Robot Error Judgment via Torque Average Comparison
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Solution Overview
Problem
Existing methods for determining robot failures in articulated robots, such as those used in welding or handling, require reference data measurement and storage, or accurate load parameters, making it difficult to detect failures during production and prone to erroneous decisions due to external forces or parameter errors.
Innovation Solution
A method that calculates and compares motor output torque and external force torque averages to determine if they exceed specific reference values, allowing for failure detection without pre-measured reference data and reducing erroneous decisions, even with inaccurate load parameters or external forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If velocity waveform data is used for failure determination, then failure detection is possible, but reference data must be measured and stored for each robot and the robot must be operated with a reference operation pattern, making it difficult to perform failure determination during production
Solution Approach 1:
The patent changes the detection parameter from velocity waveform to motor output torque, which can be obtained during normal operation without requiring reference data or specific operation patterns. This parameter change enables failure determination during production while maintaining detection capability
Solution Approach 2:
The system uses the robot's own operational data (motor output torque during normal operation) for failure determination, eliminating the need for separate reference data measurement and storage. The robot serves its own diagnostic needs during regular operation
2Loss of time
If power difference method is used for failure determination, then reference data measurement is not needed and determination is possible during operation, but accurate load parameters are required which are not always available, leading to erroneous failure decisions
Solution Approach 1:
The patent introduces a friction torque component as an intermediary factor in the power balance equation. By explicitly modeling friction torque, the system can determine motor output torque without requiring accurate load parameters, thus maintaining determination accuracy during normal operation
Solution Approach 2:
The patent shifts from using load parameters (mass, barycenter, inertia) to using friction torque characteristics for failure determination. This parameter change eliminates the dependency on accurate load parameters while maintaining the ability to detect failures during operation
3Duration of action of moving object
If motor output torque is increased to compensate for friction, then the robot can maintain operation, but the increased torque may be misinterpreted as a failure condition
Solution Approach 1:
The patent uses feedback of the friction torque component to adjust the expected motor output torque. By continuously monitoring and compensating for friction effects, the system can distinguish between torque increases due to friction compensation and torque increases indicating actual failures, maintaining determination accuracy during continuous operation
Data Source
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AI summary
The present invention does not need to measure or store reference data and able to determine a failure while the production line is operating by determining as a failure when motor output torque average value ÄmAA, which is an average value of N (N is a positive integer) pieces of motor output torque values ÄmA, exceeds first failure determination reference value Ämth, and external force torque estimated average value ÄdAA, which is an average value of N pieces of external force torque estimated values ÄdA, exceeds second failure determination reference value Ädth.