Characteristics of Position and Pressure Control of Separating Metering Electro-Hydraulic Servo System with Varying Supply Pressure for Rolling Shear

Abstract

The traditional valve-controlled hydraulic servo system has large throttling losses and undergoes serious heat problems when used in electro-hydraulic servo systems (EHSSs) for a rolling shear. In order to improve the energy efficiency of the EHSS for the rolling shear while also ensuring the position tracking accuracy, the separate metering electro-hydraulic servo system with varying supply pressure (VSP-SMEHSS) is proposed in this work. The inlet valve controls the position of a hydraulic cylinder, while the outlet valve controls the back pressure of the hydraulic cylinder. However, due to the disturbance caused by the varying supply pressure, the proportional–integral–derivative (PID) controller or active disturbance rejection controller (ADRC) cannot meet the requirements of accuracy. In order to solve this problem, based on a nonlinear disturbance observer (NDO) and a tracking differentiator (TD), a dynamic surface control (DSC) is proposed in this work. Firstly, the stability of the controller is validated using the Lyapunov method. Then, experiments are conducted to verify the proposed control strategy. As a result, the hydraulic cylinder can accurately track the reference displacement signal and effectively reduce the pressure drop at the valve’s orifice, due to which the hydraulic system achieves significant energy-savings. Compared with that of the EHSS, the energy consumption of the VSP-SMEHSS is reduced by 44.6%.