Motor Backlash Correction Using Dynamic Position Difference
Solution Overview
Problem
Existing motor control systems face challenges in accurately correcting backlash, especially when the movement from the initial position is smaller than the backlash, leading to either excessively large or insufficient correction amounts, which affects positional accuracy in machine tools and industrial robots.
Innovation Solution
A motor control system that includes position detecting parts for the moving and driven parts, a difference calculating part, a judging part to determine engagement, a holding part for initial differences, and a correction amount calculating part to calculate the optimal backlash correction amount based on current and initial positions, ensuring the correction amount does not exceed the backlash.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a correction amount corresponding to the backlash is added to the position command of the motor at the time of reversal, then the positional accuracy is improved, but the correction amount becomes excessively large when the movement from initial position is smaller than the backlash
Solution Approach 1:
The patent changes the parameter of correction amount calculation from a fixed value (full backlash) to a variable value based on actual movement distance. The correction amount is calculated as the difference between the backlash and the actual movement distance when movement is smaller than backlash, thereby adapting the correction parameter to the specific operational condition and avoiding excessive correction.
2Quantity of substance
If a predetermined correction amount smaller than the backlash is used, then the correction amount does not become excessively large, but the correction amount becomes insufficient at the time of reversal
Solution Approach 1:
The patent makes the correction amount dynamic rather than static. The correction amount is determined based on the relationship between the actual movement distance and the backlash value. When movement distance is less than backlash, the correction amount is set to the difference value; when movement distance equals or exceeds backlash, the correction amount is set to zero. This dynamic adjustment ensures the correction amount is always appropriate for the current operational state.
3Device complexity
If the correction amount is calculated based on fixed backlash value, then the calculation is simple, but the correction is inaccurate when movement from initial position is smaller than the backlash
Solution Approach 1:
The patent performs preliminary detection of the movement distance from the initial position before calculating the correction amount. By first determining whether the movement distance is smaller than the backlash, the system can then select the appropriate correction calculation method. This preliminary action ensures accurate correction without requiring complex real-time analysis during the reversal process.
Data Source
AI summary
A motor control system (10) which includes a difference calculating part (31) which calculates a difference between a first position detection value of a moving part and a second position detection value of a driven part, a judging part (32) which judges if a moving part has engaged with the driven part when the moving part is made to move from any initial position in a first and second drive directions, a holding part (33) which holds the difference as initial difference linked with the first or second drive direction, when the moving part has engaged with the driven part, and a correction amount calculating part (34) which calculates a backlash correction amount, the correction amount calculating part using the difference based on the current positions of the moving part and the driven part and the initial difference to calculate the backlash correction amount.