effects. Motivated by this gap, this work investigates the mechanical insertion force and electrical contact resistance of by-pass switches with axially canted coil spring by combining analytical modeling and finite element simulation. The variations in mechanical insertion force, contact force and associated contact resistance as functions of the insertion displacement are presented. The total electrical contact resistance could comprise three components of resistance, that is, constriction resistance between multiple turns of coil spring wires and pin, constriction resistance between multiple turns of coil spring wires and V-shape groove, and the bulk resistance. The effects of structure feature parameters (including turns, spring wire diameter, inclination angle of axially canted coil spring wire, cylindrical pin chamfer radius and V-shape groove angle) are evaluated. Subsequently, the associated empirical formulas are established to guide the design of by-pass switches with axially canted coil springs. Full article

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

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23 pages, 6256 KB

Open AccessArticle

Study on Corrugated Tube Structure Within the Tempcore Process Based on Large Steel Bar Cooling Efficiency

by Youhua Li, Kun Li, Qinglong Wang, Guangzhou Wang, Qing Hu, Guoqing Zhang, Wenbo Wang and Hechun Yu

Machines 2025, 13(9), 877; https://doi.org/10.3390/machines13090877 - 20 Sep 2025

Viewed by 111

Abstract

As a key component of the Tempcore process, the Tempcore cooler plays a critical role in enhancing the cooling efficiency of steel bars. A cylindrical corrugated tube designed specifically for the Tempcore cooling process of large diameter steel bars, where the corrugated surface [...] Read more.

As a key component of the Tempcore process, the Tempcore cooler plays a critical role in enhancing the cooling efficiency of steel bars. A cylindrical corrugated tube designed specifically for the Tempcore cooling process of large diameter steel bars, where the corrugated surface induces turbulence to enhance cooling efficiency. The influence of its structural parameters on the cooling performance was investigated through a combination of numerical simulations and experimental validation. First, based on the law of mass conservation, the influence of structural parameters of the corrugated tube on their internal flow field was analyzed. Then, a simulation model of the Tempcore cooler was developed to explore the variation in steel bar cooling efficiency under different structural parameters. The results show that increasing the maximum inner diameter of the corrugated tube enhances cooling efficiency, which subsequently tends to stabilize. With increasing minimum inner diameter and pitch, the cooling efficiency of the bars first increases and then decreases. And based on the influence of individual parameters, an orthogonal simulation was performed to identify the optimal corrugated tube structural configuration for achieving maximum cooling efficiency. The minimum inner diameter was identified as a critical factor influencing the heat transfer efficiency of the steel bar. Finally, based on the results of orthogonal simulations, five corrugated tubes were fabricated and integrated into the Tempcore cooler for experimental validation. The accuracy of the simulation was verified through microstructural analysis of the produced steel bars, which exhibited a 38% increase in martensite volume fraction. The designed corrugated tubes significantly improve the cooling efficiency of the Tempcore process without requiring an upgrade to the water supply system capacity. Full article

(This article belongs to the Topic Micro-Mechatronic Engineering, 2nd Edition)

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24 pages, 5275 KB

Open AccessArticle

Enhancing Human–Machine Collaboration: A Trust-Aware Trajectory Planning Framework for Assistive Aerial Teleoperation

by Qianzheng Zhuang, Kangjie Huang, Xiaoran Jin, Pengfei Li, Yunbo Zhao and Yu Kang

Machines 2025, 13(9), 876; https://doi.org/10.3390/machines13090876 - 20 Sep 2025

Viewed by 111

Abstract

Human–machine collaboration in assistive aerial teleoperation is frequently compromised by trust imbalances, which arise from the vehicle’s complex dynamics and the operator’s constrained perceptual feedback. We introduce a novel framework that enhances collaboration by dynamically integrating a model of human trust into the [...] Read more.

Human–machine collaboration in assistive aerial teleoperation is frequently compromised by trust imbalances, which arise from the vehicle’s complex dynamics and the operator’s constrained perceptual feedback. We introduce a novel framework that enhances collaboration by dynamically integrating a model of human trust into the unmanned aerial vehicle’s trajectory planning. We first propose a Machine-Performance-Dependent trust model, specifically tailored for aerial teleoperation, that quantifies trust based on real-time safety and visibility metrics. This model then informs a trust-aware trajectory planning algorithm, which generates smooth and adaptive trajectories that continuously align with the operator’s trust level and intent inferred from control inputs. Extensive simulations conducted in diverse forest environments validate our approach. The results demonstrate that our method achieves task efficiency comparable to that of a trust-unaware baseline while significantly reducing operator workload and improving trajectory smoothness, achieving reductions of up to 23.2% and 43.2%, respectively, in challenging dense environments. By embedding trust dynamics directly into the trajectory optimization loop, this work pioneers a more intuitive, efficient, and resilient paradigm for assistive aerial teleoperation. Full article

(This article belongs to the Special Issue Advances in AI-Powered Human-Machine-Augmented Intelligence)

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15 pages, 5285 KB

Open AccessArticle

A Multi-Layer Triboelectric Material Deep Groove Ball Bearing Triboelectric Nanogenerator: Speed and Skidding Monitoring

by Zibao Zhou, Long Wang, Zihao Wang and Fengtao Wang

Machines 2025, 13(9), 875; https://doi.org/10.3390/machines13090875 - 19 Sep 2025

Viewed by 189

Abstract

With the ongoing advancement of triboelectric nanogenerator (TENG) technology, a novel internal integrated monitoring sensor has been introduced for traditional industrial equipment. A multilayer triboelectric material deep groove ball triboelectric nanogenerator (DGTG) device has been proposed to monitor the rotational speed and slip [...] Read more.

With the ongoing advancement of triboelectric nanogenerator (TENG) technology, a novel internal integrated monitoring sensor has been introduced for traditional industrial equipment. A multilayer triboelectric material deep groove ball triboelectric nanogenerator (DGTG) device has been proposed to monitor the rotational speed and slip state of the rolling elements. The DGTG utilizes a copper inner ring charge supplementation mechanism to maintain the maximum charge density on the rolling element, thereby ensuring a strong electrical signal output. The deviation between the output frequency of the electrical signal and the theoretical value allows for effective monitoring of the slip state during bearing operation. Experimental results demonstrate that when the inner ring speed ranges from 100 to 2000 rpm, the open-circuit voltage generally remains above 30 V. The short-circuit current signal exhibits a fitting coefficient of R² = 0.99997 with respect to the roller’s rotational speed frequency and motor speed, while the open-circuit voltage signal shows a fitting coefficient of R² = 0.99984, indicating a strong linear relationship and a good response to varying speeds. Compared to the traditional photoelectric sensors commonly used in industry, the measurement difference between the three signals is consistently less than 5.5%, and real-time monitoring of the slip rate is possible when compared to the theoretical value. The DGTG developed in this study occupies minimal space, offers high reliability, and fully leverages the bearing structure, enabling real-time monitoring of bearing speed and slip. Full article

(This article belongs to the Special Issue Vibration Energy Harvesting and Intelligent Monitoring for Rotating Machinery)

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16 pages, 3271 KB

Open AccessArticle

Study on the Influence of Different Dropper Models in Pantograph–Catenary System on Dropper Load Simulation

by Like Pan, Liming Chen, Yan Xu, Bo Dong, Xiaoli Guo and Weidong Zhu

Machines 2025, 13(9), 874; https://doi.org/10.3390/machines13090874 - 19 Sep 2025

Viewed by 184

Abstract

The dropper load directly influences the fatigue mechanism of the high-speed catenary system. A proper dropper model for a pantograph–catenary system can be used to accurately and efficiently investigate this phenomenon. In this work, the influence of different dropper models in pantograph–catenary systems [...] Read more.

