Apparatus and methods for implementing error correction in real time for machine tools with encoder-type position feedback

US5375066A · kind A · utility

Assignee

• Government of the United States of America, as represented by the Secretary of Commerce · US

Inventors

• Kenneth W. Yee · Rockville, US
• Robert M. Gavin · Cupertino, US

Key dates

• Filing date: Mar 1, 1993
• Grant date: Dec 20, 1994
• Expiry date: Mar 1, 2013

Classification

• Technology area (CPC G): Physics
• CPC primary: G05B2219/50071
• WIPO field: Control
• WIPO sector: Instruments

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. When the correction process is completed, the incoming …