Digital exchange of design models between marine equipment libraries using hybrid neutral formats

Transcription

1 J Mar Sci Technol (2004) 9: DOI /s Digital exchange of design models between marine equipment libraries using hybrid neutral formats Ho-Jin Hwang 1, Han-Min Lee 2, and Soonhung Han 2 1 Maritime Safety and Pollution Control Laboratory, Korea Ocean Research and Development Institute, Yusong-gu, PO Box 23, Daejeon , Republic of Korea 2 Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Republic of Korea Abstract The selection of marine equipment is a timeconsuming process for a ship outfitting designer. The inefficiency originates from the paper-based exchange of design information between shipyards and equipment manufacturers. We propose a method to exchange equipment models for electronic commerce. Shipyard practices were investigated to find out how the outfitting CAD library is being used. We also surveyed international standards for the exchange of digital equipment models, and analyzed the macroparametric methodology. We propose a hybrid method to represent the geometric information using STEP AP203 or the macroparametric method. The nongeometric information is defined according to the Parts Library (PLIB) standard. We implement a pilot system and test it with a ship design data set. The equipment model proposed can be used in the design process with heterogeneous shipbuilding CAD systems. The equipment model can improve the design and purchase process in shipyards. Key words Data exchange Electronic commerce Macroparametric method Marine equipment library Introduction Overview Korean shipyards have been developing a design system based on a 3D product model to shorten the period of production. 1 During the outfitting design process for a ship, designers spend time and labor in understanding the specifications of equipment and then selecting it. They also have the additional task of creating a 3D model of the equipment after they have chosen it. It is also troublesome to input nongeometric data, such as Address correspondence to: H.-J. Hwang (hjhwang@kriso.re.kr) Received: December 16, 2002 / Accepted: February 17, 2004 the properties of items of equipment, into the design system. The fundamental cause of this inefficiency is that there is no exchange system for design information between shipbuilders and equipment suppliers. Some equipment suppliers provide models of digital representations using DXF or IGES formats, but most equipment manufacturers use 2D CAD systems with limited scope. If equipment models could be represented and exchanged via 3D digital data, shipbuilders could reduce the cost and time taken to recreate 3D models of items of equipment in their ship design systems. 2 4 They could also improve the design process by removing errors originating from design changes from the equipment models. Equipment suppliers could improve their service to customers, because they could supply the same information about their product to several different shipyards. Through the electronic commerce of equipment models, benefits can be realized by constructing an equipment library in an electronic market place (e-mp). The equipment library should have 3D geometric models as well as all the properties of the equipment because it must be possible to use it directly in the design process of shipyards. A parts library would improve the information reusability because it is supplied and managed in the form of an electronic catalog. 5,6 For electronic commerce between shipyards and equipment manufactures, we suggest a method to express the properties and the 3D shape of equipment models as a digital representation, and apply this to the shipyard process. We have analyzed CAD systems and processes which use equipment models in Korean shipyards, and we discuss a method to combine 3D models of equipment. Equipment models should include nongeometric information that expresses the properties of the equipment along with the 3D shape information. A standard format can be applied to various systems and utilized in the design process in shipyards.

2 H.-J. Hwang et al.: Digital exchange between marine equipment libraries 183 Fig. 1. Structure of the ZoHaku Web system. Italic, Provided by the ZoHaku Web system Previous research ZoHaku Web 7 is a web-based system that was developed for mutual cooperation and assistance between shipyards and equipment manufacturers in Japan. Zo means the building of ships. Haku corresponds to the equipment of ship machinery and equipment manufacturing. This project was started in 1998, and is for the electronic exchange of technical and design information among 21 shipyards and 73 equipment manufacturers. Currently, an independent company operates the system. Figure 1 shows the structure of the ZoHaku Web system. The system consists of three elements. First is the common server, which provides the sharing service between participating companies. Second is the client system, which is located in a shipyard or with an equipment manufacturer, and the ZoHaku Web tools help in the exchange of information between companies. Third is the Internet link that connects the common server and the client system. Data are then transferred securily across the ZoHaku Web. This provides a good framework for exchanging equipment data between shipyards and equipment manufacturers, but it is not good at translating an equipment model with 2D drawings. In 3D CAD environments, it is able to carry out this additional task. The designers in a shipyard still have to recognize 2D drawings and remodel in 3D. Information such as standardized data, drawings, and documents is shared and exchanged as a digital catalog between shipyards and equipment manufacturers. General information, such as the manufacturer s name, the classification code, the model name, and part properties, are recorded in the digital catalog. In case of a pump, the maximum capacity, the minimum capacity, and the power are given in the catalog. In addition to the property information, 2D drawings are also exchanged. The DXF format is the de facto standard of the AutoCAD drawing format. TRIBON.com of Sweden provides an equipment library and digital catalogs for ship design based on the TRIBON system, 8 and also provides TRIBON models and 3D models of SAT and DXF file formats. The 3D models provided by TRIBON.com represent geometric shape information, but the nongeometric information that is important to outfitting design, is not provided. Shipyards that use different CAD systems from TRIBON cannot use this library effectively. In Korea, a 3D model database construction project, which is one of the B2B (business to business) pilot programs for the shipbuilding industry, was established in late The translators into TRIBON, GSCAD, and CADDS5 were developed during the second year of the project. A viewer and the digital catalog for 3D geometric information exchange have also been developed. However, proprietary formats are used instead of international standards in this early work. CAD library for equipment Business process of the equipment CAD models Big shipyards in Korea use CADDS5 of Computer Vision (CV) for outfitting design, and different CAD systems for structural design. To integrate the structural design CAD with the outfitting design CAD, Korean shipyards have been developing the next generation CAD systems since In a shipyard, equipment models are generated and stored in a parts library through the process shown in Fig. 2. The designer who receives a drawing from an equipment manufacturer generates the geometry and

