Research On The Key Techniques Of Combined Surfaces Reverse Design

This dissertation mainly research on data communication, pre-processing, combined surfaces boundary segmentation & pick-up, data compression and IGES export technologies in reverse engineering about the combined surfaces, in order to establish the basic technologies for development of reverse engineering software orient to the combined surfaces. Seven chapters are included in this dissertation.In chapter 1, some concepts on reverse engineering are briefly introduces firstly. Then, some considerable studies on data collection, surfaces modeling in reverse engineering are discussed in detail. Finally, the meanings of this projept are pointed out and the research contents are summarized.Data communication technology between CMM and ReCad data process system and automatic creation technology of the line-type based on scattered data are mainly studied and discussed in chapter 2. The methods of data communication and automatic creation of the line-style are proposed from the view of engineering application in order to make a foundation for the study of curve fairing, data compression, extracting feature points and surfaces modeling etc.Some pre-processing technology of measurement data and curve modeling are systemic researched in chapter 3. First, interactive curve fairing technology based on curvature difference is studied. Through interactive smoothing the measurement data, the noise data would be deleted. Sequentially, a new curve fairness procedure is proposed to meet the requirement of curve design and guarantee quality of surfaces modeling. Second, the half-baked data at hole area and some situation where that data is lacked are filled in because of measurement method. Finally, the methods and steps of NURBS curve modeling are analyzed further.The technology on extracting boundary curves of patches in the combined surface according to cross-section scanning beam information is studied in chapter 4. The research contents in this chapter include the methods of extracting feature points and boundary curves modeling. The method that interactively extract feature points based on curvature difference break is proposed to complete extracting feature points. Finally, how to link the extracting feature points into feature curves is analyzed.Data compression method and interface design between ReCad data process system and CAD/CAM are proposed in chapter 5. The data compression method that may realize a high compression ratio is proposed to meet curves modeling requirement. In order to make fully use of commercial CAD/CAM system resource to complete surface modeling and NC process function, IGES export interface is designed.In chapter 6, some ReCad system running instances are demonstrated. They prove that the proposed algorithms and methods in this dissertation are feasibility and rationality.Some results are included in the last chapter. Some futures tasks on this project are also pointed out.