Browse Prior Art Database

In-Situ Head-Asperity Contact Detection

IP.com Disclosure Number: IPCOM000119772D
Original Publication Date: 1991-Feb-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 3 page(s) / 130K

Publishing Venue

IBM

Related People

Smith, GJ: AUTHOR

Abstract

Disclosed is a method which permits the detection of head- asperity contacts within an operating Disk Drive. Nearly all of the required analog electronics is contained within a Disk Drive. With the advent of digital recording channels, the analog to digital conversion and signal processing hardware is also available. The most useful implementation of the invention is to include the necessary hardware and software in every Disk Drive so that when the host system detects a Disk Drive in danger of a head crash, that file can be backed up and the Disk Drive scheduled for replacement.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 51% of the total text.

In-Situ Head-Asperity Contact Detection

      Disclosed is a method which permits the detection of head-
asperity contacts within an operating Disk Drive.  Nearly all of the
required analog electronics is contained within a Disk Drive.  With
the advent of digital recording channels, the analog to digital
conversion and signal processing hardware is also available.  The
most useful implementation of the invention is to include the
necessary hardware and software in every Disk Drive so that when the
host system detects a Disk Drive in danger of a head crash, that file
can be backed up and the Disk Drive scheduled for replacement.

      Fig. 1 displays a block diagram of the hardware.  The Arm
Electronics Module 1, which is connected to the recording heads in a
Disk Drive (not shown), has its output connected to an automatic gain
control (AGC) 2, which for the purpose of contact detection, has the
AGC action suppressed by use of the hold control 6.  The AGC output
is connected to a low pass filter 3, and then further amplified by a
linear amplifier 4.  The linear amplifier output is thus suitable for
input to an amplitude modulation (AM) detector 5, which effectively
detects the envelope of the readback signal waveform.  The AM
detector output is further filtered by low-pass filter 7 and then
processed to obtain a running average of the signal by DC average 8.
The output of the DC average circuitry and the filter 7 is subtracted
by difference amplifier 9 so that the input to the analog to digital
converter 10 is a voltage proportional to the difference between the
track average amplitude and the instantaneous signal changes which
may be caused by head contact with asperities.  To determine if
contact has occurred, the finite impulse response filter 11 has its
impulse response set to the time reversed version of the expected
contact signature.  This matched filter detection scheme will give
the greatest possible signal to noise for the expected white noise at
the filter's input.  The output of the FIR is examined by the
microprocessor 12 to verify the contact and furth...