3 184 H.-J. Hwang et al.: Digital exchange between marine equipment libraries Fig. 3. TRIBON volume primitives Fig. 2. Development process of the CAD equipment database work space for a model. In addition to the geometric information, the nongeometric properties such as equipment specification are recorded. Geometric and nongeometric information is generated and registered in an equipment database (DB) at the same time. Registered equipment models are utilized in the CAD system for ship design. Equipment manufactures generally use paper drawings for data exchange, and use 2D CAD systems such as AutoCAD. Because of the cost and shortage of human resources, they are reluctant to introduce 3D CAD systems. Generation of CAD equipment models Equipment models which will be used in the design process must include all the important properties, such as those listed below. Geometry: overall dimensions such as width, height, and length should be exact. The detailed shape can be simplified to some degree as long as the designer can visually identify the model. Connection point: connection points for pipes, cables, and ventilation equipment should be exact in terms of position and dimension. Space: space information for the equipment, such as maintenance space and operational space, should be represented. Equipment specifications: detailed information of equipment properties such as weight and center of gravity (CoG) should be included. The solid model that is supported by general-purpose CAD systems such as Pro/E and CATIA has a large amount of information. Because a ship has numerous equipment models, it is difficult to handle such a heavy load with ordinary computer capacity. In the case of the TRIBON system, the model size problem is handled by combining basic primitives instead of full-blown solid models. Figure 3 shows the basic primitives which are used in TRIBON. The geometric information about the equipment can be approximated by combining these primitives. Standard technologies for the digital model IGES Initial graphics exchange specifications (IGES) is a neutral data format for the digital representation and communication of product-definition data. This format was developed by the ANSI Y44 Committee of the USA, and has been widely used. Compared with STEP, IGES is less useful in terms of extensibility and compatibility owing to the limited number of entities; also its datastructure is very simple. Currently, most CAD systems support the IGES format. However, because IGES dose not represent nongeometric information, it cannot express all the properties of a part. STEP AP203 Application Protocol 203 (AP203) 10 supports exchanges of the configuration-controlled 3D design information of mechanical parts and assemblies between different application systems. 11 Most STEP translators use the entities defined in AP203 to exchange CAD data. To represent solid models, AP203 supports boundary representation (B-Rep), and a little constructive solid geometry (CSG). STEP AP203 has six conformance classes to express defined shapes, and solid models are usually exchanged using CC6 (advanced boundary representation). Because STEP AP203 is used for the modeling of mechanical parts, it is suitable for the exchange of equipment models between shipyards and equipment manufacturers. One of the next-generation CAD sys-

