Industrial Robot Arm Backlash Compensation via Delayed Signal
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing control methods for industrial robots with speed reducers struggle to maintain the amplitude of reciprocating motion when compensating for backlash, especially when the position command signal is periodic, resulting in phase delays and reduced behavioral range.
Innovation Solution
A control method that generates a final position command signal by delaying a backlash quantity signal and adding it to the original position command signal, effectively compensating for backlash by adjusting the control direction and phase alignment with the periodic motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a correction signal is added to compensate for backlash in the speed reducer, then the positional deviation of the arm is eliminated, but the behavioral range (amplitude) of periodic motion is reduced
Solution Approach 1:
The invention applies preliminary action by delaying the backlash correction signal in time. Instead of applying the full backlash correction immediately when direction reversal is detected, the correction is postponed by a predetermined time period. This allows the correction to be applied at the appropriate moment in the periodic cycle, preserving the full behavioral range while still eliminating positional deviation. The delayed correction signal is added to the position command signal at the optimal time to compensate for backlash without reducing the amplitude of reciprocating motion.
2Reliability
If backlash correction is applied immediately upon direction reversal detection, then the effect of backlash is eliminated, but phase delay occurs in periodic motion
Solution Approach 1:
The invention uses preliminary action by pre-calculating the appropriate timing for backlash correction. The delay time is predetermined based on the periodic characteristics of the motion, allowing the correction to be applied in advance of when it would naturally be needed. This ensures that the correction takes effect at the optimal moment in the cycle, eliminating backlash effects while maintaining proper phase alignment and avoiding time loss in periodic operations.
3Length of moving object
If the amplitude of the position command signal is increased to compensate for backlash effects, then the behavioral range is maintained, but the positional accuracy deteriorates due to increased error
Solution Approach 1:
The invention applies feedback by continuously monitoring the actual position of the arm and comparing it with the commanded position. The backlash correction signal is generated based on this feedback, specifically detecting when direction reversal occurs and applying correction only at those moments. This feedback mechanism ensures that the full amplitude command signals are used to maintain behavioral range, while positional accuracy is preserved through precise, condition-based correction that eliminates backlash effects without introducing additional errors.
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
Provided are a control method and a control device that can make the range of periodic activity (amplitude of reciprocal movement) of an object of control, such as an industrial robot, the same as a case in which the reduction device has no backlash or the same as the amplitude of a position instruction signal. A control device (3) that carries out position control for an arm (5), which carries out periodic movement, while compensating for backlash in the arm (5) is provided with a control unit (15) that adds to a position instruction signal, which gives instructions for the position of the arm (5), a backlash quantity signal after the backlash quantity signal has been shifted so as to be delayed by a delay time, generates a final position instruction signal, and carries out position control of the arm (5) on the basis of the final position instruction signal that has been generated, said backlash quantity signal compensating for backlash.