Design of an H∞ controller with internal model principle for disturbance rejection in optical disk drives

Improving the position control of the optical pickup head is important step in increasing the storage capacity of an optical disk drive, especially in the presence of internal and external disturbances. To tackle this problem, a disturbance observer is often used to attenuate the disturbances. However, using this method, the robust stability issue cannot be guaranteed. In this paper, a disturbance-observer-based H_∞ controller with internal model principle is proposed to achieve the disturbance rejection and to guarantee the robust stability of the system. The proposed control scheme is applied to a DVD-ROM servo system. Simulation studies how the effectiveness of the proposed scheme.