On Sliding Mode Variable Structure Control For Electro-Hydraulic Position Servo Systems

Hydraulic servo system is an important component of the control field. It is a new science and technology developed on the basis of hydraulic transmission and automatic control technology. In recent years, electro-hydraulic servo system has been widely used in aviation, metallurgy and other important areas. It combines both electrical and hydraulic advantages and has high precision control, fast response, large output power and flexible signal processing. Electro-hydraulic servo system is a serious uncertain nonlinear systems widespreading parameter change and outside interference. Sliding mode variable structure control for system parameter perturbation and external disturbance has a strong robustness and has been widely applied. This paper designed sliding mode variable structure controller for electro-hydraulic position servo system. The main contents of this paper is as follows:Firstly, this paper summarizes the composition and development of the electro-hydraulic servo control system, and analyses nonlinear characteristic and uncertainties of the electro-hydraulic servo control system along with their causes, then the development and research status of the sliding mode variable structure control is detailed.This paper analyses the working principle and mathematical model of the various components of the electro-hydraulic position servo system. After doing the assumptions in favor of simplifying analysis and research, the paper established the state-space mathematical model of the electro-hydraulic position servo system.Because the continuous improvement of the control quality and the uncertainties and nonlinear characteristic of the electro-hydraulic position servo system. From the point of the improvement of the system robustness, sliding mode variable structure controller for electro-hydraulic position servo system is designed.In order to improve the rapidity, the global terminal sliding mode controller is designed for the electro-hydraulic position servo system to enhance the output respons. When the upper bound of the input disturbance is unknowed, the above controller is invalid. Then, adaptive global teminal sliding mode controller is desigened to solve the problem.In many practical control systems, the plant is controlled by the computer. The discrete-time sliding mode controller based on index approximation laws is designed for the electro-hydraulic position servo system. The problem of the chattering phenomenon and the system switch range of the control are also considered. This paper designed the improved discrete-time approximation laws to better the dynamic performance.