Machines

28 pages, 5623 KB

Open AccessArticle

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 (registering DOI) - 19 May 2026

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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24 pages, 5498 KB

Open AccessArticle

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 (registering DOI) - 18 May 2026

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)

27 pages, 3134 KB

Open AccessArticle

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 (registering DOI) - 16 May 2026

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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21 pages, 1506 KB

Open AccessArticle

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 (registering DOI) - 16 May 2026

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)

27 pages, 12648 KB

Open AccessArticle

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 (registering DOI) - 16 May 2026

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)

41 pages, 8185 KB

Open AccessArticle

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 (registering DOI) - 16 May 2026

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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27 pages, 4164 KB

Open AccessArticle

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 (registering DOI) - 15 May 2026

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, 2587 KB

Open AccessArticle

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 (registering DOI) - 15 May 2026

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)

29 pages, 23263 KB

Open AccessArticle

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 (registering DOI) - 15 May 2026

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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31 pages, 1979 KB

Open AccessArticle

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 (registering DOI) - 15 May 2026

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)

20 pages, 21059 KB

Open AccessArticle

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 Goldstein and Mahmoud Mostafavi

Machines 2026, 14(5), 554; https://doi.org/10.3390/machines14050554 (registering DOI) - 15 May 2026

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

Open AccessArticle

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 (registering DOI) - 15 May 2026

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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28 pages, 7871 KB

Open AccessArticle

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 (registering DOI) - 14 May 2026

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

Open AccessArticle

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 (registering DOI) - 14 May 2026

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, 87897 KB

Open AccessReview

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 (registering DOI) - 14 May 2026

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)

37 pages, 2898 KB

Open AccessArticle

General Geometric Model for the Cutting Edge in Thread Turning

by Cristian Barz, Oleh Onysko, Volodymyr Kopei, Yaroslav Kusyi, Lesia Shkitsa, Predrag Dašić and Saulius Baskutis

Machines 2026, 14(5), 549; https://doi.org/10.3390/machines14050549 (registering DOI) - 14 May 2026

Abstract

Modern requirements for highly critical threads, such as drilling tool-joint threads or trapezoidal threads of heavy machine tools, impose requirements for high accuracy and at the same time wear resistance of thread cutters. Conventional thread cutters available on the global market have a [...] Read more.

Modern requirements for highly critical threads, such as drilling tool-joint threads or trapezoidal threads of heavy machine tools, impose requirements for high accuracy and at the same time wear resistance of thread cutters. Conventional thread cutters available on the global market have a profile that coincides with the thread profile. Their rake angle and the angle of inclination of the cutting edge are typically zero. However, to ensure long tool life and high cutting performance, such tools should have optimal values of the geometric parameters of the cutting part, particularly the rake angle and the inclination angle of the cutting edge. Non-zero values of these angles distort the thread profile, and there are currently no established algorithms for profiling such cutters. This analytical study aims to develop an algorithm that enables the straightforward manufacture of high-performance and at high-precision thread cutters with interpolated straight sides profile flanks for producing trapezoidal, triangular and buttress threads, including those made of difficult-to-machine materials. The obtained analytical expressions accurately describe the cutting edge of such cutters as a hyperbola, functionally dependent on geometric parameters such as pitch, diameter and thread profile angle, as well as on the rake angle and the inclination angle of the cutting edge. To simplify manufacturing, methods of rectilinear approximation of the curvilinear profile are proposed. The validity of such a replacement has been theoretically confirmed, as the maximum deviation of the hyperbolic profile from the linear approximation does not exceed 2 micrometers. The results indicate no significant deviations in the profile angle of the cutters with relatively large rake and inclination angles (γ = 10° and λ = 7°). Deviations from the nominal profile angle of the trapezoidal thread profile angle of 15° do not exceed 0.1°, while for tool-joint threads (30°), they range from 0.01° to 0.09°. However, significant deviations in the profile (up to 0.49°) occur in the case of machining buttress threads with a profile of 7°/45°. Experimental verification on a lathe confirms the theoretical results. Full article

(This article belongs to the Special Issue Innovations in the Design, Simulation, and Manufacturing of Production Systems)

40 pages, 3065 KB

Open AccessReview

The Application of Four-Quadrant Pump-Controlled Technology in the Recovery of Boom Potential Energy Current Status, Challenges, and Future Directions

by Lan-Kang Li, Bao-Yu Liu, Zhi Li, Gao-Cheng An, Hong-Quan Dong and Li-Feng Ma

Machines 2026, 14(5), 548; https://doi.org/10.3390/machines14050548 (registering DOI) - 14 May 2026

Abstract

Against the backdrop of the global energy crisis and the urgent pursuit of dual-carbon goals, improving energy efficiency and reducing energy consumption in construction machinery have become central to the industry’s green and low-carbon transition. As key equipment in infrastructure construction, hydraulic excavators [...] Read more.