The dropper load directly influences the fatigue mechanism of the high-speed catenary system. A proper dropper model for a pantograph–catenary system can be used to accurately and efficiently investigate this phenomenon. In this work, the influence of different dropper models in pantograph–catenary systems on dropper load simulations is investigated. Based on the Euler beam element, a finite element model-based pantograph–catenary system is formulated, and beam, rod, and spring dropper models are considered in this model. After the validation of the present model, the influence of different dropper models on dropper loads and pantograph–catenary interaction dynamics is studied. The calculation efficiency of different dropper models is also analyzed. Based on the investigation results, different dropper models can accurately simulate the pantograph–catenary interaction dynamics, but the spring model is not as accurate as the beam and rod models for dropper loads, and the calculation time of the beam model is much longer than that of other models. Therefore, the use of a rod dropper model in a pantograph–catenary system is suggested for dropper dynamic analysis. Full article

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

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25 pages, 9602 KB

Open AccessArticle

Magnetic Circuit Analysis and Design Optimized for Cost-Effectiveness of Surface-Inserted Rare Earth Consequent-Pole Permanent Magnet Machines

by Li Wang, Muhammad Saqlain Saeed, Zhaoyang Fu, Jinglin Liu, Xiqiao Wu and Qi Wang

Machines 2025, 13(9), 873; https://doi.org/10.3390/machines13090873 - 19 Sep 2025

Viewed by 239

Abstract

In consequent-pole permanent magnet (CPPM) machines, the configuration where PM poles and iron poles are alternately arranged causes distortion in the air-gap magnetic field. This results in significant differences in magnetic circuit characteristics compared to conventional PM machines. To address the requirements of [...] Read more.

In consequent-pole permanent magnet (CPPM) machines, the configuration where PM poles and iron poles are alternately arranged causes distortion in the air-gap magnetic field. This results in significant differences in magnetic circuit characteristics compared to conventional PM machines. To address the requirements of reducing torque ripple and enhancing average output torque, the cogging torque and optimization methods for CPPM machines were investigated. A general analytical model for cogging torque was established. This model accounts for asymmetric pole configurations and is particularly well-suited for analyzing CPPM machines. The mechanism through which the consequent-pole (CP) structure improves the utilization rate of PM material was explored, and the parameters influencing the main flux were analyzed. By replacing PMs with soft magnetic materials, the conventional topology of a 12-slot/8-pole surface-inserted PM machine with stator skewing was directly converted into a CP topology. Performance optimization was conducted based on this original scheme. This approach ensures manufacturing convenience while maximizing the sharing of identical components. Simulation results demonstrate that, compared to the benchmark machine, the optimized CPPM machine uses only 60.16% of the PM material while producing 88.19% of the electromagnetic torque, resulting in a 46.61% increase in torque generated per unit volume of PM material. Finally, the benchmark and optimized CPPM prototypes were fabricated, and their torque output capabilities were tested. The finite element simulation results and the measured data show good consistency, validating the correctness of the theoretical analysis and the effectiveness of the finite element model. This study provides a theoretical basis and engineering reference for the performance analysis and optimal design of CPPM machines. Full article

(This article belongs to the Special Issue Wound Field and Less Rare-Earth Electrical Machines in Renewables)

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18 pages, 4465 KB

Open AccessArticle

Control Strategy of PMSM for Variable Pitch Based on Improved Whale Optimization Algorithm

by Zhiqiang Sun, Mingxing Tian and Xiaoqing Li

Machines 2025, 13(9), 872; https://doi.org/10.3390/machines13090872 - 19 Sep 2025

Viewed by 164

Abstract

A PI control approach grounded in an optimized improved whale algorithm is devised to tackle the characteristics of multivariable, nonlinear, strong coupling, and uncertain and fluctuating wind speeds in electric variable pitch systems. In the improved whale algorithm optimization algorithm, the reverse learning [...] Read more.

A PI control approach grounded in an optimized improved whale algorithm is devised to tackle the characteristics of multivariable, nonlinear, strong coupling, and uncertain and fluctuating wind speeds in electric variable pitch systems. In the improved whale algorithm optimization algorithm, the reverse learning mechanism is utilized within the population initialization stage, the nonlinear inertial weight coefficient is introduced in the global and local search processes of whale predation, and the convergence factor is updated by the exponential function, which effectively addresses the issue of sluggish convergence speed and low convergence efficiency of the whale optimization algorithm. The position control of the electric variable pitch system is implemented with the application of the improved whale optimization algorithm. According to the performance index of the position ring, the appropriate objective function is established, and the adaptive control of the position ring is realized through the adaptive adjustment of PI parameters. The simulation outcomes demonstrate that the PI control, which is founded on an improved whale optimization algorithm, is superior to the PI control based on the whale optimization algorithm in dynamic and steady performance. When the load torque changes, using PI control based on the improved whale optimization algorithm, the pitch angle reaches the steady-state value in 0.06 s without overshoot, while using PI control based on the whale optimization algorithm, the pitch angle reaches the steady-state value in 0.09 s with a maximum overshoot of 2.4°. When the load torque is constant, PI control based on the improved whale optimization algorithm can achieve pitch angle tracking in 0.16 s, while PI control based on the whale optimization algorithm can achieve pitch angle tracking in 0.48 s. Full article

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

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40 pages, 10028 KB

Open AccessArticle

Collaborative Optimization Control of Gravity Center and Pose of Hexapod Robot in Complex Terrains

by Chenjiang Yu, Diqing Fan and Xintian Liu

Machines 2025, 13(9), 871; https://doi.org/10.3390/machines13090871 - 18 Sep 2025

Viewed by 161

Abstract

The adaptability of a hexapod robot to complex terrain is highly dependent on its own posture, which directly affects its stability and flexibility. In order to adapt to a change in terrain, it is necessary to adjust posture in real time when walking. [...] Read more.