4 H.-J. Hwang et al.: Digital exchange between marine equipment libraries 185 tems for shipbuilding uses SolidEdge as the preprocessor to input equipment models because SolidEdge supports STEP AP203. STEP AP226 Ship STEP is an international standard that is being developed to represent characteristic product information for a ship in heterogeneous environments. 12,13 It consists of several APs. 14,15 AP is the standard for ship mechanical systems. A ship has a range of machinery to generate power with a large engine ( horsepower). Other machines, such as boilers, are installed in a limited space, and various pieces of electric equipment for automatic operation are also packaged. AP226 contains the standard information about the design of an engineroom. AP226 expresses the main equipment and elements that are loaded in merchant ships and warships, and it defines product information such as specification, design information, and tips for the installation of equipment. It can also define functional, physical connectivity among structural elements, and express shape information related to system structural elements which can be used during the whole life-cycle. The AP226 project was cancelled by ISO in November 2002, and its work will be handled by AP227 (plant spatial configuration) 17 or ISO (oil and gas). 18 No shipbuilding CAD systems yet support AP226. Parts library (PLIB) Products consist of parts. Information about parts is defined by parts suppliers. Parts information is exchanged and shared among different organizations which generate and use the parts information. ISO Parts Library (PLIB) provides the mechanism for the exchange, operation, revision of parts information, and representation method of that information. An exchange of information occurs among heterogeneous computer systems and environments during the lifecycle (design, manufacturing, use, maintenance) of a product. 19 PLIB has three models of the system management method. In level 3, geometric information is represented by ISO STEP, and nongeometric information is expressed by ISO PLIB. All information is transferred through the STEP Part 21 physical file. Parts library information about the electronic catalog and geometric information of all parts can be transferred into the CAD system of shipyards. As most shipbuilding CAD systems have their own library, nongeometric information can be exchanged by using PLIB. Fig. 4. Concept of the macroparametric method Macroparametric method The macroparametric approach is one of the historybased parametric methods. The idea comes from the database recovery process, where the transaction log file is used to restore the database after a crash. 20 The sequence of user commands issued by a CAD operator during the design task is recorded as the modeling history, which implicitly includes the designer s intent. To translate data models between CAD systems, the macro file generated by a commercial CAD system is translated into a standard macro file, which is again translated into a macro file of the receiving CAD system. Figure 4 shows the concept of the macroparametric method. The conceptual layer includes the native modeling command set of a commercial CAD system and the standard command set. Through the mapping between these two sets, the linkage between the commercial CAD system and the standard command set is created. In the physical layer, there is a macro file which is created during the design process, and this file can be translated into the standard macro file through the data translator that uses the schema mapping relationship between command sets. The standard macro file is the macro file that consists of standard modeling commands. By exchanging the recorded modeling history, the macro file can regenerate the same model in the receiving CAD system. Digital implementation of marine equipment models Representation of geometric information STEP AP203, or the macroparametric method, is used to represent the geometric information of marine equipment. STEP will be widely used as an international standard, and is compatible with some of the shipbuilding CAD systems. If we use the STEP AP203 standard, the exchange of shape information is possible among systems that support it. AP226 is not yet an international standard, and there is no CAD system which supports AP226. It would be ideal to exchange

5 186 H.-J. Hwang et al.: Digital exchange between marine equipment libraries Fig. 6. Pump model in the macroparametric method Fig. 5. Pump model in STEP AP203 ship equipment models based on AP226, but it is not possible at the moment. To solve this problem, we use the macroparametric method for the systems which do not support STEP AP203. The design history recorded in the macro file is used to regenerate models in the design process. In the case of TRIBON, the input to create a volume has similar form as the macroparametric approach. We tested the method by exchanging a pump model. Figure 5 shows the physical file of the pump model shown in Fig. 9. It is represented by the advanced boundary representation according to STEP AP203. Figure 6 shows the pump model based on the macroparametric method. It represents exact connection point information as well as primitives (cubic, cylinder, cone, etc.) that represent the approximate model. Fig. 7. The hybrid neutral formats Representation of nongeometric information We have used PLIB to represent nongeometric information. The data dictionary of PLIB requires a classification system of parts. Nongeometric information represented by PLIB can be exchanged using the STEP Part 21 physical file or XML. Figure 7 shows a schematic diagram of the hybrid contents. Geometric information is represented by either STEP AP203 or the macroparametric method, and is exchanged in the format of STEP Part 21. Nongeometric information is represented by PLIB, and is exchanged in the format of STEP Part 21 or XML. Figure 8 shows an example that Fig. 8. Pump model in PLIB

