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Machines
Volume 14
Issue 5
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Machines, Volume 14, Issue 5 (May 2026) – 120 articles

Cover Story (view full-size image): This work presents a machine-vision-based measurement and control framework for laser wire directed energy deposition (LWDED) processes. A visible-light camera system is used to capture meltpool images, from which a novel vision algorithm extracts the wire–meltpool interface location. By utilizing a camera that is rigidly mounted to the deposition head, the vision algorithm provides a relative measurement of the distance between the nozzle tip and the workpiece, also referred to as wire stickout. A proportional-derivative (PD) control strategy is implemented using the measured stickout as feedback to adjust deposition feedrate. Results show that the control system successfully compensates for improper layer height increments, enabling thin-wall builds to consistently reach target geometry. View this paper
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27 pages, 10006 KB  
Article
Physics-Informed Digital Twin of a Milling System for Vibration Prediction and Surface Roughness Modeling
by Muhamad Aditya Royandi, Wei-Zhu Lin, Jui-Pin Hung, Yu-Sheng Lai and Zheng-Mou Su
Machines 2026, 14(5), 579; https://doi.org/10.3390/machines14050579 - 21 May 2026
Viewed by 370
Abstract
The application of digital twin (DT) technology to intelligent machining shows promise, but its effectiveness in predicting vibration and assessing surface quality has not been thoroughly validated for widespread industrial use. This study presents a physics-informed predictive digital twin framework operating in an [...] Read more.
The application of digital twin (DT) technology to intelligent machining shows promise, but its effectiveness in predicting vibration and assessing surface quality has not been thoroughly validated for widespread industrial use. This study presents a physics-informed predictive digital twin framework operating in an offline or near-real-time predictive configuration for vibration prediction and surface roughness modeling in milling processes. Impact hammer testing was conducted to extract the dominant modal properties of the spindle–tool assembly, which were embedded into a Simulink-based dynamic framework to predict tool vibration under varying cutting conditions. Full-immersion slot milling experiments on AL6061 were performed for validation. Within all datasets, including training phase and validation phase, the predicted vibration amplitudes exhibit a coefficient of determination R2=0.94 with measured values. The overall MAPE and RMSE are about 10.39% and 0.234, respectively. Power-law regression-based surface roughness prediction models were subsequently established using cutting parameters and both measured and DT-predicted vibration features through logarithmic transformation and least-squares fitting. The results show that the roughness prediction model using vibration features predicted by the digital twin model achieved a correlation coefficient of approximately R2=0.84, with MAPE = 9.57% and RMSE = 0.16 μm, which is comparable to the predictive model based on experimentally measured vibration. These results indicate that, within the investigated machining conditions, the digital twin can provide vibration features suitable for surface roughness prediction, demonstrating its potential as a virtual sensing approach. This work advances digital twin applications from process monitoring toward predictive, quality-oriented machining systems and provides a foundation for adaptive parameter updating in intelligent manufacturing environments. Full article
(This article belongs to the Special Issue Intelligent Fault Diagnosis and Predictive Maintenance Systems: Advanced Methods for Industrial Equipment and Dynamic Operating Conditions)
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18 pages, 5090 KB  
Article
Design and Implementation of a Model Elevator System for Mechatronics Education
by Casey Egan, Jack Lague and Musa K. Jouaneh
Machines 2026, 14(5), 578; https://doi.org/10.3390/machines14050578 - 21 May 2026
Viewed by 249
Abstract
Elevators exemplify mechatronics by integrating mechanical, electrical, and software systems. This paper discusses a four-story tabletop elevator model developed to demonstrate mechatronics and automation concepts in engineering education. The system utilized an Arduino MEGA microcontroller, 3D-printed components, an integrated servo motor, and standard [...] Read more.
Elevators exemplify mechatronics by integrating mechanical, electrical, and software systems. This paper discusses a four-story tabletop elevator model developed to demonstrate mechatronics and automation concepts in engineering education. The system utilized an Arduino MEGA microcontroller, 3D-printed components, an integrated servo motor, and standard electronics to replicate commercial elevator logic. The physical design features a ball screw linear actuator for vertical motion. It replicates dual-door systems with one door on the moving car and fixed doors at each floor that open simultaneously upon arrival. Development included designing the physical model, prototyping control algorithms, and integrating hardware and software. The model successfully demonstrated key functions: automatic dual-door operation, safety interlocks, smooth inter-floor motion, responsive floor-selection buttons with LED feedback, and efficient routing algorithms prioritizing requests based on current direction and location. Performance testing confirmed that the model accurately replicates modern elevator behavior and serves as an effective educational tool. Full article
(This article belongs to the Special Issue The New Digital Era in Industrial Robotics, Mechatronics and Factory Automation)
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17 pages, 1194 KB  
Article
Material Homogeneity Criterion for Assessing Heterogeneous High-Strength Steel Joints with Austenitic Welds
by Yaroslav Kusyi, Vitalii Ivanov, Andriy Dzyubyk, Nazarii Kusen and Juraj Hajduk
Machines 2026, 14(5), 577; https://doi.org/10.3390/machines14050577 - 21 May 2026
Viewed by 180
Abstract
The modernization of global energy infrastructure within the Industry 5.0 framework requires the use of high-strength steels and reliable joining technologies to ensure safe, sustainable pipeline transport. This study focuses on the analysis of heterogeneous welded joints formed between high-strength alloy steel (34KhN2MA/EN [...] Read more.
The modernization of global energy infrastructure within the Industry 5.0 framework requires the use of high-strength steels and reliable joining technologies to ensure safe, sustainable pipeline transport. This study focuses on the analysis of heterogeneous welded joints formed between high-strength alloy steel (34KhN2MA/EN 34CrNiMo6) and an austenitic welded seam (ER 307). While austenitic welds mitigate the risk of cold cracking, they introduce significant structural and mechanical heterogeneity. To address this, the research proposes and validates a material homogeneity criterion (MHC) derived from the LM-hardness methodology. By analyzing the statistical dispersion of macrohardness (HRC) through indicators such as the Weibull homogeneity coefficient (m) and the coefficient of variation (ν), the study establishes a quantitative approach to assess material degradation and structural uniformity across key weld zones. Results demonstrate that macrohardness profiling effectively distinguishes between structurally heterogeneous regions near the weld axis characterized by low homogeneity coefficients (m = 4.04 < 10, Am = 0.742 < 0.878), elevated variability (ν = 29.68% > 11.6%), and high technological damageability (D = 0.92 > 0.81, jD = 11.87 > 4.38) with pronounced step-like variation in macrohardness (HRC ∈ [12.6; 47]), on the one hand, and stabilized homogeneous zones in the base material, where m = 24.89 > 10, Am = 0.947 > 0.878, ν = 4.39% < 11.6%, D = 0.52 ⟶ 0, jD = 1.09 ⟶ 0, and characteristic range of HRC = 47–55, on the other hand. This methodology provides a robust, quasi-non-destructive tool for enhancing predictive maintenance, digital twins, and the overall integrity management of “smart” pipeline systems. Full article
(This article belongs to the Special Issue Innovations in the Design, Simulation, and Manufacturing of Production Systems)
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35 pages, 8591 KB  
Article
Displacement Centre of Gravity and Stability Arm in Longitudinal Tilt of a Floating Body with Circular Floats
by Leopold Hrabovský, Pavla Karbanová and Ladislav Kovář
Machines 2026, 14(5), 576; https://doi.org/10.3390/machines14050576 - 21 May 2026
Viewed by 166
Abstract
Floating belt conveyor routes consisting of serially arranged belt conveyors, the end parts of which are mechanically attached to floating bodies, are designed for the continuous transport of extracted granular materials from water. This paper deals with the analytical determination of the position [...] Read more.
