Research on high precision control of joint position servo system for hydraulic quadruped robot

Electro-hydraulic servo valve-controlled cylinder(EHSVCC) is a highly integrated and high-performance electro-hydraulic servo driving unit(EHSDU), which is the basic driving unit of the leg joint for hydraulic quadruped robot. The robot impedance control mostly adopts control methods based on position inner loop and impedance outer loop, the high precision control of position inner loop is the key to improve impedance control. Therefore, it is of great significance to study a high precision position control method. Firstly, the electro-hydraulic servo drive unit of the foot robot is taken as the research object. The model of the nonlinear system is established, and the feedback linearization of the system is carried out. Secondly, in order to improve the tracking performance and anti-jamming ability of the position inner loop input/output a sliding mode variable structure robust controller(SMVSRC) with switching function, variable structure control rate and improved boundary layer function is designed. Finally, the electro-hydraulic servo drive unit(EHSDU) and the hydraulic foot robot test platform are tested, the influence of the two control algorithms on the position response and tracking error for EHSDU is analyzed and compared under the control of sinusoidal signals with different amplitudes and frequencies and diagonal gait signals. The experimental results show that the improved SMVSRC algorithm is feasible and effective, which provides a theoretical basis for the later study of impedance control based on position inner loop.