International Journal of Hydromechatronics (30 papers in press)

Regular Issues

• Transmission Systems Using PDC And PMU in Machine Learning for Enhanced Efficiency, Fault Detection and Diagnosis  
  by A. Sekar, D. Sri Vidhya, S. Jaividhya, R. Gopalakrishnan 
  Abstract: The primary issue in contemporary transmission systems is ensuring operational efficiency and reliability and facilitating rapid and precise fault detection. Traditional fault detection techniques are not real time responsive as they do not reflect intricate temporal dynamics and spatial-temporal dependencies of wide-area power systems. To overcome this limitation, this paper suggests an intelligent phasor-based fault detection (IPFD) model that enhances the accuracy, efficiency, and robustness of the detection system. This framework uses synchronised data of phasor measurement units (PMUs) and phasor data concentrators (PDCs) and then preprocessing phases to remove noise, and normalise the data. Adaptive spectral-spatial decomposition (ASSD) is used to extract features, which minimise dimensionality and yet important fault features to be effectively classified. The method is tested in a digital twin setting with OPAL-RT and PSCAD in the conditions of real faults. Performance and transmission system efficiency are confirmed by the results.
  Keywords: Transmission Networks; Phasor Measurement Units (PMU); Spatial-Temporal Learning; Digital Twin Technology; Adaptive Spectral-Spatial Decomposition (ASSD); Fault Detection.
  DOI: 10.1504/IJHM.2025.10076881
   
  
• Multi-Objective Trajectory Planning and Optimisation of Excavators Based on Energy Consumption Analysis  
  by Zhaoyuan Yao, Wenli Zhang, Qihuai Chen, Tianliang Lin 
  Abstract: The realization of automatic excavator operation has become a key component in the intelligent development of construction machinery. Trajectory planning and optimization is the core technologies for achieving automated excavator operations, with its primary objective being to ensure a smooth and continuous operation process while achieving low energy consumption, high efficiency. Therefore, a comprehensive trajectory planning and optimisation framework is proposed in this paper, based on energy consumption analysis. This framework aims to effectively balance time, energy consumption, and bucket fill rate during excavator operations. Initially, the kinematic model, dynamic model, and excavation resistance model of the excavator are established to provide a theoretical foundation for subsequent trajectory planning and optimisation. Subsequently, the proposed models are analysed and validated. Finally, the excavation path for channel excavation is optimised using five non-uniform rational B-spline curves, with an improved chaotic adaptive particle swarm optimisation algorithm employed to solve the multi-objective optimisation problem.
  Keywords: excavator; autonomous operation; dynamic model; trajectory planning and optimization.
  DOI: 10.1504/IJHM.2025.10077065
   
  
• Design, Modelling and Verification of Powerful Electro-hydrostatic Actuators with Impact Absorption for Heavy-Load Joints Application  
  by Huipeng Zhao, Junjie Zhou, Shanxiao Du, Yi Wu, Sanxi Ma, Wenbo Liao, Hui Liu 
  Abstract: This study proposes a joint electro-hydrostatic actuator (JEHA), designed to enable heavy-load wheel-legged robots to jump over obstacles and absorb impact when landing The JEHA can operate in four-quadrant with high-power density To further analyze its inherent impedance and energy consumption, an improved spring-damping model for the JEHA was formulated considering the oil as an elastic element, and the internal leakage and pressure losses as damping effects The experimental results demonstrate that the JEHA enables a 70 kg single-leg mechanism to achieve jumping and exhibits outstanding joint performance, including high torque output, high-speed operation, and enhanced safety features Notably, its inherent impedance reduced landing impact forces by 47% And the safe reverse operation under impact demonstrated potential energy recovery This study highlights the ability of JEHA to combine high power output with superior impact absorption, promising a novel solution for heavy-load robots requiring robust and efficient interaction with challenging environments.
  Keywords: Electro-hydrostatic actuator; heavy-load robots; modeling analysis; impact absorption; energy recovery.
  DOI: 10.1504/IJHM.2025.10077424
   
  
• Measurement and Mapping of Acoustic Pressure and Standing Wave in an Ultrasonic Medium: Effect of Power and Frequency  
  by Muhammad Shafiq Mat Shayuti, Tuan Mohammad Yusoff Shah Tuan Ya, Mohamad Zaki Abdullah 
  Abstract: Sonication is an emerging technique in green processes, but complication arises when non-uniform cavitation in acoustic field goes under-comprehended, especially in combinations of various ultrasonic power & frequency. As acoustic pressure is the indicator for cavitation activity, this report explores the impact of varying ultrasound power & frequency towards the acoustic pressure within a bath reactor. Result indicates that 25 to 60 kHz sonication thrusted by 30 to 120 W power generated 174 kPa-783 kPa of acoustic pressure corresponding to shockwaves & microjets from cavitation bubbles implosion, with higher frequencies required more power to achieve comparable acoustic pressure. Furthermore, the ratio of standing wave to traveling wave regions was discovered to be influenced by attenuating acoustic pressure, where visibly vigorous bubble activity correlated with stronger acoustic pressure readings. This qualitative observation, supported by acoustic pressure measurements, suggests that regions of intense cavitation can be indirectly identified by pressure mapping.
  Keywords: acoustic pressure; frequency; mapping; power; standing wave; ultrasonic bath.
  DOI: 10.1504/IJHM.2025.10077452
   
