Robust Track-Following for Dual-Stage Servo Systems by Sensitivity Shaping with Degree Constraint

This paper presents track-following control design, with a new sensitivity shaping technique, for dual-stage servo systems in hard disk drives. The shaping technique simultaneously takes care of both complexity of controllers and robustness, important issues for controller implementation. As dual-stage servo systems, in addition to the conventional voice coil motor, a microactuator at the slider is adopted. Using these actuators, two types of feedback structures are to be considered; one is the structure for the sensitivity decoupling method, and the other is for the PQ method. After controller design, robust stability and robust performance against parametric uncertainties are evaluated. The simulation results show that, with the new shaping technique, nominal performance of track-following can be improved without losing robust stability.