| At present most small and medium-sized shipbuilding enterprises use AutoCAD todesign main hull. Improvement of the design efficiency and quality of main hull shape,is of vital importance to the shipbuilding enterprises. This paper designs andimplements a main hull CAD system based on engineering database technology byusing the method of software engineering and theory of NURBS.First of all, the paper introduces the background and development of CAD systemat home and abroad. Then, an analysis of the NURBS surface and the traditional mainhull design process is delivered, according to which the main hull model based onskinning method, a definition of the kernel data of main hull CAD engineering databaseand an algorithm for extracting main hull model from drawings are presented. Second,the demand analysis of the main hull CAD system including user requirements, systemfunctional requirements and non-functional requirements is put forward and describedin static and dynamic models, according to the business needs of small andmedium-sized shipbuilding enterprises in the main hull design process. Third, this paperdivides the architecture of the main hull CAD system into three layers: application layer,presentation layer and storage layer. And the singleton and observer pattern isconsidered to improve the quality of the system development. At the same time,according to definitions of the kernel data of main hull CAD engineering database, thispaper takes the E-R model as conceptual model, which improves the capacity of themain hull CAD system to discribe the main hull model with the non-relational data.Finally, this paper implements the main hull CAD system in ObjectARX, which is asecondary development platform of AutoCAD.The results of system runing and testing show that the system is stable and easy tooperate, and the functionality offered by the main hull CAD system could meet theactual needs of small and medium-sized shipbuilding enterprises to achieve theexpected goal. |
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