Research And Implementation Of Surface Feature Extraction Technologies Based On Line Geometry

Reverse engineering is the process of creating a computer-aided model from the sensordata of an existing physical part. Currently reverse engineering has been one of the fourmain supporting technologies of rapid product development. Based on the review of itscurrent condition and development home and abroad, the thesis expounds someachievements in the technology and methodology of geometric modeling in reverseengineering. In this thesis an integrated modeling method is proposed and improved. Two keytechnologies of reverse engineering, retrieving the initial design parameters (RIDP) andfeature technology, are systematically studied. The concept, definition, theoretic frame andwhole parameter system of RIDP are established. Fundamental theories of featuretechnology in reverse engineering, such as feature definition, feature classification andfeature representation are proposed. All of above are the theoretic base of extracting surfacefeature. Feature extraction and surface reconstruction of four types of simple surfaces and twotypes of special surfaces are discussed. Based of screw theory and line geometry, the freemotion of simple surface could be easily recognized. Moreover, simple surfaces could beautomatically reconstructed and the associated geometric parameters can be computed fromtheir identified free motions. The simple surfaces consist of plane, sphere, cylinder and cone.Based of line geometry and moving least-squares theory, the novel algorithm ofreconstructing and extracting two types of special surfaces namely surface of revolution andpipe surface are proposed. As for the extensively application of ruled surfaces, this thesis is also concerned withKlein images of six special ruled surfaces with the help of line geometry. And on the base ofthis, a new method of extracting these special ruled surfaces is presented. This method isalso useful in approximating other kinds of surfaces by special ruled surfaces. The specialruled surface recognition algorithm is derived based on the Klein maps of generating andnormal lines extracting from the surface. Ruled surfaces have six special types, which areplane, cylinder, cone, hyperboloid, paraboloid and helicoid. Finally,the reverse engineering CAD modeling software MIMDFM is designed andrealized to overcome the disadvantages of general CAD/CAE/CAM systems and special IIreverse engineering softwares. MIMDFM system consists of four layers: algorithmsupporting layer,geometric object layer,scene node layer,drawing and interactive layer.All of the key algorithms presented above have been implemented in MIMDFM withapplications.