Robust high speed tracking servo system for optical disk system

This paper proposes a new high speed robust tracking control system based on both "zero phase error tracking" (ZPET) control system and disturbance observer for an optical disk recording system. In optical disk recording systems (for example CD-R), the tracking servo system must have a precise tracking response whose error is less than 0.1[mum] for a reference input signal with an amplitude of 100[mum]. Moreover, the tracking servo system can detect only the tracking error, i.e. the position difference between the optical spot and the track to be followed. For this purpose, the tracking servo system proposed in this paper estimates the reference input signal from the tracking error, and realizes the high speed robust tracking control based on ZPET control. Numerical simulation results point out that the proposed system has a quid and robust tracking response.