  
• Robustness of the injection characteristics for a hydraulically-actuated fuel system  
  by Qi Lan, Zixin Wang, Yun Bai, Ying Xu, Yong Wang, Xinming Yan, Dehao Kong, Chuan Ma 
  Abstract: This study investigated the injection characteristics robustness in a hydraulically-actuated fuel system under parameter drift caused by harsh operating conditions. Utilizing Monte-Carlo method integrated with Latin hypercube sampling, 1000 parameter samples were analysed to derive frequency distribution histograms and quantify robustness via statistical indicators. Key structural parameters influencing fuel injection quantity (FIQ), opening delay time (ODT), and closing delay time (CDT) were evaluated. Regression models linking normalized parameters to robustness metrics reveals that nozzle hole diameter predominantly affects FIQ robustness (43.4%58.1% contribution). ODT robustness is strongly governed by control and outlet orifice diameters (combined > 86% contribution). CDT mean and kurtosis correlate with nozzle hole and inlet orifice diameters, while outlet orifice diameter dominates CDT standard deviation (74.1% contribution). CDT skewness is sequentially influenced by outlet orifice, nozzle hole, control orifice, and inlet orifice diameters. These findings provide quantitative insights into optimising parameter design for enhanced injection consistency.
  Keywords: Hydraulic-driven fuel system; Injection characteristics; Robustness indicators; Monte-Carlo method; Quantitative analysis.
  DOI: 10.1504/IJHM.2026.10077633
   
  
• Data-Driven Suitability Mapping for Optimised Electric Vehicle Charging Infrastructure: A Comprehensive Literature Review  
  by Nissisolomon Rudrapogu 
  Abstract: The rapid growth of electric vehicle (EV) adoption has led to an increased demand for efficient and accessible electric vehicle charging stations (EVCS). This paper reviews the literature on data-driven methods for selecting EVCS locations and mapping facility suitability, focusing on the use of geographic information systems (GIS), machine learning (ML), and multi-criteria decision-making (MCDM) approaches. It explores current optimisation techniques, including models like analytic hierarchy process (AHP), fuzzy AHP, stepwise weight assessment ratio analysis (SWARA), and predictive models such as random forest. The review identifies common trends in the application of synthetic data generation, micro-simulations, and digital twins for estimating EV charging demand. Key contributions of the paper include the systematic categorisation of methodologies used for EVCS planning, a critique of hybrid GIS-ML-MCDM frameworks, and an assessment of gaps related to data sparsity, privacy, and multi-period adaptive planning. The findings highlight the importance of integrating GIS spatial analysis with explainable ML models and robust decision-support factors to enhance the resilience and transparency of EVCS infrastructure planning. The study provides valuable insights for policymakers and researchers, offering a roadmap for the sustainable deployment of EVCS and supporting the transition to cleaner urban transportation.
  Keywords: Electric Vehicle Charging Infrastructure (EVCS); Geographic Information Systems (GIS); Machine Learning (ML); Multi-Criteria Decision-Making (MCDM); Hybrid Models and Optimization.
  DOI: 10.1504/IJHM.2025.10077634
   
  
• Effect of the Diameter of the Diaphragm Hydrolic Diode Connecting Fitting on its Diodicity  
  by Sergey Kaigorodov, Egor Dorofeev 
  Abstract: The object of the study in the presented manuscript is hydraulic diodes. Analysis of scientific and technical literature showed that the use of hydrodiodes as an analogue of check valves has a number of advantages, but does not ensure the complete absence of reverse fluid flow. By studying the geometric and design parameters of hydrodiodes, it is possible to reduce the amount of reverse fluid flow, thereby increasing the efficiency of the hydrodiodes. The article contains a set of theoretical and experimental studies aimed at determining the effect of the diameter of the connecting nipple on the diode capacity of the hydraulic diode. As a result of the studies, recommendations were developed for selecting the diameter of the connecting nipple, ensuring the best efficiency of the hydrodiode.
  Keywords: diaphragm hydrolic diode; diodicity; diameter of the connecting fitting.
  DOI: 10.1504/IJHM.2025.10077789
   
