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/sub /spl infin// 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.

We focus on the design of robust reduced-order dynamic feedback control for a class of nonlinear systems with uncertainties. A robust nonlinear reduced-order dynamic controller (RNRDC) is proposed. The resulting closed-loop system can be robustly stabilized for all admissible uncertainties via the proposed controller. The application of the proposed RNRDC to a permanent magnet brush DC motor driving a single-link manipulator is also considered. The parameters uncertainties can be up to /spl plusmn/80%. The load can vary ranging from 50% to +100% of the nominal value. Our simulation results show that for the example system the proposed RNRDC can achieve good performance.