Floating belt conveyor routes consisting of serially arranged belt conveyors, the end parts of which are mechanically attached to floating bodies, are designed for the continuous transport of extracted granular materials from water. This paper deals with the analytical determination of the position of the centre of gravity of the buoyancy force, the coordinates of which change depending on the longitudinal deflection of the floating body from the equilibrium state, which acts as a supporting element of individual conveyor belts. Analysis of the individual phases of deflection of the floating body, consisting of a pair of floats with a circular cross-section, shows that the complete submergence of one of the floats occurs at a higher value of the angle of inclination in the case when the floats are initially submerged under the surface to exactly half their diameter. On the realized experimental device, the buoyancy force was detected using strain gauges during the deflection of the floating body from the equilibrium position for three defined levels of immersion. The floating body of the experimental device consists of a pair of floats with a circular cross-section with a diameter of 80 mm. The output is a structured methodological procedure for determining the position of the centre of gravity of the displacement (centre of buoyancy) of a floating body when it deviates from the equilibrium position and a methodology for calculating the stability arm, which is a key parameter for assessing the buoyancy and stability of the body. On the basis of the laboratory measurements, the magnitude of the buoyancy force can be quantified as a function of the immersion depth of the floating body. It was found that the buoyancy force remains constant when the body deflects only when the immersion corresponds to half the diameter of a float with a circular cross-section. If the depth of the immersion is less than the radius of the float, the buoyancy force increases during deflection; however, if the immersion is greater than the radius of the float, the buoyancy force decreases. Full article
(This article belongs to the Section Automation and Control Systems)
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16 pages, 9542 KB  
Article
Analytical Modeling of Slot Leakage Inductance for Hairpin Windings
by Hasnain Nisar and Ali M. Bazzi
Machines 2026, 14(5), 575; https://doi.org/10.3390/machines14050575 - 21 May 2026
Viewed by 264
Abstract
With the increasing demand for higher efficiency and power density, innovative winding techniques have become crucial in modern electric machines. Hairpin windings are increasingly used in electric machines, particularly in high-current applications. A novel analytical model is proposed to estimate slot leakage inductance [...] Read more.
With the increasing demand for higher efficiency and power density, innovative winding techniques have become crucial in modern electric machines. Hairpin windings are increasingly used in electric machines, particularly in high-current applications. A novel analytical model is proposed to estimate slot leakage inductance in hairpin windings. Traditional models are limited to random windings, which fail to capture the complex mutual inductance between multiple coil layers. This paper derives a generalized model to estimate specific permeance and total mutual specific permeance for the hairpin windings, which are key factors in determining slot leakage inductance. The proposed model is also valid for fractional-pitch windings. The derived analytical model is validated through finite element analysis (FEA) on an electric motor similar to that employed in Tesla Model S. In addition, experimental validation is performed to further validate the proposed model. Furthermore, parametric analysis is conducted to analyze the influence of slot geometry and conductor dimensions on the slot leakage inductance. This paper contributes an accurate method for predicting slot leakage inductance in hairpin windings; this provides electrical machine designers with a valuable tool for precise modeling and optimization for improved efficiency and performance in various applications. Full article
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28 pages, 10854 KB  
Article
The Unreasonable Effectiveness of Neural Operators and Mambas in Detecting and Quantifying Electrical Machine Faults: A Case Study on Eccentricity
by Latifa Yusuf, Belaid Moa and Ilamparithi Thirumarai Chelvan
Machines 2026, 14(5), 574; https://doi.org/10.3390/machines14050574 - 21 May 2026
Viewed by 234
Abstract
Reliable fault detection and quantification are essential for the operational integrity of electric machines. While traditional current-based analysis relies on harmonic signatures or wavelet-based time-frequency representations, this study investigates modern learning formulations that capture spectral, multiscale, and temporal characteristics of fault-affected signals. Moving [...] Read more.
Reliable fault detection and quantification are essential for the operational integrity of electric machines. While traditional current-based analysis relies on harmonic signatures or wavelet-based time-frequency representations, this study investigates modern learning formulations that capture spectral, multiscale, and temporal characteristics of fault-affected signals. Moving beyond conventional models, including our earlier CNN-based approaches, we develop sequence-based and operator-learning architectures within a multi-output formulation for eccentricity fault analysis. Three models are investigated: Mamba for temporal dynamics, the Fourier Neural Operator for global spectral mapping, and the Wavelet Neural Operator for localized multiscale decomposition. Evaluated on induction, salient pole synchronous, and inverter-based reluctance synchronous machines, each model maps stator current waveforms to multiple diagnostic quantities, including voltages, operating conditions, and fault severity. With time-delay embedding, all three achieve low prediction errors, with severity RMSE reaching the 10−4 scale for the induction machine, a notable reduction from the 0.04 errors of our earlier hierarchical CNN models. These results show that modern sequence-based and operator-learning formulations can broaden machine fault analysis by enabling simultaneous prediction and estimation of multiple aspects of machine condition within a single model. Full article
(This article belongs to the Special Issue Data-Driven Fault Diagnosis for Machines and Systems, 2nd Edition)
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18 pages, 45483 KB  
Article
Friction and Wear Behavior of General Freight Train Composite Brake Shoes with Reinforced Steel Fibers
by Hengxi Wang, Xin Zhang, Guansong Chen, Jiazheng Song, José Manuel Martínez-Esnaola and Chun Lu
Machines 2026, 14(5), 573; https://doi.org/10.3390/machines14050573 - 21 May 2026
Viewed by 217
Abstract
High friction composite brake shoes containing reinforced steel fibers are now widely used in freight train tread braking systems. With the demand for higher transportation efficiency on railway lines with long steep slopes, it is necessary to explore the braking capabilities of existing [...] Read more.
High friction composite brake shoes containing reinforced steel fibers are now widely used in freight train tread braking systems. With the demand for higher transportation efficiency on railway lines with long steep slopes, it is necessary to explore the braking capabilities of existing general freight train high friction composite brake shoes under continuous braking conditions. In this paper, continuous braking tests at different speed levels were conducted using a friction and wear test rig. Through material characterization and interface damage analysis, it was found that reinforced steel fibers can exist as a contact platform at the brake shoe friction interface. Due to the strip-like morphology and high strength features of steel fibers, even after the steel fiber layer is fragmented, it can still promote the formation of a continuous contact platform with complex material composition on the surface, maintaining the progress of the braking process. For existing general freight train high friction composite brake shoes, at speeds up to 80 km/h, although the friction coefficient decreases to some extent, the wear rate maintains a relatively low range. When the speed increases to 100 km/h, the friction coefficient of the braking interface deteriorates severely, and the wear rate of the brake shoe increases sharply, seriously endangering braking safety. The research results reveal the evolution of wear behavior of high friction composite brake shoes containing reinforced steel fibers at different speed levels, providing theoretical support for exploring the braking capabilities and design optimization of brake shoes. Full article
(This article belongs to the Special Issue Research and Application of Rail Vehicle Technology)
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27 pages, 50269 KB  
Review
A Review of Variable Stiffness in Continuum Robots: Mechanisms, Modeling and Control
by Dexin Cheng, Tianao Zhang, Huanyu Deng, Compus Gan Yu Hong, Shihai Zhao, Yongzhuo Gao, Hui Dong, Zhijiang Du and Wei Dong
Machines 2026, 14(5), 572; https://doi.org/10.3390/machines14050572 - 21 May 2026
Viewed by 461
Abstract
Variable stiffness endows continuum robots with both compliance and tunable rigidity, making them promising alternatives to traditional rigid manipulators in confined and unstructured environments. Over the past decade, great progress has been made in variable stiffness technologies involving structural design, actuation, modeling, and [...] Read more.