  
• Aerodynamic Behaviour of seal-Rotor System with Multivariate Working Fluid and System Parameters via Nonlinear Whirl Model  
  by Heyong Si, Zhenkui Yu, Lihua Cao, Dongchao Chen 
  Abstract: The seal dynamic pressure performance affected by fluid properties and rotor motion affected by system parameters have a strong interference coupling effect. A nonlinear whirl model of the seal-rotor system considering the spatiotemporal gas-solid coupling effect between seal aerodynamic effect and rotor dynamics behaviour was established to restore the actual rotor motion. The co-simulation of seal flow and rotor dynamics was achieved via mesh deformation and user-defined function (UDF). Then the seal dynamics were calculated by differential theory, and the first-order quantitative numerical values were obtained. Finally, a comparative analysis was conducted on the different working fluids and different system parameters. The results indicated that the nonlinear whirl model can more accurately reproduce the rotor motion state and seal flow field change. Supercritical carbon dioxide (SCO2) has a stronger aerodynamic effect. The rotor elastic recovery stiffness, pressure ratio, and rotational speed have a significant influence on seal dynamic characteristics, while the impact of unbalanced mass eccentricity is relatively weak.
  Keywords: Multivariate working fluid; Seal-rotor system; Dynamic behavior; Aerodynamic performance; Nonlinear whirl model.
  DOI: 10.1504/IJHM.2026.10077949
   
  
• Optimising Pavement Crack Sealing with a Depth-Informed Reinforcement Learning Framework and Synthetic Crack Trajectory Modelling  
  by Jinchao Wang, Edwin K.P. Chong, Chenxi Li, Yihai Fang, Xin Wang 
  Abstract: Pavement crack sealing is a critical maintenance activity essential for extending roadway service life and ensuring traffic safety Traditional crack sealing methods, often modelled as the Traveling Salesman Problem, focus on minimising travel distance but overlook crack depth variations and sealing continuity This often results in inefficient material usage and inconsistent pavement quality To address these limitations, this study presents a depth-informed reinforcement learning (RL) framework for autonomous and continuous crack sealing, with the Automatic Crack Generation Model (ACGM) as its key component ACGM generates realistic synthetic crack maps and optimal sealing trajectories by simulating natural crack propagation patterns, eliminating the need for costly manual expert demonstrations and providing a robust, scalable foundation for RL training Experimental results demonstrate that the proposed approach outperforms conventional TSP-based methods, achieving a 17% reduction in material waste, a 12% decrease in operational time, and improved surface uniformity.
  Keywords: Crack Sealing; Reinforcement Learning; Behavior Cloning; Depth-informed Path Planning,.
  DOI: 10.1504/IJHM.2026.10077950
   
  
• Theoretical and numerical analysis on leakage rate of hard sealing ball valves  
  by Zhao-nian Zhou, Jia-xiang Xu, Zhe-hui Ma, Zhao-tong Wang, Yu-wei Wang, An-qi Guan, Li Fang, Wen-qing Li, Zhi-jiang Jin, Jin-yuan QIAN 
  Abstract: Hard sealing ball valves have attracted extensive attention in pipeline systems due to the significant advantages of simple structure and small flow resistance. Leakage is currently one of the key problems of hard sealing ball valves. And accurate leakage rate prediction methods are lacking for hard sealing ball valves. This paper derives the leakage rate equation of parallel spherical seals and verifies the accuracy of the derivation by simulation. Constructs a microscopic leakage model based on the rough surface model to describe the flow in parallel spherical seals. A calculation method of microscopic leakage combined with the derived leakage rate equation is proposed. This work can provide a reference for the leakage model modelling and leakage rate prediction in hard sealing ball valves.
  Keywords: theoretical derivation; hard sealing ball valves; leakage rate; flow factor.
  DOI: 10.1504/IJHM.2026.10078212
   
  
• Characteristics of Self-excited Cavitating Flow Oscillations in V-Notch Spool Valves  
  by Wenkang Zhang, Liang LU 
  Abstract: The streamlined v-notch geometry in spool valves is susceptible to flow-induced instabilities. Experimental and numerical studies demonstrate that cavitating jet at the notch generate strong self-excited oscillations with a distinct dominant frequency. Contour analysis reveals that the shear-layer vortices in the jet evolve as cavitation develops, providing the compressible medium required for vortex-acoustic coupling. The vortices generated by the notch disturbance interact with each other through acoustic feedback, leading to lock-in and ultimately producing sustained self-excited oscillations. A reduction in outlet pressure increases the jet velocity but lowers the frequency, owing to the reduced speed of sound induced by intensified cavitation. Modifying the notch geometry can attenuate oscillations but inevitably reduces flow capacity. To quantify the suppression effect, a hydraulic-diameter-based dimensionless index is proposed. Results show that reducing the notch angle provides stronger damping than decreasing the wedge angle, with up to 46.74% reduction in oscillation amplitude.
  Keywords: V-notch spool valve; Cavitation; Oscillations; LES; Vortex-acoustic coupling; Oscillation suppression strategies;.
  DOI: 10.1504/IJHM.2026.10078299
   
