Robert T Gavin

US Patent:

53750667, Dec 20, 1994

Filed:

Mar 1, 1993

Appl. No.:

8/024137

Inventors:

Kenneth W. Yee - Rockville MD
Robert Gavin - Frederick MD

Assignee:

The United States of America as represented by the Secretary of Commerce - Washington DC

International Classification:

G06F 1546
G06G 764
G06G 766

US Classification:

36447435

Abstract:

Methods and apparatus for performing error compensation by modifying encoder-type position feedback signals supplied to a machine tool controller is illustrated by four embodiments. The first embodiment inserts compensation pulses into position feedback signals by using OR gates, when both square waves of the feedback signals are logically low. The addition or subtraction of the compensation pulses is performed by inserting the compensation pulses at a particular phase relative to each other. The second embodiment is capable of inserting correction pulses when the square waves are in any logical state. The third embodiment is capable of correcting the error completely controlling the feedback signals and not using OR gates to insert correction pulses, but requires a faster microcomputer. The fourth embodiment uses inverters incorporated sequentially, instead of OR gates, to invert the square wave signals before they are supplied to the machine tool controller. An additional feature is a gate control circuit which holds the incoming signals in the current state to prevent the signals from changing during the correction process.