Dynamic Nonlinear Control for Fast Seek-Settling Performance in Hard Disk Drives

This paper proposes a dynamic nonlinear control scheme to improve the seek-settling performance in hard disk drive servo system by a combination of a novel designed reference generator and a nonlinear feedback controller. The feedback controller consists of a linear one for short rise time and an associated nonlinear one for small overshoot. In order to improve the settling performance and system stability due to actuator saturation, reference trajectory is designed based on the performance of feedback loop so that the position error signal in the tracking stage is decreased greatly, which effectively avoids the actuator saturation with a high gain feedback control design. A parameterized second-order system is proposed to generate such desired reference trajectory. The stability of the proposed control scheme is proved through appropriate Lyapunov functions. The results in simulation and implementation show that the proposed control design performs better as compared with linear and optimal control laws for both short and long tracking lengths