  
• Graphene Pressure Sensor with Supportive Arm Integration: A Novel Approach for Accurate Low Hydraulic Pressure Measurement in Microelectromechanical Systems  
  by Meetu Nag, Bhanu Pratap 
  Abstract: This paper proposes an innovative Graphene Pressure sensor for measuring low-pressure up to 1 psi in Microelectromechanical Systems. This design optimizes the balance between sensitivity and nonlinearity of the output. The proposed design enhances the stress concentration area and offers improved stability while maintaining high sensitivity in the low-pressure range (0-1 psi). This paper provides a complete study of the proposed sensor geometry and a comparative evaluation with the presently available geometry. Finite element analysis was conducted in COMSOL Multiphysics to analyse the design for stress distribution and output characteristics. The output of the proposed sensor provides a sensitivity of 28.42 mV/kPa with a low nonlinearity of 0.016% at full scale. The proposed sensor introduces a novel supportive arm structure that enhances stress concentration, leading to improved sensitivity and linearity in the low-pressure range (0-1 psi) compared to prior designs. The sensors exceptional sensitivity and low-pressure detection make it ideal for applications such as airflow detection in microfluidic systems, low-pressure sensing in aerospace cabin environments, and low hydraulic pressure measurement in microhydraulic systems.
  Keywords: Microelectromechanical Systems; Graphene; Low Hydraulic Pressure; Micro-Hydraulic Systems; Low pressure range; Sensitivity; Linearity.
  DOI: 10.1504/IJHM.2025.10078504
   
  
• Coupled Modelling and Characteristics Analysis of Rotary System of Deep Drilling Rig Under Multiple Loading Conditions  
  by Yong Zhu, Bo Lan, Shida Zhang, Qiang Gao 
  Abstract: The inherent uncertainty of deep-well formations, coupled with the nonlinear and time-varying dynamics of hydraulically driven drilling rigs, results in highly complex rotary system behavior. In this paper, the rotary system of a deep well drilling rig was investigated. Firstly, the rotational speed transfer equation and the torque balance equation for the drilling tool were established, and an electromechanical-hydraulic multi-field coupled co-simulation model of the rotary system was constructed. Additionally, the dynamic responses under constant, impact, and alternating loads were systematically analyzed. Finally, extensive experiments were conducted to validate the dynamic characteristics and response behavior of the rotary system under various loading conditions. The results indicate that the hydraulic pressure of the rotary system responds to load changes within 0.03 s and returns to a stable state within 1.5s. The variations in pressure, flow, and rotational speed of the rotary system closely correspond to the load changes.
  Keywords: deep-well drilling; rotary system; coupled modeling; multiple loading conditions; dynamic characteristics.
  DOI: 10.1504/IJHM.2026.10078663
   
  
• Experimental and numerical research on vapor cavity surge properties in poppet valve with thick-wall-orifice structural characteristics  
  by Kan Li, Sitong Liu, Liang LU, Guolei Si 
  Abstract: Poppet valves are extensively utilised in hydraulic systems for pressure, switching, and flow control owing to their simplicity and rapid response, yet suffer from cavitation due to vena contracta effect at the notch. This study investigates cavitation surge dynamics in face-sealing poppet valves which is coupled with pressure and flow variations in the flow field, revealing that large-scale cavitation originates from low-pressure vortex cores. The frequency-amplitude characteristics of surge and collapse exhibit consistent trends: higher velocity increases dominant frequency, while higher flow rate enhances oscillation amplitude. To evaluate oscillation energy comprehensively, time-averaged power density is introduced. In consideration of the limitations imposed by flow resistance and sealing performance requirements, which stipulate a length-to-diameter ratio ranging from 2 to 4, an optimised design with throttling angle of 45
  Keywords: poppet valve; thick-wall orifice; vortex cavitation; surge instability.
  DOI: 10.1504/IJHM.2026.10079345
   
  
• Spectral Characteristics of Unsteady Cavitation in a Venturi Tube: A Numerical Study on Vortex Dynamics and Flow Monitoring  
  by Bokai Fan, Mengxue Dong, Maosen Xu, Yun Ren, Denghao Wu, Jiegang Mou 
  Abstract: Cavitation-induced pressure fluctuations in Venturi tubes can lead to vibration, noise, and performance degradation in hydraulic systems. This study investigates the spectral characteristics of cavitating flow in a slit Venturi tube and clarifies their relationship with vortex dynamics and cavitation structures. Time-resolved pressure measurements and high-speed imaging are combined with three-dimensional large-eddy simulations based on the volume-of-fluid method and the Zwart-Gerber-Belamri cavitation model. The validated numerical results resolve the evolution of vortex structures, vapour distributions, and streamwise pressure responses. According to the evolution of cloud cavitation, the flow is divided into several streamwise zones with distinct vortex-bubble interaction behaviours and spectral features. An energy-threshold-based identification method is introduced together with two indicators, the dual-peak index and the dual-peak frequency ratio, to characterise broadband dual-peak spectra. The results show that the upstream region exhibits a dual-peak spectrum governed jointly by cloud shedding and high-frequency local bubble dynamics, whereas the downstream spectrum gradually evolves into a low-frequency-dominated single-peak pattern because recirculation suppresses high-frequency components. Keywords: cavitating flow; Venturi tube; spectral
  Keywords: Cavitating flow; Venturi tube; Spectral evolution; Dual-peak spectrum; Vortex dynamics; Large-eddy simulation.
  DOI: 10.1504/IJHM.2026.10079421
   
