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Thus, the inconsistency between points of generation and requirement time of the information exists. For the case of the IntelliShip system, which is being co-developed by the Intergraph, Samsung Heavy Industries of Korea, Universal Shipbuilding (Hitachi) in Japan, and Odense Staalskibsverft, Denmark, it fixes a goal of generating the 3D CAD model from the initial design stage at first. However, it is reported by many specialists on a matter that the size of the 3D CAD model generated by the system is huge and the system speed is slow, because of various problems caused by converting a general-purpose CAD system into a shipbuilding CAD system. The IntelliShip system can be used for modeling of building blocks in the detail or production design stages, similarly to the TRIBON system, because it is hard to apply the system to the initial design stage for generating 3D CAD model. In the IntelliShip system, the inconsistency between points of generation and requirement time of the information exists, as well. As mentioned above, many shipbuilding companies require a CAD system supporting the generation of the 3D CAD model in the initial design stage, however, the existing systems could not satisfy the requirement. Thus, production material information in the initial production planning stage has been assumed by the experience of design experts. It is needed to develop the CAD system, which can support rapid modeling of the initial hull structure, that is, can generate the 3D CAD model and production material information for the production planning. Outline of the Initial Hull Structural CAD System “EzSTRUCT” System Configuration Initial Hull Structural CAD System “EzSTRUCT” Initial Hull Structural CAD System “EzSTRUCT”Semantic Product ModelData StructureSemantic Product ModelData StructureA container to store hull structural information (geometric and topological information, design attributes, relationship information between parts, etc.)A container to store hull structural information (geometric and topological information, design attributes, relationship information between parts, etc.)Semantic ProductModeling FunctionSemantic ProductModeling FunctionA function to store the hull structural information in the data structureA function to store the hull structural information in the data structureUser Interface User InterfaceA tool to get input data from a designer for performing the modeling functionA tool to get input data from a designer for performing the modeling functionNon-manifold GeometricModeling KernelNon-manifold GeometricModeling KernelGraphic Library Graphic LibraryA tool to store geometric and topological information in the data structureA tool to store geometric and topological information in the data structureA tool to visualize the 3D CAD model A tool to visualize the 3D CAD model1 12 2 4 45 5 6 6Generating Function ofProduction Material InformationGenerating Function ofProduction Material InformationA function to generate the production material information for production planningA function to generate the production material information for production planning3 3 Fig. 1:
Configuration of the Developed System As shown in Fig. 1, the developed system consists of six elements. The first part is a data structure, called “semantic product model data structure”. It is a container to store hull structural information defined in the initial design stage. In this study, this data structure was designed according to the object-oriented methodology, and contains geometric and topological information, design attributes, relationship information between structural parts, etc. in order to define each structural part. The second part is a modeling function, called “semantic product modeling function”. It is a function to store user input data and the data generated from internal calculation such as intersection calculation in the data structure. The third part is a function generating production material information for production planning by using the hull structural information. It generates such information of building blocks by using the intersection calculation. The fourth part is a user interface. It is a tool to get input data, which are needed for performing the modeling function, from a designer. The fifth part is a geometric modeling kernel. It is a tool to store geometric and topological information in the data structure through the modeling function. In this study, a non-manifold geometry modeling kernel (Lee et al., 1996) (Lee et al., 2001) (EzGRAPH, 2004), which was co-developed by the Advanced Ship Design Automation Lab. at Seoul National University and EzGRAPH. Co. Ltd., was used. The last part is a graphic library, which is used to visualize the 3D CAD model on the graphic display. In this study, the graphic library “EzGL” (Lee al., 2001) (EzGRAPH, 2004), which was also co-developed by Advanced Ship Design Automation Lab. at Seoul National University and EzGRAPH. Co. Ltd., was used. In the below, details of each system element are described except for the geometric modeling kernel and graphic library. For details of these elements, please see references. Semantic Product Model Data Structure The developed system represents design information, which is defined on 2D drawings in the initial design stage, as the information with design semantics, called “semantic product model”. The semantic product model means a product model which can represent a product with semantic entities, such as minimal shape information and design attributes for obtaining boundary shape in specific design domain, instead of a product model of a general-purpose CAD system which represents a product with full boundary information. And, the semantic product model can be automatically transformed into other type if required. In order to store efficiently the semantic product model information, a data structure of a semantic product model was proposed, in which geometric and topological information, design attributes, relationship information between structural parts, etc. of a hull structure can be stored, in this study (Fig. 2). The proposed data structure manages the hull structural information as a unit of a “Panel”, which is an independent structural part and is comprised of some plates. Thus, it is easy to perform the modification and deletion of a unit of a panel when design changes are made, and it is possible to perform hull structural modeling by multi-user. Model managementof a panel unit* Semantic Product Model Data Structure: a container in order to store hull structural informationA B : A can refer BA B : B is inherited from A Fig. 2: Semantic Product Model Data Structure Proposed in this Study For example, in the case of modeling a stiffener on a panel, these structural parts can be represented with the proposed data structure, as shown in Fig. 3. In this figure, the panel and the stiffener were modeled as independent structural parts. A seam, which can be regarded as a welding line, was used in order to represent how the structural parts connected. That is, “Seam 1” in the figure represents relationship information between the panel and the stiffener. This relationship information between the structural parts is needed in order to generate production material information such as joint length, and can be used in order to generate a finite element model for global structural analysis later. Part representation by the data structureSeam 1 Seam 1EEdgeList EEdgeList Layer1 Layer1FrontLayer FrontLayerPanelPanelLayer2 Layer2MiddleLayer MiddleLayerStiffener Stiffener* BB (Base Boundary): Means an outer boundary and source object of a part.* Model: Means real shape and copied object, and represents plate list of a panel.* Layer: Means the front side, back side, and lateral side.* Seam: Means a welding line- Represent if a part is welded with which part or not.- Used to represent the relationship between parts.- Relationship between parts is needed to generatethe production material information and FE model.Seam 1PanelStiffenerHoleSeam 2PanelPanelBB 1 BB 1 ModelModelLayer LayerFrontLayer FrontLayerSeam 1 Seam 1EBody EBodyPlate PlateEFace 1’ EFace 1’MiddleLayer MiddleLayerHole HoleEFace 1 EFace 1StiffenerSeam 1HoleSeam 2Panel (comprised of some plates)Stiffener Stiffener…………