Variable stiffness endows continuum robots with both compliance and tunable rigidity, making them promising alternatives to traditional rigid manipulators in confined and unstructured environments. Over the past decade, great progress has been made in variable stiffness technologies involving structural design, actuation, modeling, and control. However, current research is fragmented and mostly focuses on individual aspects, lacking a systematic review and a unified framework integrating structure, modeling, and control. This paper presents a comprehensive review of variable stiffness in continuum robots, emphasizing the interrelationships among stiffness principles, modeling, and control strategies. We summarize classical and emerging variable stiffness methods, analyze their integration with control approaches, and evaluate the evolution of control strategies, especially multi-modal fusion of actuation, sensing, and control. Such fusion can improve control accuracy and robustness in human-centered environments and is regarded as a key driver for next-generation intelligent continuum robots. Finally, we outline future directions, highlight the “actuation–stiffness–control” paradigm, and discuss existing challenges and open research opportunities for high-performance intelligent control. Full article
(This article belongs to the Special Issue Design and Control of Surgical Robots)
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35 pages, 3776 KB  
Article
Design of Virtual Disturbance Feedforward Controller for Motion Sickness Mitigation
by Seongjin Yim
Machines 2026, 14(5), 571; https://doi.org/10.3390/machines14050571 - 20 May 2026
Viewed by 213
Abstract
This study presents a virtual disturbance feedforward controller (VDFC) to mitigate motion sickness in vehicles equipped with active suspension systems. Because feedforward control is difficult to implement in practice owing to the limited availability of measurable or estimable road-disturbance information, a half-sine virtual [...] Read more.
This study presents a virtual disturbance feedforward controller (VDFC) to mitigate motion sickness in vehicles equipped with active suspension systems. Because feedforward control is difficult to implement in practice owing to the limited availability of measurable or estimable road-disturbance information, a half-sine virtual disturbance (HSVD) corresponding to a bump input is introduced and incorporated into the feedforward controller design. The proposed VDFC is integrated with a feedback controller developed from quarter-car and half-car models using linear quadratic static output feedback (LQ SOF) control. Furthermore, to enhance the motion-sickness-mitigation performance of the VDFC, a simulation-based optimization framework is formulated and solved using a heuristic optimization technique. Simulations with bump inputs are carried out in a vehicle dynamics simulation environment using the LQ SOF controller together with the optimized VDFCs. A sensitivity analysis is also performed for the parameters of the optimized virtual disturbance. The results indicate that, under the bump-like excitation conditions considered, the proposed method can improve ride comfort and reduce motion-sickness-related response measures. Full article
(This article belongs to the Special Issue Passive and Active Approaches for the Control of Nonlinear Vibrations in Mechanical Systems)
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27 pages, 4753 KB  
Article
Longitudinal Finite-Time Control of Intelligent Vehicle Fleet Considering Time-Delay and Interference
by Songbo Wang, Dehua Shi, Shaohua Wang, Yongquan Xie and Yan Chen
Machines 2026, 14(5), 570; https://doi.org/10.3390/machines14050570 - 20 May 2026
Viewed by 179
Abstract
To address the robustness degradation of intelligent vehicle fleet longitudinal control systems caused by the coexistence of disturbances and time-delay, a longitudinal finite-time control strategy based on a predictive finite-time extended state observer (PFTESO) is proposed. First, a finite-time extended state observer (FTESO) [...] Read more.
To address the robustness degradation of intelligent vehicle fleet longitudinal control systems caused by the coexistence of disturbances and time-delay, a longitudinal finite-time control strategy based on a predictive finite-time extended state observer (PFTESO) is proposed. First, a finite-time extended state observer (FTESO) is designed to estimate system disturbances. To address the observer input asynchrony induced by time-delay, an improved Smith predictor is integrated into the FTESO to construct the PFTESO, thereby improving disturbance observation accuracy under delayed conditions. Meanwhile, a proportional–integral (PI) compensation controller is introduced based on the estimation error to further enhance control accuracy. Subsequently, a global fast integral terminal sliding mode controller (GFITSMC) is developed based on the PFTESO to improve the robustness and finite-time convergence performance of the intelligent vehicle fleet system under disturbances and time-delay. Finally, comparative simulation studies under different operating conditions are conducted to evaluate the effectiveness of the proposed strategy. Simulation results demonstrate that the proposed PFTESO effectively improves state observation accuracy under delayed conditions, where the RMSE values of z1 and z2 are reduced from 0.082 and 0.214 to 0.021 and 0.067, respectively. In addition, compared with conventional sliding mode control strategies, the proposed FTESO-GFITSMC reduces the peak acceleration chattering from ±0.23 m/s2 to 0.03 m/s2 while achieving a finite-time convergence time of 13 s. The proposed method exhibits superior robustness, faster convergence performance, and smoother acceleration response for an intelligent vehicle fleet under disturbances and delayed conditions. Full article
(This article belongs to the Special Issue New Journeys in Vehicle System Dynamics and Control)
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34 pages, 12041 KB  
Article
Study on Thermal–Fluid–Solid Coupling Characteristics of a Scroll Compressor in an Oil–Gas Waste Heat Recovery Heat Pump System
by Yingju Pei, Jingxian Zeng, Lei Zeng, Li Kou, Xu Luo and Yangqi Liu
Machines 2026, 14(5), 569; https://doi.org/10.3390/machines14050569 - 20 May 2026
Viewed by 269
Abstract
Heat pump technology can efficiently recover waste heat from oil and gas gathering, processing, and transportation. However, the energy transfer mechanism of high-speed rotating internal flow in the scroll compressor remains unclear under unbalanced load conditions, leading to low equipment energy efficiency and [...] Read more.
Heat pump technology can efficiently recover waste heat from oil and gas gathering, processing, and transportation. However, the energy transfer mechanism of high-speed rotating internal flow in the scroll compressor remains unclear under unbalanced load conditions, leading to low equipment energy efficiency and high operation and maintenance costs. This study adopted dynamic grid technology, finite element analysis and one-way thermal–fluid–solid coupling method to quantitatively study the flow field characteristics and mechanical response of four characteristic phases. The results showed that the internal pressure and temperature fields of the compressor presented a non-uniform distribution. The deformation of the scroll wraps was mainly concentrated in the compression chamber, and the maximum stress was concentrated at the wraps’ root. Further analysis revealed that temperature loading played a dominant role in the structural responses. At a spindle rotation angle of 0°, under temperature loading alone, the maximum deformation and maximum stress were 28.605 μm and 521.81 MPa, respectively, while the corresponding values under pressure loading alone were small. In addition, the deformation and stress under coupled loading were not a linear superposition of the individual loading effects, with a deformation deviation of 0.938 μm and a stress deviation of 7.18 MPa at a spindle rotation angle of 0°. In this study, a numerical model of the scroll compressor was established and experimentally verified, which provided a theoretical basis for optimizing scroll profile design, suppressing wrap tip wear and improving the energy efficiency of heat pump systems. Full article
(This article belongs to the Section Turbomachinery)
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29 pages, 6695 KB  
Article
Robust Locomotion Control of Quadrupedal Wheel-Legged Robots via Contrastive History-Aware Reinforcement Learning in Complex Environments
by Deyun Dai, Tao Liu and Tengfei Tang
Machines 2026, 14(5), 568; https://doi.org/10.3390/machines14050568 - 20 May 2026
Viewed by 205
Abstract
Quadrupedal wheel-legged robots possess exceptional mobility in complex terrains, but their robust locomotion control is severely hindered by the difficulty of accurate state estimation without external sensors. Existing reinforcement learning methods relying on two-stage imitation often suffer from representation collapse and information loss [...] Read more.
