Browse Prior Art Database

Spindle Motor Feedback to Actuator Servo to Compensate for Casting

IP.com Disclosure Number: IPCOM000104161D
Original Publication Date: 1993-Mar-01
Included in the Prior Art Database: 2005-Mar-18
Document File: 4 page(s) / 78K

Publishing Venue

IBM

Related People

Hearn, AR: AUTHOR

Abstract

A low-cost solution to a significant cause of track misregistration (TMR) in future rotary disk drives is disclosed.

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

Spindle Motor Feedback to Actuator Servo to Compensate for Casting

      A low-cost solution to a significant cause of track
misregistration (TMR) in future rotary disk drives is disclosed.

      To continue the ever increasing track densities in disk drives,
it is necessary to reduce TMR.  One of the major elements of TMR in
the future will be the overshoot after a seek - the settle.  There
are many causes of settle, one of which is the resultant casting
motion caused by a seek.  The reaction of the seek moves the casting
in its isolation mounts, resulting in motion well after the seek has
completed.  This amplitude is significant in linear actuators and
becoming more so with rotary actuators.

      A well-known solution to this is to feed back the casting
acceleration into the actuator servo to compensate for the motion.
Traditionally, it was necessary to use an accelerometer attached to
the base casting which is quite an expensive item.  With a rotary
actuator, two such accelerometers would be required to determine the
rotary acceleration of the casting.  With smaller and smaller drives,
the cost of the devices and associated electronics would be
inhibitive.

      This disclosure achieves the casting acceleration by using the
second differential of the spindle motor error.  At the frequencies
of concern, the spindle can be considered to have constant speed so
the error will contain the casting angular motion.  The error would
also contain unwanted features, and these would have to be filtered
out.  For example, t...