Free Curve And Surface Reconstruction Of The System Key Technologies

In industrial fields, the reverse engineering has being received great attention and widely applied. It offers an effective means to digest and trace advanced technology and capture its original idea for reference, to hold the key of technology for a further development of more advanced congeneric product. Because the shape of free-form surface is generally rather complicated, the free-form surface reconstruction has ever been and is still one of the difficulties and focus in reverse engineering.In this paper, some key technologies of surface reconstruction based on the point cloud data obtained from laser scanner are deeply studied and discussed, including the preprocessing of data points, the methods of surface reconstruction, IGES interface, and the graphics display of three dimensions.This paper chiefly has finished the tasks as follows:(1) The study for preprocessing of data points in this paper is mainly concentrated on the noise error reduction of point cloud data, data compression, data segmentation, and data points smoothing. A weighed-median filter and wavelet packet analysis filtering algorithm for reducing noise error and a method for data compressing algorithm according to the curvature variation of points and an algorithm of weighted average curve fairing are proposed in this paper. The principle and the procedure are described in detail. These methods are proved to be effective by some examples.(2) After analyzing and evaluating the related references, a rapid algorithm working out control points of uniform cubic B-spline is proposed, and is realized in Matlab, the complexity of program is greatly reduced and the operation efficiency is improved. At the same time, the curvature of the two endpoints on the reconstructed curve is not zero, C~1 continuity is achieved. Finally the process of reconstruction surface is put forward, as well as the index of precision evaluation.(3) Based on discussing in detail IGES file structure and data record form, and referring to the corresponding literatures published in the domestic and international journals, IGES interface program is presented. So data transfer and exchange between surface reconstruction system in this paper and professional software of CAD is realized.(4) Visualization is one of main means for man-machine interface, the designer can interactively observe the results from reconstruction and carry out operation if...