The Connection Between Surface Patches And Its Application In Automotive Body Surface Design

As to the very important part of automobile, the research and design of auto body is the first step to the development of new vehicle. The cycle of research and manufacture cost approximated half of whole cost. The composite automotive body surface patches should be smooth joining and satisfy fairing requirement. The running and cost performance of vehicle is influenced by its design and manufacture technique. The design precision and quality of blending surface were restricted by expression of surface and its joining algorithm. Less data and the most control freedom are the important criterion of good joining algorithm. In view of Bezier and NURBS method, the following works were included in this paper:An algorithm of applied rectangular Bézier surfaces C~r parametric continuity smooth joining is discussed firstly. Then the algorithm of triangular Bézier patch G~1 smooth joining is proposed, it simple and required little data. Accordance to high performance of automotive body exterior surfaces, a rational Bézier surface joining algorithm is discussed and the sufficient condition to surface patches satisfy C~~r continuity on their boundary is obtained. As the base of rational B spline, B-spline surface has high performance on whole control. The algorithm of B-spline surfaces joining is discussed. And the sufficient condition to B-spline G~1 smooth joining is gained, which are two B-splines have common tangent surface and normal on public boundary. We can make the two B-splines G~2 continuity and satisfy the requirement of Class A surface if generalized this algorithm.The following content of the paper concludes the criterion of Class A Surface from the view of mathematics, and it in a developing process with the quick development of CAD and CAM system. The method of design Class A surface and the principle of surface division are introduced. A new math model for surface division is proposed. We have analyzed the fairing surface with energy method. The broadly used Gauss curvature-based method and the illumination model are summarized.At the last the paper discuss the main functions of CATIA V5, and analysis the general methods of development on the CATIA platform from the view of the software engineering. These methods based on component and macro. The CATIA V5 provided a powerful free surface design function and evaluation of surface, and the criteria were applied in the surface's formation of shape and interior of cars. This paper makes some works using these functions of CATIA V5.