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Spindle Control Compensation Method for Spindle Load Variations in DASD Files

IP.com Disclosure Number: IPCOM000107787D
Original Publication Date: 1992-Mar-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 2 page(s) / 103K

Publishing Venue

IBM

Related People

Erickson, KJ: AUTHOR [+3]

Abstract

A method that can be used to improve the spindle speed control in direct-access storage devices (DASDs) for conditions where the spindle load changes based on the position of the actuator for the read/write heads is disclosed. This method provides a means to help reduce the effects of the load changes through the anticipation of the changes, thereby reducing the spindle speed perturbations which can occur during actuator access operations. This method is especially useful in applications where the spindle systems of several DASD files must be synchronized, such as in DASD arrays.

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Spindle Control Compensation Method for Spindle Load Variations in DASD Files

       A method that can be used to improve the spindle speed
control in direct-access storage devices (DASDs) for conditions where
the spindle load changes based on the position of the actuator for
the read/write heads is disclosed.  This method provides a means to
help reduce the effects of the load changes through the anticipation
of the changes, thereby reducing the spindle speed perturbations
which can occur during actuator access operations. This method is
especially useful in applications where the spindle systems of
several DASD files must be synchronized, such as in DASD arrays.

      Most spindle control systems in use today employ some form of
integration control (in addition to the traditional proportional
control) to compensate for spindle load changes such that the steady-
state error in the spindle speed is zero.  However, integrators by
nature tend to have a slow response to changes, which affects the
response of the control system for significant changes in the load,
such as that which occurs during actuator-access operations in DASD
files.

      A method can be implemented such that the spindle load changes
can be predetermined for those changes which occur due to the
repositioning of the actuator in the file (see the figure).

      The control value that is generated by the Spindle Control
Processor typically consists of a proportional term and an integrator
term.  The proportional term is the result of the instantaneous error
in the desired spindle speed versus the actual spindle speed, whereas
the integrator term settles to a relatively constant value that is
representative of the average spindle load over a period of time.
Therefore, as the spindle load changes due to a change in the
position of the actuator, the integrator term will change accordingly
to compensate for this change, but it cannot do so instantaneously.

      In order to provide for a faster integrator response for when
the position of the actuator is changed, the integrator term can be
measured with the actuator positioned at two or more locations over
its range of travel,...