Disk drive servo controller design using H∞-LTR

Design of disk drive servo controller using H_∞-optimization technique to recover the loop transfer function is presented here. In the first phase of the two step algorithm, a full state feedback controller is designed to obtain desired gain and phase margins, and satisfactory sensitivity and complementary sensitivity for the nominal plant model. The observer gains are determined in the second phase, loop transfer recovery (LTR), so that the characteristics of the full state feedback are preserved. Recovery is achieved using minimization of the H_∞-norm of a transfer function called the recovery function, which represents the difference between the loop gain of the static full state feedback and feedback with observer. Simulation results for the continuous time design are shown