Spatial circular geometric parameter binocular stereo vision measurement method

Abstract

The invention discloses a spatial circle geometrical parameter dual-eye solid visual measurement method suitable for non-contact type online measurement of the spatial circle geometrical parameter of an industrial product, aiming at overcoming the existing problems of low measurement precision, slow measurement speed and low automation degree. The method is divided into a calibrating stage, an image processing stage and a spatial circle fitting stage. A neural network technique is firstly adopted to carry out the calibration of a camera; a dual-camera is utilized to carry out the extraction of sub-pixel image edges of the spatial circle, a simple algorithm is developed based on the image gray gradient distribution characteristic so as to realize the match of edge points, the practical 3D spatial coordinates of the circle edges are then obtained, and the geometrical parameters of the spatial circle comprise radius, position of center of circle and orientation of the plane where the spatial circle is arranged are gained by the fitting of the spatial circle with corresponding mathematical geometrical knowledge. The spatial circle geometrical parameter dual-eye solid visual measurement method has fast image processing speed and high automation degree, and has relative measurement error of the spatial circle of superior to plus or minus 0.6% when the plane where the spatial circle is arranged has an angle of about 50 DEG with the image plane.

Description

technical field [0001] The invention relates to a method for non-contact on-line measurement of spatial circle geometric parameters suitable for industrial products, more specifically, it relates to a binocular stereo vision measurement method of spatial circle geometric parameters. Background technique [0002] The circle is the basic element of the geometric shape of the object, and its precision characteristics often affect the final performance of the entire product. Therefore, it is of great significance to accurately measure the geometric parameters of the space circle. The traditional method of measuring the geometric parameters of a space circle is carried out with a three-coordinate measuring machine, but the three-coordinate measuring machine is bulky, inconvenient to carry, and is a contact measurement, which cannot meet the needs of online measurement and large-scale circular hole measurement. With the continuous development of image processing, computer technolo...

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Problems solved by technology

[0004] 1. The method used by Comrade Zhang Jianxin of Tianjin University is to first fit the circle with the edge points of the ellipse image on the image plane to obtain the center coordinates, and then obtain the three-dimensional coordinates of the center of the space circle by the inverse process of calibration (Zhang Jianxin, Shuang Application of Stereo Vision Technology in Industrial Measurement, Tianjin University Doctoral Dissertation, 1996), this method has a principle error, because it ignores the shape change brought by perspective projection, when the image plane and the plane where the space circle is located The larger the included angle, the greater the error, and the radius of the space circle and the plane equation of the circle cannot be measured

[0005] 2. Comrades Hu Chunhua, Liu Shiqing and Zhu Jihong published a paper titled "Research on the Image Distortion Error Model of the Center of the Circle in Visual Measurement" in the 2004 China Control and Decision-Making Academic Annual Conference Proceedings, which analyzed the relationship between the center of the ellipse image and the space circle in detail. The difference between the projected points of the center of the circle, but no method for error compensation is given

[0006] 3. Chinese Patent No. ZL 03142659.X, Publication No. CN1566900, Publication Date 2005.01.19, the applicant Beijing University of Aeronautics and Astronautics, invented and created a visual measurement method for the geometric parameters of a space circle. The application proposes the use of epipolar lines The disadvantage of this method is that it needs to manually determine the position and number of epipolar lines, and the final measurement accuracy will be affected by human factors. The camera measurement distance under its accuracy is not given

[0007] 4. Chinese patent application number 200710043742.2, application date 2007.07.11, publication number CN101093160, publication date 2007.12.26, the applicant Shanghai Jiaotong University, invented and created a method for measuring geometric parameters of a space circle based on binocular stereo vision, the application The proposed binocular stereo vision space circle measurement method is very suitable for autonomous navigation, but in the measurement of industrial products, the method of establishing the world coordinate system at the center of the circle, or establishing a relationship with the left camera coordinate system is not conducive to global calibration

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