Robot Arm Brake Control After Contact to Prevent Unintended Motion
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Solution Overview
Problem
Industrial robots lack sufficient safety measures to prevent unintended motion after contact with objects, leading to potential accidents due to uncontrolled arm movement post-brake release.
Innovation Solution
A control method and system that includes a robot arm with a drive unit and a brake, where the brake is actuated to decelerate the arm upon contact, then released based on specific conditions (velocity, contact stability, and time) before being re-actuated to restrict arm movement, ensuring safety and preventing unintended motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the brake is released after contact to allow work restart, then productivity is improved, but the robot arm may unintentionally move causing safety issues
Solution Approach 1:
The control unit performs preliminary actions by evaluating multiple conditions (velocity threshold, contact state stability, elapsed time) before releasing the brake. This ensures the robot arm is in a safe state before allowing movement, preventing unintended motion while enabling work restart.
Solution Approach 2:
The system continuously monitors robot arm velocity, contact state, and elapsed time, using this feedback to dynamically control brake release. The brake is released only when feedback indicates safe conditions (velocity below threshold, stable contact state, sufficient time elapsed), resolving the safety-productivity contradiction.
2Reliability
If the brake is actuated to decelerate the robot arm upon contact, then safety is improved by preventing excessive load, but the robot arm becomes free after brake release causing unintended motion
Solution Approach 1:
The control unit uses feedback from velocity sensors, contact state detectors, and time measurements to determine when to release and re-actuate the brake. This feedback mechanism ensures the brake is released only under controlled conditions and re-actuated when safety conditions are met, preventing unintended motion.
Solution Approach 2:
The brake control operates in periodic cycles: actuation during contact, conditional release after contact, and re-actuation after verifying safety conditions. This periodic control pattern ensures safety while preventing unintended motion after brake release.
Data Source
AI summary
A control method executes a first step of actuating a brake to decelerate a robot arm, a second step of releasing or relaxing the actuation of the brake when one of Conditions A1, A2, and A3 is satisfied after deceleration of the robot arm, and a third step of actuating the brake again to restrict driving of the robot arm when one of Conditions B1, B2, and B3 is satisfied after release or relaxation of the brake, Condition A1: a velocity of the robot arm becomes a predetermined value or less; Condition A2: a contact state between the robot arm and the object becomes stable; Condition A3: time TA elapses; Condition B1: time TB elapses; Condition B2: a movement amount of the robot arm becomes a predetermined value or more; and Condition B3: the contact state between the object and the robot arm is released or relaxed.