International Journal of Hydromechatronics (7 papers in press)

Regular Issues

• Robust active disturbance rejection control for modular fluidic soft actuators  
  by Yunce Zhang, Tao Wang, Xuqu Hu 
  Abstract: Delicate dynamic control of soft actuators is a challenging task due to their strongly nonlinearities. This article focuses on the dynamic control of the modular fluidic soft actuators governed by pneumatic proportional valves. Since it is difficult to accurately describe the complex coupling relationships among the chambers of the soft actuators, the dynamic control of the soft actuators cannot be implemented by using advanced control algorithms based on precise model in usual. To improve the manipulability and extend the application scenarios, we design a robust active disturbance rejection control method based on linear extended state observer, which only requires an approximate model of the soft actuators. Experimental results show that closed-loop stability and good tracking performance are achieved by the proposed method, meanwhile better disturbance rejection ability is guaranteed in comparison to the commonly used proportional-integral-differential control method.
  Keywords: controller design; state observation; dynamic performance; fluidic power; modular soft actuators.
  DOI: 10.1504/IJHM.2023.10059853
   
  
• Research on electro-mechanical actuator fault diagnosis based on ensemble learning method  
  by Jianxin Zhang, Muyang Liu, Wenzhu Deng, Zhen Zhang, Xiaowang Jiang, Geng Liu 
  Abstract: With the rapid development of the aviation industry, people have increasingly higher requirements for the performance of aircraft. Therefore, effective health management of the airborne electro-mechanical actuator (EMA) is particularly critical. Aiming at the problem of aircraft health management, this paper first establishes the simulation model of EMA, and chooses the three-phase current as the characteristic quantity of subsequent fault diagnosis through the analysis of the model. Then an EMAs fault diagnosis framework based on ensemble learning method is proposed. The study compares the advantages and disadvantages of different ensemble learning strategies and proposes a fault diagnosis framework based on the Boosting ensemble learning method, which is based on XGBoost, LightGBM, and CatBoost models. Compared with popular deep learning frameworks (CNN), this method requires fewer computing resources and has stronger interpretability of the model. The test results indicate that the proposed framework has higher diagnosis accuracy compared to traditional machine learning methods and shorter training time and lower memory usage compared to deep learning methods (CNN), making it a valuable tool for engineering applications.
  Keywords: electro-mechanical actuator; EMA; permanent magnet synchronous motor; health management; fault diagnosis; ensemble learning.
  DOI: 10.1504/IJHM.2023.10060525
   
  
• Determination of the flow rate characteristics of porous media under the positive pressure and vacuum  
  by Wei Zhong, Yihao Wang, Kaiwen Fu, Chong Li, Jiang Shao, Pengfei Qian 
  Abstract: Porous media is widely used to replace the conventional orifices as restrictors in vacuum handling process. In this study, a theoretical model describing the flow rate characteristics, including effects from both viscosity and inertia, is established based on Darcy-Forchheimer’s law. The simulation work is firstly conducted, followed by establishing apparatuses to determine permeability and inertial coefficients. The permeability is determined within a small pressure difference (< 2 kPa) and the inertial coefficient is obtained with Re > 0.1 as the boundary. The average permeability is 1.21 × 10^-12 m² , 1.56 × 10^-12 m² , 3.41 × 10^-12 m² and 12.21 × 10^-12 m² , respectively. The inertial coefficient is determined under the positive pressure at the maximum pressure difference and vacuum with pressure difference from 50 kPa to 70 kPa. For different pressure conditions, it is confirmed that the theoretical flow rate can predict the experimental data within a 3% uncertainty which is sufficient for most applications. Finally, to obtain the inertial coefficient, two methods including the single-point method and the multi-point method are proposed. We found that the single-point method gives an error of 3.1% while the multi-point method gives an error of 1.9% for the determination of the entire flow rate characteristics.
  Keywords: flow rate characteristics; porous media; positive pressure; vacuum; permeability; inertial coefficient.
  DOI: 10.1504/IJHM.2024.10062649
   
