Robust control optimization for high performance track following in hard disk drives

This paper develops a robust control optimization framework for the micro actuator system in dual stage hard disk drives. The controller is parameterized using a cascade of different stabilizing and loop-shaping filters including lead/lag compensators, and peak and notch filters, resulting in over 30 optimization variables. We use a single-sided quadratic penalty function to formulate the cost function for multiple objectives, such as sensitivity transfer function shape, closed-loop system bandwidth, stability margins, and the non-repeatable position error spectrum, simultaneously. Finally, we use a neighborhood search algorithm to minimize the cost function around the initial design. Results indicate that the stability and robustness properties of the closed-loop system are significantly improved as a result of the proposed control optimization strategy.