Robot Arm Position Correction Under Large Error Constraints
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Solution Overview
Problem
Industrial robots, especially collaborative robots, face safety issues due to large position errors when encountering obstacles or external forces, leading to potential malfunctions and unsafe movements, as conventional malfunction detection methods either deactivate the robot or increase the risk of divergent speed commands.
Innovation Solution
A method for controlling robots that iteratively sets a corrected command position between the current and target positions, limits speed commands, and projects positions onto constraint planes to ensure safe movement, reducing the likelihood of abrupt changes and maintaining safety during position correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the robot returns to the command position when a large position error occurs, then the position error is corrected, but the speed command may diverge and the robot may move abruptly, impairing safety
Solution Approach 1:
The patent segments the position correction process into multiple iterative steps. Instead of correcting the entire position error in one step, the controller divides the correction into smaller increments, moving the robot from current position to command position through multiple controlled movements. This segmentation prevents speed command divergence while achieving position accuracy.
Solution Approach 2:
The patent dynamically adjusts the speed command based on the current position error magnitude. The speed command is calculated to be proportional to the position error but limited by a maximum value, allowing the system to adapt its response dynamically. This dynamic adjustment ensures safe operation while correcting position errors effectively.
2Productivity
If the malfunction detection function is deactivated or threshold increased to allow position correction, then the robot can return to command position, but safety may be impaired due to potential abrupt movements
Solution Approach 1:
The patent changes the control parameters dynamically during position correction. The speed command parameter is adjusted based on position error magnitude and iteration number, with a maximum limit imposed. This parameter change allows operational continuity while maintaining safety through controlled speed limits.
Solution Approach 2:
The patent implements a feedback mechanism where the controller continuously monitors the position error and adjusts the speed command accordingly. The feedback loop ensures that if position error persists or exceeds safety limits, the system can detect and respond appropriately. This feedback maintains both productivity and safety.
3Object-affected harmful factors
If collaborative robots are designed with smaller generated torque for intrinsic safety, then safety is improved, but the probability of having larger position error increases when external force is applied
Solution Approach 1:
The patent takes preliminary action by detecting position errors before they become safety issues. The controller continuously monitors position error and initiates correction procedures when errors exceed a threshold. This preliminary detection and correction allows collaborative robots to maintain position accuracy despite lower torque, while preserving safety through controlled correction movements.
Data Source
AI summary
There is provided a method and an apparatus for controlling a robot arm. In this control scheme, a position error indicating a deviation between a command position, which is a control target position, and a current position, which is a position where the arm of the robot is currently located, is acquired. When the acquired position error exceeds a threshold, a new corrected command position between the current position and the command position is set. After the arm of the robot is moved to the corrected command position, a new corrected command position reset between the corrected command position serving as a new current position and the command position. Reconfiguration of a corrected command position is iterated until a current position of the robot arm becomes equal to the command position so that movement of the robot arm is achieved from the current position to the command position.