Study On Key Modeling Techniques Based On Section Feature In Reverse Engineering

Reverse engineering techniques are the integration of associated methods, means and techniques with the principle and knowledge related to product design, manufacture and management etc. The main task reverse engineering performs is to extract these information from a physical object to reconstruct a CAD model for a particular purpose like redesign, reproduction or quality control. Along with the introduction of feature technology into reverse engineering, the feature-based reverse engineering is proposed and has been becoming a hot topic of current research in this area.At present, surface-feature based reverse engineering has been studied deeply, and has reached the state where quadric surface, simple free-form surface and blend surface feature can be extracted from point cloud directly and conveniently. Otherwise, the section feature, as an important element in model reconstruction, has rarely been studied. In this paper, a methodology for section-feature based remodeling is introduced, and the flow, architecture, and key techniques related to this methodology are studied. After the investigation of associated mathematics- and technology basis, the feasibility of this methodology is analyzed.In feature-based reverse engineering, with the research of surface feature handling done wieldy and deeply, a methodology of surface-feature based re-modeling has come into being, with which the quadric surface, simple free-form surface and blend surface feature can be directly extracted from point cloud conveniently. Otherwise, the section feature, as an important element of model reconstruction, has rarely studied, and the methodology of section-feature based re-modeling has not come into being. Aiming at this problem, based on the summarizing of feature-based remodeling method, a methodology of section-feature based re-modeling are proposed, the flowchart, architecture, and key techniques of this methodology are studied. The feasibility of this methodology is analyzed based on the investigating of mathematics basement and technology basement.In the section-feature based re-modeling methodology, the section data acquisition and preprocessing is the first step. The point cloud slicing is a main method for section data acquisition from point cloud. Based on the study of slicing algorithms, five slicing principles, applied to the point cloud of free-form surface feature, are proposed. Among them, the method of calculating the slicing planedirection of point cloud, whose curvature map has the property of band distribution, is studied in detail. Other preprocessing methods such as discrete curvature estimation and feature point extraction are also studied, and a section-feature recognition algorithm, based on curve fitting, is proposed.Global constrained model optimization is the most important step in section-feature based re-modeling methodology. The least square method (LSM), applied to fitting line, arc, and B-spline, is the mathematical basis. Under the efficient representation of objects and constraints, the global optimization model is proposed. The penalty function method and modified Newton iteration method are adopted to solve the constrained nonlinear optimization problem. The effectiveness and robustness of the two methods are compared and analyzed through 3 examples.Simple free-form surface reconstruction problem, where the surface is formed by the extrusion, revolution and sweep of section feature curve, has been well solved. So the feature corresponding based skinning method are discussed in detail. Contrast to the traditional skinning surface reconstruction method, the section-feature based re-modeling method and feature corresponding based skinning method can guarantee the small detail feature on surface model. So, with the new methodology, a surface model with better quality can be obtained.The proposed methodology has been approached in the feature based reverse engineering software: RE-SOFT. Through a re-modeling example in RE-SOFT, the feasibility and applicability of the section-feature based re-modeling met...