Robot Arm Teaching Point Correction Under Load Variation
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Solution Overview
Problem
Industrial robot arms face challenges in accurately positioning their distal ends due to deformation of reduction gears, which is exacerbated by varying forces applied during teaching and actual work operations, leading to inaccuracies in positioning and increased man-hours for teaching playback methods.
Innovation Solution
A robot system and method that involves obtaining first teaching points while supporting a tool, then moving and obtaining second data points when supporting a workpiece, and correcting the first teaching points based on the differences to create accurate second teaching points, allowing for precise positioning of the robot arm during actual work operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the robot arm is taught while supporting a tool (camera or jig), then teaching can be performed, but the force applied to the distal end differs from actual work conditions, causing positioning inaccuracy
Solution Approach 1:
The system performs preliminary teaching while supporting a tool, then later corrects the teaching points based on the difference between teaching conditions and actual work conditions. This preliminary action followed by correction allows the system to adapt to different working conditions while maintaining the benefits of structured teaching.
Solution Approach 2:
The system changes the parameter being corrected from joint angles to distal end position coordinates. By correcting positional parameters rather than angular parameters, the system directly addresses the positioning inaccuracy caused by different loading conditions without requiring complex joint-by-joint adjustments.
2Measurement precision
If the spring constant of the reduction gear is used to calculate deformation, then deformation can be estimated, but the spring constant changes with applied force, making accurate calculation difficult
Solution Approach 1:
The system replaces the mechanical deformation calculation model (which requires spring constants and torque measurements) with a positional correction approach. By measuring the actual position difference between teaching and work conditions, the system bypasses the need for complex mechanical parameters and directly corrects the teaching points.
Solution Approach 2:
The system changes from using mechanical parameters (spring constant, torque, joint angles) to using positional parameters (distal end coordinates). This parameter transformation simplifies the model by directly measuring the effect of deformation rather than calculating it through complex mechanical relationships.
3Measurement precision
If manual teaching with teaching pendant is used, then teaching points can be accurately determined, but man-hours increase significantly
Solution Approach 1:
The system enables automatic teaching by having the robot arm autonomously move to teaching positions and capture images with a mounted camera. The image processing automatically identifies target positions, eliminating the need for manual operation of teaching pendants while maintaining teaching accuracy.
Solution Approach 2:
The system replaces manual mechanical teaching operations with an automated vision-based system. The camera captures images and image processing algorithms automatically determine teaching points, substituting human operators with automated optical and computational systems.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach improves the positional accuracy of robot arms by accounting for deformation and varying forces, reducing the need for extensive manual teaching and increasing the reliability of tasks such as assembly work by minimizing positional discrepancies.
Implementation Method 1
The reduction gear has stiffness which is lower than that of links of the robot arm. Thus, when the reduction gear disposed in each joint of the robot arm deforms, the position of the distal end of the robot arm may be displaced.
Data Source
AI summary
A robot system includes a robot arm, and a controller configured to control posture of the robot arm. The controller configured to obtain a first teaching point, and first data on posture of the robot arm determined when the first teaching point is created. The controller configured to move the robot arm in accordance with the first teaching point in a state where the robot arm is supporting the workpiece or nothing, and obtain second data on posture of the robot arm determined when the robot arm has been moved in accordance with the first teaching point. The controller configured to create a second teaching point by correcting the first teaching point based on a difference between the first data and the second data.