  
• Dynamic characteristics of rotary-percussion drilling systems under vibrational loading  
  by Yong Zhu, Shida Zhang, Bo Lan, Qiang Gao 
  Abstract: With the rapid expansion of deep-earth and deep-sea resource exploration, technological innovation in deep-well drilling equipment has become essential for improving drilling efficiency. However, drilling rigs often experience random and uncertain loads under complex formation conditions. To address these challenges and enhance drilling automation, an electro-mechanical-hydraulic-pneumatic multi-field-coupled rotary-percussion drilling system was developed. Firstly, a dual hydraulic-motor drive scheme integrated with load-sensing technology was designed. Secondly, a multi-field-coupled dynamic simulation platform was established based on motion and flow equations of the actuating mechanisms. Finally, a theoretical framework for vibrational loading was developed, and the dynamic responses of the hydraulic systems under pulsating and alternating loads were analysed. The results indicate that the proposed rotary-percussion drilling system demonstrates a response time of 0.18 s to load variations, exhibiting rapid responsiveness and excellent dynamic tracking performance. When the load amplitude changes abruptly, the system quickly returns to a stable state within 0.19 s, indicating high operational stability.
  Keywords: deep-well drilling; rotary-percussion drilling system; coupled modeling; vibrational loading; dynamic characteristics.
  DOI: 10.1504/IJHM.2026.10079562
   
  
• Surface Acoustic Wave Micro Robotic System for Long-Stroke, High-Precision Micro Targets Manipulation
  by Ziyu Guo 
  Abstract: Automated microrobotic systems based on field-driven micromanipulation serve as critical foundations for advanced manufacturing and testing, enabling key applications such as micro-scale assembly, metamaterial structure fabrication, micro-sample testing, and imaging. Surface acoustic wave micromanipulation technology offers distinctive advantages including non-contact label-free operation and minimal damage, while supporting diverse functions such as positioning, translation, assembly, and patterning of micro-scale targets. However, conventional SAW methods are constrained by transducer architecture and acoustic field range, limiting their ability to execute complex trajectory control. In this study, we present a multilayered SAW micromanipulation system that achieves precise resonance and acoustic field motion within complex stratified structures, enabling gradient force driven manipulation of micro-objects via standing wave fields. By integrating real-time image recognition and closed-loop feedback control, we demonstrate precise regulation of complex motion paths for micro-scale targets, realizing a long-stroke, high-precision SAW microrobotic platform.
  Keywords: Micro electromechanical systems; micro manipulation; micro robotics; acoustofluids.
  
  
• A Deep Learning-Based Multi-Parameter Fault Diagnosis Method for Hydraulic Motors in Polar Low-Temperature Environments  
  by Haiming Wen, X.V. Yangguang, Meng Cui, Chenyang Liu, Yijia Yuan, Yan Chen, Wei Sun, Dayong Zhang 
  Abstract: Hydraulic motors are vital for polar ship deck systems, where extreme cold severely degrades reliability, yet real fault data are scarce because failures are hard to reproduce and transient events are difficult to capture. We built a polar-like field experimental system in China (?40 ?) to collect high-confidence fault data and developed a calibrated MATLAB/Simulink hydraulic model with simulationmeasurement error below 5%, enabling sample expansion across fault types. A CNN-LSTM-attention framework is proposed for multi-parameter fault diagnosis under high-noise, multi-channel conditions, combining local feature extraction, temporal dependency learning and attention-based feature selection. A four-class dataset, including switching valve faults, achieves 99.1% accuracy and a macro F1-score of 0.992, outperforming baseline models by 7.911.6%. SHAP analysis highlights physically consistent predictors, with hydraulic motor return-oil temperature and pump-station outlet pressure as dominant features, enabling accurate, interpretable diagnosis and supporting intelligent maintenance of polar engineering systems.
  Keywords: Polar ship systems,Hydraulic motors,Simulink-based simulation,Multi-parameter fault diagnosis,CNN-LSTM.
  DOI: 10.1504/IJHM.2026.10079645
   
  
• A rigid-soft robotic finger with pneumatic actuation and hyperelastic flexure hinge  
  by Jiabiao Li, Kaiwen Zheng, Zhuo Ma, Jianbin Liu 
  Abstract: This paper presents a rigid-soft hybrid bioinspired robotic finger that combines rigid support with pneumatic soft actuation to achieve both compliance and reliable output. The design integrates a thin-film pneumatic actuator with thermoplastic polyurethane (TPU) hyperelastic flexure hinges to realize large joint deformation without traditional rigid revolute joints. A large-deformation mechanical model based on the Mooney-Rivlin constitutive law is developed for the flexure hinge, and joint kinematic models are established for the interphalangeal (IP) and metacarpophalangeal (MCP) modules. Experiments show maximum bending angles of 45 [distal interphalangeal (DIP)] and 85 [proximal interphalangeal (PIP)], and the MCP joint achieves 54.3 bending with 22.3 lateral swing. The full finger reaches a combined bending angle of 182.6 and produces a maximum fingertip force of 3.36 N at 0.15 MPa.
  Keywords: Finger; flexure hinge; pneumatic actuator; TPU; 3D printing.
  DOI: 10.1504/IJHM.2026.10080016
   
