Camera-Equipped Multiaxis Robot Calibration for Geometric Model Accuracy
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Solution Overview
Problem
Existing methods for calibrating the geometric model of multi-axis robots equipped with cameras are imprecise and rely on assumptions of perfect robot alignment and operation, which is not feasible in industrial settings where robots operate at high speeds and in potentially disturbed environments.
Innovation Solution
A method that adjusts the geometric model of a multi-axis robot by determining the coefficients of passage matrices through a series of camera positions, minimizing overall difference values to account for real-world assembly tolerances and robot structure, without relying on calculations of expected characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a geometric model based on perfect robot alignment and rigid camera connection is used, then the model is simple to implement, but it does not correspond to physical reality due to mounting tolerances and robot imperfections
Solution Approach 1:
The patent transforms the geometric model parameters from theoretical perfect values to actual measured values by capturing images of a calibration target at multiple known robot positions. The passage matrices are recalculated based on actual image coordinates and robot pose data, thereby adapting the model parameters to reflect real-world mounting tolerances and robot imperfections.
2Ease of manufacture
If existing calibration methods assuming perfect robot operation are used, then the calibration process is simple, but it is unreliable in industrial settings with high-speed operation and disturbed environments
Solution Approach 1:
The patent implements feedback by using the camera to capture images of a calibration target and comparing the observed positions with the expected positions based on the geometric model. The passage matrices are then adjusted based on this feedback to minimize the difference between observed and expected characteristics, creating a self-correcting calibration process that adapts to actual robot performance.
3Productivity
If the camera position is defined in a relatively imprecise manner, then the setup process is quick, but the positioning precision of the application member is compromised
Solution Approach 1:
The patent performs preliminary calibration by capturing images of a calibration target at multiple predetermined robot positions before actual production work begins. This preliminary action establishes accurate passage matrices that account for real-world imperfections, enabling precise camera positioning and application member control during subsequent high-speed operation without requiring repeated calibration.
Data Source
Figure 1A~1C
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AI summary
A geometric model of a multi-axis robot equipped with a camera (30) comprises a first matrix (TCamera→PG) and a second matrix TPG→BF) of passage. A method of adjusting this model comprises: aiming (1004), with the camera arranged in a first location (k1), at least two points among L points of the target; determining the coordinates (Vk1,lCamera) of each aimed point; moving (1005) the camera; d) aiming (1006), with the camera arranged in a second location (k2), the same points (Pl); determining the coordinates (Vk2,lCamera) of each aimed point; calculating (1008), for each aimed point, a difference (vk1,k2,l) between its coordinates in a base frame (BF), expressed using the first and second matrix of passage (TCamera→PG, TkPG→BF); calculate (1010, 1018) a global difference value (F, G).Variables (X1-X6, Δαi, Δli, Δθi, Δri) of coefficients of the first and second passage matrices (TCamera→PG, TPG→BF) are determined by minimizing (1012, 1018; 1021) the global value calculated in step g). The camera is successively brought to K locations. The product of the number (L) of target points by the number (K) of locations reduced by 6 (L * K - 6) is greater than or equal to the number of variables of the geometric model of the multi-axis robot.