The Effects of Controller Saturation on Dynamic Characteristics of Commercial Positioning Systems and Their Countermeasures

Commercial positioning systems usually consist of several cascade parts, such as a position controller, a velocity controller, a current controller, and an electric motor. Controller design is normally based on linear analysis; however, in practice, controllers frequently drive actuators into saturation, and, sometimes, controllers themselves saturate. Owing to the saturation effect in the servomotor systems, the linear analysis of the servo systems is not sufficient for controller design. Thus, in this paper, the effects of controller saturation on dynamic characteristics of servomotor drivers are investigated by using the numerical simulation; then, the nonlinear position controller for countermeasures of the saturation effects is proposed. The simulation results show that the saturation effect of the controllers degrade frequency responses of the servo system, and make overshoot occur, and they show that the proposed position controller could satisfy fast step responses with no overshoot