IEEJ Transactions on Industry Applications
Online ISSN : 1348-8163
Print ISSN : 0913-6339
ISSN-L : 0913-6339
A Higher Bandwidth Servo Design for Magnetic Disk Drives: A Head-positioning Control System with Strain Feedback Control
Shinsuke NakagawaTakashi Yamaguchi
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2003 Volume 123 Issue 11 Pages 1321-1329


In magnetic disk drives, mechanical resonance modes prevent a higher bandwidth servo being used for head positioning control. To overcome this limitation and realize more precise head positioning, a strain feedback controller which is added to a conventional head-position feedback loop was developed. The controller of a strain-feedback control system was designed so that the gain and the phase delay of the sensitivity function of the strain-feedback control system were both reduced below the frequency of a primary mechanical resonance. The controller achieves gain suppression by about 10dB at a primary mechanical resonance and phase delay of about zero degrees. It was found that the head-position control system (i.e., the strain feedback plus the conventional head-position feedback loop) increases the servo bandwidth by 17% and improves the positioning accuracy by 18%. It was also confirmed that unlike conventional servo system, the new servo design does not suffer degradation of servo characteristics at high temperature.

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© 2003 by the Institute of Electrical Engineers of Japan
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