Corrections to "Adaptive repetitive control for an eccentricity compensation of optical disk drivers"

This paper presents an adaptive repetitive control scheme for optical disk drivers to track a periodic reference signal with dynamic change in period. Periodic disturbances can be adequately attenuated using the concept of repetitive control, when provided with the known period. Optical disk drivers support various speeds. So optical disk drivers have a varying periodic disturbance. To deal with time varying periodic disturbances, a proposed repetitive controller is turned based on repetitive control to change the sampling frequency to follow the change of reference period. The proposed adaptive repetitive control consists of two portions, the repetitive controller and the frequency multiplier, where the former uses a varying sampler operating at a variable sampling rate maintained at fixed multiple times of the disturbance frequency and the latter generates a vary sampling frequency based on the disturbance frequency. An adaptive repetitive control scheme is proposed, implemented on an experimental set of an optical disk driver. We have demonstrated the effectiveness of the proposed methods and the improvement of the random access time.