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Digital Control System for Detenting a DC Servomotor

IP.com Disclosure Number: IPCOM000042364D
Original Publication Date: 1984-May-01
Included in the Prior Art Database: 2005-Feb-03
Document File: 2 page(s) / 13K

Publishing Venue

IBM

Related People

Bloom, RD: AUTHOR [+3]

Abstract

A digital control system uses a microprocessor (MP) 20 to correct for drift from and to maintain a DC servomotor 10 at a zero or standstill position. The control system includes applying a plug brake to restrain drift of motor 10 after a detent correction operation and/or periodically applying an anti-drift pulse after a number of successive detent correction operations have occurred. The control system has particular application to the DC servomotors used for driving a paper carriage in a line printer where the print paper must be maintained at an accurate line position during printing. As seen in the drawing, a DC servomotor 10 is connected between upper power transistors 11 and 12 and lower power transistors 13 and 14 connected in an H-drive network 15. Network 15 includes upper diodes 16 and 17 and lower diodes 18 and 19.

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Digital Control System for Detenting a DC Servomotor

A digital control system uses a microprocessor (MP) 20 to correct for drift from and to maintain a DC servomotor 10 at a zero or standstill position. The control system includes applying a plug brake to restrain drift of motor 10 after a detent correction operation and/or periodically applying an anti-drift pulse after a number of successive detent correction operations have occurred. The control system has particular application to the DC servomotors used for driving a paper carriage in a line printer where the print paper must be maintained at an accurate line position during printing. As seen in the drawing, a DC servomotor 10 is connected between upper power transistors 11 and 12 and lower power transistors 13 and 14 connected in an H-drive network 15. Network 15 includes upper diodes 16 and 17 and lower diodes 18 and 19. Motor 10 is operated in either direction in response to direction and current level signals from MP 20 to motor control 21, which contains the circuits for switching the power transistors. Forward direction, shown by the arrow, would occur by motor control 21 switching upper transistor 11 and lower transistor 14. Reverse drive is done by switching upper transistor 12 and lower transistor 13. Reverse power braking,
i.e., when motor 10 is moving in the direction of the arrow, is done by switching upper transistor 12 and lower transistor 13. Reverse power braking, i.e., when motor 10 is rotating contra the direction of the arrow, is done by switching upper transistor 11 and lower transistor 14. Electrodynamic braking or plugging when motor 10 is rotating in the direction of the arrow is done by switching transistor 13 only. This provides a low impedance path for the large current generated by motor 10 from ground through diode 18, motor 10 and transistor 13 to ground. A low current or detent plug when motor 10 is moving at low speed in either direction is made by switching transistors 11 and 12. This applies a low impedance short directly across motor 10. The detent plug is used for holding...