Research On The Key Technology Of The Topological Feature Reconstruction And Sampling Point Distribution In OMV

Access to quality information processing, expression, transfer and use is an important part of the digital manufacturing technology. The On Machine Verification (OMV) system can enhance the availability factor of the high-grade NC equipment in effect and reduce the cost of production. The investigation on the key technology of the topological feature reconstruction and sampling point distribution in OMV system was carried out. The OMV system for complex curved surfaces was developed.The topological reconstruction and surface division for the triangular faces is one of the preconditions for the feature recognition for some surfaces of the part model in the OMV system. On the base of the topological relation between vectors and edges, a new algorithm of topological reconstruction for triangular mesh based on Correlation-Hashing was proposed. The redundant data were filtered in the algorithm, meanwhile, the topological relations were built. A new method based on the relation model of undirected graph for surface division, which is on the base of the basic topological relations expansion in STL(stereo lithographic) models, was proposed.The calculation examples demonstrated that the algorithms were efficient and stable. A determination of sampling strategy trajectory planning of measurement according to the geometric features and their parameters of work pieces is one of the important steps in OMV system. According to the mapping images of the triangular faces'normal vectors on the Gauss sphere, the geometric features of natural quadric surfaces were judged. The characteristic parameters were calculated by fast clustering algorithm method and Gauss-Newton. A new method for the characteristic parameter extraction, which is suitable for the STL format, was given. The characteristics of the sampling strategy based on CVT(Centroidal Voronoi Tessellations) and the distinguishing features of developable surfaces are analyzed and the sampling strategy based on the CVT for developable surfaces were proposed aiming at the limitation of common random sampling strategy.Aiming at the limitation of sampling point distribution algorithms for that of complex curved surfaces in dispersed data environment, the curvature characteristic parameters of local grid were introduced to construct the method of mesh simplication based on the differential geometric properties of triangles. On the basis of this, the sampling distribution strategy of complex curved surfaces based on triangle collapse was proposed. The LOD(Level Of Detail) model was constructed. The Fitting curve equations were established according to the relationship of the distance between the different levels of meshes to the amount of simplification triangles. The effectivity of curvature weights optimization in improving precision of the sampling point distribution strategy based on triangle simplification in dispersed data environment was verified.At last, on the basis of requirement analysis for the OMV system, the prototype experiment environment was constructed. The hierarchically functionalmodeling of the OMV system for complex curved surfaces was proposed. The OMV process simulation module was developed using computer modeling and simulation technology. Combining technology of standardized report outputting, the OMV system for complex curved surfaces whose key technology was composed of that methods was developed.