Quadrupedal wheel-legged robots possess exceptional mobility in complex terrains, but their robust locomotion control is severely hindered by the difficulty of accurate state estimation without external sensors. Existing reinforcement learning methods relying on two-stage imitation often suffer from representation collapse and information loss during sim-to-real transfer. To address these challenges, this paper proposes a novel end-to-end reinforcement learning framework for implicit state estimation, incorporating terrain and external force features. Inspired by internal model control, the proposed method leverages a history of purely proprioceptive observations to extract explicit kinematic responses, as well as implicit environmental and external force representations via prototypical contrastive learning, completely circumventing explicit terrain regression and the need for physical force sensors. Furthermore, a tailored composite reward function and a progressive curriculum training strategy with large-scale domain randomization are integrated to ensure dynamic stability and hardware safety. Extensive cross-simulator validations and real-world deployments demonstrate that the approach achieves highly agile and robust locomotion, including adaptive traversal over diverse terrains. Experiments show that the method significantly enhances robustness under external disturbances, notably reducing the lateral linear velocity tracking error from 0.2421 m/s to 0.1319 m/s. The proposed method realizes zero-shot sim-to-real transfer with superior sample efficiency, providing a reliable and universal control paradigm for wheel-legged robots in unstructured environments. Full article
(This article belongs to the Section Robotics, Mechatronics and Intelligent Machines)
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1 pages, 125 KB  
Correction
Correction: Song et al. SERail-SLAM: Semantic-Enhanced Railway LiDAR SLAM. Machines 2026, 14, 72
by Weiwei Song, Shiqi Zheng, Xinye Dai, Xiao Wang, Yusheng Wang, Zihao Wang, Shujie Zhou, Wenlei Liu and Yidong Lou
Machines 2026, 14(5), 567; https://doi.org/10.3390/machines14050567 - 20 May 2026
Viewed by 159
Abstract
In the original publication [...] Full article
(This article belongs to the Special Issue Dynamic Analysis and Condition Monitoring of High-Speed Trains)
18 pages, 6135 KB  
Article
Optimization of Lightweight Design for a Certain Range Hood Model Under Strength and Vibration Limitations
by Lihui Zhu, Zhiwei Hu, Xixia Zheng, Xiangrui Zhao, Feng Ye, Chunling Yu and Zhenlei Chen
Machines 2026, 14(5), 566; https://doi.org/10.3390/machines14050566 - 19 May 2026
Viewed by 220
Abstract
To address structural redundancy and excessive vibration in a specific range hood model, this study focuses on structural lightweighting design optimization. Under strength and resonance avoidance constraints, optimization integrates experimental testing and finite element analysis. Modal analysis reveals a prominent resonance at 49.8 [...] Read more.
To address structural redundancy and excessive vibration in a specific range hood model, this study focuses on structural lightweighting design optimization. Under strength and resonance avoidance constraints, optimization integrates experimental testing and finite element analysis. Modal analysis reveals a prominent resonance at 49.8 Hz, which coincides with the test results. Topography optimization of the impeller side plate ribs shifts its natural frequency, eliminating resonance while reducing weight significantly. Subsequently, topography optimization of key parts such as the fan housing improves stiffness, facilitating further lightweighting. Two optimization methods, direct solver and orthogonal experiment were applied to minimize the total mass under strength and dynamic constraints. Both schemes met all design requirements with weight reductions of 17.7% and 18.3%, respectively. Vibration test of the optimized design shows that accelerations at key points were reduced significantly. Full article
(This article belongs to the Section Machine Design and Theory)
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17 pages, 23434 KB  
Article
Quantitative Investigation into Friction-Induced Vibration During Mold-Opening Transience in Ultra-High-Tonnage Two-Platen Injection Molding Machines with Massive Inertia and Constraint-Guided Sliding
by Xiaozhou Chen, Bin Han, Wei Gu, Meng Chen, Chongyang Xie, Lu Ren and Haibo Huang
Machines 2026, 14(5), 565; https://doi.org/10.3390/machines14050565 - 19 May 2026
Viewed by 220
Abstract
As extreme-scale manufacturing evolves, the dynamic response of heavy moving components under ultra-high loads becomes a critical design challenge. This study focuses on friction-induced vibration of a more than 30-ton movable mass during the mold-opening stage in a two-platen machine with a clamping [...] Read more.
As extreme-scale manufacturing evolves, the dynamic response of heavy moving components under ultra-high loads becomes a critical design challenge. This study focuses on friction-induced vibration of a more than 30-ton movable mass during the mold-opening stage in a two-platen machine with a clamping force >17,000 kN. A mathematical model and a validated rigid/flexible multibody dynamics model with PID co-simulation were developed to analyze transient vibration using maximum acceleration amplitude and stability time as core metrics. The results show vibration stems from imbalance between anti-opening resistance and hydraulic driving force, amplified by vacuum collapse, static-to-dynamic friction transition at slide feet/rail interface and PID overshoot, featuring high amplitude density (>0.75 g), transience (<50 ms) and high impact (>60,000 N). The maximum vibration acceleration amplitude remains 79.22% even after there is no mold vacuum suction, indicating that a static friction force other than the vacuum suction is the dominant factor resulting in a severe friction-induced vibration. These mechanistic insights establish an applicable framework for the dynamic optimization of the heavy components in extreme-large-scale manufacturing equipment. Full article
(This article belongs to the Special Issue New Advances in Science of Mechanisms and Machines)
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28 pages, 5623 KB  
Article
Using Type-1 and Type-2 Fuzzy Logic Controllers for the Trajectory Tracking Task of a Wheeled Robot: A Comparison Study
by Mohammed Taqiyeddine Mahdi, Lakhmissi Cherroun, Mohamed Nadour, Puig Vicenç, Ahmed Hafaifa, Giovanni Angiulli and Fabio La Foresta
Machines 2026, 14(5), 564; https://doi.org/10.3390/machines14050564 - 19 May 2026
Viewed by 317
Abstract
The robotic path-tracking task is of interest to researchers because it offers the potential to develop an efficient navigation system for robots. Fuzzy logic is successfully used in many control systems, especially in robotic tasks, due to its ability to model the uncertainties [...] Read more.
The robotic path-tracking task is of interest to researchers because it offers the potential to develop an efficient navigation system for robots. Fuzzy logic is successfully used in many control systems, especially in robotic tasks, due to its ability to model the uncertainties and vagueness of the physical world. In this paper, the application of type-1 and type-2 fuzzy logic controllers for trajectory tracking of differential drive robots has been investigated. Initially, a comprehensive review of related work is provided, followed by a detailed description of the differential-drive robot, including its kinematic and dynamic models. Both type-1 and type-2 fuzzy controllers are implemented to evaluate their performance in tracking complex, challenging trajectories. Simulation results demonstrate the effectiveness of each fuzzy controller, with a focus on comparative analysis. All comparisons are conducted under strictly identical conditions to ensure a fair and unbiased evaluation of both controllers. A comparison study highlights differences in performance metrics across scenarios, revealing that the type-2 fuzzy logic controller outperforms the type-1 controller in improving trajectory tracking accuracy. Quantitative performance indicators, including root-mean-square errors (RMSEs) for distance and orientation, as well as transient response times, are employed for comparison. Specifically, the type-2 fuzzy controller reduced the average tracking error by more than 75% and the angular error by over 80% across different trajectories, while also decreasing the response time by up to 80% compared to the type-1 fuzzy controller. Full article
(This article belongs to the Section Automation and Control Systems)
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23 pages, 6667 KB  
Article
Hydrogen Enrichment in Methanol Dual-Fuel CI Engines: A Computational Assessment of Engine Performance and Major Combustion Parameters and Emissions
by Takwa Hamdi, Samuel Molima, Juan J. Hernández, José Rodríguez-Fernández and Mouldi Chrigui
Machines 2026, 14(5), 563; https://doi.org/10.3390/machines14050563 - 18 May 2026
Viewed by 238
Abstract
Hydrogen enrichment of compression ignition (CI) engines has emerged as a promising strategy to simultaneously enhance thermal efficiency and reduce carbon-based emissions. This study numerically investigates how hydrogen enrichment affects engine performance and emissions in methanol–diesel dual-fuel CI engines, a combustion mode gaining [...] Read more.
