Practice Of Freeform Surfaces And Fairing Research

Automobile industry is a highly intensive technology mature industry, which is the carrier of many of today's high and new technology, and product development is the core of automobile industrial technology. In recent years, computer and information technology have been more and more widely used in the researcher of car. From this now, the automobile body design has gone into the era of the 3d geometric modeling. The reverse engineer technology is produced and developed in this background. The reverse engineer, which is relative to the forward engineering, produce products of three-dimensional digital model basing on the existing products, samples or prototypes, and then on the basis of the digital model for production and processing or secondary development to realize the innovation. Reverse engineering is a process of digestion, absorption and innovation design. It can fully inherit the various advantages of original products, and make further innovation on this basis.this can greatly shorten product development cycle and improve the competitiveness of the products.Due to the gradual popularization of three-dimensional CAD design software and CAD data standards increasingly rich and perfect, the requirement of mathematical model of body surface quality is higher and higher. Smooth appearance is indispensable for modern automobile quality requirement, and is also key to automobile products in the fierce competitive of market, which requires the more fairing of the body of A level surface.To solve above problems, this paper have made some related researcher of a-class car body surface fairing on the key techniques, including the point cloud data collection and pretreatment, the reconstruction of curve and surface, and fairing of curve and surface.First of all, it explains the method of point cloud data collection process and the processing technology of early stage of the reverse engineering based on the ATOS and determines point cloud data symmetry plane in engineer programs. Combined with a rally car body outer surface data acquisition, this paper has put forward a kind of data acquisition method of large complex surface characteristics.Second, it discusses the practical application on the continuity conditions of fairing part of the Bezier curve and surface. Based on A level surface control vertex arrangement of car body and starting from the essential reasons of influencing surface fairing, it puts forward control vertex arrangement principles under a level surface fairing conditions. According to the difficulty of car body a-class surface fairing in the practice, this paper introduces the complex transitional surface fairing method, and gives two concrete examples of the wheel transitional surface fairing and transitional complex surface fairing of waist line. It also put forward method for comprehensive evaluation of the body surface based on fuzzy analytic hierarchy process, and established the concrete comprehensive evaluation model.Finally, it analyzed key and difficult problems in detail based on the ICEM Surf surface reconstruction of the key technologies, and has obtained the good modeling effect in the application of this technology of smoothing and surface reconstruction in car body outer surface reverse development of a rally.