On high-performance servo control algorithms for hard disk drive

In conventional hard disk drive servo systems, Mode Switching Control (MSC) is employed which consists of two different control schemes to achieve both optimal seek time and satisfactory track-following performance. The MSC makes the design complicated and has other problems such as obtaining smooth transition at the hand-off.; This research focuses on developing a unified servo algorithm to replace the MSC method. Three different types of unified controllers are proposed. Firstly, a nonlinear observer-based inner-loop control method is proposed. It proves to be able to deal with the high-frequency resonance and then achieve good control performances. The second is a nonlinear Time-Optimal Unified Servo Controller (TOUSC). It is designed by using discrete time-optimal principle and can provide good track seek performance and good robustness for the track following. Finally, a Two-Degree-Of-Freedom (2DOF) control method based on the TOUSC is proposed. Using a feed-forward control, it has better track-seek performance.; The first method is verified on a 2.032kTPI (kilo Track Per Inch) hard disk drive simulation model and the second and the third ones on a 13kTPI hard disk drive plant in simulations. Simulation studies show that good performances for both the track seek and the track following are achieved by the proposed control algorithms.