Servo Controller Threshold Switching for Machine Abnormality Detection
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Solution Overview
Problem
Existing servo controllers face difficulties in distinguishing between abnormalities caused by collisions and machining disturbances in machine tools, making it challenging to detect abnormalities independently of the motor's load state.
Innovation Solution
A servo controller with a position abnormality detection unit, load abnormality detection unit, and threshold change unit that adjusts thresholds based on the motor's load state, allowing for independent abnormality detection by switching between position and load abnormality detection methods, and issuing a notification to stop the motor when a combined threshold is exceeded.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If load torque-based abnormality detection is used, then abnormality detection capability is improved, but ability to distinguish collision from machining disturbance deteriorates
Solution Approach 1:
The patent divides the abnormality detection function into two separate detection units: a position abnormality detection unit that detects positional errors between command and actual position, and a load abnormality detection unit that detects load torque abnormalities. This segmentation allows each unit to specialize in detecting specific types of abnormalities, thereby improving the overall ability to distinguish between collision and machining disturbance while maintaining reliable abnormality detection.
2Ease of operation
If fixed thresholds are used for abnormality detection, then detection simplicity is improved, but detection accuracy under varying load states deteriorates
Solution Approach 1:
The patent introduces a threshold change unit that dynamically adjusts the thresholds for both position abnormality detection and load abnormality detection based on the current load state of the motor. When the load state changes (e.g., from light load to heavy load), the thresholds are automatically modified to maintain appropriate detection sensitivity. This dynamic adjustment preserves detection simplicity while significantly improving detection accuracy across varying operating conditions.
3Reliability
If dual detection units are added, then abnormality detection comprehensiveness is improved, but device complexity increases
Solution Approach 1:
The patent designs the servo controller so that the position detection unit and load detection unit, which are inherently part of the servo control system, serve dual purposes: their primary functions remain unchanged, but they also contribute to abnormality detection. The position detection unit provides position feedback for both control and abnormality detection, while the load detection unit provides load information for both control and abnormality detection. This multi-functionality approach improves detection comprehensiveness without significantly increasing device complexity.
Data Source
AI summary
A servo controller includes: a servo control unit that controls a motor in a machine based on a position command; a position detection unit that detects the position of the motor; a positional error calculation unit that calculates a positional error between the position command and the position of the motor; a position abnormality detection unit that detects a position abnormality in the motor when the positional error is a first threshold or more; a load detection unit that detects a load torque on the motor; a load abnormality detection unit that detects a load abnormality in the motor when the load torque is a second threshold or more; an abnormality detection unit that detects an abnormality in the machine when the position abnormality or the load abnormality is detected; and a threshold change unit that changes the first or second threshold in response to the load state of the motor.