Hydrogen enrichment of compression ignition (CI) engines has emerged as a promising strategy to simultaneously enhance thermal efficiency and reduce carbon-based emissions. This study numerically investigates how hydrogen enrichment affects engine performance and emissions in methanol–diesel dual-fuel CI engines, a combustion mode gaining increasing attention for replacing fossil diesel with sustainable fuels, particularly in hard-to-abate sectors such as maritime transport. The simulations are based on the Unsteady Reynolds-Averaged Navier–Stokes (URANS) equations, incorporating the RNG k-ε turbulence model, the Eddy Dissipation Concept (EDC) for turbulence–chemistry interaction, and the G-equation for turbulent premixed flame propagation. The numerical model is validated against experimental data for in-cylinder pressure and heat release rate at 45% methanol substitution ratio (by energy). The results indicate that increasing the hydrogen enrichment ratio (HER, defined on an energy basis) from 5% to 20% raises the Sauter mean diameter (SMD) of the diesel fuel from 20.2 µm to 28.0 µm (+38%), driven by reduced aerodynamic breakup intensity associated with modified gas-phase properties under hydrogen enrichment. Furthermore, hydrogen’s elevated adiabatic flame temperature and superior mass diffusivity intensify combustion, raising peak in-cylinder pressure from 75.2 to 79.1 bar (+5.2%), amplifying the peak heat release rate from 129 to 211 J/°CA (+63.6%), and elevating maximum in-cylinder temperature from 1542 to 1735 K (+193 K). Under the investigated CFD operating conditions, these thermodynamic gains translate into an engine-level 6% improvement in indicated thermal efficiency and a 14% reduction in indicated specific fuel consumption (accounting for hydrogen, methanol, and diesel) at HER 20%. On the emissions front, CO2 declines by 24% in direct proportion to the carbon-containing fuel mass displaced by hydrogen substitution, while NOx increases approximately twofold from 0.10 g/kWh at HER 0 to 0.21 g/kWh at HER 20, driven by peak temperature elevation. These findings establish hydrogen-enriched methanol–diesel dual-fuel combustion as a viable pathway toward high-efficiency, low-carbon CI engine operation for heavy-duty transport applications. Full article
(This article belongs to the Special Issue Advances in Combustion Science for Future IC Engines, 2nd Edition)
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27 pages, 3134 KB  
Article
A Physics-Informed Stability-Driven Approach to Wavelet Packet Band Selection for Crack Severity Classification Across Operating Conditions
by Francesco Melluso, Vincenzo Niola, María Jesús Gómez García and Cristina Castejon
Machines 2026, 14(5), 562; https://doi.org/10.3390/machines14050562 - 16 May 2026
Viewed by 302
Abstract
Accurate crack severity classification in rotating shafts remains a challenging task due to the strong spectral overlap between adjacent damage levels and the absence of distinct fault-specific frequency components. In such conditions, conventional vibration-based approaches relying on global spectral descriptors often fail to [...] Read more.
Accurate crack severity classification in rotating shafts remains a challenging task due to the strong spectral overlap between adjacent damage levels and the absence of distinct fault-specific frequency components. In such conditions, conventional vibration-based approaches relying on global spectral descriptors often fail to provide sufficient discriminatory information. This work proposes a stability-driven multi-resolution framework for crack severity classification based on the Wavelet Packet Transform (WPT). The approach aims to identify frequency bands that exhibit consistent diagnostic relevance across multiple decomposition levels while maintaining a monotonic relationship with crack severity. To this end, an interpretability-driven analysis based on Random Forest feature importance is combined with a frequency stability criterion and a monotonicity constraint, enabling the selection of physically meaningful and consistent spectral regions. The proposed framework has been evaluated on vibration data acquired from a rotating shaft test bench under multiple operating speeds and damage conditions. The results have shown that crack progression is characterised by distributed energy variations across specific frequency regions rather than by the emergence of isolated spectral peaks. It can be concluded that the proposed stability-driven band selection approach enables the identification of these regions in a consistent manner across spectral resolutions and operating conditions. Furthermore, the integration of WPT-based features with conventional time- and frequency-domain descriptors leads to a hybrid multi-scale representation that improves classification performance, particularly in intermediate severity regimes where spectral overlap is most pronounced. Overall, the proposed methodology provides a physically interpretable and consistent framework for vibration-based crack severity classification, with potential applicability to a wide range of rotating machinery diagnostics problems. Full article
(This article belongs to the Special Issue Advanced Machine Condition Monitoring and Fault Diagnosis)
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19 pages, 1843 KB  
Article
Partial Natural Torsional Frequency Modification of Vehicle Driveline Considering Modal Damping
by Kui-Yang Gao, Guo-Feng Yao, Min Wang, Jun-Lin Chen and Zhi-Wen Xu
Machines 2026, 14(5), 561; https://doi.org/10.3390/machines14050561 - 16 May 2026
Viewed by 229
Abstract
Torsional resonance is a common phenomenon in engineering vehicle drivelines. To avoid the influence of resonance on the driveline, it is typical to modify the frequency. However, traditional frequency modification methods cannot precisely achieve expected frequencies while keeping others unchanged. They often cause [...] Read more.
Torsional resonance is a common phenomenon in engineering vehicle drivelines. To avoid the influence of resonance on the driveline, it is typical to modify the frequency. However, traditional frequency modification methods cannot precisely achieve expected frequencies while keeping others unchanged. They often cause frequency ‘overflow’ and fail to account for the influence of modal damping on drivelines. To address the issues above, a passive modification method is proposed to modify the natural frequencies of engineering vehicle drivelines, considering modal damping. In this paper, the dynamic equations for gears and shafts are derived by a lumped-parameter model that employs the Lagrange method to establish a reasonably equivalent model as a serial-parallel system consisting of (moment of inertia)-(torsional spring)-(torsional damper) with free boundary conditions. Additionally, the passive structural modification for the partial eigenvalue assignment (PEVAPSM) method is employed to modify the specified partial natural torsional frequencies to realizable expected values, while others remain unchanged. The modal damping of the original driveline is modified based on the orthogonal decomposition method. Finally, the practical applicability of the method proposed in this paper is demonstrated through a specific example. Results indicate that the PEVAPSM method has been successfully extended and supplemented from a theoretical translational system, ignoring modal damping, to a practical torsional system considering modal damping to modify natural frequencies of the structure. The improved PEVAPSM method enables to precisely determine the moment of inertia and modal damping of gears in the driveline, preventing resonance with other structures at the same frequency. It offers valuable guidance for studying the torsional vibration characteristics of engineering vehicle drivelines. Full article
(This article belongs to the Section Vehicle Engineering)
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27 pages, 12622 KB  
Article
Safety-Filtered Residual Reinforcement Learning over Model Predictive Control for Friction-Aware Autonomous Vehicle Platooning
by Ali S. Allahloh, Atef M. Ghaleb, Mohammad Sarfraz, Abdalla Alrashdan, Mohammed A. H. Ali and Adel Al-Shayea
Machines 2026, 14(5), 560; https://doi.org/10.3390/machines14050560 - 16 May 2026
Viewed by 250
Abstract
This paper presents a deployment-oriented longitudinal platoon-control architecture for connected and autonomous vehicles operating under repeated leader hard-braking, cut-ins, and spatially varying road friction. The proposed stack combines four elements: (i) a lightweight scalar Kalman filter (KF) that smooths a friction-related signal and [...] Read more.
