Method for kinematic calibration of six-degree-of-freedom robot based on monocular vision

Abstract

The invention relates to a method for kinematic calibration of a six-degree-of-freedom robot based on monocular vision. The method comprises the steps that an MDH model of the six-degree-of-freedom robot is built, and instruction displacement of the tail end of the six-degree-of-freedom robot and the coordinate transformation relation (please see the formula in specifications) between a monocular vision sensor installed on the six-degree-of-freedom robot and the tail end of the six-degree-of-freedom robot are obtained according to an initial calibration variable U; according to the initial calibration variable U of the six-degree-of-freedom robot, grading ranging and optimizing are conducted on multiple sets of displacement delta' of the monocular vision sensor installed on the six-degree-of-freedom robot through an absolute value coding checkerboard; actual displacement delta of the tail end of the six-degree-of-freedom robot is obtained, and multiple sets of observed variables Vk are obtained; and the constraint relation is used, the multiple sets of observed variables Vk are combined to optimize the calibration variable U, whether the calibration variable U reaches positioning precision or not is judged, if yes, the kinematic calibration of the six-degree-of-freedom robot is completed, and otherwise, returning is conducted. Compared with the prior art, the method for the kinematic calibration of the six-degree-of-freedom robot based on the monocular vision has the advantages that ranging precision is high, practicability is high, and the cost is saved.

Description

technical field [0001] The invention relates to the field of industrial robot calibration, in particular to a monocular vision-based six-degree-of-freedom robot kinematics calibration method. Background technique [0002] Accurately measuring the displacement of the working end of the robot is the core of completing the robot calibration. Its pose is usually measured with the help of external sensors. Commonly used equipment includes precision measuring instruments such as three-coordinate measuring instruments and theodolites. However, the common disadvantages of these solutions are that the equipment is expensive (hundreds of thousands or even millions), and the use method is cumbersome and complicated. It often requires on-site calibration and manipulation by professionals, and the threshold for use is high; on the other hand, such equipment usually requires a large It is difficult to meet the requirements of the production site for high efficiency and convenience. [...

AI Technical Summary

Problems solved by technology

[0005] 1. Robots often need a larger working space. In order to keep the target always within the field of view, this requires the camera to have a large field of view, and the corresponding size of each pixel is very large (difficult to control within 1mm 2 Within), it is difficult to accurately locate

[0006] 2. More targets will appear in the edge area of ​​the picture in the field of view

And this part has very serious radial distortion

Even after the camera is calibrated, the error it brings will cause large fluctuations in the measurement results, which will interfere with the accuracy of the results

[0007] In addition, the traditional met

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