The adaptability of a hexapod robot to complex terrain is highly dependent on its own posture, which directly affects its stability and flexibility. In order to adapt to a change in terrain, it is necessary to adjust posture in real time when walking. At the same time, external factors such as ground state and landing impact will also interfere with posture. Therefore, it is necessary to maintain balance after adjustment. This paper proposes a pose adjustment method utilizing joint angle control. It enhances robot stability, flexibility, and terrain adaptability through torso posture and center of gravity optimization, aiming to maintain balance. The strategy’s effectiveness was validated via Adams–Simulink co-simulation. Optimal position and posture adjustment for the torso was then implemented at the six-legged support stage after each step, employing inverse kinematics and a triangular gait. It is found that without pose adjustment, the direction deviation will accumulate and significantly deviate from the trajectory. The introduction of this adjustment can effectively correct the direction deviation and torso posture angle, increase the stability margin, ensure stable straight-line walking, and significantly reduce joint energy consumption. Crawling experiments with the physical prototype further validate the strategy. It rapidly counters instantaneous attitude fluctuations during leg alternation, maintaining a high stability margin and improving locomotion efficiency. Consequently, the robot achieves enhanced directional stability, overall stability, and energy efficiency when traversing terrain. Full article

(This article belongs to the Topic New Trends in Robotics: Automation and Autonomous Systems)

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22 pages, 5813 KB

Open AccessArticle

A Method for Optimizing the Precision of a Five-Axis Machine Tool Based on Tolerance

by Hongxia Yan and Jinwei Fan

Machines 2025, 13(9), 870; https://doi.org/10.3390/machines13090870 - 18 Sep 2025

Viewed by 182

Abstract

The tolerance of critical components in five-axis machine tools directly impacts the overall machining accuracy of the entire system. This paper presents a tolerance optimization method for machine tools that is grounded in sensitivity theory and the NSGA-II algorithm. First, a mapping model [...] Read more.

The tolerance of critical components in five-axis machine tools directly impacts the overall machining accuracy of the entire system. This paper presents a tolerance optimization method for machine tools that is grounded in sensitivity theory and the NSGA-II algorithm. First, a mapping model is established to relate tolerance parameters to geometric and spatial motion errors. Second, a gradient-based sensitivity index, which has a clear physical interpretation and high computational efficiency, is defined to quantify the influence of individual tolerances on the spatial motion errors. Recognizing the limitations of existing tolerance allocation methods, this study introduces the innovative concept of tolerance control cost (the sum of the products of tolerance sensitivity and tolerance value for each parameter), and an optimization model is formulated to minimize this while ensuring the spatial motion error meets the requirement. The NSGA-II algorithm is employed to solve this model. Simulation results demonstrate that the tolerances of components can be significantly relaxed (thereby indirectly reducing manufacturing costs) while still ensuring the desired spatial motion error of the entire machine, validating the feasibility and effectiveness of the proposed method. Full article

(This article belongs to the Section Advanced Manufacturing)

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26 pages, 6597 KB

Open AccessArticle

Analysis of Flow Characteristics in a Hydrogen Circulation Pump Featuring a Variable Radius Circular Arc

by Jiankang Lu, Zhengdian Xu, Changdong Wan and Renrui Wang

Machines 2025, 13(9), 869; https://doi.org/10.3390/machines13090869 - 18 Sep 2025

Viewed by 186

Abstract

This study proposes a novel variable-radius arc rotor, developed based on the conventional arc rotor, for application in a hydrogen circulation pump. Numerical simulations are conducted to analyze and compare the flow characteristics of the optimized rotor with those of the baseline rotor. [...] Read more.

This study proposes a novel variable-radius arc rotor, developed based on the conventional arc rotor, for application in a hydrogen circulation pump. Numerical simulations are conducted to analyze and compare the flow characteristics of the optimized rotor with those of the baseline rotor. Results show that the optimized rotor increases outlet mass flow rates by over 15%; however, it has little effect on pressure pulsation, indicating limited influence on flow stability. Flow field analysis reveals that the optimized rotor promotes a more stable and streamlined internal velocity distribution, suppressing localized disturbances and vortices that are prevalent with the baseline rotor. Furthermore, assessments of turbulent kinetic energy (TKE) and three-dimensional vortex structures show that the optimized rotor confines high-energy zones to essential areas and facilitates controlled vortex evolution. These effects collectively lead to lower turbulence intensity, reduced energy loss, improved operational efficiency, and enhanced mechanical reliability of the pump. Full article

(This article belongs to the Special Issue Advanced Research and Development in Fluid Machinery: Design, Optimization, and Applications)

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19 pages, 20163 KB

Open AccessArticle

Voxel-Based Roadway Terrain Risk Modeling and Traversability Assessment in Underground Coal Mines

by Wanzi Yan, Zhencai Zhu, Yidong Zhang, Hao Lu, Minti Xue, Yu Tang and Shaobo Sun

Machines 2025, 13(9), 868; https://doi.org/10.3390/machines13090868 - 18 Sep 2025

Viewed by 192

Abstract

Effective roadway environment sensing is critical for intelligent underground vehicle navigation. Dust pollution and complex terrain in underground roadways present key challenges for quantifying passability risks: (1) Over-filtering of dust noise in lidar point clouds can inadvertently remove valuable information. (2) The enclosed [...] Read more.

Effective roadway environment sensing is critical for intelligent underground vehicle navigation. Dust pollution and complex terrain in underground roadways present key challenges for quantifying passability risks: (1) Over-filtering of dust noise in lidar point clouds can inadvertently remove valuable information. (2) The enclosed and chaotic nature of underground roadways prevents planar information from fully representing spatial constraints. To address these challenges, this paper proposes a method for constructing terrain risk voxels and assessing navigability in coal mine tunnels. First, an improved particle filter combined with image features performs two-stage dust filtering. Second, D-S theory is applied to fuse and evaluate three-dimensional tunnel risks, constructing 3D terrain risk voxels. Finally, navigable spaces are identified and their characteristics quantified to assess passage risks. Experiments show that the proposed dust filtering algorithm achieves 96.7% average accuracy in primary underground areas. The D-S theory effectively constructs roadway terrain risk voxels, enabling reliable quantitative assessment of roadway passability risks. Full article

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

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20 pages, 5577 KB

Open AccessArticle

Electromagnetic Vibration Analysis and Mitigation of FSCW PM Machines with Auxiliary Teeth

by Huang Zhang, Wei Wang, Xinmin Li and Zhiqiang Wang

Machines 2025, 13(9), 867; https://doi.org/10.3390/machines13090867 - 18 Sep 2025

Viewed by 141

Abstract

Auxiliary teeth are usually used in fractional-slot concentrated winding (FSCW) machines for fault tolerance. However, the influence of auxiliary teeth on torque and electromagnetic vibration performance differs with different slot–pole configurations. Thus, this paper investigates electromagnetic vibration and mitigation methods in FSCW permanent [...] Read more.

