International Journal of Hydromechatronics (10 papers in press)

Regular Issues

• Quantitative analyses of the influence of practical aspects on hydraulic force control performance  
  by Elisa G. Vergamini, Cícero Zanette, Lucca Maitan, Leonardo F. Dos Santos, Marcos P. Nostrani, Thiago Boaventura 
  Abstract: Hydraulic actuators are a strong alternative for robotics, offering high mobility and a favourable power-to-weight ratio. However, in many industrial and robotic applications, key system parameters - such as oil temperature, hose length, supply pressure, valve bandwidth, and control frequency - can vary over time due to operational demands, wear, or environmental conditions. Despite their importance, the impact of these variations on force control performance is often underestimated. This study investigates how such parameters affect the performance of a standard PI force controller in hydraulic actuators. Using the IC2D test bench, experiments were performed with different servovalves (Moog E024 and G761) and parameters setups. Results show that pressure level and hose length significantly impact controller performance, while valve model produces less predictable effects. Control frequency has little influence. Interestingly, temperature affected force tracking in unexpected ways, with valve opening and flow rate playing a more dominant role.
  Keywords: practical aspects; hydraulic actuators; servovalves; force control performance; hydraulic force; oil temperature; hose length; valve bandwidth; control frequency; supply pressure.
  DOI: 10.1504/IJHM.2025.10072847
   
  
• Design of bearings load uniform structure and study on load uniform effect of submersible screw pump  
  by Rui Dong, Zhiqiang Wang, Beilin Han, Salvinder Singh Karam Singh, Chenxu Chen, Tianxing Tu 
  Abstract: The submersible screw pump (SSP) is widely utilised due to its low cost, high energy efficiency, and exceptional pumping performance. However, under high-speed and heavy-load operating conditions, key components such as bearings experience significant axial loads, which lead to reduced bearing lifespan and reliability. To enhance bearing lifespan and reliability, this study combines both simulation and experimental approaches to design a multi-stage bearing load uniform structure. Simulation analysis was performed on components such as disc springs. The results indicate that the multi-stage bearing load uniform structure can effectively uniform axial loads. The study also identifies that factors, such as the gap between the disc spring and the bearing as well as assembly gaps, negatively impact load uniformity. Therefore, this research offers an effective design strategy for the structural optimisation of SSPs, contributing to improved bearing group lifespan and reliability.
  Keywords: submersible screw pump; bearings load uniform structure; multi-stage bearings; load uniform effect.
  DOI: 10.1504/IJHM.2025.10072877
   
  
• Fuzzy PID Control Strategy Optimised by Sparrow Search Algorithm for Digital Proportional Valve with Differential Control of Dual High-Speed On/Off Valves  
  by Chunjie Xu, Fangwei Xie, Zuzhi Tian, Ziyan Zhao, Zibo Chen, Yumeng Li 
  Abstract: This study explores the potential of pilot-controlled digital valves in balancing high flow rates and fast response, focusing on suppressing spool oscillations for precise position control. A prototype and multi-physics simulation model of a digital proportional valve with differential control of dual high-speed on/off valves are developed. The motion characteristics of main spool under varying control frequencies and duty cycles are analysed. A differential control method to reduce oscillation is proposed, along with a fuzzy PID control strategy optimized by the sparrow search algorithm to adaptively adjust the duty cycle difference. Simulation results show that, under the SSA-FPID control, the valve spool position step response rise time decreases by 38.2%, the steady-state average absolute error reduces by 16.1%, and the tracking error under typical excitations is under 0.1 mm. Experimental verification confirms the effectiveness of the control strategy, offering insights for valve design, optimisation, and control.
  Keywords: Digital proportional valve; spool oscillation characteristics; high-speed on/off valve; differential control; fuzzy PID; sparrow search algorithm.
  DOI: 10.1504/IJHM.2025.10073232
   
