A linear matrix inequality approach to initial value compensation for mode switching control in hard disk drive servo systems

In switching from the track-seeking or track-jumping control mode to the track-following control mode in hard disk drives, initial values of the feedback controller are tuned such that the transient response is improved. We present a simple initial value compensation (IVC) method using linear matrix inequalities (LMIs) instead of the conventional method that uses a Lyapunov equation. The LMIs include conditions for improving the transient response performance in the L₂-norm sense and minimizing the H_∞ norm of the closed-loop system in order to reduce the controlled outputs such as plant states, tracking error, and control efforts. We obtain optimal initial values of the controller by solving an optimization problem with constraints represented by only one LMI. We verified the feasibility of the method by using a series of simulations.