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Motor Velocity Control

IP.com Disclosure Number: IPCOM000040588D
Original Publication Date: 1987-Dec-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Kisaka, M: AUTHOR

Abstract

This article describes a technique for controlling a velocity of a motor during a high velocity phase. The velocity control is performed based on measurement of cycle time of an output signal from an encoder associated with the motor. Fig.1 illustrates a velocity control system for a motor 7 which is usable to drive a head in a disk drive. An encoder 8 generates a cyclic output (Fig.2) depending on the rotation of the motor 7. A processor 1 including a timer 2 operates to measure a time length Ti (i=1, 2, 3 ..... ) of one cycle of the encoder output after each zero-cross point. The processor 1 gives a signal representing an inverse of the time length Ti to a digital-analog converter (DAC) 3.

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Motor Velocity Control

This article describes a technique for controlling a velocity of a motor during a high velocity phase. The velocity control is performed based on measurement of cycle time of an output signal from an encoder associated with the motor. Fig.1 illustrates a velocity control system for a motor 7 which is usable to drive a head in a disk drive. An encoder 8 generates a cyclic output (Fig.2) depending on the rotation of the motor 7. A processor 1 including a timer 2 operates to measure a time length Ti (i=1, 2, 3 ..... ) of one cycle of the encoder output after each zero-
cross point. The processor 1 gives a signal representing an inverse of the time length Ti to a digital-analog converter (DAC) 3. Since the inverse of the time length Ti is proportional to an actual velocity of the motor 7, the DAC 3 produces an output representing the actual velocity. Simultaneously, an another DAC 4 produces an output representing a predetermined velocity in response to a signal from the processor 1 representing an inverse of a predetermined time length. The outputs of the DAC's 3 and 4 are respectively applied to plus and minus input terminals of an analog adder 5 which in turn produces a velocity error signal representing the difference between the actual and predetermined velocities. The velocity error signal is used to drive the motor 7 through a power amplifier 6.

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