Adaptive Feature Based Control of Compact Disk Players

Many have experienced the problem that their Compact Disc players have difficulties playing Compact Discs with surface faults like scratches and fingerprints. The cause of this is due to the two servo control loops used to keep the Optical Pick-up Unit focused and radially on the information track of the Compact Disc. The problem is to design servo controllers which are well suited for handling surface faults which disturb the position measurement and still react sufficiently against normal disturbances like mechanical shocks. In previous work of the same authors a feature based control scheme for CD-players playing CDs with surface fault is derived and described. This feature based control scheme uses precomputed base to remove the surface fault influence from the position measurements. In this paper an adaptive version of the feature based control scheme is proposed and described. This adaptive scheme can in contrast with the other scheme adapt to the given fault. The adaptive scheme recomputes the feature extraction bases which is used to remove fault components from the measurements, at each encounter of the given fault. The improvements of this adaptive scheme are illustrated by simulations, with the clear result that the adaptive scheme clearly adapts better to the given faults compared with the non-adaptive version of the feature based control scheme.