  
• Artificial intelligence-based viscosity prediction of polyalphaolefin-boron nitride nanofluids  
  by Omer A. Alawi, Haslinda Mohamed Kamar, Mustafa Mudhafar Shawkat, Mohammed M. Al-Ani, Hussein A. Mohammed, Raad Z. Homod, Mazlan A. Wahid 
  Abstract: Predicting viscosity’s nanofluids can benefit all domains, including energy, thermofluids, power systems, energy storage, materials, cooling, heating, and lubrication. The objective of this study to predict the dynamic viscosity of polyalphaolefin-hexagonal boron nitride (PAO/hBN) nanofluids using four main parameters: shear rate, shear stress, nanomaterials mass fraction, and temperature. Moreover, three hybrid ensemble learning models (Bayesian ridge-random forest, Bayesian ridge-MLP regressor and Bayesian ridge-AdaBoost regressor) were developed for the current task. The forward sequential feature selector (FSFS) created four input combinations (models). Model 4 showed the best prediction accuracy, followed by models 2, 3 and 1. The computational findings showed that ensemble learner 1 was slightly outperformed by ensemble learner 3. Meanwhile, among the predictive models, ensemble learner 2 consistently placed third. Besides, the research results demonstrated that creating predictive models based on all input parameters can produce a precise prediction matrix. Overall, the study recommended exciting conclusions on predicting a nanolubricant’s viscosity for use in heat transfer applicants.
  Keywords: nanofluids; viscosity; polyalphaolefin; PAO; machine learning; ensemble learning; boron nitride.
  DOI: 10.1504/IJHM.2024.10063148
   
  
• Neuroadaptive control for pneumatic cylinder servo systems with input saturation and time-varying constraints  
  by Qiuzhen Yan, Zhaoxu Hu 
  Abstract: In this paper, an anti-windup barrier neuroadaptive control approach is proposed to solve the trajectory tracking problem for pneumatic cylinder servo systems with time-varying constraints and input saturation. Time-varying barrier Lyapunov functions are constructed for controller design to restrict the displacement error and velocity error within their respective preset time-varying boundaries, thereby ensuring the specified tracking performance during control process. An improved anti-wind strategy is developed to achieve saturation compensation. Two finite-time differentiators are constructed to estimate the derivatives of virtual control signals for lowering the design difficulty. Adaptive ELM neural network is established for disturbance rejection and uncertainty approximation. The comparative simulation results verify the effectiveness of the proposed anti-windup neuroadaptive control scheme.
  Keywords: adaptive control; pneumatic cylinder systems; input saturation; barrier Lyapunov function; finite-time differentiators.
  DOI: 10.1504/IJHM.2024.10063430
   
  
• Position servo with variable speed pump-controlled cylinder: design, modelling and experimental investigation  
  by Haigang Ding, Yalong Li, Quanmin Zhu, Jingyi Su 
  Abstract: This paper proposes a position servo system with variable-speed pump-controlled cylinder (VSPC), which controls an asymmetric cylinder in four quadrants by adjusting servomotor speed, and elucidates the system working principle. The system mathematical model is established, an anti-integral saturation PID controller is designed, and the resonance frequency and damping ratio are obtained. The system simulation model and experimental bench are established, and step response and sinusoidal tracking experiments are carried out, revealing the change rule of servomotor speed and torque, and analysing the gas volume and pressure change process of accumulators. The results show that the actuator can accurately and quickly track the command signal under positive and negative loads by regulating the pump speed; when the cylinder position is unchanged, the motor operates at low speed with a fixed steering to compensate for system leakage and maintain pressure to keep the desired position.
  Keywords: variable speed pump control; variable-speed pump-controlled cylinder; VSPC; position servo; resonance frequency; four quadrants; servomotor.
  DOI: 10.1504/IJHM.2024.10063432
   
  
• CFD-based method for hydrostatic bearings performance: static characteristics with various recess shapes  
  by Minghui Guo, Zhuxin Tian, Xiaolin Feng, Yu Huang, Guojun Zhang, Youmin Rong 
  Abstract: Hydrostatic bearings with recess are vulnerable to non-uniform oil film pressure and area effects. The above situation leads to decrease in stability and load carrying capacity (LCC) of bearings. In this paper, the influence of oil recesses structure on hydrostatic thrust bearings performance is discussed. The six oil recesses shapes were selected, and the static characteristics of bearings were simulated by using CFD method. The obtained results show that there are many differences in static characteristics of the hydrostatic thrust bearing caused by different recess shapes. The LCC increases with the recess circumference, and the maximum on equilateral triangle recess. It decreased 16.46% when the rotation speed from 0 to 5,000 rpm. The recess shape has no significant influence on the temperature distribution of oil film, but the average temperature is inversely proportional to the width of middle circle. Experiments are carried out to validating the simulations. When the bearings rotate speed at 1,000 rpm, the difference between experimental and simulation remains within 5%, indicating the validation of the CFD method.
  Keywords: hydrostatic bearings; recess shape; CFD method; static characteristics.
  DOI: 10.1504/IJHM.2024.10063433