Robust and Quick Response Tracking Servo System for High Rotational Speed Optical Disk System

Generally, tracking control for optical disk system is accomplished by the feedback control designed by using PID control, repetitive control and so on. However, it is difficult to reduce the tracking error on condition of high disk rotation speed. In the near future, the disk rotation speed of the optical disk system becomes higher than 10000[rpm]. Therefore, the tracking servo system for optical disk system must have the new structure and highly performance. This paper proposes a new free parameter and desgin method of feedback servo system, which suppresses the high speed periodic disturbance. It has the widebandwidth and high gaim margin. Moreover, in order to suppress this periodic disturbance, this paper proposes a new control structure of robust feedforward servo system, which includes the prediction of tracking error, a new design method of disturbance observer and the zero error phase tracking control. The experimental results point out that the proposed system well regulates the high precision tracking servo control on condition of the disk rotation speed 8000[rpm], which is equal to CD system of 40 X speed.