Robot Joint Backlash Control During Direction Inversion
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Solution Overview
Problem
When a robot arm's motor rotation direction is inverted, especially during operation, backlash correction timing is not synchronized, leading to increased trajectory errors and vibrations, which worsen when the inversion occurs from a stopped state.
Innovation Solution
A robot control method that determines whether a joint portion is stopped or operational before inverting the rotation direction, adjusting the frequency component of the backlash correction amount to either a low frequency for gentle change when stopped or a high frequency for steep change when operational, to minimize vibrations and timing delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the correction amount is steeply changed when the rotation direction is inverted in the middle of operation, then the timing of backlash correction is not delayed, but a large fluctuation occurs in the turning shaft and the robot arm vibrates
Solution Approach 1:
The patent applies dynamics by making the correction amount change characteristic adjustable based on operational state. When the joint is detected to be in operation, a steep change in correction amount is applied to maintain correction timing. When the joint is stopped, a gentle change is applied to suppress vibrations. This dynamic adaptation resolves the contradiction between correction timing and vibration suppression.
Solution Approach 2:
The patent changes the parameter of correction amount characteristics (steep vs. gentle change) based on the operational state of the joint. By detecting whether the joint is operating or stopped, the system adjusts the correction amount application strategy, thereby resolving the contradiction between maintaining correction timing and suppressing vibrations through parameter adaptation.
2Stability of the object's composition
If the correction amount is gently changed when the rotation direction is inverted from the stopped state, then vibrations are suppressed, but the timing of backlash correction may be delayed
Solution Approach 1:
The system dynamically adjusts the correction amount change rate based on the joint's operational state. When the joint is stopped, a gentle change is applied to suppress vibrations. When the joint is operating, a steep change is applied to ensure timely correction. This dynamic switching resolves the contradiction between vibration suppression and correction timing.
Solution Approach 2:
The patent changes the correction amount characteristics parameter based on detected operational state. By switching between gentle and steep change modes according to whether the joint is stopped or operating, the system resolves the contradiction between vibration suppression and maintaining correction timing through parameter adaptation.
3Stability of the object's composition
If the frequency component of the correction amount is changed to a low frequency, then vibrations are suppressed, but the responsiveness of backlash correction is reduced
Solution Approach 1:
The patent dynamically changes the frequency component of the correction amount based on the joint's operational state. When the joint is operating, a high frequency component is used to maintain responsiveness. When the joint is stopped, a low frequency component is used to suppress vibrations. This dynamic frequency adjustment resolves the contradiction between vibration suppression and correction responsiveness.
Solution Approach 2:
The patent changes the frequency component parameter of the correction amount based on operational state detection. By switching between low and high frequency components according to whether the joint is stopped or operating, the system resolves the contradiction between vibration suppression and maintaining correction responsiveness through parameter adaptation.
4Speed
If the frequency component of the correction amount is changed to a high frequency, then the responsiveness of backlash correction is enhanced, but vibrations occur in the robot arm
Solution Approach 1:
The patent applies dynamics by making the frequency component of the correction amount adjustable based on operational state. When the joint is detected to be in operation, a high frequency component is applied to enhance responsiveness. When the joint is stopped, a low frequency component is applied to suppress vibrations. This dynamic frequency adjustment resolves the contradiction between responsiveness and vibration suppression.
Solution Approach 2:
The patent changes the frequency component parameter based on the operational state of the joint. By detecting whether the joint is operating or stopped and adjusting the frequency component accordingly, the system resolves the contradiction between enhancement of responsiveness and suppression of vibrations through parameter adaptation.
Data Source
AI summary
Stop and start detection block (63) determines whether or not a joint portion is in a stopped state before a rotation direction of the joint portion is inverted based on stop flag signal (Stop_Flg). When it is determined that the joint portion is in the stopped state, filter processing block (65) changes a frequency component of a correction amount for correcting backlash to a low frequency lower than a predetermined threshold value.