Auxiliary teeth are usually used in fractional-slot concentrated winding (FSCW) machines for fault tolerance. However, the influence of auxiliary teeth on torque and electromagnetic vibration performance differs with different slot–pole configurations. Thus, this paper investigates electromagnetic vibration and mitigation methods in FSCW permanent magnet (PM) machines with auxiliary teeth. The relationship between yoke forces and tooth parameters of two dual three-phase (DTP) FSCW-PM machines with 12-slot/14-pole configuration and 12-slot/10-pole configuration is studied and compared. Results reveal that (1) the 2p-order airgap electromagnetic force reduces second-order yoke force in the 12-slot/14-pole machine but increases it in the 12-slot/10-pole machine. (2) Through optimized tooth width, slot harmonics can be mitigated, but the fundamental winding magnetic field in the 12-slot/10-pole machine is also weakened, whereas the 12-slot/14-pole machine achieves fundamental field preservation or enhancement. Based on these findings, auxiliary tooth optimization and rotor pole profile shaping are proposed for vibration reduction in 12-slot/14-pole machine. Electromagnetic–mechanical coupled simulations conducted in ANSYS Maxwell/Workbench 2023 demonstrate that the optimized design reduces the cogging torque peak from 11.4 mN·m to 2.9 mN·m (74.6% reduction), suppresses housing surface vibration acceleration by 21%, and maintains the average output torque without reduction. Full article

(This article belongs to the Special Issue Advances in Analysis, Control and Design of Permanent Magnet Machines)

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22 pages, 9427 KB

Open AccessArticle

Development of a Hydraulic Conical Valve for the Linearization of Flow

by Suyambu Pandian Asok, Balasubramanian Vijayaragavan, Thirumalachari Sundararajan and Gurunathan Rajaguru Manikandan

Machines 2025, 13(9), 866; https://doi.org/10.3390/machines13090866 - 18 Sep 2025

Viewed by 217

Abstract

Conventional throttling valves have non-linear flow characteristics. However, in precise processes of flow control requiring them, appropriate flow modulations are necessary to enable a linear flow response even under partial valve actuations. This paper formulates a hydraulic conical valve configuration that exhibits linear [...] Read more.

Conventional throttling valves have non-linear flow characteristics. However, in precise processes of flow control requiring them, appropriate flow modulations are necessary to enable a linear flow response even under partial valve actuations. This paper formulates a hydraulic conical valve configuration that exhibits linear flow. Flow studies were conducted on a 24 mm orifice-sized Conventional Conical Valve (CCV) using Computational Fluid Dynamics (CFD) analysis with commercial code ANSYS Fluent 2022 R1 and through experiments. The mass flow curve for the CCV had a convex upward shape, implying that at all valve openings, its discharges lay above the linear discharge line. To create greater resistance to flow, a venturi was incorporated into the valve casing close to the downstream side of the valve seat, leading to a Venturi Conical Valve (VCV). CFD analysis revealed that the addition of the venturi added more flow resistance, while the identified optimal VCV was still unable to make the flow linear. Subsequently, labyrinth cavities were machined on the conical valve body of the VCV, changing it into a Labyrinth Venturi Conical Valve (LVCV). Experiments revealed that the discharge curve for the identified LVCV was nearly linear. The maximum linearity deviation of 45.76% found in the CCV decreased to 9.95% in the LVCV. The reduction in linearity deviation indicates an improved closeness of the valve discharge to the linear conditions. Full article

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

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32 pages, 28470 KB

Open AccessArticle

A Bearing Fault Detection Method Based on EMDWS-CNT-BO

by Dayou Cui, Zhaoyan Xie, Zhixue Wang, Xiaowei Li and Sihao Wu

Machines 2025, 13(9), 865; https://doi.org/10.3390/machines13090865 - 17 Sep 2025

Viewed by 231

Abstract

Accurate diagnosis of bearing faults is crucial for ensuring the safe and reliable operation of rotating machinery. To enhance the recognition accuracy of rolling bearings under nonlinear and non-stationary vibration conditions, this study proposes an integrated approach combining a multi-stage signal preprocessing strategy, [...] Read more.

Accurate diagnosis of bearing faults is crucial for ensuring the safe and reliable operation of rotating machinery. To enhance the recognition accuracy of rolling bearings under nonlinear and non-stationary vibration conditions, this study proposes an integrated approach combining a multi-stage signal preprocessing strategy, termed EMDWS (Empirical Mode Decomposition with Wavelet denoising and SMOTE), with a hybrid deep learning architecture that integrates a Convolutional Neural Network (CNN) and a Transformer model, hereinafter referred to as CNT (CNN-Transformer). The method first applies empirical mode decomposition (EMD) in conjunction with wavelet denoising to enhance the representation of non-stationary fault features. Subsequently, the synthetic minority oversampling technique (SMOTE) is employed to address the issue of class imbalance in the dataset. A hybrid CNN-Transformer model is constructed by integrating convolutional neural networks and Transformer modules, enabling the extraction of both local and global signal characteristics. Furthermore, Bayesian optimization is applied to fine-tune the model’s hyperparameters, thereby enhancing both the efficiency and robustness of the model. Experimental results demonstrate that the proposed method achieves a high identification accuracy of 99.83%, indicating its effectiveness in distinguishing various bearing fault types. Full article

(This article belongs to the Section Machines Testing and Maintenance)

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21 pages, 9815 KB

Open AccessArticle

Influence of Previous Turning on the Surface Integrity Stability of Diamond-Burnished Medium-Carbon Steel

by Jordan Maximov, Galya Duncheva, Kalin Anastasov, Mariana Ichkova and Petya Daskalova

Machines 2025, 13(9), 864; https://doi.org/10.3390/machines13090864 - 17 Sep 2025

Viewed by 176

Abstract

There is a lack of information in the literature on the influence of technological heredity on surface integrity characteristics after diamond burnishing (DB). The present study fills this gap. Here, we present the effects of DB on the roughness parameters and surface microhardness [...] Read more.

