Browse Prior Art Database

Quiescent Active Retract System for Disk File

IP.com Disclosure Number: IPCOM000118259D
Original Publication Date: 1996-Nov-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 2 page(s) / 63K

Publishing Venue

IBM

Related People

Albrecht, TR: AUTHOR [+2]

Abstract

When a disk file is powered off, accidental shocks can cause the actuator to move from its "parking" position (unload device or start/stop zone) to the data zone, resulting in unrecoverably high stiction. Although most files use a latching device to hold the actuator in the parking position, low-cost latches often have significant probability of failure during shocks to the file.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Quiescent Active Retract System for Disk File

      When a disk file is powered off, accidental shocks can cause
the actuator to move from its "parking" position (unload device or
start/stop zone) to the data zone, resulting in unrecoverably high
stiction.  Although most files use a latching device to hold the
actuator in the parking position, low-cost latches often have
significant probability of failure during shocks to the file.

      For many types of head/disk interfaces, the stiction level
increases with time (at least initially), and if the actuator is
retracted quickly upon accidental landing in the data zone, stiction
will not yet have reached an unrecoverable level.  Testing results
have shown that stiction force typically rises by a factor of three
or more during the first several minutes after landing; such stiction
increase is attributed to the flow of lubricant at the interface and
other factors.  The method described here uses a sensor system to
continuously monitor shock levels (or actuator motion) during
power-off times to activate a retract circuit immediately upon
sensing a shock.  The sensor system draws a very small amount of
current from an  unswitched power supply or battery back-up when the
host computer (or drive) is switched off.  While this system is not
effective in the event  that no power at all is available (e.g., a
dead battery in a laptop computer), it can operate under all
circumstances when power is available.

      The shock sensor can be one of two types:  (1) one or more
accelerometers can directly monitor shock, or (2) shocks can be
detected by monitoring the VCM voltage (back-emf) which results from
any actuator m...