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Multi-Rate Servo for the Reduction of Magneto-Resistive Head 'ON' Time

IP.com Disclosure Number: IPCOM000101925D
Original Publication Date: 1990-Sep-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 2 page(s) / 60K

Publishing Venue

IBM

Related People

Stich, MC: AUTHOR

Abstract

A Magneto-resistive head (MR) for Direct Access Storage Device (DASD) applications is believed to have a lifetime that is too short for present DASD files. Some of the methods suggested to relieve this problem involve turning off the head when it is not being used to read or write data. Disclosed is a method for improving the performance of the servo control when this is done.

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This is the abbreviated version, containing approximately 58% of the total text.

Multi-Rate Servo for the Reduction of Magneto-Resistive Head 'ON' Time

       A Magneto-resistive head (MR) for Direct Access Storage
Device (DASD) applications is believed to have a lifetime that is too
short for present DASD files.  Some of the methods suggested to
relieve this problem involve turning off the head when it is not
being used to read or write data.  Disclosed is a method for
improving the performance of the servo control when this is done.

      In a sector (or embedded) servo environment, the head would
have to be turned on to read each servo burst even when not reading
or writing data.  Some of these bursts could be skipped by leaving
the head turned off, but this results in a lower performance loop due
to the lower sampling rate.  Since the head is not reading or
writing, this is acceptable to a certain degree.  There will be some
time necessary to recover to a high performance loop when a read or
write operation is initiated, and thus some loss of performance.
This method will improve the performance of the loop when not reading
or writing by using a multi-rate servo control so that the recovery
time is minimized and, thus, the overall performance is improved.

      Multi-rate control systems have been around for a long time.
One of the common configurations is to apply control effort to the
plant at a higher sample rate than that used to measure the plant
output.  The figure shows a block diagram of this situation.  A
control loop...