  
• Wear Defect Detection of Hydraulic Pump using a Hybrid Method of VGG and LSTM  
  by Shengnan Tang, Yixuan Jiang, Hong Su, Kian Meng Lim, Zhijian Zheng, Yong Zhu 
  Abstract: Hydraulic pump is an important power element among the core components of the hydraulic transmission system in mechanical equipment. The concealment of typical faults in hydraulic pumps makes accurate fault detection challenging. Fault signals are typically temporal, and this paper proposes an intelligent method based on Synchrosqueezing Wavelet Transform (SWT) and an improved fusion model. The method fully incorporates (i) SWT to improve the time-frequency separation of fault information, (ii) deep feature extraction from image information of VGG, and (iii) Long Short-Term Memory (LSTM) to control network information transmission and optimise memory stacking methods of the network to achieve high-precision fault detection. The proposed hybrid VGG-LSTM is evaluated by analysing pressure signals from the hydraulic pump. Compared with other models, the proposed model has excellent fault recognition ability with minimum error and standard deviation, which proves that the theory of fusion reconfiguration network is reasonable.
  Keywords: hydraulic pump; convolutional neural network; defect detection; long short-term memory.
  DOI: 10.1504/IJHM.2025.10073233
   
  
• Investigation of Non-Homogeneous Thick-Walled Cylinder Ceramic Matrix Composites (CMCs) for Biochemical and Medical Innovations  
  by Pankaj Thakur, Priya Gulial 
  Abstract: This study investigates thick-walled cylinder Ceramic Matrix Composites (CMCs) in biochemical and medical applications. High-performance materials, such as Zirconia (ZrO2)-based and Alumina (Al2O3)-based composites, are identified as optimal for high-stress biomedical applications due to their exceptional pressure resistance. Conversely, lightweight composites, including Boron Carbide (B4C)-based and Silicon Carbide (SiC)-based materials, are highlighted as cost-effective and well-suited for low-load medical devices. The research emphasizes the relationship between wall thickness and surface pressure, alongside the importance of stress distribution in determining material performance. The findings advocate for strategic material selection and design optimisation to enhance the safety, performance, and durability of medical devices across diverse operational conditions.
  Keywords: Thick-Walled Cylinder; Ceramic Matrix Composites; Biochemical Applications; Medical Device Performance; Stress Distribution; Material Optimization.
  DOI: 10.1504/IJHM.2025.10073291
   
  
• Design and Control of the Bionic Ankle Joint with Multiple Pneumatic Artificial Muscles  
  by Delei Fang, Fangyuan Ren, Hao Wen, Zhenyu Yan, Jianwei Wang, Feipeng Li, Jie Tang, Junxia Zhang 
  Abstract: To address the time-varying output force and compliance issues in pneumatic artificial muscle-driven robots, this paper proposes a bionic ankle joint inspired by human muscle structure. By recruiting multiple pneumatic artificial muscles and implementing compliance control, the overall output performance is enhanced. This study presents the structural design of the bionic ankle joint with multiple pneumatic artificial muscles and analyzes its bionic actuation mechanism. Furthermore, impedance control and adaptive impedance control models are developed, followed by a simulation-based analysis of the output angular characteristics and force response. A performance evaluation platform is constructed for experimental validation. The results indicate that the bionic ankle joint with adaptive impedance control effectively reduces angular tracking errors and output force deviations, while improving joint compliance.
  Keywords: Bionic ankle joint; pneumatic artificial muscle; impedance control.
  DOI: 10.1504/IJHM.2025.10073593
   
  
• Research on Magnet Structure Design and Torque Performance Optimisation of Permanent Magnet Synchronous Motors  
  by Zhiqiang Wang, Chenxu Chen, Rui Dong, Xu Zhao, Salvinder Singh Karam Singh, Beilin Han 
  Abstract: Based on the issues of substantial torque fluctuation, severe magnetic leakage, and low efficiency in conventional rectangular embedded permanent magnet synchronous motors (PMSM), this paper introduces an arc-trapezoidal magnet (ATM) structure aimed at enhancing the torque performance of the motor. Through comprehensive simulation analysis and experimental validation, the design parameters are optimised via orthogonal experimental, leading to the identification of the optimal parameter set. Experimental results reveal a 26.8% increase in average motor torque, a 51.2% reduction in torque fluctuation, and a significant improvement in the motor's output torque performance.
  Keywords: permanent magnet synchronous motor; magnet structure design; torque performance optimization; orthogonal experiment design.
  DOI: 10.1504/IJHM.2025.10073599
   
