Analysis of Optical Data Storage Systems—Tracking Performance With Eccentricity

The tracking control performance of optical data storage systems is analyzed in the presence of the disc eccentricity. The eccentricity is the maximum deviation from the geometric center of the circular tracks and the rotating center of the disc, which is inevitable in practice. This is mainly caused by the inaccuracy of the tracking forming devices. In the paper, tracking control performance is discussed in terms of pull-in capability and steady track-following ability. Firstly, it will be explicitly shown that the pull-in capability will degrade in proportion to the multiplication of the eccentricity and rotational frequency. This analysis provides a guide for tracking controller design with reliable pull-in actions. Secondly, in order to improve the steady track-following performance, a feedforward compensation method is introduced, which is simple enough to be implemented in practice. Furthermore, an interesting connection to the disturbance observer approach in the time domain is examined.