Research on the Low Velocity Accuracy Control of the Direct Drive Volume Control Electro-Hydraulic Servo System

Abstract

The Direct Drive Volume Control (DDVC) Electro-hydraulic Servo System is a new Electro-hydraulic Servo System. With the development of its application, how to improve the trajectory tracking precision of the DDVC system in low velocity motions becomes more important in the field. So that, the level of the low velocity characteristic impacted the system become to an important subject. In this paper, the mathematical mode of AC asynchronism motor Direct Torque Control was established, and the simulation mode was built. In addition, the idealized model of the DDVC system which based on united simulation of AMEsim/Simulink was established, simulation was executed. In order to make the research available, the low velocity characteristic of the DDVC system was also analyzed, and the low velocity characteristic simulation model was built. Computer simulation validated that the friction is seriously influenced the system performance when the system working on the low velocity mode. An integral back stepping adaptive control law is designed to realize the friction compensation and load disturbance estimation. From the Lyapunov theory, the stability of the closed-loop system is proved. Simulation results show that LuGre friction in servo systems will lead to the effect of limit cycles and stick-slip. Moreover, the proposed compensation method can greatly reduce the effect and improve the system tacking accuracy and robustness.