There is a lack of information in the literature on the influence of technological heredity on surface integrity characteristics after diamond burnishing (DB). The present study fills this gap. Here, we present the effects of DB on the roughness parameters and surface microhardness of heat-treated C45 steel under conditions of changing initial roughness (Ra^init) due to wear on the cutting insert in the previous turning. The aim was to quantitatively assess the ability of DB to maintain sustainable surface integrity characteristics. We found that the service life of the cutting insert up to complete wear or fracture when operating at an optimal feed rate and cutting velocity was 163 min, at which point the roughness changed unevenly from an average roughness (Ra) value of 0.38 to 1.31 μm and an average height of the profile microroughness (Rz) value of 2.21 to 6.13 μm. Under conditions of an artificially created Ra^init (through different combinations of feed rate and cutting velocity) of 0.308 to 10.688 μm, DB provided Ra values in the range of 0.042 to 0.316 μm, with the surface microhardness varying from 461 to 568 HV. Stable Ra values were maintained from 0.042 μm to 0.089 μm, after which the Ra^init increased to 3.379 μm. Under production conditions, where the previous turning was performed at an optimal feed rate of 0.05 mm/rev and a cutting velocity of 180 m/min, DB provided a stable Ra of ≤0.059 μm of a resulting mirror-like surface during the first 90 min of operation of a new (unused) cutting insert, after which the Ra values increased linearly from 0.059 to 0.133 μm in the 150th minute. After 30 min of operation, until the cutting insert was completely worn, the microhardness after DB varied from 676 to 795 HV, the high surface microhardness resulting from a complex process of surface thermo-mechanical strengthening (including strain and transformation hardening) in the previous turning due to wear on the cutting insert. Full article

(This article belongs to the Section Advanced Manufacturing)

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26 pages, 7959 KB

Open AccessArticle

Effect of Boundary Conditions on Vibration Characteristics of a Sandwich Plate with Viscoelastic Periodic Cores

by Zhiwei Guo, Meiping Sheng and Kai Zhang

Machines 2025, 13(9), 863; https://doi.org/10.3390/machines13090863 - 17 Sep 2025

Viewed by 153

Abstract

The effects of boundary conditions on the vibration characteristics of a sandwich plate with viscoelastic periodic cores were examined. The tangential, vertical, transverse, and torsional springs were utilized to restrict the sandwich plate’s edge in order to model a general boundary condition, bringing [...] Read more.

The effects of boundary conditions on the vibration characteristics of a sandwich plate with viscoelastic periodic cores were examined. The tangential, vertical, transverse, and torsional springs were utilized to restrict the sandwich plate’s edge in order to model a general boundary condition, bringing the benefit that the conventional free, clamped, and simply supported boundary conditions became special cases in the proposed model as these spring constants took extreme values. A theoretical model was established to calculate the forced response and band structure of the periodic sandwich plate, providing computational support for evaluating its vibration characteristics. The correctness of the theoretical model was also validated by the finite element method. The results show that the boundary spring stiffness has a significant effect on the band-gap frequencies and band-gap width of the periodic sandwich plate. Increasing the boundary spring stiffness contributes to achieving broader band gaps. In addition, the band-gap frequencies and band-gap width are more sensitive to transverse spring stiffness than the tangential, vertical, and torsional spring stiffnesses. Therefore, changing transverse spring stiffness is more effective for adjusting the band gap property. This study may provide helpful guidance on vibration and noise reduction design in engineering. Full article

(This article belongs to the Special Issue Mastering Vibrations: The Latest Breakthroughs in Control for Mechanical Systems)

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19 pages, 2587 KB

Open AccessArticle

Remaining Secondary Voltage Mitigation in Multivector Model Predictive Control Schemes for Multiphase Electric Drives

by Juan Carrillo-Rios, Juan Jose Aciego, Angel Gonzalez-Prieto, Ignacio Gonzalez-Prieto, Mario J. Duran and Rafael Lara-Lopez

Machines 2025, 13(9), 862; https://doi.org/10.3390/machines13090862 - 17 Sep 2025

Viewed by 303

Abstract

Multiphase electric drives (EDs) offer important advantages for high-demand applications. However, they require appropriate high-performance control strategies. In this context, finite-control-set model predictive control (FCS-MPC) emerges as a promising strategy, offering a notable flexibility to implement multiobjective regulation schemes. When applied to multiphase [...] Read more.

Multiphase electric drives (EDs) offer important advantages for high-demand applications. However, they require appropriate high-performance control strategies. In this context, finite-control-set model predictive control (FCS-MPC) emerges as a promising strategy, offering a notable flexibility to implement multiobjective regulation schemes. When applied to multiphase EDs, standard FCS-MPC exhibits degraded current quality at low and medium control frequencies. Multivector solutions address this issue by properly combining multiple voltage vectors within a single control period to create the so-called virtual voltage vectors (VVVs). In this way, this approach achieves flux and torque regulation while minimizing current injection into the secondary subspace. For this purpose, the VVV synthesis typically prioritizes active vectors with low contribution in secondary subspaces, avoiding the average deception phenomenon. VVV solutions commonly enable an open-loop regulation of secondary currents. Nevertheless, the absence of closed-loop control in the secondary subspace hinders the compensation of nonlinearities, machine asymmetries, and unbalanced conditions in the ED. Considering this scenario, this work implements a multivector FCS-MPC recovering closed-loop control for the secondary subspace. The capability of the proposal to mitigate secondary current injection and compensate for possible dissymmetries is experimentally evaluated in a six-phase ED. Its performance is compared against a benchmark technique in which secondary current regulation is handled in open-loop mode. The proposed control solution significantly improves in current quality, achieving a reduction in harmonic distortion of 54% at medium speed. Full article

(This article belongs to the Special Issue Recent Progress in Electrical Machines and Motor Drives)

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24 pages, 8964 KB

Open AccessArticle

Dynamic Siting and Coordinated Routing for UAV Inspection via Hierarchical Reinforcement Learning

by Qingyun Yang, Yewei Zhang and Shuyi Shao

Machines 2025, 13(9), 861; https://doi.org/10.3390/machines13090861 - 17 Sep 2025

Viewed by 304

Abstract

To enhance the efficiency and reduce the operational costs of large-scale Unmanned Aerial Vehicle (UAV) inspection missions limited by endurance, this paper addresses the coupled problem of dynamically positioning landing/takeoff sites and routing the UAVs. A novel Hierarchical Reinforcement Learning (H-DRL) framework is [...] Read more.

