| Automotive industry is a technology-intensive and matured industry; it is a good carrier for many leading automotive techniques. Also we know that the product development is the kernel of automotive technology. With more than ten years' improvement, the development of integrated technology has a large speed and keeps along with the international advancement. The technology of computer and information has been used in automotive design and development wider and wider. From “throwing off the T-square” to 3D digital design, we have stepped into a new area in new product development process. Comparing with the high technologies of the overseas, it needs great improvement for domestic automotive development technology. We just begin to design all-digital automotive body models, and to study many new applications. For some unfamiliar high techniques, we need more time to recognize and research them, such as surface fairing technique, computer-based evaluation technique, rapid prototype process of automotive body model, etc. With the quick development of computer and information technology, its applications become more and more important. The Automotive body design has crossed the stage of manual drafting, and entered the era of 3D geometric modeling. Because of the pervasive application of MCAD skills, it brings more and more requests to the quality of automotive body surface model. To maintain the design quality, and make the downstream processes operation smoothly, this paper depicts a new concept, the automotive body fairing surface model (AFSM), and presents in detail the method of construction and evaluation to the AFSM. There are many studies and applications on surface farness and smoothness in overseas. Also some new theories and methods are added to the application field, such as wavelet-based surface faring method, illumination model of surface, etc. The domestic high-level studies belong to Beijing Aviation and Astronautics University and Zhejiang University. Many scholars have taken much effort from Professor Su buqing. Professor Shi fazhong and Zhu xinxiong of BAAU brought out the fairing criteria of surface. Professor Wang guojin of Zhejiang University studies in detail on the leading methods of surface creation and data process, derives new formulae and algorithms, and writes many programs. In order to realize design intent and keep the data quality of automotive body surface model and make the downstream operation easy to do, the paper presents the definition of automotive body fair surface model, gives detail discussion about the creation and evaluation methodology of body fair surface model. At the beginning the paper briefly depicts the track of the automotive body design technology, introduces the body 3D design technology and some new applications, especially about the reverse engineering and virtual product development technology. Many shape presentation theories and methods are used in automotive body surface design. The paper reviews the famous Bézier algorithm and NURBS method, and gives some programs. It discusses the characteristic and difficulties of B-spline method in detail. The B-spline method has become the standard of ISO data representation. Based on the review, the paper brings about an improved de Boor algorithm, which is a chordal parameterization method. Using this method to compute the node vector array, the B-spline curve meets the requirement of design intent. Then the paper describes the tensor product surface, the least square fitting method, and the thin plate B-spline method to obtain standard surfaces and patches. Also the paper reviews the filtering method of point cloud data process, introduces the principles of Voronoi tessellation and Delaunay triangulation. Then the paper defines the concept of automotive body fair surface model, and deeply discusses the five principles and some detail requirements of the fair surface model. It mainly focused on the quality of single surface or patch and the adjacent continuity between surfaces. Also the pap... |
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