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Positioning precision is crucial to today's increasingly high-speed, high-capacity, high-data-density, and miniaturized hard disk drives (HDDs). The demand for higher bandwidth servo systems that can quickly and precisely position the read/write head on a high track density becomes more pressing. The idea of applying dual-stage actuators to track servo systems has been studied. However, the current dual-stage actuator design uses only piezoelectric patches without passive damping. In this paper, we propose a dual-stage servo system using enhanced active-passive hybrid piezoelectric actuators. The proposed actuators will improve the existing dual-stage actuators for higher precision and shock resistance, due to the incorporation of passive damping in the design. We aim to develop this hybrid servo system not only to increase the speed of track seeking but also to improve the precision of track following servos in HDDs. New piezoelectrically actuated suspensions with passive damping have been designed and fabricated. In order to evaluate positioning and track following performances for the dual-stage track servo systems, experimental efforts are carried out to investigate the damping abilities and transmissibilities of the microactuators and to implement the synthesized active-passive suspension structure using a composite nonlinear feedback controller.
Date of Publication: Feb. 2008