This paper presents a deployment-oriented longitudinal platoon-control architecture for connected and autonomous vehicles operating under repeated leader hard-braking, cut-ins, and spatially varying road friction. The proposed stack combines four elements: (i) a lightweight scalar Kalman filter (KF) that smooths a friction-related signal and feeds friction-dependent constraint tightening; (ii) a model predictive control (MPC) backbone whose weights and horizon are selected offline using multi-objective GA/NSGA-II tuning; (iii) a bounded proximal policy optimization (PPO) residual policy, trained with the aid of a learned surrogate model, that refines the MPC command during transient events; and (iv) a command-level safety projection that enforces instantaneous actuation and clearance constraints at the fast control tick. The contribution is therefore not a new MPC formulation or a new reinforcement-learning algorithm in isolation, but an integrated and experimentally characterized control stack that keeps the safety-critical structure explicit while using learning to improve transient behavior. The method is evaluated in a CARLA digital twin of a six-vehicle platoon over a 5 km mixed urban–highway route and is further assessed in hardware-in-the-loop (HIL) on an automotive ECU using a multi-rate ROS 2/AUTOSAR implementation (50 Hz estimation/safety loop, 10 Hz MPC/RL refresh). Across 10 held-out disturbance seeds, the full stack improves spacing regulation, maintains non-amplifying disturbance propagation according to the reported string-stability indices, and reduces a route-normalized positive tractive-energy-at-the-wheels proxy by about 12% relative to Manual MPC and by up to 18% relative to a PID-CACC reference. Because the PID-CACC baseline does not enforce hard constraints and can collide under the tested disturbance suite, the main performance comparison is among collision-free controllers. The friction signal used in CARLA is derived from simulator road-surface annotations before filtering, so the present study should be interpreted as a friction-aware control and integration study rather than a validated onboard friction-estimation result. Likewise, the reported energy metric is an effort proxy and is not a calibrated fuel or battery consumption model. Full article
(This article belongs to the Special Issue Reinforcement Learning for Autonomous Vehicle Control)
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43 pages, 9331 KB  
Article
Sustainable Multi-Energy Microgrid Operation: Birds of Prey-Based Day-Ahead Scheduling Under Seasonal Renewable Uncertainty
by Hany S. E. Mansour, Hassan M. Hussein Farh, Abdullrahman A. Al-Shamma’a, AL-Wesabi Ibrahim, Abdullah M. Al-Shaalan, Amira S. Mohamed and Honey A. Zedan
Machines 2026, 14(5), 559; https://doi.org/10.3390/machines14050559 - 16 May 2026
Viewed by 205
Abstract
The increasing integration of renewable energy resources into modern microgrids requires reliable scheduling methods capable of managing uncertainty, seasonal variability, operating cost, and environmental impact. This study proposes a stochastic day-ahead scheduling approach for a representative grid-connected multi-energy microgrid comprising photovoltaic generation, wind [...] Read more.
The increasing integration of renewable energy resources into modern microgrids requires reliable scheduling methods capable of managing uncertainty, seasonal variability, operating cost, and environmental impact. This study proposes a stochastic day-ahead scheduling approach for a representative grid-connected multi-energy microgrid comprising photovoltaic generation, wind generation, a microturbine, a fuel cell, an energy storage system, and utility-grid exchange. The proposed model was implemented and simulated in a MATLAB (2024b) environment. The Birds of Prey-Based Optimization algorithm is applied to determine the optimal 24 h dispatch schedule by minimizing a weighted objective function that combines operating and emission costs. Uncertainties in solar irradiance, wind speed, electrical load, ambient temperature, and electricity prices are modeled using probabilistic distributions and Monte Carlo simulations. To improve computational efficiency, 1000 generated scenarios are reduced to 10 representative scenarios using Fast Forward Selection based on Kantorovich distance. Seasonal case studies for winter, spring, summer, and autumn are used to evaluate the proposed method. Compared with five metaheuristic algorithms, the proposed approach achieves the lowest fitness value in all seasons, with reductions of 15.2%, 26.5%, 6.8%, and 23.9%, respectively. The results confirm improved economic and environmental microgrid operation under seasonal renewable uncertainty. Full article
(This article belongs to the Special Issue Sustainable Intelligent Design, Control and Optimization for Renewable-Integrated Power Systems)
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26 pages, 4164 KB  
Article
Experimental Evaluation of LuGre-Based Friction Compensation in Multi-Surface Sliding Mode Control for Electro-Hydraulic Actuators
by Phu Phung Pham, Hai Nguyen Ngoc and Bo Tran Xuan
Machines 2026, 14(5), 558; https://doi.org/10.3390/machines14050558 - 15 May 2026
Viewed by 247
Abstract
Electro-hydraulic servo systems are widely used in industrial machinery and automation due to their high power density and fast dynamic response; however, their achievable positioning accuracy is often limited by nonlinear friction effects. In many robust control strategies, including sliding mode control and [...] Read more.
Electro-hydraulic servo systems are widely used in industrial machinery and automation due to their high power density and fast dynamic response; however, their achievable positioning accuracy is often limited by nonlinear friction effects. In many robust control strategies, including sliding mode control and its multi-surface variants, friction is commonly treated as a lumped bounded disturbance. This simplification neglects the dynamic and operating condition-dependent nature of friction, leaving the practical value of explicit friction compensation insufficiently clarified, especially for electro-hydraulic actuators operating near their bandwidth limits. This paper presents an experimental evaluation of LuGre-based dynamic friction compensation integrated into a multi-surface sliding mode control framework for electro-hydraulic actuators. Rather than proposing a new control methodology, the study focuses on clarifying, from a control-oriented mechanical engineering perspective, how friction compensation influences closed-loop tracking performance under different operating regimes. The proposed scheme is implemented on a laboratory-scale electro-hydraulic test bench and evaluated using step and sinusoidal reference motions over a wide range of excitation frequencies, from low-speed operation to the practical bandwidth limit of the actuator. Comparative experiments with a conventional proportional–integral–derivative controller and a multi-surface sliding mode controller without friction compensation are conducted to isolate the effect of explicit friction modeling. The experimental results reveal a strongly frequency-dependent influence of friction on tracking performance. At low excitation frequencies (e.g., 0.1 Hz), friction compensation provides only marginal improvement in root mean square (RMS) tracking errors. In contrast, as the excitation frequency approaches the actuator bandwidth limit (1 Hz), explicit LuGre-based friction compensation reduces the relative RMS tracking error by approximately 57% compared with the baseline MSSM controller and by up to 82% relative to a conventional PID controller. These results demonstrate that the effectiveness of friction compensation is highly dependent on operating conditions, providing experimentally grounded guidance for the design of control strategies for bandwidth-limited electro-hydraulic machines. Full article
(This article belongs to the Special Issue Control and Mechanical System Engineering, 2nd Edition)
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16 pages, 5594 KB  
Article
Research on the Crack Evolution Mechanism and Design Guidance for Internal Ring Gears Considering Support Configuration Flexibility
by Tiantang Duan, Shuo Wang, Quansheng Jiang, Qin Yao, Shengsheng Xia and Yang Xu
Machines 2026, 14(5), 557; https://doi.org/10.3390/machines14050557 - 15 May 2026
Viewed by 149
Abstract
The widespread application of planetary gear trains is accompanied by inevitable crack failures, especially for the internal ring gear, which may lead to catastrophic accidents. There is relatively little research on internal ring gear cracks and mostly only make assumptions about the crack [...] Read more.
