Application of a disturbance observer for a relative position control system

In a relative position control system, where feedfoword control can not be applied and the position control performance is restricted only by the bandwidth of the position controller, a disturbance observer are used actively to enhance the control performance. The position reference is considered as a disturbance by the proposed method. Therefore, the relative position control is performed by the disturbance observer as well as by the position controller. As a result, the position control performance is enhanced up to about 33 [%] compared to that of the conventional method with the disturbance observer. The feasibility of the proposed method has been verified by the experimental results using a high precision linear motion control system as well as by the analysis based on Bode plot.