  
• Modelling and Experimental Investigation of Longitudinal-Torsional Ultrasonic Assisted Honing for Small-Diameter Holes  
  by Yingying Yuan, Changyong Yang, Jingfei Yin, Yucan Fu, Wenfeng Ding, Jiuhua Xu, Rehman Mustafizur 
  Abstract: To break the efficiency bottleneck of conventional honing when machining small holes in electro-hydraulic servo-valve sleeves, this study introduces a novel longitudinal-torsional ultrasonic-assisted honing ( LTUAH) process. An analytical model is established for predicting both material-removal rate (MRR) and surface roughness (Ra) by integrating abrasive-grain distribution, force-balanced feed, and material removal behaviour. Experimental results show a prediction error below 15 %. The ultrasonic amplitude and the torsional-longitudinal ratio are main factors in LTUAH. Compared to the conventional honing, MRR rises by up to 69.95 %, whereas Ra exhibits a non-monotonic dependence on amplitude yet improves continuously with a higher torsional-longitudinal ratio, yielding a maximum Ra reduction of 47.6 %. The results indicate that the air-cutting phenomenon and the variable-speed impact effect play dominant roles in the performance enhancement of LTUAH. The findings confirm the superiority of LTUAH and lay a solid theoretical and technological foundation for the high-performance machining of precision small-hole components.
  Keywords: Longitudinal-torsional ultrasonic vibration; Ultrasonic-assisted honing; Predictive modeling; Material removal mechanism; Surface roughness; Honing force.
  DOI: 10.1504/IJHM.2026.10080136
   
  
• Enhancing Operating Duration and Energy Efficiency through Combined Accumulator Systems: A Simulation and Experimental Study  
  by Manish Kumar Barnwal, Rakesh Nayak, Jayanta Das, Sanjoy K. Ghoshal 
  Abstract: Accumulator-assisted hydrostatic systems operating under dynamic load conditions face the critical challenge of extending operating duration while minimising energy consumption. This paper presents a simulation and experimental investigation of single and combined accumulator configurations, with a specific focus on novel controlled energy discharge using a proportional flow control valve (PFCV). The PFCV is employed to actively regulate accumulator discharge flow, enabling precise control of energy release. A proportional pressure relief valve (PRV) is used in loading side to modulate the system pressure. The hydro-motor is controlled by giving sinusoidal demand speeds of different amplitudes and frequencies. The tracking of hydro-motor speed, accumulator pressure decay, discharge characteristics, and released energy is reported. The results demonstrate that the proposed configuration with PFCV-controlled accumulator discharge significantly enhances operating duration and energy efficiency compared to a single accumulator. Also, the combination of two accumulators (10L+30L) shows a longer discharge time compared to a single accumulator (40L).
  Keywords: HEMM; BOND GRAPH; HYDROSTATIC TRANSMISSION; ACCUMULATOR; LAB VIEW CONTROL.
  DOI: 10.1504/IJHM.2026.10080175
   
  
• Nonlinear parametric frequency domain analysis of a valve-controlled asymmetrical hydraulic cylinder  
  by Heng Du, Pingting Zhuang, Min Liu, Youhui Cheng, Chen Zhang 
  Abstract: Electro-hydraulic systems possess high control bandwidth and high-power density, widely adopted in traditional and green energy applications. Yet, their inherent nonlinearity and fluctuating loads impede optimizing efficiency and control. This study extends inverse Generalized Frequency Response Functions (iGFRFs) analysis to asymmetrical valve-controlled hydraulic cylinders. It identifies supply pressure and area ratio as key parameters influencing control bandwidth, load capability, and durability, with symmetric cylinders as special cases. A valve-controlled asymmetrical hydraulic cylinder model is inverted, followed by the iGFRFs analysis. Results show that both odd and even harmonics decrease with higher supply pressure and area ratio, with odd harmonics more pressure-sensitive and even ones more ratio-sensitive. Energy consumption is primarily influenced by supply pressure, not area ratio, making pressure critical for balancing control and efficiency. Comparative experiments between valve-controlled symmetric and asymmetrical systems validate the Volterra analysis, providing theoretical and practical guidance for designing efficient electro-hydraulic systems for green energy.
  Keywords: Valve-controlled asymmetrical cylinders; nonlinear parametric frequency domain analysis; inverse generalized frequency response functions (iGFRFs); electro-hydraulic systems.
  DOI: 10.1504/IJHM.2026.10080639
   
