Robot Encoder Fault Detection Using Vibration-Compensated Position Signals
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Solution Overview
Problem
Existing methods for detecting encoder abnormalities in general-purpose motor systems are costly and require additional sensors and complex configurations, leading to increased time and effort, and are prone to erroneous detection due to vibrations and load variations.
Innovation Solution
An abnormality detection method using a controller to output speed commands and commanded position information, with a driver to control the motor based on these signals, and an abnormality detection device that corrects for vibration components and time delays, allowing for accurate abnormality determination without additional configurations or functions in the existing system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional sensors and complex configurations are used to detect encoder abnormalities, then detection accuracy is improved, but system cost and complexity increase
Solution Approach 1:
The existing encoder serves dual purposes: normal position feedback and abnormality detection. The detection mechanism utilizes the encoder's own output signals and the controller's existing computational resources, eliminating the need for additional dedicated detection sensors or hardware.
Solution Approach 2:
The encoder and controller are made multi-functional by enabling them to perform both their primary control functions and encoder abnormality detection functions simultaneously, rather than requiring separate dedicated components for detection.
2Reliability
If vibration components are removed from commanded position information, then false abnormality detection is reduced, but processing complexity increases
Solution Approach 1:
Vibration components are removed from the commanded position information before it is used for abnormality detection, in advance of the actual detection process. This preliminary filtering prevents vibration-induced false positives without requiring complex real-time analysis during detection.
Solution Approach 2:
The vibration removal process uses dynamic filter constants that are switched according to the attachment load weight, allowing the system to adapt to varying operating conditions and maintain reliability across different scenarios.
3Measurement precision
If filter constants are switched according to attachment load, then vibration removal accuracy is improved, but detection time increases
Solution Approach 1:
The appropriate filter constant is switched to match the attachment load weight before abnormality detection is performed. This preliminary alignment ensures that the detection process uses the optimal filter settings from the outset, avoiding time-consuming adjustments during detection.
Solution Approach 2:
The filter constant parameter is changed according to the attachment load weight, allowing the system to optimize vibration removal accuracy for different operating conditions while maintaining efficient detection performance.
4Measurement precision
If commanded position information is corrected for time delay, then detection accuracy is improved, but processing steps increase
Solution Approach 1:
Time delay compensation is applied to the commanded position information in advance of the abnormality detection comparison. This preliminary correction ensures that the comparison between commanded and actual position is made between equivalent time-referenced values, improving accuracy without adding complexity to the detection logic itself.
Data Source
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AI summary
An abnormality detection method for detecting an abnormality of an encoder 5 provided for a robot A includes: a step of obtaining corrected position information according to commanded position information output from a controller 7 that designates the rotational position of a motor 4 and an output signal output from the encoder 5; and, a step of determining, after comparing the corrected position information with the detected position information according to the output signal output from the encoder 5, the abnormality of the encoder 5, if there is a difference greater than or equal to a predetermined value between the corrected position information and the detected position information. The controller 7 removes a vibration component of the robot A corresponding to the weight of an attachment load 13 from the commanded position information and compensates for a time delay to obtain the corrected position information.