Robot Servo Control for Reduction Gear Bending Correction
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Solution Overview
Problem
In articulated robots, the bending of reduction gears due to gravitational and interference torques leads to position errors that are not accurately corrected by existing methods, which sum both torques for correction, resulting in inadequate precision.
Innovation Solution
A robot control device that separates the gravitational and interference torques to calculate distinct bending correction values, allowing for precise correction of position errors by adjusting the position command and motor current commands accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the external torque (sum of gravitational and interference torques) is used for bending correction, then the correction process is simple, but the position error correction accuracy is insufficient
Solution Approach 1:
The patent segments the external torque into two distinct components: gravitational torque and interference torque. By calculating and correcting for each torque component separately rather than as a combined value, the system achieves more accurate position error correction. The gravitational torque correction addresses the bending caused by the robot's own weight, while the interference torque correction addresses bending caused by forces from other joints, thereby resolving the technical contradiction between simplicity and accuracy.
2Measurement precision
If gravitational and interference torques are corrected separately, then the position error correction accuracy is improved, but the control system complexity increases
Solution Approach 1:
The control system is segmented into distinct modules: one for calculating gravitational torque based on robot configuration and mass properties, another for calculating interference torque based on joint forces, and separate correction pathways for each. This modular segmentation improves accuracy while managing complexity through structured organization of the control algorithms.
Solution Approach 2:
The system performs preliminary calculations of gravitational and interference torques before executing the position correction. By pre-calculating the torque components and their respective correction values, the system prepares the correction data in advance, which streamlines the actual correction process and reduces real-time computational complexity despite the enhanced accuracy requirements.
Data Source
AI summary
A robot control device includes the following: a main control unit; a servo control unit, which receives a position command θc from the main control unit; and a bending correction block (24), which corrects the bending of the reduction gear connected to the servo motor. The bending correction block (24) includes the following: a first position-correction-value calculation means (63), which finds a first position-command correction value θsgc based on the position command θc; and a second position-command-correction-value calculation means (64), which finds a second position-command correction value θskc based on the interference torque τa. The servo control unit drives the servo motor based on a new position command obtained by adding the first position-command correction value θsgc and the second position-command correction value θskc to the position command θc.