Research On Elbow Measurement Technology Based On Binocular Vision

As a kind of special curved metal parts,elbow pipe is widely used in aerospace,energy transmission,automobile manufacturing,medical equipment and other industries in China.The complex space shape and lagging measurement methods of elbow pipe make it difficult to meet the needs of precision assembly.Accurate,efficient and complete measurement technology has become a hot issue to be solved in the domestic elbow pipe manufacturing industry.Aiming at the problem of poor accuracy and low efficiency in elbow measurement at home and abroad,this paper makes a systematic study on the non-contact elbow measurement technology based on binocular vision.According to the complex and diverse characteristics of the spatial shape of the elbow bend,this paper simplifies the elbow measurement as the measurement of the spatial parameters of the elbow centerline,including the straight length of the straight line of the centerline,the bending angle and the bending radius of the bending section The point cloud data of the center line of the elbow is reconstructed,the point cloud of the center line of the elbow is processed and fitted,and the spatial parameters of the center line of the elbow are calculated to achieve the purpose of measuring the elbow.,In the research of the bending measurement technology based on binocular vision,the following aspects of work have been completed.(1)Hardware construction and system calibration of elbow measurement systemFor the selection of camera,light source and calibration board,the binocular camera and backlight are used to realize the image acquisition of elbow.The binocular stereo vision imaging model is established.The OpenCV stereo calibration method is used to complete the system calibration.The projection matrix,distortion coefficient and external parameters of the camera are obtained.The reprojection method is used to calculate the calibration error,which shows that the calibration result can be used in the elbow three-dimensional reconstruction measurement experiment.(2)Software design of elbow measurement systemA system software is designed to reconstruct the point cloud of the elbow centerline.The elbow image is filtered and preprocessed to extract the region of interest.The elbow centerline is extracted by edge erosion algorithm.The parallax image of the elbow centerline is obtained by OpenCV stereo matching algorithm.The 3D coordinates of each matching point are calculated according to the binocular stereo parallax principle,and the point cloud data of the elbow centerline is obtained.(3)Point cloud data processing of elbow centerlineThrough filtering,de-noising and sorting of the point cloud of the elbow centerline,the fitting model of the spatial line and the spatial circle is established,and a method of accurately locating the dividing point between the straight line segment and the circular arc segment of the elbow centerline is proposed to realize the overall fitting of the point cloud of the elbow centerline,and calculate the length of the straight line segment of the elbow centerline,the bending radius and the bending angle of the bending segment.In this paper,single bend and double bend are used as the experimental objects.Based on the elbow measurement system,the center line point cloud of the elbow is reconstructed,and the center line point cloud is fitted by the method of fitting the center line point cloud of the elbow.The length of the straight line segment of the elbow center line,the bending angle and the bending radius of the bending segment are measured.The accuracy of the experimental data is within the acceptable range;at the same time,by comparing the measured data with the design parameters,the processing quality of the two kinds of elbow pipes is summarized.Through the analysis of the experimental results,the measurement efficiency and practicability of the elbow measurement technology based on binocular vision are verified.