The widespread application of planetary gear trains is accompanied by inevitable crack failures, especially for the internal ring gear, which may lead to catastrophic accidents. There is relatively little research on internal ring gear cracks and mostly only make assumptions about the crack damage morphology at a certain stage. Moreover, there is no answer on what will happen in the next stage after the crack occurs, or how to avoid serious failure. In view of this, this study considers rim and support configurations, tooth geometries, and crack parameters, and analyzes crack evolution mechanisms. The results indicate that compared to the internal ring gear outer surface constraint condition, the use of pin support for the internal ring gear increases the risk of severe rim-fracture failure. A thicker rim can avoid rim failure, especially when the initial crack is close to the tooth root. In addition, a larger root fillet helps to reduce the occurrence of rim failure over tooth failure. Increasing pin support diameter and stiffness results in a tendency for the crack trajectory to move away from the rim. This study gives support for the cracked ring gear failure analysis and safety design. Full article
(This article belongs to the Section Machine Design and Theory)
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29 pages, 23263 KB  
Article
Hydraulic Characteristics of Large-Scale Vertical Mixed-Pump Device Under Pump as Turbine (PAT) Mode Applying Chaos Theory
by Can Luo, Kangzhu Jing, Wei Zhang, Ruimin Cai, Li Cheng, Chenzhi Xia, Bowen Zhang and Baojun Zhao
Machines 2026, 14(5), 556; https://doi.org/10.3390/machines14050556 - 15 May 2026
Viewed by 234
Abstract
As an important option for energy storage projects, pumping stations can also generate electricity when the upstream has surplus water and the pump system operates as a turbine (PAT mode). When it switches from pump mode to PAT mode, the pump operation state [...] Read more.
As an important option for energy storage projects, pumping stations can also generate electricity when the upstream has surplus water and the pump system operates as a turbine (PAT mode). When it switches from pump mode to PAT mode, the pump operation state changes significantly. This study adopts a numerical simulation to investigate the flow characteristics, time-frequency domain performance and chaotic features of pressure pulsation in a vertical mixed-flow pump device when it operates in different PAT modes. The results show that, when the pump operates in PAT mode, the flow in the straight passage remains smooth, but it deteriorates in the elbow-shaped draft tube, such as developing a spiral stream in the straight section, a disordered stream in the elbow section, and vortexes and flow separation at the beginning of the diffuser section, but it gradually becomes smooth after passing through the diffuser section. Under low-head PAT conditions, circumferential circulation cross flow occurs at the impeller inlet, reducing energy conversion efficiency. Under all PAT conditions, the flow on the blade surface near the hub is stable, but obvious vortexes happen near the shroud. As the head increases, the small-scale vortexes disappear on the mid-blade surface, and the flow becomes smoother on the blade surface near the shroud of the impeller. Except at the impeller outlet, pressure pulsation of the monitoring probes exhibits clear periodicity, with dominant frequencies corresponding to the rotational frequency, and its amplitudes decreasing from shroud to hub. Pressure pulsation under all PAT conditions is chaotic, and phase trajectories exhibit ring-shaped structures consisting of the ring circle and the ring surface. Differences in the circle spacing, size, and spatial position of the ring circle phase locus and ring surface phase locus are observed, and these variations are closely related to the PAT conditions. A correlative relationship exists between the chaotic correlation dimension and flow performance, which is of great significance for the condition monitoring and fault diagnosis of pump units. These findings not only enrich the theoretical research on the PAT mode of pumps, but also provide a reference for similar engineering applications and offer new insights into condition monitoring of hydraulic machinery. Full article
(This article belongs to the Special Issue Advanced Research and Development in Fluid Machinery: Design, Optimization, and Applications)
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27 pages, 2954 KB  
Article
Exploring Rotational Dynamics of a Symmetric Rigid Body Under Combined Forces and Torques
by T. S. Amer, M. A. Ibrahem, Rageh K. Hussein, A. I. Ismail and H. F. El-Kafly
Machines 2026, 14(5), 555; https://doi.org/10.3390/machines14050555 - 15 May 2026
Viewed by 220
Abstract
This study investigates the rotational dynamics of a symmetric rigid body (RB) about a fixed point under the combined effects of a Newtonian force field (NFF), an electromagnetic field (EF), and external torques. A large parameter (LP) approach, together with the averaging method [...] Read more.
This study investigates the rotational dynamics of a symmetric rigid body (RB) about a fixed point under the combined effects of a Newtonian force field (NFF), an electromagnetic field (EF), and external torques. A large parameter (LP) approach, together with the averaging method (AM), is used to simplify the nonlinear equations of motion (EOMs). Both analytical and numerical solutions are applied to examine the system behavior under different conditions. The results indicate stable motion within certain parameter ranges, where angular velocity components show either exponential decay or periodic behavior depending on the applied torques. These findings are useful for practical applications, particularly in spacecraft attitude control and other engineering systems involving rotating bodies. Full article
(This article belongs to the Section Machines Testing and Maintenance)
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20 pages, 21059 KB  
Article
Full-Scale Laboratory Testing of Laser Clad Rail Track—Results of Sub-Surface Microstructural and Residual Stress Analysis
by Roger Lewis, Lucas Biazon Cavalcanti, Kazim Yildirimli, David Fletcher, Kate Tomlinson, Henrique Boschetti Pereira, Helio Goldenstein and Mahmoud Mostafavi
Machines 2026, 14(5), 554; https://doi.org/10.3390/machines14050554 - 15 May 2026
Viewed by 266
Abstract
Additive manufacturing through a laser cladding has been shown to be an effective technology for the mitigation of wear and rolling contact fatigue (RCF) of railway track. Small-scale tests have consistently shown that creating a thin layer of premium material on the tribo-active [...] Read more.
Additive manufacturing through a laser cladding has been shown to be an effective technology for the mitigation of wear and rolling contact fatigue (RCF) of railway track. Small-scale tests have consistently shown that creating a thin layer of premium material on the tribo-active surface of the railhead vastly reduces wear and suppresses the onset of RCF due to the ratcheting mechanism being almost eliminated in comparison to standard rail material. Cladding reduces material plastic flow by 60% which is a cause of insulated track joint failure. This paper reports results from the first full-scale trials of additively manufactured laser clad layers on railway rails by studying their mechanical properties and microstructure. This is a vital step in safely progressing this technology from lab scale to network application. Tested full-scale insulated block joint (IBJ) specimens, clad with martensitic stainless steel (MSS) and Stellite 6, were sectioned, polished and etched and the microstructures of the clad, heat-affected zone and parent rail materials were inspected using optical and scanning electron microscopy (SEM) (Hitachi TM3030 plus, Tokyo, Japan). Residual stress was also measured. Cladding with MSS and Stellite 6 showed high wear and RCF resistance after the tests. Material flow was reduced with the clad layer applied. No defects such as porosity or large precipitates were observed in the heat-affected zone (HAZ), particularly close to the rail surface at the clad end which could act as a point of weakness. Residual stress states varied between materials, MSS being compressive (−344 MPa average) and Stellite 6 being tensile (+391 MPa average) which could have an impact on the fatigue life of the clad. This finding matches previous work, indicating that MSS may be preferable in the field, where bending of rails can occur. Overall, the work showed that laser cladding can provide a good solution to lipping issues and wear problems of rail in IBJs. Analysis in this work confirmed that the HAZ where clad meets the bulk rail at the surface has good structural integrity; however, this needs to be a focus of attention in field application of these layers. Full article
(This article belongs to the Special Issue Rolling Contact Fatigue and Wear of Rails and Wheels)
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18 pages, 3049 KB  
Article
Influence of Process Parameters on Geometry and Thermal Behavior in Wire Laser Cladding of Bronze on Stainless Steel Substrates
by Armin Siahsarani, Mohsen Barmouz, Farideh Davoodi, Bahman Azarhoushang and Vendel Harta
Machines 2026, 14(5), 553; https://doi.org/10.3390/machines14050553 - 15 May 2026
Viewed by 244
Abstract
Wire laser cladding (WLC) of bronze on stainless steel offers a promising approach for combining the structural strength of steel with the superior tribological and corrosion properties of copper alloys. In this study, the influence of key process parameters, including wire preheating current, [...] Read more.
