Comparison and design of servo controllers for dual-stage actuators in hard disk drives

A systematic design procedure is presented that can be used to construct servo controllers for dual-stage actuation in a hard disk drive. The systematic approach is based on optimal control theory using an H_∞-norm-based control design, where servo design specifications are formulated in terms of relatively simple weighting functions. Different possible servo control strategies are designed and compared on performance and energy consumption. Results based on a piezoelectric milli-actuator from Hutchinson Technology Inc. illustrate the design of a dual-stage servo controller that is able to perform high-density track recording, with a significant reduction in power consumption.