Robust tracking control based on triple compensation loop for high speed optical disk

This paper proposes a new tracking control system for high speed optical disk recording system. The proposed tracking control system consists of triple compensation loops of tracking error which are the robust feedback control loop, Zero Phase Error Tracking (ZPET) feedforward control loop and a new additional DC offset compensation loop. The feedback controller is the most inner loop which is based on the high gain design method by phase compensation. The ZPET control loop is the middle loop which suppresses the influence of periodic disturbance whose frequency is same as the revolution velocity of spindle motor. The final outer loop is a new additional DC offset compensation loop which suppresses the DC offset caused by the steady state error element of the other frequency. The experimental results point out that the proposed system well realizes the fine tracking performance whose tracking error is less than 10[nm].