REPETITIVE CONTROL FOR THE TRACK-FOLLOWING SERVO SYSTEM OF AN OPTICALDISK-DRIVE

Disturbances acting on the track-following servo system of an optical disk drive inherently contain significant periodic components that cau se tracking errors of a periodic nature. Such disturbances can be effe ctively rejected by employing a repetitive controller, which must be i mplemented carefully in consideration of system stability. Plant uncer tainty makes it difficult to design a repetitive controller that will improve tracking performance yet preserve system stability, In this pa per, we examine the problem of designing a repetitive controller for a n optical disk drive track-following servo system,vith uncertain plant coefficients. We propose a graphical design technique based on the fr equency domain analysis of linear interval systems, This design method results in a repetitive controller that will maintain system stabilit y against all admissible plant uncertainties. We show simulation and e xperimental results to verify the validity of the proposed design meth od.