Modeling product variations in hard disk drive micro-actuator suspensions

The increase in aerial storage capacities of future magnetic hard disk drives has fostered the use of dual-stage actuators for high track density data recording. In a hard disk drive with a dual-stage actuator the standard rotary actuation of the voice coil motor is combined with an additional micro or milli actuation to accomplish high-bandwidth and highly accurate track following. In order to guarantee error less data transfer, the track following servo controller needs to perform robustly under different operating conditions, that include changes in flying height and product manufacturing tolerance of the dual-stage actuator. Essential in the controller design is to characterize these uncertain conditions and design a robust track following servo accordingly. In this paper we present an experiment based methodology to characterize the varying servo conditions in the form of an uncertainty model. The uncertainty model can be used for analysis and synthesis of robust servo controllers.