Robust tracking control of optical disk recording system based on sudden disturbance observer

In optical recording system, the tracking servo system must follow the track of optical disk against the influence of the track eccentricity and the force disturbance. The influence of the track eccentricity becomes periodic disturbance. The influence of force disturbance caused by shaking is treated as sudden disturbance. The conventional tracking servo system is constructed by using the only feedback control structure, Therefore, it is difficult to suppress the influence of both periodic disturbance and sudden disturbance. This paper proposes a new structure of robust tracking servo system, which suppresses the both periodic disturbance and the sudden disturbance, respectively. In order to suppress the periodic disturbance quickly, this paper designs the ZPET feedforward servo system with prediction of tracking error. The multi rate sudden disturbance observer estimates the only sudden disturbance, more accurately. The experimental results point out that the proposed tracking servo system has a precise tracking response against both periodic disturbance and sudden disturbance.