A Discrete Time Optimal Control Solution for Hard Disk Drives Servo Design

This paper concerns with the challenge in high performance motion control systems, typified by the computer hard disk drive positioning control problem. Not only such systems seek very high accuracy, there is also an insatiable appetite for speed. To make the problem more challenging, the design has to address the actuator saturation issue. This is, in essence, a time optimal control problem and a novel solution, a discrete time optimal control law, is proposed in this paper. It is shown that such solution is: (1) a single controller that unifies the separate track-seeking and track-following control functions in existing methods; (2) robust against unknown resonant modes; and (3) easy to implement and tune. The new control law is compared with existing methods and the results are quite promising in simulation studies of two different hard disk drives.