Robot Joint Control for Backlash and Reverse Torque Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing robot control methods fail to adequately address path errors caused by backlash and reverse torque, leading to increased positional deviations in robot arms, as they do not consider the influence of torsion resulting from reverse torque during motor acceleration.
Innovation Solution
A robot control method that calculates the angular velocity, torque, and reversal timing of joint portions to determine torsion correction amounts and times, and adjusts position commands based on backlash and torsion correction values, depending on the magnitude of reverse torque or acceleration, to reduce path errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a known backlash correction device is used to correct only backlash errors, then backlash correction is achieved, but path error increases due to uncorrected torsion from reverse torque
Solution Approach 1:
The correction process is segmented into two distinct components: backlash correction and torsion correction. The control device separately calculates backlash correction amounts based on reversal timing, and torsion correction amounts based on reverse torque magnitude and correction time, then combines both corrections to address the complete path error problem
Solution Approach 2:
A torsion correction mechanism is introduced as an intermediary component between the backlash correction and the final position command. This intermediary calculates the torsion correction amount based on reverse torque and applies it over a determined correction time period, effectively mediating the transition from backlash-only correction to comprehensive path error correction
2Productivity
If the rotational speed of the motor is accelerated, then productivity increases, but reverse torque increases causing instantaneous torsion and path error
Solution Approach 1:
The control device performs preliminary calculation of the reverse torque and determines the necessary torsion correction amount and correction time before executing the high-speed acceleration. By pre-calculating the torsion effects that will occur during rapid acceleration, the system can apply appropriate correction in advance, allowing high productivity to be maintained without sacrificing precision
3Manufacturing precision
If correction time is extended to reduce torsion effects, then path error decreases, but productivity is reduced due to slower correction
Solution Approach 1:
The control device dynamically adjusts the correction time parameter based on the calculated reverse torque magnitude. When reverse torque is small, a longer correction time is applied to ensure complete torsion correction. When reverse torque is large, the correction time is reduced while maintaining adequate correction效果, thus adapting the correction process to actual conditions to balance precision and productivity
Data Source
AI summary
In an angular velocity calculation block, an angular velocity component is calculated based on a position command for a joint portion. In a kinetic calculation block, a kinetic torque is calculated based on the position command for the joint portion. In a command velocity component reversal detection block, a reversal timing is calculated based on the angular velocity component. In a reverse torque detection block, a reverse torque is calculated based on the kinetic torque and the reversal timing. In a backlash correction amount calculation block, the correction amount of the joint portion is calculated based on the kinetic torque, the reverse torque, and the reversal timing.