Browse Prior Art Database

Digital Summing Point for a Servomechanism

IP.com Disclosure Number: IPCOM000075892D
Original Publication Date: 1971-Dec-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Palmer, RS: AUTHOR

Abstract

This digital summing point is a simplified implementation of the full-digital subtractor and much faster, the difference can be updated as fast as the counter will run. Furthermore, it provides for the small uncertainty in position after the move is complete. This fact, and the method for jam transfer of a reference number into an asynchronous counter insures the servomechanism will never lose counts.

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Digital Summing Point for a Servomechanism

This digital summing point is a simplified implementation of the full-digital subtractor and much faster, the difference can be updated as fast as the counter will run. Furthermore, it provides for the small uncertainty in position after the move is complete. This fact, and the method for jam transfer of a reference number into an asynchronous counter insures the servomechanism will never lose counts.

Feedback information is obtained from a digital transducer, an interferometer 1 in this case. Space quadrature signals are logically processed at 3 in order to determine direction. A "Between Counts" signal is also detected at 2, which signals a time when the counter is not changing or about to change and is used for synchronization. An up/down counter 4 accumulates the counts and provides digital signals to a D/A converter 7 which drives a motor 10 through an appropriate amplifier 8, which in turn positions the mechanism 12. Initially, the counter "servos" about zero within a static error band (+/- 2 counts shown here). Decodes 5 of +/- 2 counts signal when the counter 4 passes outside this error band. When a new reference position is desired, a command from a process controller, not shown, degates the servo and energizes the motor 10, the mechanism 12 moves and the up/down counter 4 begins to count. As many as four counts can occur before a +/- 2 decode occurs. The correct decode is selected by the process controller. Thi...