Precise Position Control of Pneumatic Servo System Considered Dynamic Characteristics of Servo Valve

Abstract

Precise positioning system is required in the fields of semi-conductor manufacturing process. A pneumatic servo table system is one of a precise positioning system. The features of the table are little friction force and little heat generation. Generally, the controller of this system is designed by neglecting the characteristics of servo valves. However, in high frequency band, the response of this system becomes unstable because of the characteristics of the valves. In this paper, we demonstrate that by considering the characteristics of servo valves, the position control of a pneumatic servo table could be improved. First, the dynamic characteristics of servo valves were examined. It became clear that the characteristics could be described as a second-order system. Then, the servo table system was designed as a fifth-order system. It became clear that the position accuracy of this system were greatly improved.