Radial tracking in high-speed DVD players (an application of notch filtering and multirate control)

The problem considered is the radial tracking of the optical pick-up in a DVD-ROM. For low-speed players, it is known that this problem can be solved by means of simple lead-lag regulators. For high-speed players, the servo design is much more tricky, and a more sophisticated control scheme is required. The control scheme proposed is constituted by a lead-lag filter, two notch filters and a low-pass filter. This set of filters is implemented in a parallel structure. This architecture is adequate to provide a good radial tracking. The performance of the controller are tested on a real plant, and experimental results are reported.