To enhance the efficiency and reduce the operational costs of large-scale Unmanned Aerial Vehicle (UAV) inspection missions limited by endurance, this paper addresses the coupled problem of dynamically positioning landing/takeoff sites and routing the UAVs. A novel Hierarchical Reinforcement Learning (H-DRL) framework is proposed, which decouples the problem into a high-level strategic deployment policy and a low-level tactical routing policy. The primary contribution of this work lies in two architectural innovations that enable globally coordinated, end-to-end optimization. First, a coordinated credit assignment mechanism is introduced, where the high-level policy communicates its strategic guidance to the low-level policy via a learned “intent vector,” facilitating intelligent collaboration. Second, an Energy-Aware Graph Attention Network (Ea-GAT) is designed for the low-level policy. By endogenously embedding an energy feasibility model into its attention mechanism, the Ea-GAT guarantees the generation of dynamically feasible flight paths. Comprehensive simulations and a physical experiment validate the proposed framework. The results demonstrate a significant improvement in mission efficiency, with the makespan reduced by up to 16.3%. This work highlights the substantial benefits of joint optimization for dynamic robotic applications. Full article

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

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17 pages, 5501 KB

Open AccessArticle

Humidity Influence on Aero-Engine Control Plan Inflection Point and Performance

by Jinlu Yu, Wujun Lin and Yang Yu

Machines 2025, 13(9), 860; https://doi.org/10.3390/machines13090860 - 16 Sep 2025

Viewed by 184

Abstract

To investigate the influence of ambient humidity on the aero-engine control plan, a twin-spool mixed-exhaust turbofan aero-engine is used as the research object. After establishing a numerical calculation model of the aero-engine using the component method and incorporating the humidity correction factor into [...] Read more.

To investigate the influence of ambient humidity on the aero-engine control plan, a twin-spool mixed-exhaust turbofan aero-engine is used as the research object. After establishing a numerical calculation model of the aero-engine using the component method and incorporating the humidity correction factor into the model, the mechanism of the influence of ambient humidity on the aero-engine’s control plan inflection point and performance is investigated. Furthermore, this paper examines the degradation factors of the performance parameters of each aero-engine component in the model, as well as the impact of the coupling effect of ambient humidity and the degradation of the performance parameters of each component on the aero-engine’s performance. The results show that the control plan inflection point shifts rightward when ambient humidity rises, increasing thrust output beyond the displacement point throughout ground tests, take-off, and cruising conditions. On the other hand, when deterioration and humidity work together, the original inflection point location is typically maintained, and very slight thrust variations occur. However, the growth rate of specific fuel consumption is far higher than when humidity effects are used alone. These results provide important information for enhancing the performance of aviation engines in different humidity and component degradation scenarios. Full article

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

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19 pages, 4490 KB

Open AccessArticle

Design and Vibration Characteristics Analysis of Marine Hydraulic Pipelines Under Multi-Source Excitation

by Xin Ma and Chunsheng Song

Machines 2025, 13(9), 859; https://doi.org/10.3390/machines13090859 - 16 Sep 2025

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Abstract

To address the difficulty in eliminating low-frequency vibrations in the hydraulic pipelines of large marine vessels, this study first investigates the vibration characteristics of hydraulic pipelines. The research is conducted based on the stress states of pipelines under external excitations—specifically axial (X-direction), radial [...] Read more.

To address the difficulty in eliminating low-frequency vibrations in the hydraulic pipelines of large marine vessels, this study first investigates the vibration characteristics of hydraulic pipelines. The research is conducted based on the stress states of pipelines under external excitations—specifically axial (X-direction), radial (Y-direction), and combined radial–axial (X + Y) excitations and integrates theoretical derivation, simulation, and experimental validation. Firstly, a multidimensional directional vibration equation for the pipeline was derived based on its stress distribution, yielding a more accurate vibration model for marine pipelines. Subsequently, simulations were performed to analyze the effects of fluid velocity, pipeline layout, and support distribution on the pipeline’s vibration characteristics. Finally, experiments were designed to verify the simulation results and examine the impact of external interference on pipeline vibration. The experimental results indicate the following: the influence of flow velocity variations on pipeline modes is generally negligible; increasing the number of pipeline circuits effectively reduces its natural frequencies; increasing the number of supports not only lowers the overall vibration intensity of the pipeline but also achieves peak shaving, thereby effectively reducing the maximum vibration amplitude; and the impact of external environmental interference on the pipeline’s vibration characteristics is complex, as it not only enhances vibration intensity but also weakens vibrations in specific directions. This study lays a theoretical foundation for subsequent vibration reduction efforts for marine hydraulic pipelines. Full article

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

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17 pages, 15165 KB

Open AccessArticle

Analysis and Evaluation of a Joint Path Planning Algorithm for the Quasi-Spherical Parallel Manipulator, a Master Device for Telesurgery

by Daniel Pacheco Quiñones, Daniela Maffiodo and Med Amine Laribi

Machines 2025, 13(9), 858; https://doi.org/10.3390/machines13090858 - 16 Sep 2025

Viewed by 181

Abstract

This work presents the experimental validation of a reset control mode for a Quasi-Spherical Parallel Manipulator (qSPM), designed as a master device for bilaterally teleoperated telesurgical systems. The reset functionality enables autonomous repositioning of the master device to its central configuration via a [...] Read more.

This work presents the experimental validation of a reset control mode for a Quasi-Spherical Parallel Manipulator (qSPM), designed as a master device for bilaterally teleoperated telesurgical systems. The reset functionality enables autonomous repositioning of the master device to its central configuration via a joint-space path planning algorithm, executed entirely within the local control loop. Given the non-convex nature of the joint space, the algorithm computes feasible trajectories using a simplified optimization scheme that ensures compliance with mechanical and kinematic constraints. The algorithm was implemented within an ROS Noetic framework and tested across multiple scenarios, including both simulated and physical configurations. The experimental results confirm the device’s ability to reset to the central position in approximately 5 s, maintaining an average residual error below

0.25 °

. Computational evaluations demonstrate that each path is generated in less than 10 milliseconds, supporting real-time execution. Additional trials show successful motion toward arbitrary points within the joint space, suggesting the potential for future integration of user-driven repositioning features. These findings highlight the responsiveness, reliability, and experimental feasibility of the proposed control mode, marking a key step toward improving usability in telesurgical environments. Full article

(This article belongs to the Special Issue Advances in Mechanism and Machine Science Within the IFIT 2024 Conference)

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17 pages, 4283 KB

Open AccessArticle

A Cloud-Edge Communication Resource Slicing Allocation Method for Data Monitoring in Integrated Energy Systems

by Mingrui Zhang, Xuguang Hu, Jingyu Wang, Huilin Pan and Chengze Ren

Machines 2025, 13(9), 857; https://doi.org/10.3390/machines13090857 - 16 Sep 2025

Viewed by 156

Abstract

With the continuous growth in both volume and variety of monitoring services in integrated energy systems, the disparities between time scales and tasks of heterogeneous energy flow data monitoring pose significant challenges to rational resource allocation and efficient data transmission. To address these [...] Read more.

