H∞ compensation of external vibration impact on servo performance of hard disk drives in mobile applications

Abstract

H∞ compensation for external vibration impact on the positioning accuracy of hard disk drives is considered in this paper. A feedforward controller is designed to attenuate the impact with the aid of a sensor to detect external vibrations. Loop shaping in frequency domain and H∞ method in state space are used to design the feedforward controller. The linear matrix inequality approach is adopted for solving the H∞ feedforward control design problem. The application results in a 1.8-in disk drive with an accelerometer to measure acceleration signal show that 97% reduction of the position error signal is achieved with the feedforward control designed by the H∞ method. The effectiveness of the two methods is also evaluated and compared when external vibration model is subjected to gain variations. Copyright © 2007 John Wiley & Sons, Ltd.