Structural Reverse Of Modeling In Data Processing Technology

Reverse engineering is one branch developing rapidly in CAD/CAM research field. And instances of reconstruction of structural part models arise in numerous scientific and engineering applications such as aircraft industry, automobile industry and so on. According to the idea of structural part reconstruction from sketches, this thesis addresses the data points simplification, data points fairing, sketch-plane fitting and sketch-profile creating in structural part reconstructing. The main contents of this thesis are listed as follows: Based on the k-neighbor structure of data points, this thesis presents an algorithm of data point simplification according to normal errors, which is adaptive to the curvature variation of surfaces. By referring to some classical approaches of mesh fairing, a new algorithm of data point denoising is designed on the basis of Gaussian filter which introduces a combination of Laplacian and the second Laplacian. The algorithm is characteristic of short time-consumption and anti-shrinkage of models. Structural parts are made up with features, which are usually obtained by extruding, rotating and sweeping of one or several sketches. According to the idea of structural part reconstruction from sketches, The algorithms of sketch-plane fitting and sketch-profile creating are studied in this thesis, including the Least-Square fitting algorithms of plane, line, circle and spline based on design intent. This thesis also realizes an B-spline fitting algorithm with optimized control vertices under given tolerances, and puts forward an approach of reconstructing free-style surfaces from the curves on planar sections and characteristic curves using the sketch-element creating and B-spline fitting algorithms for reference. This thesis gives a brief introduction to CATIA developing platform (CAA), the main framework and API in the implementation of the above mentioned algorithms. All the proposed algorithms have been implemented with CAA API and C++ API.