Browse Prior Art Database

Feed Forward Spindle Motor Control

IP.com Disclosure Number: IPCOM000118625D
Original Publication Date: 1997-Apr-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Rowan, BS: AUTHOR [+3]

Abstract

High-end disk drives use feedback control systems to maintain constant spindle motor speed and in disk array applications, constant phase relative to a reference signal or disk. If the drag forces on the spindle are constant, precise control can be maintained. Unacceptable disturbances to motor speed and phase can result from changes in drag force of sufficient magnitude and frequency content. These disturbances may not be adequately corrected by a traditional feedback control system.

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This is the abbreviated version, containing approximately 65% of the total text.

Feed Forward Spindle Motor Control

      High-end disk drives use feedback control systems to maintain
constant spindle motor speed and in disk array applications, constant
phase relative to a reference signal or disk.  If the drag forces on
the spindle are constant, precise control can be maintained.
Unacceptable disturbances to motor speed and phase can result from
changes in drag force of sufficient magnitude and frequency content.
These disturbances  may not be adequately corrected by a traditional
feedback control system.

      This invention compensates for changes in spindle motor drag
forces induced by sudden changes in actuator position by applying a
predetermined correction to the motor speed control signal.  This
correction counteracts the effect of the drag change on the motor,
and helps maintain constant spindle speed while the actuator position
changes relative to the disk.

      The windage load can be characterized under steady state
conditions by monitoring spindle motor idle current versus actuator
position.  This characterization can be done each time the drive is
recalibrated, once per drive at the factory, or with an average drag
profile obtained by examining many drives.  The results can be stored
as a polynomial or in a table of drag versus radial actuator
location.

      Any pending actuator movement is recognized by the control
system, which applies a simultaneous correction to the spindle motor
control signal.  The correcti...