Research On Key Technologies Of 3D Contour Measurement For Complex Parts

As the global manufacturing industry is accelerating toward high-end and intelligent,complex parts,as an important component of modern manufacturing industry,have complex surface structure and difficult processing,representing the development level of modern manufacturing industry.It is very important to obtain the 3D contour information of complex parts surface for its processing,molding and performance improvement.At present,3D contour measurement method of complex parts is not mature,which cannot satisfy the needs of modern manufacturing industry,therefore,the research on 3D contour measurement method of complex parts needs to be further improved.In this paper,in allusion to the issue of difficulty in measurement of patterns on the surface of complex parts,the key technologies of 3D contour measurement system of complex parts such as overall scheme design,calibration technology and image processing techniques were researched.The main research work and innovation are as follows:(1)Based on the surface structure characteristics of complex parts,the measurement principle of measurement system was analyzed,and the direct laser triangulation method was applied as the theoretical basis of measurement system to design and establish a 3D contour measurement system of complex parts.(2)The calibration method of measurement system was studied,the Zhang Zhengyou's camera calibration method was adopted for camera calibration.The improved checkerboard target was applied to light-plane calibration,the parameters of light-plane equation was calculated based on the invariant theorem of cross ratio.The calibration method of rotating center axis based on the combination of projection method and least square method was adopted for the calibration of rotating table,which realized the integrated calibration of the whole measuring system.(3)The characteristics of the linear structured light images on the surface of complex parts were analyzed,image preprocessing method was applied to image processing,an algorithm for extracting the center of light stripe based on gray center method was adopted in allusion to light-plane calibration light stripe images.A Steger center extraction algorithm based on morphological processing was adopted in allusion to light stripe images on the surface of complex parts,and the center point of the extracted light stripe was optimized.(4)The transformation relationship between different coordinate systems of measurement system was solved,the coordinate transformation of 3D point cloud data of tested parts was achieved.A closest point iterative registration algorithm based on principal component analysis was adopted to realize the integration of dual perspective point cloud data.The experiment platform for 3D contour measurement system of complex parts was established to complete dimensional measurement and 3D reconstruction experiment for complex parts.The Experimental results demonstrate that this measurement system can meet the measurement requirements of industrial components.The 3D contour measurement system of complex parts designed in this paper effectively solved the issue of incomplete point cloud data on the surface of the tested objects caused by occlusion in single camera measurement,realized the 3D measurement of patterns on the surface of complex parts,and plays a positive role in the development of3 D measurement technology of complex parts.