Robust dual stage HDD track follow control systems design for hand-off shaping

One of the challenges for the controller in a two-stage actuator system is determining the relative output contribution of the stages as a function of frequency. Two popular methods for controller design for two stage disk drive systems are /spl mu/-synthesis, and the PQ method. The PQ method specifically exploits the two-stage structure, while /spl mu/-synthesis is a more general multi-input multi-output (MIMO) robust control technique. This paper compares a design using /spl mu/-synthesis alone with a design using a combination of the PQ method and /spl mu/-synthesis. Both approaches account for modeling uncertainty in the primary actuator.