Adaptive resonance compensation for hard disk drive servo systems

An add-on compensator is designed to adapt, in a stable, robust, and direct manner, to uncertainty in the resonance characteristics of hard disk drives (HDDs). The design and analysis is based on the linear discretized plant comprising a parallel structure of known nominal voice coil motor (VCM) dynamics and uncertain resonance dynamics. The add-on compensator complements any pre-designed stable nominal control. To prevent the nominal control from being canceled out in adaptive control design, we utilize, as adaptation signal, the error between the output and the auxiliary output, a computable quantity exploiting knowledge of the nominal plant and pre-designed nominal control. Extensive simulation results on a model of the Hitachi 1.8-inch HDD demonstrate the effectiveness of the proposed adaptive compensator in attenuating resonance peaking.