SERVO CONTROLLER FOR REDUCING SYNCHRONOUS ERROR IN SYNCHRONOUS MACHINING

• US 20150286197A1
• Filed: 04/07/2015
• Published: 10/08/2015
• Est. Priority Date: 04/08/2014
• Status: Active Grant

• Current Assignee: Fanuc Corporation
• Original Assignee: Fanuc Corporation
• Inventors: SONODA, Naoto
• Granted Patent: US 9,523,975 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G05B 1/01 electric
• CPC Class Codes: G05B 11/011 details of the correcting means
• CPC Class Codes: G05B 15/02 electric

Abstract

A servo controller includes: a first position feedback acquisition unit; a second position feedback acquisition unit; a converter converting the acquired position feedback of the first shaft to a value corresponding to the position feedback of the second shaft based on a synchronous ratio; a synchronous error calculator calculating synchronous error which is difference between the converted position feedback of the first shaft and the position feedback of the second shaft; a positional deviation calculator calculating a positional deviation of the second shaft which is difference between the position command for the second shaft and the position feedback of the second shaft; a filtering processor extracting components in a predetermined frequency range from the difference between the synchronous error and the positional deviation of the second shaft; and, a positional deviation corrector correcting the positional deviation of the second shaft by use of the output from the filtering processor.

Claims

1. A servo controller for use in a machine tool for machining a workpiece by driving first and second shafts in synchronization with a predetermined synchronous ratio by means of electric motors, comprising:

a first position feedback acquisition unit for acquiring a position feedback of the first shaft;

a second position feedback acquisition unit for acquiring a position feedback of the second shaft;

a converter for converting the acquired position feedback of the first shaft to a value corresponding to the position feedback of the second shaft by use of the synchronous ratio;

a synchronous error calculator for calculating synchronous error which is difference between the converted position feedback of the first shaft and the position feedback of the second shaft;

a positional deviation calculator for calculating a positional deviation of the second shaft which is a difference between a position command for the second shaft and the position feedback of the second shaft;

a filtering processor for extracting components in a predetermined frequency range from a difference between the synchronous error and the positional deviation of the second shaft; and

,

a positional deviation corrector for correcting the positional deviation of the second shaft by use of the output from the filtering processor.

2. A servo controller for use in a machine tool for machining a workpiece by driving first and second shafts in synchronization with a predetermined synchronous ratio by means of electric motors, comprising:

a speed command acquisition unit for acquiring a speed command for the first shaft;

a speed command converter for converting the acquired speed command for the first shaft to a value corresponding to the speed command for the second shaft by use of the synchronous ratio;

a first speed feedback acquisition unit for acquiring a speed feedback of the first shaft;

a first speed feedback converter for converting the acquired speed feedback of the first shaft to a value corresponding to the speed feedback of the second shaft by use of the synchronous ratio;

a speed difference calculator for calculating a speed difference between the converted speed command for the first shaft and the converted speed feedback of the first shaft;

a filtering processor for extracting speed difference components in a predetermined frequency range from the speed difference; and

,

a speed command corrector for correcting a speed command for the second shaft by use of the output from the filtering processor and the converted speed command for the first shaft.

3. The servo controller according to claim 1, further comprising a synchronous ratio acquisition unit for acquiring the synchronous ratio from a host controller.

4. The servo controller according to claim 1, further comprising a synchronous ratio calculator for calculating the synchronous ratio from a command for the first shaft and a command for the second shaft.

5. The servo controller according to claim 1, wherein the positional deviation corrector corrects the positional deviation of the second shaft in accordance with a machining state signal that indicates whether the tool and the workpiece are operating in synchronization.

6. The servo controller according to claim 2, wherein the speed command corrector corrects the speed command for the second shaft in accordance with a machining state signal that indicates whether the tool and the workpiece are operating in synchronization.