Robot Joint Control for Arm Twisting Error Compensation
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Solution Overview
Problem
Existing robot control devices face challenges in accurately estimating axial torsion angular velocity when motor current command values include compensation elements, leading to interference with other control mechanisms and reduced trajectory accuracy.
Innovation Solution
A robot system with multiple joints, each driven by a motor and equipped with detection units and control units that calculate current values to compensate for errors due to bending and twisting, preventing interference and enhancing vibration suppression and trajectory accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the robot control device estimates axial torsion angular velocity based on motor angular velocity and current command value, then vibration suppression can be achieved, but the estimation fails when the current command value includes other compensation elements
Solution Approach 1:
The control system is segmented into multiple independent control units (first joint control unit, second joint control unit) with separate detection and estimation functions. The error estimation unit specifically estimates errors for the second joint based on first joint data, allowing independent vibration compensation without interfering with other compensation mechanisms in different control channels.
Solution Approach 2:
The error estimation unit acts as an intermediary that estimates operational errors due to bending and twisting based on current values and actual operation data, then feeds this estimated error to the second joint control unit for compensation. This mediator approach allows vibration suppression without directly modifying the motor current command value, thus avoiding conflicts with other compensation elements.
2Manufacturing precision
If the second joint control unit calculates current value to compensate for bending and twisting errors, then trajectory accuracy improves, but control interference occurs with other control mechanisms
Solution Approach 1:
The control system divides vibration compensation into separate segments: the error estimation unit estimates errors for the second joint, while the second joint control unit applies compensation specifically to that joint. This segmented approach allows trajectory accuracy improvement without creating control interference, as each control unit operates independently on its designated joint.
Solution Approach 2:
The system implements feedback control where the error estimation unit continuously estimates operational errors based on actual operation data and current values, then feeds this information back to the second joint control unit. The control unit calculates corrected current values that compensate for estimated errors, creating a closed-loop feedback system that improves trajectory accuracy while maintaining control stability.
3Measurement precision
If the system uses separate detection and control units for each joint, then measurement accuracy improves, but device complexity increases
Solution Approach 1:
The system merges the error estimation function into a separate error estimation unit that receives data from multiple sources (current values, actual operation data) and produces unified error estimates. This merged estimation unit then serves multiple control units, reducing overall system complexity while maintaining high measurement precision through centralized data processing and error analysis.
Data Source
AI summary
A robot system has first and second joint control units that respectively calculate first and second current values to be supplied to first and second motors based on deviations between first and second operation targets for the motors that are input from a higher device and actual operation of output shafts of the motor, and control operation of the output shafts by supplying current to the motors based on the current values, and an error estimation unit estimating an error in operation of a second joint due to bending and/or twisting of a robot arm based on the first current value and the actual operation of the output shaft of the first motor, in which the second joint control unit calculates the second current value to control the rotation angle of the output shaft of the second motor in a manner compensating for an angle error of the second joint.