| Nowadays, the world automobile industry develops at full speed. The competition among the manufacturing industries of the international automobile is fierce day by day. In order to pursue scale merit, lower costs and improve product quality, enterprises regard realizing that " regards user as the centre , meet the market quickly , meet the user's needs fast " as the main goal of strengthening competitive power. The development period of the automobile is shortened constantly, and the new style is emerging constantly. The renewal of the style is mainly the renewal of the automobile body. So the development of autobody occupys very important position in the drastic market competition. Adopting computer auxiliary technology is one of the most effective methods among the various measures adopted for shortening developing period in the course of designing and developing automobile. However, existing CAD systems used in the designing automobile body are universal CAD systems in common. These systems have offered the design methods facing various kinds of products. But the products type of automobile body is more fixed, and there are certain succession and comparability among them, and while designing we only need specific method. Therefore for design of the autobody products, on one hand existing CAD systems are miscellaneous, and there are some functions that do not need to be used for users. They can't offer the effective specific design methods during designing the specific products on the other hand. Therefore adopting common use CAD systems is not only time-consuming, but also we need propose higher demand for the designer. So developing one special CAD system for designing automobile body has a practical meaning to a certain extent. What this text introduce is that a special CAD system I develop for designing the autobody panel. Developing platform of this system is ACIS. And it adopts the parameter technology based on characteristic. The system has some basic function such as surface design, graphic display, parameter revise and so on. And it has the data interface with other software. One of the kernels of the autobody panel parameter design is building autobody panel parameter model. The model need adopt the parameter to describe form, size of the autobody panel and etc.. And we can revise these parameters in order to design and modify autobody panel. In the course of structural design, computer exports the accurate geometry model automatically according to the parameter that the user inputs, and does not need input the accurate figure. Modifying figure only needs change corresponding parameter. Because of adopting parameterized drawing, the design work of the complicated autobody panel becomes easy. The main content of this text is following: The first chapter tells us the current situation of CAD technology and future development trend, fundamental thought of the parameterized technology based on characteristic, and main research contents and meaning of this text. The content of the second chapter is that Having explained the reason of selecting ACIS to act as developing platform, and then introducing the function and characteristic of ACIS, expression method of model, its data structure and its develop interface one by one. In the third chapter I have solved some technological problem about applying NURBS method into the surface model of autobody panel, for example, parameterizing data point, calculating node vector, inversely calculating control point and calculating point on surface etc.. I still introduce NURBS surface technology in ACIS at the same time. The fourth chapter is the key chapter of the whole text. In the chapter I develop one system for designing autobody panel. Platform of this system is ACIS geometry model platform. And it is based on NURBS method. This system has some functions about describing space complicated surface, and... |
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