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In-situ Measurement of Crash Stop Stiffness in a Direct Access Storage Device

IP.com Disclosure Number: IPCOM000107863D
Original Publication Date: 1992-Mar-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 2 page(s) / 68K

Publishing Venue

IBM

Related People

Smith, GJ: AUTHOR

Abstract

This invention permits the measurement of in-situ crash stop stiffness in a direct-access storage device (DASD). The crash stop stiffness is important for maintaining adequate head/disk clearance during an actuator run-away situation during which the actuator motion is arrested using the crash stop. The crash stop stiffness is determined by measuring the radial displacement of a slider with respect to a previously written track while applying known forces against the crash stop. The radial displacement is measured by interpreting the readback signal amplitude from the recording head in terms of the amount of off- track displacement. The applied force is adjusted by varying the current in the actuator voice coil.

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In-situ Measurement of Crash Stop Stiffness in a Direct Access Storage Device

       This invention permits the measurement of in-situ crash
stop stiffness in a direct-access storage device (DASD).  The crash
stop stiffness is important for maintaining adequate head/disk
clearance during an actuator run-away situation during which the
actuator motion is arrested using the crash stop.  The crash stop
stiffness is determined by measuring the radial displacement of a
slider with respect to a previously written track while applying
known forces against the crash stop.  The radial displacement is
measured by interpreting the readback signal amplitude from the
recording head in terms of the amount of off- track displacement.
The applied force is adjusted by varying the current in the actuator
voice coil.

      This method is possible because the head output signal changes
with the distance the head read element is relative to a written
track.  As the read element moves away from the written track, the
amplitude of the signal (particularly the higher harmonics of the
recorded fundamental) decreases in amplitude.  By comparing the
amplitude of two harmonics, the distance that the crash stop deflects
as a function of the actuator force can be measured.

      To make the measurement, a single track is written with the
head- arm assembly held against a crash stop (either the inner or
outer crash stop can be used).  Ideally, the crash stop should be
undeflected. Th...