Abstract
When a closed-loop control system especially with integral compensators, has an input saturation in control object, it will become unstable for the worst case, of which unstable phenomenon is called wind up. To realize a high-speed and high-accuracy trajectory control, disturbance observer and controller are used in this paper. Because the characteristics of positive feedback of disturbance observer cause the unstable phenomenon in control system with input saturation in control object, a method, adding saturation model to disturbance observer is used to reduce its unstable phenomenon. Even if the saturation model is used, response may still deviate from the desired path because the tracking error can't be suppressed. To prevent it, a predictive control is proposed in this paper, which offers a torque input first and then inverts it at proper time respectively based on a result of future response prediction. This method is applied to both intermittent and repetitive motions. Also, to improve the predictive control, some methods are discussed, which use an estimated disturbance to modify the predictive control accuracy and adjust the inverted torque waveform and value to reduce jerk of control object. The simulation results and the experimental results show the effectiveness of the proposed methods.
