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Browse Prior Art Database

Method for Achieving a Customized Spindle Rotation Speed

IP.com Disclosure Number: IPCOM000100529D
Original Publication Date: 1990-May-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 1 page(s) / 45K

IBM

Related People

Siverling, MM: AUTHOR

Abstract

Disclosed is a method for deriving an arbitrary rotation speed which is synchronized to the system clock from an off-the-shelf DC motor and driver circuit.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 71% of the total text.

Method for Achieving a Customized Spindle Rotation Speed

Disclosed is a method for deriving an arbitrary rotation
speed which is synchronized to the system clock from an off-the-shelf
DC motor and driver circuit.

Commercially available non-customized brushless DC motor
drivers typically are designed to receive a clock pulse, which is
internally divided to obtain a reference frequency for the motor.
The speed at which the motor will operate is adjusted by varying the
frequency of the input pulse.  When the motor is used to drive a disk
storage device, it is desirable to maintain a precise rotation speed
which has some relation to the system clock.

This method involves deriving a synthetic input signal from the
system clock by dropping clock pulses in a predetermined pattern.
Two integers, N and M, are selected such that: Fs * (N/M) = Fd where
Fs is the frequency of the system clock and Fd is the frequency of
the desired input pulse to the motor driver. The equality need not be
exact; it is only necessary that the error be less than errors
introduced by mechanical tolerances and other effects.  The synthetic
input signal is derived by dropping a distributed pattern of (M-N)
pulses from every M system clock pulses.

The driver circuit is not concerned with symmetry of the input
and so divides the input pulse string down notwithstanding the fact
that some pulses are missing.  With each succeeding division of the
input, the error in...