DESIGN OF INTEGRAL VARIABLE STRUCTURE CONTROLLER AND APPLICATION TO ELECTROHYDRAULIC VELOCITY SERVOSYSTEMS

An integral variable structure controller (IVSC) for robust servotracking is proposed. It comprises an integral controller, which is designed for achieving zero steady-state error under step input, and a variable structure controller (VSC) which is designed for enhancing robustness. A procedure is developed for determining the coefficients of the switching plane and the integral control gain such that the overall closed-loop system has the desired eigenvalues. Furthermore, a modified proper continuous function is introduced to overcome the chattering problem. An electrohydraulic velocity servocontrol system using the proposed IVSC approach is illustrated. Simulation results show that the proposed IVSC approach can achieve accurate servotracking and is fairly robust to plant parameter variations and external load disturbances.