Numerical Controller Torque-Based Position Error Correction
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Solution Overview
Problem
Conventional numerical controllers face challenges in accurately correcting machine position errors in feed-axis synchronization control due to mechanical strain, which affects motor current stability and requires time-consuming measurements with laser instruments.
Innovation Solution
A numerical controller that corrects machine position errors based on torque differences between master and slave axes, calculating a correction amount by excluding torque differences derived from mechanical strain, and applying this correction in real-time to maintain precise synchronization control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If machine position correction is made using laser measuring instruments to measure actual position errors, then manufacturing precision is improved, but loss of time increases due to time-consuming measurements
Solution Approach 1:
The patent replaces optical measurement systems (laser measuring instruments) with a mechanical sensing approach using torque sensors on the motor shafts. The torque difference between master and slave axes serves as a proxy for position error, eliminating the need for external laser measurement equipment and reducing measurement time while maintaining correction accuracy
Solution Approach 2:
The system uses its own operational parameters (motor torque) to detect position errors rather than requiring external measurement instruments. The torque difference acquired during normal operation provides information about machine position errors, allowing the system to self-diagnose and self-correct without stopping for separate measurement procedures
2Productivity
If machine position correction is made using torque differences without considering mechanical strain, then productivity is improved by eliminating measurement steps, but manufacturing precision deteriorates due to inaccurate correction
Solution Approach 1:
The patent segments the torque difference into two distinct components: torque difference due to position error (useful for correction) and torque difference due to mechanical strain (to be excluded). By calculating the average torque difference across multiple observation points to represent mechanical strain, and then subtracting this from individual torque differences, the system isolates the position error component for accurate correction
Solution Approach 2:
The patent measures torque differences at multiple observation points (more than the minimum single point) to accurately characterize the mechanical strain component. This excessive measurement approach ensures that the average torque difference reliably represents mechanical strain, enabling more accurate exclusion of this factor from individual corrections
3Ease of operation
If pitch error correction is made without considering mechanical strain, then ease of operation is improved, but manufacturing precision worsens due to uncorrected mechanical strain effects
Solution Approach 1:
The patent implements a feedback mechanism where torque difference information is continuously acquired during operation, processed to extract position error components, and used to adjust pitch error corrections. This closed-loop approach automatically compensates for mechanical strain effects without requiring manual intervention or complex operational procedures
Data Source
AI summary
A numerical controller, which is configured to correct a machine position error based on a torque difference between a master axis and a slave axis, acquires the torque difference after movement of the master and slave axes that move in response to a movement command, and corrects the machine position error by a correction amount based on a value obtained by excluding a torque difference derived from a mechanical strain from the acquired torque difference. The corrected machine position error is added to the movement command for next time.