At present, open-loop synchronous control for hydraulic systems widely using synchronous valves has low synchronous accuracy due to weak anti-bias capacity, and is hard to adjust synchronization velocity, so it could not meet the requirements of accurate synchronization under severe conditions. In this paper, a load-sensing synchronous control is developed to obtain accurate synchronization in open-loop control, which is made up of a load-sensing unit and a synchronous valve. In the load-sensing loop, a load-sensing pump supplies pressure and flow required by the system through pressure closed-loop control, and a load-sensing valve could improve the capability of anti-offset loads by pressure compensation. The synchronous valve is between the load-sensing pump and load-sensing valve, to achieve equal distribution of flow supplied by the pump, which could improve the divider accuracy of the load-sensing system. A test system within load-sensing synchronous control is established, and then comparison experiments under different partial loads are carried out. The experimental results show that, compared with the traditional synchronous valve control, the load-sensing synchronous control has the advantages of higher synchronous precision, higher energy efficiency and also the ability of velocity regulation. Load-sensing synchronous control has the potential of high precision synchronization control in server environments.

This study proposes a compound control method based on sliding mode and active disturbance rejection control to address the difficulty of controlling the cutting head for boom-type roadheader with parameter changes and uncertain disturbances. The fastest discrete tracking differentiator and extended state observer based on the traditional active disturbance rejection control are designed. Additionally, the controller of the sliding mode and active disturbance rejection control is constructed. Theoretical analysis indicates that the proposed controller ensures asymptotic stability, despite the existing uncertain disturbances. Moreover, a system based on AMESim and MATLAB/Simulink Co-simulation model is developed to further verify the performance of proposed algorithm. Compared with traditional active disturbance rejection control, proportional-integral-derivative(PID) and sliding mode control, co-simulation results demonstrate that the sliding mode active disturbance rejection compound control improves the tracking accuracy and robustness of the position servo system.

The valve-controlled cylinder position servo system has the advantages of large output force and large power. As characteristics of nonlinearity and uncertainty exist in the hydraulic servo system, it is difficult for the traditional PID control to meet the requirements of high precision and control. The active disturbance rejection control (ADRC) considers the uncertainty of the system and external disturbances as the total disturbance. In this paper, the valve-controlled cylinder servo system is designed based on ADRC, its working principle is described, and its mathematical model and cosimulation model based on MATLAB-AMESim are established. In the case of constant load, variable load, and long pipeline, the comparative simulation of ADRC and PID is carried out. The simulation results show that the ADRC can effectively suppress the disturbance of the internal parameter changes and external load changes of the hydraulic system and has strong robustness and high control accuracy. This study provides a reference for the application of ADRC in electrohydraulic servo systems.

Different from the rigid separation of biological tissue by scalpel, medical waterjet technology utilizes the impact kinetic energy of high-speed waterjet to instantly destroy the surface of biological tissue to achieve better clinical separation effect. Since the gelatin samples are transparent biomaterials, they were taken as the only substitute for soft tissue in experimental studies and observation in the current studies of medical waterjet separation technology, but the mechanical behavioural difference between the two has not been reported. To verify the adaptability of gelatin as a substitute of soft tissue under the impact of high-speed waterjet. Firstly, the dynamic process of impact was described through the energy balance equation. Then, based on the principle of altering a single variable, the difference of damage depth between 8 wt. %, 10 wt. %, and 12 wt. % gelatin samples and porcine liver tissue under various impact pressure, impact distance, and waterjet speed of motion (as opposed to flow velocity) was compared. The results show that the gelatin sample replicates the damage behaviour of porcine liver samples under the specific waterjet impact conditions, and the direction of the waterjet hydraulic power optimisation of the two materials is also consistent: however, due to the different sampling sites and anisotropy of porcine liver samples, the mechanical response of soft tissue under high-speed waterjet impact cannot be fully expressed by gelatin samples. The experimental results can provide support for the further study of medical waterjet separation technology.

The electro-hydraulic system is widely used in industrial production due to its high power-to-weight ratio, but the heavy-duty characteristics make the electro-hydraulic system subject to large disturbance force even if the actuator moves slightly, especially in mobile machines and multi-actuators system. Therefore, a position and velocity constraints method based on barrier Lyapunov function is proposed to guarantee the tracking error limited in a strict range to avoid the large disturbance force. Besides, the external disturbance, parameters uncertainty and modeling errors in the asymmetric cylinder electro-hydraulic systems affect the accuracy of position tracking seriously. So a high-gain disturbance observer is designed to estimate the lumped disturbance of the system, which can avoid amplification of the noise during the states measurement. In addition, dynamic surface control based on backstepping method is adopted to avoid the derivative explosion phenomenon when calculating the derivatives of virtual control inputs, which reduces the computational complexity of the system significantly. To verify the effectiveness of the proposed controller, proportional-integral controller and adaptive controller are designed to be compared with the high-gain disturbance observer–based dynamic surface controller with the backstepping method, and the comparison results show that the proposed controller has a more precise trajectory tracking performance.