With the continuous growth in both volume and variety of monitoring services in integrated energy systems, the disparities between time scales and tasks of heterogeneous energy flow data monitoring pose significant challenges to rational resource allocation and efficient data transmission. To address these challenges, a monitoring resource slicing allocation method with low-cost optimization is presented for energy flow monitoring services in integrated energy systems. Firstly, a dynamic network slicing method for heterogeneous energy flow is proposed, which realizes rational resource allocation for diverse monitoring tasks and time scales through an integrate-then-slice approach. Secondly, a data transmission strategy with a cost representation method for network slicing is proposed. By establishing precise modeling of the complete data monitoring process within each slice, it solves the quantitative problem of data monitoring costs. Thirdly, an adaptive monitoring resource slice allocation algorithm is proposed, which addresses the cost optimization problem in data monitoring under slicing modes through optimized allocation of both intra-slice and inter-slice resources. Finally, tests are conducted on an integrated energy system in China. The results demonstrate that the proposed method successfully achieves data monitoring of heterogeneous energy flows across multiple time scales, while significantly reducing the data monitoring costs. Full article

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

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19 pages, 10066 KB

Open AccessArticle

Nine-Probe Third-Order Matrix System for Precise Flatness Error Detection

by Hua Liu, Jihong Chen, Zexin Peng, Han Ye, Yubin Huang and Xinyu Liu

Machines 2025, 13(9), 856; https://doi.org/10.3390/machines13090856 - 16 Sep 2025

Viewed by 233

Abstract

Large-scale, high-density flatness measurement is critical for manufacturing reference surfaces in ultra-precision machine tools. Traditional methods exhibit degradation in both accuracy and efficiency as measurement points and area size increase. In order to overcome these limitations to meet the requirements for integrated in-process [...] Read more.

Large-scale, high-density flatness measurement is critical for manufacturing reference surfaces in ultra-precision machine tools. Traditional methods exhibit degradation in both accuracy and efficiency as measurement points and area size increase. In order to overcome these limitations to meet the requirements for integrated in-process measurement and machining of structural components in ultra-precision machine tools, this paper proposes a novel nine-probe third-order matrix system that integrates the Fine Sequential Three-Point (FSTRP) method with automated scanning path planning. The system utilizes a multi-probe error separation algorithm based on the FSTRP principle, combined with real-time adaptive sampling, to decouple machine tool motion errors from intrinsic workpiece flatness deviations. This system breaks through traditional multi-probe 1D straightness measurement limitations, enabling direct 2D flatness measurement (with X/Y error decoupling), higher sampling density, and a repeatability standard deviation of 0.32 μm for large precision machine tool components. This high-efficiency, high-precision solution is particularly suitable for automated flatness inspection of large-scale components, providing a reliable metrology solution for integrated measurement-machining of flatness on precision machine tool critical components. Full article

(This article belongs to the Special Issue Error Measurement, Analysis, and Compensation Technology for CNC Machine Tools)

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19 pages, 2239 KB

Open AccessArticle

Human-Centered Assessment of Product Complexity and Its Impact on Assembly Line Performances

by Amanda Aljinović Meštrović, Marina Crnjac Žižić, Nikola Gjeldum and Nikola Banduka

Machines 2025, 13(9), 855; https://doi.org/10.3390/machines13090855 - 16 Sep 2025

Viewed by 229

Abstract

Modern production systems face the challenges of increasing personalization of products, growing structural complexity, and the need for sustainability. In this context, it is necessary to include the human dimension in the optimization of production processes, especially in line with the principles of [...] Read more.

Modern production systems face the challenges of increasing personalization of products, growing structural complexity, and the need for sustainability. In this context, it is necessary to include the human dimension in the optimization of production processes, especially in line with the principles of Industry 5.0 and the circular economy. In this paper, a complexity index is proposed that integrates the objective characteristics of the product and the subjectively perceived workload of the operator during assembly. The proposed index was used in the assembly line optimization process using linear programming to find a compromise solution between two often-conflicting objectives: maximizing output and minimizing complexity. In the analysis, two approaches to the initial balance of the assembly line were considered—by assembly time and by complexity of work elements—which were used as inputs to the optimization model. The results show that an approach that considers complexity from the operator’s point of view contributes to a more even load distribution but also can lead to higher overall performance. Such an approach confirms the importance of integrating the human factor into optimization processes and thus contributes to the creation of efficient, sustainable, and human-centric production systems of the future. Full article

(This article belongs to the Special Issue Smart Manufacturing and Beyond: Bridging Innovation in Industry 4.0 and 5.0)

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15 pages, 3555 KB

Open AccessArticle

Semi-Active Control of a Two-Phase Fluid Strut Suspension via Deep Reinforcement Learning

by Abolfazl Seifi, Yuming Yin, Yumeng Yao and Subhash Rakheja

Machines 2025, 13(9), 854; https://doi.org/10.3390/machines13090854 - 16 Sep 2025

Viewed by 232

Abstract

Gas–oil emulsion struts (GOESs), with their simplified and low-cost design and minimal friction, offer attractive potential for industrial applications. However, they exhibit highly nonlinear damping behavior due to the compressibility of the gas–oil emulsion. This study proposes a semi-active control strategy for modulating [...] Read more.

Gas–oil emulsion struts (GOESs), with their simplified and low-cost design and minimal friction, offer attractive potential for industrial applications. However, they exhibit highly nonlinear damping behavior due to the compressibility of the gas–oil emulsion. This study proposes a semi-active control strategy for modulating the emulsion flow via a dynamically controlled solenoid valve. The GOES is modeled considering pressure-dependent friction and flow characteristics. A reinforcement learning model is further developed to modulate the opening area of the control valve under random road excitations to enhance vibration ride comfort, using a quarter-vehicle model framework. The validated model is used to analyze the strut’s performance under three different scenarios, namely, the original passive, optimal passive, and semi-active. The results suggest that the proposed semi-active strategy could yield a considerably lower root mean square of the sprung mass acceleration for both the passive and optimal systems. It is further shown that real-time adjustment of the control valve could yield nearly 27.2% enhancement in ride comfort performance in comparison to optimal passive GOES. Full article

(This article belongs to the Special Issue Semi-Active Vibration Control: Strategies and Applications)

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18 pages, 3093 KB

Open AccessArticle

Optimal Scaling Parameter Analysis for Optical Mirror Processing Robots via Adaptive Differential Evolution Algorithm

by Zujin Jin, Zixin Yin, Hao Liu and Huanyin Guo

Machines 2025, 13(9), 853; https://doi.org/10.3390/machines13090853 - 15 Sep 2025

Viewed by 211

Abstract

In large optical mirror processing (LOMP), the robot is required to carry a computer-controlled optical surfacing (CCOS) polishing tool capable of both fully covering the required material removal profile and maintaining sufficient redundancy for process adaptability. The designed LOMP robot is a five-degree-of-freedom [...] Read more.