Against the backdrop of the global energy crisis and the urgent pursuit of dual-carbon goals, improving energy efficiency and reducing energy consumption in construction machinery have become central to the industry’s green and low-carbon transition. As key equipment in infrastructure construction, hydraulic excavators generate considerable gravitational potential energy in the boom during cyclic operations. However, the throttling losses inherent in conventional valve-controlled systems not only waste energy but also cause system overheating and reduced efficiency. Owing to its four-quadrant operating capability and high efficiency, the four-quadrant pump-controlled system provides an effective technical platform for recovering boom potential energy. Therefore, this paper presents a comprehensive review of four-quadrant pump-controlled boom energy recovery (FQ-PCBER) systems. First, three representative system architectures—electric, hydraulic, and hybrid—are examined, and their technical characteristics, performance limitations, and applicable scenarios are compared. Subsequently, the review focuses on the control challenges associated with these systems and summarizes advanced control strategies. Finally, practical engineering issues, technical challenges, and future research directions are discussed. This review aims to provide researchers with a clear technical roadmap, accelerate the practical implementation of four-quadrant pump-controlled boom energy recovery technology, and support the green and low-carbon transformation of the construction machinery sector. Full article

(This article belongs to the Section Electromechanical Energy Conversion Systems)

18 pages, 945 KB

Open AccessArticle

An Improved Random Forest-Based RUL Prediction Method for Elastic Supports with Vibration Signal Analysis

by Wenwen Zhang, Jinying Huang, Zhenfang Fan, Yupeng Du, Wei Wang and Jiaolin Wei

Machines 2026, 14(5), 547; https://doi.org/10.3390/machines14050547 (registering DOI) - 14 May 2026

Abstract

As core vibration-damping components in rail transportation and aerospace, elastic supports are vital to equipment operational safety and maintenance cost control. Addressing the offline cumbersomeness and insufficient accuracy of traditional methods, as well as the poor adaptability of existing models to nonlinear damage [...] Read more.

As core vibration-damping components in rail transportation and aerospace, elastic supports are vital to equipment operational safety and maintenance cost control. Addressing the offline cumbersomeness and insufficient accuracy of traditional methods, as well as the poor adaptability of existing models to nonlinear damage and small samples, this study proposes a high-precision life prediction method based on a self-constructed full-life dataset and optimized random forest (RF). A self-developed triaxial vibration test bench was used to conduct accelerated aging tests on rubber–metal composite elastic supports, constructing a unique full-life dataset (412 valid samples) by collecting vibration signals via accelerometers and eddy current sensors. After extracting features like acceleration RMS and natural frequency, core damage-sensitive features were screened through PCA and Pearson correlation coefficients. The RF was optimized with a time-decaying factor and feature and parameter joint optimization to capture temporal degradation and resist overfitting. Experimental results show that the model achieves RMSE = 0.026 and R² = 0.988, significantly outperforming Gray Prediction, BP Neural Network, and XGBoost. It accurately captures the life evolution law of elastic supports, providing reliable technical support for online life prediction and predictive maintenance. Full article

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

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17 pages, 2604 KB

Open AccessArticle

A Quasi-Zero Stiffness-Based Low-Frequency Vibration Isolation Platform: Experimental Investigation

by Ngoc Yen Phuong Vo, Thanh Danh Le and Minh Ky Nguyen

Machines 2026, 14(5), 546; https://doi.org/10.3390/machines14050546 (registering DOI) - 13 May 2026

Abstract

As is well known, vibration, especially ultra-low-frequency vibration, is harmful to machinery’s accuracy and service life and even human health. This paper experimentally validates vibration isolation technology for low-frequency applications based on quasi-zero stiffness (QZS) properties. Firstly, a platform for isolating low-frequency vibration, [...] Read more.

As is well known, vibration, especially ultra-low-frequency vibration, is harmful to machinery’s accuracy and service life and even human health. This paper experimentally validates vibration isolation technology for low-frequency applications based on quasi-zero stiffness (QZS) properties. Firstly, a platform for isolating low-frequency vibration, referred to as LFVIP, is introduced, featuring a quasi-zero stiffness characteristic. Then, the dynamic stiffness of this platform is analyzed and established. Based on this analytical model, a solution for designing the platform to obtain the desired stiffness in the equilibrium state is suggested. Secondly, an experimental setup is established to verify the isolation performance of the platform under base displacement excitation. In addition, the isolation effectiveness of the LFVIP is compared with that of its linear counterpart (LC). The experimental results indicate that the LFVIP provides the starting isolation for effective isolation at approximately 2 Hz, while that of LC is around 6 Hz. Moreover, the vibration attenuation of the LFVIP is greater than that of the LC. Vibration isolation technology based on quasi-zero stiffness is superior to the LC, particularly in the low-frequency region. This work offers useful insights for the design of vibration isolators, suspension systems, and related applications, particularly by demonstrating how the superior vibration attenuation of the LFVIP can be leveraged to improve the performance of these systems. Full article

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

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