6 H.-J. Hwang et al.: Digital exchange between marine equipment libraries 187 represents the properties of the pump model according to PLIB standards. A pump class is defined, and a part number, supplier information, and other attributes are defined as properties of the class. Implementation of the pilot translator One of the next-generation shipbuilding CAD systems uses SolidEdge to model the shapes of equipment. Visual Basic incorporated in SolidEdge or an application program interface (API) used in the programming environments allows the equipment to be modeled. The TRIBON system provides the Vittesse API which allows direct access to the model data structure. We have developed a translator which generates the TRIBON volume file. The volume file is a type of macro file that records the parameter values of primitives which are used to model equipment. We have also developed a simple 3D modeler that supports the standard formats for equipment models. Figure 9 shows the graphical user interface (GUI) of the authoring tool for equipment. The geometric information modeled using the authoring tool for equipment is translated into the STEP AP203 physical file or the standard macro file that are the standard formats proposed in this paper. The AP203 format is available in most CAD systems that support the STEP standard. The TRIBON system does not support the STEP data interface. As the TRIBON volume file is similar to the macro file, we can extract information about primitives from the standard macro file and the postprocessor generates the volume file. The volume file is transferred into the TRIBON system. PLIB is used to represent nongeometric information. We have composed a data dictionary according to the parts classification system, and defined the classes and properties of the dictionary. The properties of equipment models can be expressed by creating instances of the property information defined. For the pump model, properties such as part number, weight, outer diameter, and inner diameter are recorded based on PLIB. These properties of an equipment model can be parsed using a parser. The parsed data is transformed into the Excel format and then used as the input properties of a shipbuilding CAD system. Figure 10 shows an example of the translation of PLIB data into an Excel file by parsing the information using a visual basic application (VBA). Using the digital equipment models, Fig. 11 shows the process that can be applied to the ship design procedure. The shipyard designers need 3D equipment models, and we should be able to generate the 3D geometry from the 2D drawings which are provided by equipment manufacturers. There are two methods to create 3D geometry models of equipment models: one is to use the authoring tool and the other is to use commercial CAD systems. The model created is translated into the standard format proposed in this paper. We use STEP AP203 or the macroparametric method to represent the Fig. 9. An authoring tool for equipment modeling Fig. 10. Representation of the specifications in Excel Fig. 11. Application process of the CAD library

7 188 H.-J. Hwang et al.: Digital exchange between marine equipment libraries Fig. 12. Application of the equipment library geometric information, and use PLIB to represent the nongeometric information. By combining three formats (AP203, macroparametric, PLIB), we can develop a hybrid representation scheme of the equipment library. Equipment information is provided on the Internet in the form of an electronic catalog. Equipment models use the standard format proposed in this paper to represent equipment digitally. The designers in shipyards download a digital equipment model provided and translate it into the CAD systems used in shipyards. The standard equipment model is translated into a native format for shipbuilding CAD systems. The model is translated into the TRIBON system with a file formation macro, and is translated into the GSCAD system with a STEP AP203 file. The equipment model data is translated into the CAD system of shipyards, and is used in the outfitting design process. For the nongeometric information, the specification information is stored in the equipment database of shipyards through a GUI or the translator. Manufacturers can register in equipment model in the electronic catalog using the standard format. Designers in a shipyard download the design information about the equipment from the electronic catalog of the parts library. The downloaded equipment model will be translated into the corresponding model in the CAD system. Figure 12 shows the equipment in which a downloaded equipment model is applied in a domestic shipyard. The left-hand side of the figure shows a pump model inside the TRIBON system, and the righthand side shows an engine model inside the GSCAD system. Conclusion Business-to-business (B2B) electronic commerce is spreading over all industries, and this trend has increased the need to improve the outfitting design process in the shipbuilding industry. We have suggested a method of representing equipment models for electronic commerce. This allows the product information produced by equipment manufacturers to be used in the outfitting design process of a shipyard. The digital equipment model includes nongeometric information that represents the properties of the models. The models are registered in the parts library of shipyards. The geometric information represents the shape of the equipment. We have surveyed the current state of outfitting CAD libraries in Korean shipyards, and analyzed international standards such as IGES, STEP, and PLIB in order to suggest a hybrid neutral format for the equipment model. To represent the equipment model as digital data, we have proposed a hybrid method to define the geometric information by STEP AP203 or the macroparametric method, and the nongeometric information by PLIB. STEP AP203 is used in many commercial CAD systems, and its effectiveness has been proved. The macroparametric method can regenerate models by translating the design history information. It can be applied to a system that does not support the STEP AP203 standard, and can be used in systems that cannot exchange the correct shape information by STEP. We have implemented a pilot system based on a suggested standard format, and tested it using sample equipment models along with several shipbuilding CAD systems. The following benefits can be obtained by representing equipment models as digital data based on the proposed standard format. Designers of a shipyard can improve their design productivity because they use the 3D equipment model provided by equipment manufacturers directly, and not by maintaining their own library. They can also design with the correct data specification, because the latest information can be supplied by the near-real-time electronic catalog. As the same library can be used by several shipyards, equipment manufacturers can reduce the cost of supporting different CAD systems, and always upload the latest information into the database. Acknowledgments. This research has been supported by the Development of Maritime STEP Technology (M ) from the National Research Laboratory (NRL) Project of the Ministry of Science and Technology. References 1. Shin YJ, Han SH (1998) Data enhancement for sharing of ship design models. Computer-Aided Design 30: Baum S, Ramnkrishinan R (1997) Applying 3D product modeling technology to shipbuilding. Mar Technol 43: Wollert J, Lehne M, Hirsch B (1992) Modeling for ship design and production. J Ship Prod 8: Devale E, Guilbert J (1994) Production integration via solid modeling. J Ship Prod 10:

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