Design of controller for the dual-stage actuator in hard disk drive using internal model approach

A dual-stage actuator is considered to be the solution to meet the challenges of ever-increasing track density in hard disk drives. The low-inertia secondary actuator of the dual-stage actuator makes it possible to reposition the read/write head quickly to follow the sharp variations in the track. This allows better control of the tracking error during track-following mode of the servo system. Unfortunately, the physical characteristics of the secondary actuators vary widely due to imperfections in the manufacturing process and the variation in the material properties. Robustness is, therefore, a very important factor in the design of the servo controller. Internal model control (IMC) is regarded as a tool for designing a robust controller. We present the results of the design of servo controller for a dual-stage actuator using this internal model approach. Effectiveness of the controller is verified through simulation.