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Acceleration Control System for a DC Motor

IP.com Disclosure Number: IPCOM000081954D
Original Publication Date: 1974-Sep-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 51K

Publishing Venue

IBM

Related People

Dohanich, GJ: AUTHOR [+3]

Abstract

A digital pulse source generates a frequency analog of a desired velocity to which a DC motor is accelerated. The acceleration circuit converts a frequency analog signal to a frequency dependent direct voltage and a sawtooth voltage. A comparison circuit generates a motor drive signal having a duty cycle dependent on the relative voltage levels of the direct and sawtooth voltages. The comparative duty cycle of the motor drive signal for two different velocities is regulated, to be proportional to the square of the ratio of the two velocities.

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Acceleration Control System for a DC Motor

A digital pulse source generates a frequency analog of a desired velocity to which a DC motor is accelerated. The acceleration circuit converts a frequency analog signal to a frequency dependent direct voltage and a sawtooth voltage. A comparison circuit generates a motor drive signal having a duty cycle dependent on the relative voltage levels of the direct and sawtooth voltages. The comparative duty cycle of the motor drive signal for two different velocities is regulated, to be proportional to the square of the ratio of the two velocities.

In the acceleration circuit shown, the input is a frequency analog signal where the repetition rate represents the desired velocity of the DC motor. The signal is fed to single-shot 1 and low-pass filter 2 to produce a voltage level 10, dependent upon the repetition rate of the frequency analog signal.

The signal is also fed to frequency divider 3 to provide a lower frequency at single-shot 4 to produce uniform width-control pulses. Switch 5, capacitor 6, and current source 7 convert these control pulses into a sawtooth signal 11 clipped by diode 8. Single-shot 4 also generates reset pulses 13. Compare 9 compares voltage level 10 with sawtooth 11 and generates an output 12 of variable duty cycle to operate the motor. The duty cycle is determined by the time during which sawtooth signal 11 is greater than voltage level 10, as shown in the circuit waveforms.

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