Optimal Output Transition for Settling Control in Hard-Disk Drives with Dual-Stage Actuators

The settling problem in hard disk drives (HDD) is an output transition problem - given an initial state x(0), the goal is to bring the output to a desired value y(tf) = -y and hold it constant after the end of settling, t > tj. This article develops the direct solution to the optimal output transition (OOT) problem for seek settling, and develops a method to use post-actuation inputs to optimize the seek settling cost. The approach is illustrated with simulations on an example dual-stage system model. Simulations are also used to illustrate the reduction in the computational burden for online implementation by using linear combinations of precomputed inputs.