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Pulse Width Modulation Velocity Servomechanism

IP.com Disclosure Number: IPCOM000074948D
Original Publication Date: 1971-Jul-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 3 page(s) / 40K

Publishing Venue

IBM

Related People

Holman, BJ: AUTHOR

Abstract

This digital velocity servomechanism controls the velocity of motor 1, by measuring the number of cycles of oscillator 2 which occurs between two consecutive output pulses of digital tachometer 3. As a result of this measurement, and at the time of occurrence of a tachometer pulse, an error count is stored in strobe latches SL1, SL2, SL4 and SL8. This count is subsequently compared to the BT1, BT2, BT4 and BT8 stages of a running base counter BT. This comparison determines the PWM energization pattern for the motor until the occurrence of the next tachometer pulse.

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Pulse Width Modulation Velocity Servomechanism

This digital velocity servomechanism controls the velocity of motor 1, by measuring the number of cycles of oscillator 2 which occurs between two consecutive output pulses of digital tachometer 3. As a result of this measurement, and at the time of occurrence of a tachometer pulse, an error count is stored in strobe latches SL1, SL2, SL4 and SL8. This count is subsequently compared to the BT1, BT2, BT4 and BT8 stages of a running base counter BT. This comparison determines the PWM energization pattern for the motor until the occurrence of the next tachometer pulse.

Each time the first four stages of the base counter are zero and the oscillator output is zero, flip-flop 5 is set. Subsequently, when the bit pairs of the strobe latches and the first four stages of the base counter are equal, +AND gate 4 is enabled and flip-flop 5 is reset through inverter 6. So long as flip-flop 5 is set, the motor is energized.

Tracing one cycle of operation, the occurrence of a tachometer pulse sets single shot 7 to its unstable state. The output of this single shot sets all of stages of base counter BT to zero, and transfers whatever error count is in error counter E to the four strobe latches. The first four stages of the base counter are now zero and the first zero output of the oscillator sets flip-flop 5 through -AND gate 8.

A short time later, single shot 7 returns to its stable state and thereby sets single shot 9 to its unstable state. The output of this single shot sets the four stages of the error counter to zero.

The first four stages of the base counter are now compared t...