  
• Rheological properties and polishing performance of novel shear thickening polishing slurry for ultra-precision polishing polishing  
  by Linguang Li, Zhao Jing, Rui Huang, Jiang Guo, Jia Du, Pu Qin, Zhonghui Sun, Zili Zhang, Weiwei Liu 
  Abstract: Shear thickening polishing has emerged as a promising ultra-precision finishing technique for complex surfaces. However, existing methods often lack insights into sub-nanometer surface generation and nano-scale abrasive compatibility. In this work, a nano-abrasive shear thickening polishing slurry (STPS) was developed, and the effects of polyhydroxy polymer content and temperature on rheological behaviour were systematically studied. The compatibility and rheological behaviour of five STPSs loading different abrasives were explored and evaluated. The experimental results revealed that the overall viscosity of the shear thickening fluid increases with an increase in solid content, whereas the critical shear rate decreases. The temperature increase inhibits the shear thickening effect to a certain extent. Among the formulations, silica sol-based STPS exhibited excellent rheological stability, abrasives compatibility and material removal rate. After polishing, a sub-nanometer level ultra-smooth surface with a surface roughness Sa 0.35 nm was achieved, and tool marks were completely removed.
  Keywords: Shear thickening polishing; Rheological properties; Polishing slurry; NiP alloy.
  DOI: 10.1504/IJHM.2026.10080650
   
  
• High-Uniformity Magnetic Field and Stable Temperature Apparatus for the Parallel-Plate Magnetic Fluid Rheometer: Design, Simulation, and Experimental Validation  
  by Yijian Wei, Decai Li, Qianping Li, Yuqi Zhu, Lifen Liu, Jisheng Yang, Wenjuan Yu 
  Abstract: Magnetic fluid is a novel nano-functional material with unique applications in fields industry, aerospace, military technology, and biomedicine. Their rheological properties are crucial but hard to measure precisely with conventional rheometers. This paper designs a magnetic field and temperature control device for the parallel plate magnetohydrodynamic rheometer system, which can simultaneously achieve the measurement of ultra-low temperature and high magnetic field uniformity. An innovative three-segment rotor and structural optimization ensure 99% magnetic field homogeneity within the measurement area (>1.4 T max). By directly arranging the cooling pipes around the core and installing the insulation cover, it can achieve precise temperature control within the measurement range of -60 to 120. The device provides a guarantee for studying the multi-physics field coupled rheological behavior of magnetic fluids in extreme environments, and demonstrating significant application potential for magnetic fluids in sealing, vibration damping, sensing, and lubrication technologies.
  Keywords: Magnetic fluid; parallel-plate rheometer; magnetic field; temperature control.
  DOI: 10.1504/IJHM.2026.10081026
   
  
• A Causal Multi-Scale Temporal Attention Framework for Fault Diagnosis in Complex Hydraulic Systems Using Multi-Sensor Time Series  
  by Weidi Huang, Jiahao Sun, Zhihai Chen, Xiwen Gu, Shixi Yang 
  Abstract: Hydraulic systems are crucial in modern industry for their high power density and precise control, yet their complexity makes fault diagnosis challenging. This study introduces a novel data-driven framework that analyzes multi-sensor time-series data to predict hydraulic cylinder displacement. By comparing predictions against actual measurements, deviations signal potential anomalies. The core of the model employs an improved multi-head self-attention mechanism, enhanced with multi-scale local windows and causal masks to capture complex temporal dynamics. Validated on a custom hydraulic simulation platform, the framework demonstrated superior predictive accuracy and robustness over conventional methods. Fault injection experiments further confirmed its effectiveness in delineating system behavior and strong generalization for identifying both known and novel faults.
  Keywords: Hydraulic system; fault diagnosis; multi-sensor fusion; multi-head self-attention; time series analysis.
  DOI: 10.1504/IJHM.2026.10081203
   
  
• A Multi-stage Visual Guidance Framework for Terminal Docking of Autonomous Underwater Vehicle  
  by Shuo Liu, Xinlong Chen, Shanmin Zhou, Yijie Han, Yong Cai, Tao Wang 
  Abstract: This paper introduces a multi-stage visual guidance framework designed for terminal autonomous docking of underwater vehicles. The proposed approach integrates a single LED light for coarse positioning at medium ranges and multiple AprilTag markers for precise localization during close-range operations. A specialized subsea docking station (SDS) was developed to support the landing of a flat, fully actuated autonomous underwater vehicle (AUV). The guidance system dynamically switches between visual features based on distance, enabling robust and continuous pose estimation throughout the docking maneuver. The framework is implemented within a ROS-based software architecture and validated through pool experiments, demonstrating successful autonomous recovery of the AUV. Results confirm that the system achieves high positioning accuracy, operational robustness, and real-time performance, offering a practical solution for persistent underwater missions requiring repeated docking and charging.
  Keywords: Mechatronic system; Autonomous docking; Terminal guidance; Visual positioning; Underwater robotics.
  DOI: 10.1504/IJHM.2026.10081204
   
