Research And Application Of Techniques On Digital Comparing Inspection Of Point Cloud And CAD Model

With the development of intelligent design and smart manufacturing technology,freeform curve and curved surface is widely used in the design and manufacture of products.Due to the high efficiency,convenience,high comparing inspection precision,the 3D scanning technology and the 3D scattered point cloud acquisition technology have replaced the traditional template method and became the main means of digital model comparing inspection.Due to the sharp features in 3D models,and the limitation of 3D scanning technology and the 3D scattered point cloud acquisition technology in sharp feature region,the accuracy of the comparing inspection may greatly reduce or even failed in the sharp feature area.Based on the research on key technology about point cloud based comparing inspection,the research is focused on the sharp feature awarded CAD models and point cloud comparing inspection.And main content and research outcomes of this paper are as follows:1.Research and realize the method for extraction of sharp feature region in CAD models and point clouds.First,the displacement between the point and its local weighted centroid position is calculate and the point with salient this value is labeled as the candidate sharp feature points.The value of this projection is utilized as the criteria of whether a point can be labeled as sharp feature.2.Research and realize the establishment of relationship about all inspecting points on point cloud with the correct corresponding geometric elements on CAD model.The Half Edge data structure has been used in this paper for expressing the geometric topologic structure of CAD model.Based on point-to-surface relationship,point-to-edge and point-to-point relationship are proposed in this paper to overcome the problem of error calculation of special region such as edges and corners.3.Research and realize the visualization of inspecting deviation result.Use index color lists to visualize the deviation vividly.The key techniques proposed in this paper have been taken into experiment,analysis and practical application,and the result proves these techniques can satisfy the practical needs,and gain good effect in application.