In large optical mirror processing (LOMP), the robot is required to carry a computer-controlled optical surfacing (CCOS) polishing tool capable of both fully covering the required material removal profile and maintaining sufficient redundancy for process adaptability. The designed LOMP robot is a five-degree-of-freedom (5-DOF) hybrid robot, where the workspace of its parallel mechanism is constrained by dimensional parameters, including the moving platform radius, the fixed/moving platform radius ratio, and link lengths. This paper presents an optimization study of dimensional parameters for robotic systems, aimed at meeting the workspace requirements of 1250 mm-diameter large optical mirrors. First, analytical models of the robot’s effective workspace and driving torque under different dimensional parameters are derived. Subsequently, workspace requirements and driving torque are established as optimization constraints, and a differential evolution algorithm is implemented to determine the optimal dimensional parameters for the LOMP system. To improve computational efficiency, the conventional differential evolution algorithm is enhanced through the integration of adaptive mutation and crossover operators, resulting in a modified adaptive differential evolution algorithm (ADEA) that demonstrates accelerated convergence characteristics while maintaining solution accuracy. Finally, MATLAB simulations demonstrate that the proposed ADEA successfully obtains optimal dimensional parameter combinations while satisfying all specified constraints. Based on the optimal dimensional parameters, an engineering prototype was manufactured. Experimental results verified the accuracy of the optimized design, providing a valuable reference for optimization of dimensional and structural parameters in similar engineering equipment. Full article

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

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17 pages, 10010 KB

Open AccessArticle

Microstructure Characterization and Mechanical Properties of Dissimilar Al/Al-Li Alloy T-Joints Welded by Friction Stir Welding

by Yanjie Han, Duquan Zuo, Tianyu Xu, Guoling Ma, Shilin Feng, Haoran Fu, Zengqiang Cao and Wenya Li

Machines 2025, 13(9), 852; https://doi.org/10.3390/machines13090852 - 15 Sep 2025

Viewed by 300

Abstract

This paper investigates the influence of the internal concave surface structure of the stirring tool and welding parameters on the microstructure and mechanical properties of the T-joint. The analysis reveals that compared to the inner concave surface without spirals, T-joints welded by inner [...] Read more.

This paper investigates the influence of the internal concave surface structure of the stirring tool and welding parameters on the microstructure and mechanical properties of the T-joint. The analysis reveals that compared to the inner concave surface without spirals, T-joints welded by inner concave surfaces with spirals exhibit fewer welding defects. Meanwhile, the microscopic results showed that there is a welding juncture zone between the thermomechanical affected zone and the nugget zone, and a large number of θ’, T₁, and η’ phases precipitate in the nugget zone of the joint, which improves its strength and hardness. When welding speed v, rotational speed w and insertion depth h are 60 mm/min, 350 rpm, and 0.21 mm, respectively, the yield strength, the tensile strength, and the elongation of the T-joint reach their maximum values (352 MPa, 408 MPa and 5%), and the tensile strength represents 68.0% and 71.6% of the base materials, respectively. The fracture mechanism of the joint is a mode of ductile fracture. Furthermore, the T-joint exhibits a “W” and “Z” distribution pattern on both sides of the weld centerline B and A, respectively. Full article

(This article belongs to the Section Material Processing Technology)

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16 pages, 7120 KB

Open AccessArticle

Ultra-Long, Minor-Diameter, Untethered Growing Continuum Robot via Tip Actuation and Steering

by Pan Zhou, Zhaoyi Lin, Lang Zhou, Haili Li, Michael Basin and Jiantao Yao

Machines 2025, 13(9), 851; https://doi.org/10.3390/machines13090851 - 15 Sep 2025

Viewed by 351

Abstract

Continuum robots with outstanding compliance, dexterity, and lean bodies are successfully applied in medicine, aerospace engineering, the nuclear industry, rescue operations, construction, service, and manipulation. However, the inherent low stiffness characteristics of continuum bodies make it challenging to develop ultra-long and small-diameter continuum [...] Read more.

Continuum robots with outstanding compliance, dexterity, and lean bodies are successfully applied in medicine, aerospace engineering, the nuclear industry, rescue operations, construction, service, and manipulation. However, the inherent low stiffness characteristics of continuum bodies make it challenging to develop ultra-long and small-diameter continuum robots. To address this size–scale challenge of continuum robots, we developed an 8 m long continuum robot with a diameter of 23 mm by a tip actuation and growth mechanism. Meanwhile, we also realized the untethered design of the continuum robot, which greatly increased its usable space range, portability, and mobility. Demonstration experiments prove that the developed growing continuum robot has good flexibility and manipulability, as well as the ability to cross obstacles and search for targets. Its continuum body can transport liquids over long distances, providing water, medicine, and other rescue items for trapped individuals. The functionality of an untethered growing continuum robot (UGCR) can be expanded by installing multiple tools, such as a grasping tool at its tip to pick up objects in deep wells, pits, and other scenarios. In addition, we established a static model to predict the deformation of UGCR, and the prediction error of its tip position was within 2.6% of its length. We verified the motion performance of the continuum robot through a series of tests involving workspace, disturbance resistance, collision with obstacles, and load performance, thus proving its good anti-interference ability and collision stability. The main contribution of this work is to provide a technical reference for the development of ultra-long continuum robots based on the tip actuation and steering principle. Full article

(This article belongs to the Special Issue Advances and Challenges in Robotic Manipulation)

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14 pages, 792 KB

Open AccessArticle

Reliability Assessment for Small-Sample Accelerated Life Tests with Normal Distribution

by Jianchao Guo and Huimin Fu

Machines 2025, 13(9), 850; https://doi.org/10.3390/machines13090850 - 14 Sep 2025

Viewed by 260

Abstract

A significant challenge in the accelerated life test (ALT) is the reliance on large sample sizes and multiple stress levels, which results in high costs and long test durations. To address this issue, this paper develops a new reliability assessment method for small-sample [...] Read more.

A significant challenge in the accelerated life test (ALT) is the reliance on large sample sizes and multiple stress levels, which results in high costs and long test durations. To address this issue, this paper develops a new reliability assessment method for small-sample ALTs with normal distribution (or lognormal distribution) and censoring. This method enables a high-confidence evaluation of the percentile lifetime (reliable lifetime) under normal operating stress level using censored data from only two accelerated stress levels. Firstly, a relationship is established between the percentile lifetime at normal stress level and the distribution parameters at accelerated stress levels. Subsequently, an initial estimate of the percentile lifetime is obtained from failure data, and its confidence is then refined using a Bayesian update with the nonfailures. Finally, an exact one-sided lower confidence limit (LCL) for the percentile lifetime and reliability is determined. This paper derives an analytical formula for LCLs under Type-II censoring scenarios and further extend the method to accommodate Type-I censored and general incomplete data. The Monte Carlo simulations and case studies show that, the proposed methods significantly reduce the required sample size and testing duration while offering superior theoretical rigor and accuracy than the conventional methods. Full article

(This article belongs to the Section Machines Testing and Maintenance)

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