Robot Arm Speed Limit Switching to Prevent Forced Stops
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Solution Overview
Problem
Existing robot systems face frequent interruptions due to excessive motor speed, leading to increased production stoppages, as they are designed to stop the industrial machine when the motor speed exceeds a threshold, necessitating a method to reduce the frequency of these stoppages.
Innovation Solution
A control method and system that detects the moving speed of a robot arm, decelerates it to below the set speed limit when a safety input signal is received, and enables speed monitoring after a predetermined switching time, preventing forced stops and optimizing operation efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the robot arm is stopped when the moving speed exceeds the speed limit, then the safety of the robot system is improved, but the productivity deteriorates due to frequent stoppages
Solution Approach 1:
The control unit performs preliminary deceleration of the robot arm when a safety input signal is received, reducing the speed to below the speed limit before the functional safety unit enables the speed monitoring function. This preliminary action prevents the forced stop that would otherwise occur when the speed limit is exceeded, thereby maintaining productivity while ensuring safety.
2Reliability
If the speed monitoring function is immediately enabled when a safety input signal is received, then the safety response is improved, but the productivity deteriorates due to abrupt stopping
Solution Approach 1:
The control unit performs preliminary deceleration before the functional safety unit enables the speed monitoring function. By receiving the safety input signal first and decelerating the robot arm to below the speed limit, the system ensures that when the speed monitoring function is subsequently enabled, the robot arm will not be forcibly stopped, thus maintaining operational continuity while preserving safety response capability.
Solution Approach 2:
The system dynamically adjusts the timing of enabling the speed monitoring function based on the deceleration process. The functional safety unit enables the speed monitoring function only after a switching time has elapsed since receiving the safety input signal, allowing the robot arm speed to be dynamically reduced to an acceptable level before monitoring begins, thereby avoiding abrupt stops.
3Productivity
If the robot arm speed is not controlled, then the operational efficiency is improved, but the safety deteriorates due to excessive speed
Solution Approach 1:
The control unit performs preliminary deceleration when a safety input signal is received, reducing the robot arm speed to below the speed limit before the functional safety unit enables speed monitoring. This allows the robot arm to operate at high speeds for improved efficiency while ensuring that safety protocols are met by preemptively controlling speed before monitoring begins.
Data Source
AI summary
In a control method for controlling a robot system including a robot arm, a control unit configured to control an operation of the robot arm, and a functional safety unit configured to forcibly stop the operation of the robot arm when a speed monitoring function of the robot arm is enabled and a moving speed of the robot arm exceeds a set speed limit, the method includes: detecting, by the control unit, the moving speed of the robot arm; decelerating, by the control unit, the moving speed to less than the speed limit when a predetermined condition including that the moving speed exceeds the speed limit is satisfied in a case in which a safety input signal that enables a speed limit from a safety input device is received; and enabling, by the functional safety unit, the speed monitoring function when a switching time elapses after receiving the safety input signal.