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

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 nonlinear 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. 0957-4158/$ see front matter 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.mechatronics.2004.06.002 * Corresponding author. Tel.: +65 6874 2289; fax: +65 6779 1103. E-mail addresses: [email protected] (K. Peng), [email protected] (B.M. Chen), eleleeth@nus. edu.sg (T.H. Lee), [email protected] (V. Venkataramanan). 966 K. Peng et al. / Mechatronics 14 (2004) 965–988