Robot Control Device Adaptive Threshold Stopping
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Solution Overview
Problem
Existing robot control systems fail to accurately estimate internal and external forces when the mass of a workpiece is incorrectly set or changes during operation, leading to incorrect stopping mechanisms and potential damage or injury.
Innovation Solution
A robot control device equipped with a force detector, state detector, mass parameter setting unit, internal force estimation unit, and external force estimation unit, which sets mass parameters, estimates internal and external forces, and sends stop commands based on predefined upper limit values and change thresholds to ensure accurate stopping of the robot.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the robot stops when external force exceeds a single threshold value, then the robot can respond to contact forces, but the robot may stop incorrectly when workpiece mass changes or is misconfigured
Solution Approach 1:
The patent applies dynamics by implementing adaptive threshold selection that changes based on the robot's operational state. The control device dynamically switches between a first threshold (during operation) and a second threshold (during stop) based on whether the robot is moving or stationary, allowing the stopping criterion to adapt to the current state rather than using a fixed threshold
Solution Approach 2:
The patent changes the parameter of threshold values based on the robot's operational phase. By setting different threshold values for operation period and stop period, the system optimizes sensitivity for each phase - using a higher first threshold during operation to avoid false stops, and a lower second threshold during stop to detect even minor contact forces
2Reliability
If the robot uses average external force over a time period for stopping decision, then false stops due to transient forces are reduced, but the response time to actual contact may be delayed
Solution Approach 1:
The patent applies periodic action by calculating the average external force over a predetermined time period rather than reacting to instantaneous force values. This temporal averaging filters out transient spikes and noise, providing a more reliable indication of sustained contact forces that require stopping
3Productivity
If the robot calculates internal force using predetermined workpiece mass, then the calculation is simple and fast, but accuracy decreases when workpiece mass is incorrect or changes
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing multiple internal force values corresponding to different workpiece masses before operation begins. During operation, the system quickly retrieves the appropriate pre-calculated value based on the configured workpiece mass, avoiding real-time complex calculations while maintaining accuracy for different mass scenarios
Data Source
AI summary
A robot control device comprises a mass parameter setting unit which sets a mass parameter, and a stop command unit which sends a stop command of a robot. A first upper limit value regarding external force and a second upper limit value smaller than the first upper limit value have been set. The stop command unit stops the robot when estimated external force exceeds the first upper limit value. Furthermore, the stop command unit makes the robot to be in a stop state when an average value of the external force exceeds the second upper limit value.