Browse Prior Art Database

DC SERVO MOTOR CONTROL TECHNIQUE

IP.com Disclosure Number: IPCOM000024193D
Original Publication Date: 1979-Dec-31
Included in the Prior Art Database: 2004-Apr-02
Document File: 2 page(s) / 62K

Publishing Venue

Xerox Disclosure Journal

Abstract

K = Constant chosen to make component values reasonable. C = L Rx Volume 4 Number 6 November/December 1979 757 DC SERVO MOTOR CONTROL TECHNIQUE (Cont'd) Referring to the drawing, conventional servo systems using DC servo motors 8 require some sort of a tachometer to sense the motor velocity for use in a feedback loop. If, however, the back emf of motor 8 itself could be used for this purpose, then the cost of the tachometer could be replaced by the cost of op amp 9. Even in more complicated systems with digital sensors and phase locked loops, addition of a second feedback loop could result in a servo motor with apparently better characteristics.

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Page 1 of 2

XEROX DISCLOSURE JOURNAL

DC SERVO MOTOR CONTROL TECHNIQUE Classification Proposed Sidney W. Marshall U.S. C1. 318/301

Into C1- H02k 27/20

= D. C. Resistance of Motor.

= Motor Inductance.

= Back emf of Motor.

= Resistance of Sensing Resistor 10.

RM

LM

vM

RS
K = Constant chosen to make component values reasonable.

Rx

Volume 4 Number 6 November/December 1979 757

C =L

[This page contains 1 picture or other non-text object]

Page 2 of 2

DC SERVO MOTOR CONTROL TECHNIQUE (Cont'd)

Referring to the drawing, conventional servo systems using DC servo motors 8 require some sort of a tachometer to sense the motor velocity for use in a feedback loop. If, however, the back emf of motor 8 itself could be used for this purpose, then the cost of the tachometer could be replaced by the cost of op amp 9. Even in more complicated systems with digital sensors and phase locked loops, addition of a second feedback loop could result in a servo motor with apparently better characteristics.

To separate the back emf of motor 8 from the effects of the driving waveform, the voltage drop across a current sensing resistor 10 is sensed. The expected voltage this would cause across the motor 8 is determined and this voltage is compared by op amp 9 with the actual voltage V across the motor. The output from op amp 9 is the back emf of the motor 8 which is proportional to motor velocity and totally independent of motor drive voltage.

758

     XEROX DISCLOSURE JOURNAL Volume 4 Number 6 November/December 1...