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Generalized Head/Disk Contact Detection Using Head Readback Signal

IP.com Disclosure Number: IPCOM000107137D
Original Publication Date: 1992-Jan-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 2 page(s) / 70K

Publishing Venue

IBM

Related People

Smith, GJ: AUTHOR

Abstract

Described is a general means for obtaining in-situ head/disk contact information using the readback signal from a recording head in a direct access storage device (DASD). The head flying height change caused by asperity contact is determined from digitized samples of the readback signal from a head.

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Generalized Head/Disk Contact Detection Using Head Readback Signal

       Described is a general means for obtaining in-situ
head/disk contact information using the readback signal from a
recording head in a direct access storage device (DASD). The head
flying height change caused by asperity contact is determined from
digitized samples of the readback signal from a head.

      This invention utilizes digitized samples of the readback
signal from a head(s) and processes the information (within a DASD)
to extract head/disk contact information. Head flying height changes
affect the magnetic spacing loss and, hence, the harmonic amplitudes
in the readback signal from a recording head.  The processing of the
readback data is facilitated through the use of a digitally sampling
recording channel.  The digitized samples are passed through digital
filters in order to extract harmonic amplitudes. These amplitudes can
be considered separately or as a ratio to indicate head flying height
modulation.

      Existing partial response recording channels process digital
samples of the readback signal.  By comparing the samples to the
expected values (based on a given written pattern), the error can be
related to flying height change for example.  If these samples are
obtained frequently enough, head/disk contact can be monitored.
Because digital filtering is used in some channels, the same filters
can also be used to extract harmonic amplitudes.  In both cases, the
flyi...