Browse Prior Art Database

Active Dumping of Mechanical Resonance

IP.com Disclosure Number: IPCOM000117339D
Original Publication Date: 1996-Feb-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Kitazaki, N: AUTHOR [+3]

Abstract

Disclosed is a technique to dump sympathetic resonance of high frequency by changing DAC OUT timing. Using this technique, effective servo performance can be achieved even for a suspension with undesired frequency.

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Active Dumping of Mechanical Resonance

      Disclosed is a technique to dump sympathetic resonance of high
frequency by changing DAC OUT timing.  Using this technique,
effective servo performance can be achieved even for a suspension
with undesired frequency.

      If there is high gain of mechanical resonance at the frequency
of f,3f,5f..., where f is nyquist frequency, servo system promotes
the vibration in case DAC OUT timing doesn't match.  However, once
DAC OUT timing is adjusted to cancel mechanical force acting on
suspension, this vibration can be dumped.  For example, if a
suspension has high gain at 6kHz and sapling is done at 4kHz, it
causes 2kHz vibration when the force acting on suspension is not
cancelled enough.  But if the interval between reading servo
information and DAC OUT optimized at T/3, where T is sampling
frequency, the vibration can be dumped (shown in Fig. 1).

      Delayed DAC OUT also causes phase margin loss and degrades
track following stability.  Fig. 2 shows an algorithm to recover this
error without any phase loss of most suspensions.  Vibration check
results are written in the DELAY_DAC_TABLE for each head, and by
refering it when head is changed, the best timing to DAC OUT can
always be selected.