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Improved Pulse-Width Modulated Motor Control Technique

IP.com Disclosure Number: IPCOM000043757D
Original Publication Date: 1984-Sep-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Schulz, RA: AUTHOR

Abstract

Printer and typewriter print mechanisms, at the end of a print line, require short stopping distances and then a fast direction reversal. This causes rapid motor deceleration and acceleration, and results in undesirably large motor currents. Described is a technique whereby the reverse motion response of a direct current motor is improved by using an improved pulse-width modulated drive circuit. In present DC motor drive circuits, as shown in Fig. 1, the pulse-width modulation input is applied only to transistors 1 and 2, depending on direction. Transistors 3 and 4 are not pulse-width modulated, and are controlled by direction only. In Figs. 1 and 3, the DC motor is modelled as a series RLC circuit. When the mechanism is going to the left, capacitor 5 of this RLC circuit accumulates a charge in the direction shown.

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Improved Pulse-Width Modulated Motor Control Technique

Printer and typewriter print mechanisms, at the end of a print line, require short stopping distances and then a fast direction reversal. This causes rapid motor deceleration and acceleration, and results in undesirably large motor currents. Described is a technique whereby the reverse motion response of a direct current motor is improved by using an improved pulse-width modulated drive circuit. In present DC motor drive circuits, as shown in Fig. 1, the pulse-width modulation input is applied only to transistors 1 and 2, depending on direction. Transistors 3 and 4 are not pulse-width modulated, and are controlled by direction only. In Figs. 1 and 3, the DC motor is modelled as a series RLC circuit. When the mechanism is going to the left, capacitor 5 of this RLC circuit accumulates a charge in the direction shown. When it becomes time to reverse direction, at transition time, excessive motor voltage 6 is applied. Motor current 8 becomes larger than required, causing the motor to decelerate too rapidly. The improved circuit, as shown in Fig. 2, causes the transition voltage to be applied differently. This allows the motor to continue to rotate in the same direction while decelerating, even though a directional change was indicated. Pulse-width modulation is applied in the same way, but controlled with the addition of logic gates A, B, and C. Control line 9 is needed to identify the presence of the transition...