  
• Dynamic Characteristics Optimisation of a Pilot-Pressure Controlled Two-Stage Valve Distribution Radial Piston Motor  
  by Xinming Li, Tong Guo, Qinze Chen, Hao Liu, Fumin Que, Tianliang Lin 
  Abstract: Radial piston motors are widely used in the field of heavy-duty machinery, but leakage in conventional distribution pairs and piston pairs limits their high-pressure performance. This study proposes a pilot-pressure controlled two-stage valve distribution hydrostatic-balanced motor configuration. The proposed structure combines seat-valve distribution, pilot-pressure control, hydrostatic-balanced transmission, and piston guiding components support to improve sealing and motion stability. The working principle, pulsation characteristics, and hydraulic output performance were investigated through theoretical analysis, AMESim simulation, and prototype testing. Simulation results indicate favorable dynamic response and high-pressure operating potential under idealized conditions. Prototype tests up to 15 MPa show stable operation, with volumetric efficiency increasing from 86.91% to 88.56% as speed rises from 60 r/min to 120 r/min. The results verify the feasibility of the proposed configuration and provide a reference for high-pressure, low-leakage radial piston motor design.
  Keywords: hydraulic motors; pilot-pressure control two-stage flow distribution; radial piston; volumetric efficiency; valve distribution.
  DOI: 10.1504/IJHM.2026.10081327
   
  
• Intelligent Control Method of Rotary Percussion Drilling Rotary System Based on Deep Reinforcement Learning  
  by Yong Zhu, Chenlin Ding, Yang Zhao, Qiang Gao 
  Abstract: To address complex control challenges in rotary percussion drilling systems, a deep reinforcement learning approach based on the Soft Actor-Critic algorithm (SAC) is proposed. An intelligent controller with a multi-level reward function was developed. Its performance was rigorously validated through an electromechanical-hydraulic co-simulation model and a scaled-down physical test platform under various operational conditions. Compared to classical PID and Particle Swarm Optimisation PID methods, the SAC-based controller reduces step-response overshoot by over 30% and shortens adjustment time by nearly 90%. It also demonstrates superior robustness, improving recovery speed from instantaneous impact loads by more than 30%, while maintaining steady-state errors within 0.1 r/min (simulation) and 1.13 r/min (experiment). The comprehensive results confirm the enhanced performance of the method in overshoot suppression, response speed, and anti-disturbance accuracy, offering an effective solution for intelligent control of deep well drilling systems.
  Keywords: deep well drilling rig; rotary percussion drilling system; deep reinforcement learning; intelligent control.
  DOI: 10.1504/IJHM.2026.10081328
   
  
• Pre-matched Cooperation Control of a Proportional Directional Valve with Independence Metering Pilot Stage  
  by Luqiao Jin, Zhenyu Lu, Qi Su, Jing Ning, Guoping Liu, Junhui Zhang 
  Abstract: Pilot-operated proportional valves are widely used in hydraulic systems requiring high flow rates. Deadzone compensation in the pilot stage will be important to the control performance of the valve main stage. This paper proposes a pre-matched coordinated control method for a proportional valve with pilot stage equipped with two independently decoupled pilot stage spool valves and it almost eliminates the impact of deadzone on control performance. By pre-matching the solenoid driving currents of the two pilot stages, the initial displacements of the two spool valves are set near the upper deadzone limit, thereby shortening the overall deadzone length and achieving near-zero overlap. Experimental results validate this improvement, showing that the steady-state control accuracy is increased to 0.13%. The tracking accuracy is improved to 0.73% or 0.37%, depending on the dynamic amplitude. Notably, the hysteresis near the zero position is nearly eliminated.
  Keywords: Independent Metering; Pilot Stage; Proportional Valve; Pre-matched Cooperation Control.
  DOI: 10.1504/IJHM.2026.10081397
   
  
• Parameter estimation based motion control of electro-hydrostatic actuators with improved adaptive mechanism  
  by Zheng Chen, Jiajia Liu, Yichi Huang, Litong Lyu, Yong Nie, Deqing Mei 
  Abstract: Electro-hydrostatic actuators (EHAs) are integrated pump-controlled hydraulic systems which are widely utilized in aerospace and numerous modern industries due to their higher efficiency and greater actuating forces. Recently, adaptive methods have been incorporated into model-based control to deal with the parametric uncertainties. However, existing studies focus on trajectory tracking, neglecting that adaptive algorithms suffer from poor parameter convergence because the adaptation law relies only on tracking error and requires persistent excitation (PE). Hence, a modified adaptive backstepping control is developed for EHAs to ensure both parameter convergence and trajectory tracking. In this study, an auxiliary time-interval is used to weaken the PE condition in which the historical data of tracking and estimation errors are integrated by an auxiliary integral term. Then, the adaptive controller is formulated within backstepping, and closed-loop stability is proved theoretically. Finally, comparative experiments demonstrate the effectiveness and superiority of the proposed control method.
  Keywords: Electro-hydrostatic actuator (EHA); motion control; parameter estimation; adaptive control.
  DOI: 10.1504/IJHM.2026.10081496