A unified controller design using two different types of optimal reset control laws for HDD servo systems

This article proposes a unified reset control design method to achieve both track-seeking and track-following performance in hard disk drive servo systems. It involves a discrete Linear Quadratic Regulation (LQR) reset controller and an Hi reset controller. The LQR reset controller is much capable of improving transient response performance which includes fast raise time and little overshoot. The discrete H₂ reset controller performs a better disturbance rejection performance which is more suitable for track following stage. The unified control makes a soft switch from LQR reset controller to Hi reset controller, which avoids sharp vibrations. Simulation shows that the unified reset controller inherits the merits of both discrete LQR reset controller and discrete H₂ reset controller, and achieves both swift seeking and accurate following performance.