Wire laser cladding (WLC) of bronze on stainless steel offers a promising approach for combining the structural strength of steel with the superior tribological and corrosion properties of copper alloys. In this study, the influence of key process parameters, including wire preheating current, deposition speed, laser power, and wire feed speed on melt pool temperature and clad geometry was investigated using response surface methodology (RSM). Experiments were performed using a robot-assisted coaxial wire feeding laser cladding system, and real-time thermal monitoring was conducted using an infrared camera. The results showed that defect-free bronze clads with good metallurgical bonding and limited dilution were achieved across the investigated parameter range. Statistical analysis revealed that melt pool temperature is primarily governed by laser power and deposition speed, with a significant interaction between these parameters. Clad height was mainly influenced by wire feed speed and deposition speed, whereas clad width was controlled by laser power and deposition speed. The side angle was affected by deposition speed, laser power, and wire feed speed, reflecting the balance between vertical buildup and lateral spreading. Overall, the study demonstrates that stable and high-quality clads can be achieved by properly balancing energy input and material supply. The developed models provide valuable insight for optimizing process parameters in wire laser cladding of bronze on stainless steel. Full article
(This article belongs to the Special Issue Process Monitoring and Quality Optimization in Manufacturing Engineering)
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27 pages, 7871 KB  
Article
The Control of Handling Stability for Active Inward Tilt Vehicles Based on the Phase-Plane Lateral Stability Region
by Chen Zhang and Jialing Yao
Machines 2026, 14(5), 552; https://doi.org/10.3390/machines14050552 - 14 May 2026
Viewed by 164
Abstract
For autonomous vehicles, high-speed cornering can easily lead to degraded handling stability and increased risks of sideslip or even rollover. Therefore, vehicle phase-plane stability-region analysis has become an important topic in active safety-control research. However, most existing studies still construct phase-plane stability regions [...] Read more.
For autonomous vehicles, high-speed cornering can easily lead to degraded handling stability and increased risks of sideslip or even rollover. Therefore, vehicle phase-plane stability-region analysis has become an important topic in active safety-control research. However, most existing studies still construct phase-plane stability regions mainly based on simplified vehicle models, without sufficiently considering the influence of vertical load transfer during cornering on tire lateral forces and stability boundaries. To address this issue, this paper proposes a hierarchical control strategy based on phase-plane analysis for active inward tilt vehicles. This method adopts a three-degree-of-freedom vehicle dynamics model and a tire model. By carefully comparing the phase-plane stability regions of active inward tilt and passive roll vehicles and by further analyzing the state-trajectory convergence characteristics of active inward tilt vehicles under different longitudinal speeds, front wheel steering angles, and road adhesion coefficients, the effects of active inward tilt on stability-region expansion and vehicle-state convergence are revealed. Subsequently, a hierarchical control strategy is proposed as an integrated solution to improve vehicle handling stability. The upper-level controller dynamically adjusts the reference values and objective weights according to whether the vehicle state is located in the stable, critical, or dangerous region. The lower-level NMPC controller optimizes the front wheel steering angle and active suspension forces to achieve coordinated trajectory tracking and stability control. Double lane-change simulation results show that active inward tilt can improve the left–right vertical load distribution and expand the lateral stability region. Compared with passive roll and conventional active inward tilt control, the proposed strategy reduces the phase-plane state convergence area by 68% and 75%, respectively, thereby improving vehicle handling stability and active safety under extreme conditions. Full article
(This article belongs to the Section Vehicle Engineering)
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29 pages, 5769 KB  
Article
An AI-Based Framework Combining Categorical Alarm and Continuous Data for Power Estimation and Anomaly Detection in Photovoltaic Systems
by Jorge Ruiz Amantegui, Hai-Canh Vu, Phuc Do and Marko Pavlov
Machines 2026, 14(5), 551; https://doi.org/10.3390/machines14050551 - 14 May 2026
Viewed by 329
Abstract
This study investigates the integration of categorical inverter alarm data into data-driven frameworks for photovoltaic (PV) system monitoring. While most existing approaches rely exclusively on continuous SCADA measurements, the potential of categorical operational data remains largely unexplored. In this work, categorical alarm signals [...] Read more.
This study investigates the integration of categorical inverter alarm data into data-driven frameworks for photovoltaic (PV) system monitoring. While most existing approaches rely exclusively on continuous SCADA measurements, the potential of categorical operational data remains largely unexplored. In this work, categorical alarm signals are incorporated into power forecasting to enable anomaly detection. The proposed approach is evaluated on a large-scale real-world dataset comprising multiple PV plants and more than 100 inverters, representing over 1000 inverter-years of operation. The four most popular time series forecasting models, including Multi-Layer Perceptron, Long Short-Term Memory, Extreme Gradient Boosting, and Mamba, are used to estimate power output from continuous inputs, while categorical variables are integrated using one-hot encoding and entity embeddings. Anomaly detection is performed by analyzing residuals between predicted and measured power output. The results show that categorical alarm data contain relevant operational information and can be effectively incorporated into forecasting-based monitoring frameworks. However, their impact on predictive performance varies depending on the encoding strategy and model choice, highlighting important trade-offs between model complexity and feature representation. By providing a systematic evaluation of categorical data integration across a large, diverse dataset, this work addresses a gap in the literature and establishes a benchmark for future research on hybrid continuous–categorical approaches for PV inverter monitoring. Full article
(This article belongs to the Special Issue AI-Driven Reliability Analysis and Predictive Maintenance)
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56 pages, 87923 KB  
Review
Recent Advances in Artificial Intelligence and Machine Learning for Life Cycle-Wide Additive Manufacturing: A Comprehensive Review
by Hussein Kokash, Mohammad Kokash, Ammar Bany-Ata, Sameeh Baqain and Mwafak Shakoor
Machines 2026, 14(5), 550; https://doi.org/10.3390/machines14050550 - 14 May 2026
Viewed by 244
Abstract
Additive manufacturing (AM) has emerged as a transformative technology across multiple industries, from aerospace to biomedical applications. The integration of artificial intelligence (AI) and machine learning (ML) into AM processes represents a paradigm shift toward intelligent, autonomous manufacturing systems. This comprehensive review synthesizes [...] Read more.
Additive manufacturing (AM) has emerged as a transformative technology across multiple industries, from aerospace to biomedical applications. The integration of artificial intelligence (AI) and machine learning (ML) into AM processes represents a paradigm shift toward intelligent, autonomous manufacturing systems. This comprehensive review synthesizes recent advances in AI/ML applications across the entire AM life cycle—from design optimization and process planning through in situ monitoring, closed-loop control, and post-process qualification. The analysis is organized by ISO/ASTM AM process families, including powder bed fusion (PBF), directed energy deposition (DED), material extrusion (MEX), vat photopolymerization (VP), binder jetting (BJ), material jetting (MJT), and sheet lamination (SL). For each process family, the review examines the specific AI/ML techniques employed, the data modalities utilized (thermal imaging, acoustic signals, in situ cameras, CT/NDE data), and the current state of deployment from research prototypes to industrial implementation. The analysis reveals that while significant progress has been made in single-stage ML applications such as defect detection and parameter optimization, truly integrated life cycle-wide AI-driven AM workflows remain largely aspirational. Key challenges are identified including data scarcity, model generalization across machines and materials, real-time control constraints, and certification requirements. Finally, future research directions are outlined toward autonomous AM systems enabled by physics-informed ML, digital twins, and hierarchical AI architectures. Full article
(This article belongs to the Special Issue Innovations and Challenges in Additive Manufacturing Technologies)
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