  
• Nonlinear Thermo-Mechanics of Smart Functionally Graded Rotating Disks for Adaptive Hydromechatronics  
  by Pankaj Thakur, Priya Gulial 
  Abstract: This study investigates the nonlinear thermo-mechanical behaviour of functionally graded (FG) hyperbolic rotating disks with rigid shaft inclusions and radially varying density. The disks are composed of Ti-6Al-4V/GFRP composites, with properties following a power-law gradation indexed by m. Using a generalised strain-displacement formulation, non-dimensional equilibrium equations capture axisymmetric deformations under combined thermal and mechanical loading. Numerical results show that material gradation and shaft geometry significantly influence performance. Under isothermal conditions, GFRP-rich disks (m = 0) achieve up to 42% higher yielding angular speed than Ti-6Al-4V-rich disks (m =1.25), while thermal loading reduces this advantage. Radial stress at the bore decreases ~22% in GFRP-rich disks, whereas circumferential stress rises 15%20% in Ti-6Al-4V-rich disks. Radial displacements increase 27%30%, further amplified 16%28% under thermal effects. These findings highlight the trade-off between high-speed capacity and thermo-mechanical stability, providing a framework for optimising FG disks in aerospace, energy storage, and hydromechatronic systems.
  Keywords: functionally graded materials (FGMs); rotating disks; thermo- mechanical coupling; density gradation; smart shaft inclusions.
  DOI: 10.1504/IJHM.2025.10073734
   
  
• Investigation of Different Liquid Replenishment Schemes on the Performance of the Ionic Liquid Compressor  
  by Yi Jin, Yi Guo, Yuming Tang, Xueyuan Peng, Zhenjun Ma 
  Abstract: In ionic liquid hydrogen compressors, the liquid provides functions of sealing, piston lubrication, and hydrogen cooling. However, some liquids are expelled with hydrogen during the discharge, leading to a gradual decrease in liquid volume. Liquid replenishment is therefore necessary to maintain an adequate liquid level for effective sealing and lubrication, while also enhancing cooling efficiency and assisting the compression process closer to isothermal conditions. In this study, a transient two-phase flow model was developed to evaluate the thermal performance of the compressor under three different liquid replenishment schemes. The volume of fluid method was employed to track the interface between hydrogen and ionic liquids. Meanwhile, the two-phase flow and heat transfer were simulated over a complete compression cycle. Results showed that replenishment improved compression performance, achieving a minimum polytropic index of 1.145 and a maximum isothermal efficiency of 86.06%. However, replenishment occupied part of the suction stroke and increased liquid discharge, reducing volumetric efficiency, with the lowest value of 69.23%. Among the three schemes, the cylinder-top replenishment method demonstrated an outstanding trade-off between isothermal efficiency (83.51%) and volumetric efficiency (89.92%), making it a promising strategy for practical hydrogen refuelling applications.
  Keywords: hydrogen; liquid piston; two-phase flow; isothermal process; CFD.
  DOI: 10.1504/IJHM.2025.10073736
   
  
• An improved Harris Hawks Optimisation for the Optimal Scheduling of Cascade Pumping Stations  
  by Xiaolian Liu, Xiaopeng Hou, Yu Zhai, Xiamin Ma, Xueni Wang, Leike Zhang, Yu Tian, Can Ding 
  Abstract: For water-conveyance projects with cascade pumping stations (CPSs), ensuring stable and efficient operation is of paramount importance. This study develops an optimal scheduling model for CPSs, integrated with a one-dimensional hydraulic model, and proposes an optimisation dispatching approach based on an enhanced Harris hawks optimisation (TFHHO). To address HHO's limitations in terms of initial population diversity and exploration, the Tent chaotic map is employed to enhance the quality and distribution of initial solutions, while a starvation rate F is introduced to escape local optima and boost global optimisation. Tests on 23 benchmark functions, TFHHO achieves 15 optimal solutions, confirming its significant superiority over PSO, GA and HHO. Applied to a CPS in Beijing, TFHHO-based optimisation schemes achieve annual operational cost reductions of $5,897 (19.4 m3/s) and $12,640 (20.0 m3/s), outperforming schemes employing PSO, GA and HHO. Thus, TFHHO algorithm provides an effective methodology for the optimal scheduling problem in CPSs.
  Keywords: Improved Harris hawks algorithm; Cascade pumping stations; Economical operation; Tent mapping; The rate of starvation.
  DOI: 10.1504/IJHM.2025.10073760