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Browse Prior Art Database

Compensation of External Force

IP.com Disclosure Number: IPCOM000122506D
Original Publication Date: 1991-Dec-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 2 page(s) / 62K

Publishing Venue

IBM

Related People

Kisaka, M: AUTHOR

Abstract

Disclosed is an algorithm that can reduce memory area for a compensation table of external bias force to a voice coil motor (VCM) and reduce the time to make the table in a hard disk drive.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 63% of the total text.

Compensation of External Force

      Disclosed is an algorithm that can reduce memory area for
a compensation table of external bias force to a voice coil motor
(VCM) and reduce the time to make the table in a hard disk drive.

      Because of external force, access time to a target track
becomes longer. An integrator supplies force to balance with the
external force, and with that force, VCM can stay at a target track.
If the integrator value at a target track is stored in memory and is
set before seek, access time can be shorter than the time obtained
without setting the value. As the external force changes at track
position (inner or outer), memory for integrator value should be
assigned to every track. But avaliable memory is limited, so that the
tracks are divided into bands. For example, every 16 tracks is
assigned to a band, and the integrator value for each band is stored
in memory. That can save memory. If the number of tracks assigned to
a band becomes larger, the amount of memory required becomes smaller,
and also the time to get the integrator value at all bands becomes
shorter. But seek length between bands to make the memory table
becomes longer.  The external force changes by seek length because
some force such as friction caused by grease/oil changes by velocity.
So the external force during one track seek is different from the
external force during full track seek. In the full track case,
settling time can be 5-10 sample times in digital servo, wh...