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Optimal Means for Generating a Write Inhibit in Hard Disk Drives in Response to External Shock Using Accelerometers

IP.com Disclosure Number: IPCOM000118170D
Original Publication Date: 1996-Oct-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 2 page(s) / 57K

Publishing Venue

IBM

Related People

Belser, K: AUTHOR

Abstract

Disk drives use sector servo position sensing at a sampling rate of which is not fast enough to achieve adequate sensing of off-track external shock to control write inhibiting for the purposes of protecting the data on adjacent tracks. It is the current practice in the industry to directly compare the output of an accelerometer to a threshold value to generate a more adequate write inhibit. This current method is far from optimal since acceleration itself is not a measure of actual off-track position and may give rise to "false alarms". The method described here optimally estimates the amount of head-to-track position error that results in a hard disk drive from an external shock so as to provide adequate write inhibit data protection with a low false alarm rate.

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Optimal Means for Generating a Write Inhibit in Hard Disk Drives
in Response to External Shock Using Accelerometers

      Disk drives use sector servo position sensing at a sampling
rate of which is not fast enough to achieve adequate sensing of
off-track external shock to control write inhibiting for the purposes
of protecting the data on adjacent tracks.  It is the current
practice in the industry to directly compare the output of an
accelerometer to a threshold value to generate a more adequate write
inhibit.  This current method is far from optimal since acceleration
itself is not a measure of actual off-track position and may give
rise to "false alarms".  The method described here optimally
estimates the amount of head-to-track position error that results in
a hard disk drive from an external shock so as to provide adequate
write inhibit data protection with a low false alarm rate.

      The proposed system consists of at least one and up to six
accelerometers in any combination for the six degrees of freedom of
motion (namely X,Y,Z, Pitch, Roll and Yaw) and one filter amplifier
for each accelerometer with a filter to convert acceleration into an
estimated upper bound on the head-to-track position error for that
degree of freedom.  Each accelerometer is attached to the frame of
the disk drive near its mounting screws so as to sense as accurately
as possible the external excitation and not the natural vibration
modes of the drive itself.  The combination o...