High-Speed and High-Precision Position Control Using a Nonlinear Compensator

Abstract

To achieve high-speed, high-precision position control for semiconductor product machines and industrial robots, it is well known that PID control is widely applied Many PID control methods have been proposed for such a system so far. In general, proportional position control and proportional plus integral velocity control or integral plus proportional velocity control (P,PI/I-P), which is a type of proportional plus integral plus deferential control (PID), is applied in many industrial applications in Japan. However, the parameters of the control of P,PI/I-P must be changed to maintain a good motion performance when the characteristic of the control target change. As a method to compensate for a change of the control target, a disturbance observer is proposed (Ohishi, K. et al., 1999). Using this method, a load disturbance force is estimated based on a model set beforehand and adds an estimated disturbance force to a control input. However, it might cause the deterioration of the control performance when a control target model is different from real control target greatly. Furthermore, it is difficult to get a correct model because a lot of nonlinear elements such as the friction may change in control target in time and environment (Canudas-de-Wit, C.