Adaptive multirate control for embedded HDD servo systems

This paper presents an adaptive multirate control design for embedded hard disk drive (HDD) servo systems. To facilitate the analysis, an equivalent single rate multi-input single-output (MISO) system is derived from the original multirate control system. An LQG controller is then obtained for the MISO system with nominal parameters. To improve the system performance in the presence of plant gain variations, an adaptive scheme for the multirate system is developed. The unknown plant gain is compensated to its nominal value used in the multirate control design. Simulation tests show that the proposed adaptive multirate controller is a stable design. No external excitation signal is needed to achieve the convergence of the adaptation. By the combination of adaptive and multirate control, good system performance can be achieved in a system with unknown parameters