Industrial Robot Deceleration Control Before Overload Stop
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Solution Overview
Problem
Conventional industrial robot control systems face risks of mechanical unit damage due to excessive load from user commands, with emergency stops causing additional stress and potential premature failure, while automatic trajectory generation to stop positions may interfere with the environment.
Innovation Solution
A control system that sets threshold values and a grace time to differentiate command exceedance timing from actual robot stop timing, allowing controlled deceleration to a predetermined speed before stopping, thereby reducing mechanical load and preventing environmental interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If emergency stop is performed immediately when command exceeds threshold, then robot safety is improved, but mechanical unit load increases causing premature failure
Solution Approach 1:
The system performs preliminary deceleration action before the final stop. When a command exceeds the threshold, the robot first decelerates to a predetermined speed within a predetermined time period, then stops. This preliminary deceleration phase reduces the impact load on mechanical units compared to immediate emergency stopping, thereby preventing premature failure while still ensuring robot safety.
Solution Approach 2:
The stopping process is made dynamic by adjusting the deceleration profile based on current robot state. The control unit calculates appropriate deceleration commands considering the robot's current position, speed, and acceleration capabilities, allowing the robot to stop smoothly rather than abruptly. This dynamic adjustment optimizes the balance between response speed and mechanical load reduction.
2Strength
If automatic trajectory generation is used to stop smoothly, then mechanical load is reduced, but trajectory may deviate from user specification causing environmental interference
Solution Approach 1:
The system applies partial automatic control only to the deceleration phase rather than the entire motion trajectory. The automatic deceleration command is generated within a predetermined time period after threshold exceedance, ensuring the robot slows down safely. The predetermined time period is set to be sufficiently short to prevent environmental interference while long enough to reduce mechanical load, achieving a balance between automatic control benefits and user intent preservation.
3Strength
If deceleration time is extended to reduce load, then mechanical unit stress is reduced, but robot response time increases
Solution Approach 1:
The system changes the deceleration parameter profile dynamically. Instead of using a fixed deceleration rate, the control unit adjusts the deceleration magnitude based on the robot's current state and the time elapsed since threshold exceedance. This allows for faster initial deceleration when needed, then transitions to a gentler deceleration to minimize mechanical stress, optimizing both response time and mechanical protection.
Data Source
AI summary
Provided is a control system of an industrial robot that enables a robot to be stopped safely while reducing a load on a mechanical unit and avoiding interference with the peripheral environment when a command for which an excessive load is applied to the mechanical unit of the robot is received. A control system of an industrial robot includes: a setting unit configured to set in advance a first threshold value, a second threshold value smaller than the first threshold value, and a grace time; a determination unit configured to determine whether a command signal for controlling a robot has exceeded the first threshold value or the second threshold value; and a control unit configured to, in a case in which the command signal is determined as exceeding the second threshold value by the determination unit, continues the control according to the command only during the period until a grace time elapses since exceeding the second threshold value, and stop the robot at a timing at which an operation speed of the robot becomes equal to or less than a predetermined operation speed that is determined in advance.