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TECHNICAL PAPERS

Track-Following Control With Active Vibration Damping of a PZT-Actuated Suspension Dual-Stage Servo System

[+] Author and Article Information
Yunfeng Li

Department of Mechanical Engineering, University of California at Berkeley, Berkeley, CA 94720-1740

Federico Marcassa

Department of Information Engineering, University of Padova, PD, 35131, Italy

Roberto Horowitz

Department of Mechanical Engineering, University of California at Berkeley, Berkeley, CA 94720-1740horowitz@me.berkeley.edu

Roberto Oboe

Department of Mechanical and Structural Engineering, University of Trento, 38050, Trento, Italy

Robert Evans

 Hutchinson Technology Incorporated, Hutchinson, MN 55350

J. Dyn. Sys., Meas., Control 128(3), 568-576 (Nov 01, 2005) (9 pages) doi:10.1115/1.2229257 History: Received April 02, 2004; Revised November 01, 2005

In this paper we discuss the controller design of a PZT-actuated suspension dual-stage servo system in hard disk drives. The proposed control structure includes an active vibration damping control loop and a track-following control loop. The vibration damping control loop, which runs at a faster rate than the track-following control loop, utilizes a PZT element on a PZT-actuated suspension as a vibration sensor to damp the resonance modes of the voice coil motor (VCM) and the PZT actuator. The vibration damping controller is designed using Kalman filter based state feedback control techniques. A simple dual-stage track-following controller is designed, based on the damped actuator model, using the sensitivity function decoupling design method. Simulation and experimental results are presented to demonstrate the benefits of this control scheme in expanding servo control bandwidth and suppressing airflow excited structural vibrations.

Copyright © 2006 by American Society of Mechanical Engineers
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Figures

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Figure 1

Frequency response from VCM input to head displacement

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Figure 2

Frequency response from PZT actuator input to head displacement

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Figure 3

Frequency response from VCM input to PZT sensor output

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Figure 4

Frequency response from PZT actuator input to PZT sensor output

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Figure 5

An illustration of modes shape of the assembly butterfly mode and suspension sway mode

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Figure 6

PSDs of the head off-track motion and the PZT sensor output due to airflow excited vibrations

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Figure 7

A block diagram of the control system

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Figure 8

Simulated frequency response from the VCM to the head displacement

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Figure 9

Simulated frequency response from the PZT actuator to the head displacement

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Figure 10

Block diagram of the track-following controller design

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Figure 11

Open-loop Bode plots

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Figure 12

Measured frequency response from the VCM to the head displacement

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Figure 13

Measured frequency response from the PZT actuator to the head displacement

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Figure 14

Measured PSD of head off-track motion with damping control

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Figure 15

FFT of the head off-track motion with both damping and track-following control

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Figure 16

Time traces of position error with and without damping control

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