| This dissertation has done lots of researches on locomotive three dimensions curve surface modeling and has widely absorbed some advantages of other user application software's arithmetic. Through researching into lots of correlative information of domestic and abroad locomotive's streamlined surface design, we have developed a locomotive surface CAD system-LSurfCAD based on AutoCAD2000 platform, which can satisfy the insistent demands of the works for more needs of locomotive curve surface design.The main objective of this research is to explore a new method how to find a simple and convenient solution to surface design of locomotive. Obviously, this research mainly focused on the scope of locomotive 3-D surface modeling. At the same time, based on recent study of locomotive surface design, the development trend of curve surface design has been understood. Specially using the base theory of three dimensions curve and curve surface in CAGD and utilizing the new 3-D surface modeling function of AutoCAD2000, a suit of application procedure has been developed with ObjectARX2000 technology which can directly design the complex surface of locomotive.B-Spline curves and curve surfaces are the most commonly used parametric curves and surfaces in Computer Graphics. Further more, B-Spline is also one of the most popular and successful method for designing complex surfaces in Computer Aided Geometric Design. In the design of locomotive's surface, double cubic B-Spline surfaces are mainly used here. Through reasonably separating into distinct parts and sewing these pairs of surfaces together, what's more, it can attain C2 under the guarantee of tangent surface's continuum. Some particular methods are told in this paper, which includes 3-D parametric curve surfaces modeling methods under developing locomotive surface CAD system.Based on analyzing in detail the characteristics curve of B-Spline and B-Spline surfaces, a practical method for three-dimensions locomotive surface system in fieldwork has been proposed in this dissertation. As we all know, locomotive surface design include cab and bodywork design. What's more, thedesign difficulty is in cab surface because it is composed of analytic surface and free form surface design. By means of the new methods proposed in this paper the difficult problem can be solved in designing a three dimensions curve surface.The main framework of this CAD system includes many function modules, such as initialization module, parameter design module, computing module, judging module, 3-D surface modeling module and FEM (finite element module) import module and simple aerodynamics analysis module.For that, a kind of base thought way in this paper is introduced how to develop a application CAD system based on AutoCAD2000 platform with Visual C++6.0 tools and ObjectARX2000 technology.The character of main modules, data processing technology and interface design technology are introduced in this CAD system in detail. The key technology how to customize AutoCAD is discussed also in this paper. Some ObjectARX2000 application procedures for locomotive surface design are provided in this paper simultaneously.In conclusion, through the research and development on locomotive's three-dimensions surface design CAD system, we have implemented an integrated CAD system which combine 2-D with 3-D projects and specially solved the difficult problem of a 3-D locomotive's surface. The locomotive surface system - LSurfCAD has made a test to unite the design theory of 3-D curve surface with the difficult technology problem in fieldwork. These efforts are not only to alleviate the difficulty and workload of structure designer, but also will generate great effects to locomotive surface CAD...
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