Compensator design for a dual-stage actuator in the track-following servo system of optical disk drives

In this paper, a compensator design method is presented for track-following control in an optical disk drive, a common mechanism for which is a dual-stage actuator composed of a fine and a coarse actuators. Most of previous works, however, have focused on tracking precision enhancement using only the fine actuator without systematic design method for a coarse actuator compensator. As the dual-stage actuator is categorized as a dual-input single-output system, the overall stability is affected not only by the fine actuator but also by the coarse actuator. In addition, the coarse actuator compensator should satisfy a performance specification to prevent overall system failure. The PQ design method is slightly modified based on the obvious difference between the bandwidths of the two actuators, and then two compensators can be designed independently. It is proved that the overall system stability is ensured by the designed compensators, and performance specifications are also satisfied. Validity of the design method is proved by some simulations and experiments.