Browse Prior Art Database

DASD with In-situ Monitor of Head Disk Adhesion

IP.com Disclosure Number: IPCOM000107716D
Original Publication Date: 1992-Mar-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 2 page(s) / 74K

Publishing Venue

IBM

Related People

Best, GL: AUTHOR [+2]

Abstract

Presented here is a system which allows the motor torque necessary to free a given head from a disk to be conveniently determined. The system is designed to measure the current to the motor, which gives the torque supplied to the spindle and disk(s). Movement of the slider with respect to the disk is determined through low velocity measurement of the magnetic read signal. This can be achieved by use of a magnetoresistive read head or other sensor which has response characteristics at DC or low frequencies. The design of the system is as follows: 1. Write a set of magnetic transitions on the disk at a known spacing. Typically, spacings of less than a micron are quite possible. This is done prior to stopping the disk, so that they can be monitored during startup.

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DASD with In-situ Monitor of Head Disk Adhesion

       Presented here is a system which allows the motor torque
necessary to free a given head from a disk to be conveniently
determined.  The system is designed to measure the current to the
motor, which gives the torque supplied to the spindle and disk(s).
Movement of the slider with respect to the disk is determined through
low velocity measurement of the magnetic read signal.  This can be
achieved by use of a magnetoresistive read head or other sensor which
has response characteristics at DC or low frequencies.  The design of
the system is as follows:
      1. Write a set of magnetic transitions on the disk at a known
spacing.  Typically, spacings of less than a micron are quite
possible.  This is done prior to stopping the disk, so that they can
be monitored during startup.  If necessary, these transitions can be
rewritten if data loss occurs due to multiple start/stop cycles.
      2.  On startup, measure the current to the spindle motor, and
thus sense the motor torque.  For a typical spindle motor,

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      For a typical motor torque constant of 0.04 N-m/A, a current
measurement resolution of 10 mA will provide a torque measurement
resolution of 0.4 N-mm.  At a radius of 50 mm this is equal to a
force resolution of 8 mN or 0.8 gram.
      3.  Detect the relative head-to-disk motion using the readback
signal.  If a magnetoresistive head element is used, potential
electrical damage to the he...