Design and implementation of a dual-stage actuated HDD servo system via composite nonlinear control approach

Abstract

We consider in this paper the design and implementation of a dual-stage actuated hard disk drive (HDD) servo system, in which an additional piezoelectric actuator is mounted on top of the conventional voice-coil-motor (VCM) actuator to provide a faster and finer response. More specifically, the dual-stage actuated HDD servo system consists of a primary VCM actuator and a secondary suspension piezoelectric microactuator. The VCM actuator is used to quickly move the read/write (R/W) head of the HDD servo system to a target track, whereas the microactuator is used to fine-tune the R/W head position when it is getting closer to the target. In our design, the primary actuator is controlled by a newly developed composite non-linear feedback (CNF) control law, which has fast rise time and small overshoot, and the microactuator is controlled through a simple static gain together with a low-pass filter and a notch filter. Simulation and implementation results show that in track following, the dual-stage actuated HDD servo system has outperformed the single-stage actuated counterpart by more than 47% in settling time and by 39% in position error signal (PES) tests. © 2004 Elsevier Ltd. All rights reserved.