Internet-based intensive product design platform for ... - GRACO

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8 manufacturing architecture based on the Internet, with the World Wide Web (WWW) as the user interface. A design expert system controlled through the Internet and integrated with a CAD system visualizes the product shape [6]; a Concept-Modeler and an expert systems shell with CAD ability, has also been used. The interface between the expert system shell and the web was developed by Common Gateway Interface (CGI) script using Pearl [7]. A distributed design expert system should use an expert system shell and provide information related to design and manufacturing through the Internet and multi-agents. However, the current distributed design expert system is not based on distributed design knowledge, but is limited to an expert system shell remotely operated through the Internet. Until now, there is still a little research on how to achieve the integration of multidisciplines, distributive knowledge resources, and product design platform over the Internet to support product design. From the author’s viewpoint, and for the sake of quickly acquiring design knowledge and improving the speed of product development, a kernel problem is the mechanism of knowledge acquisition. Another problem is the form of knowledge representation (i.e. how to achieve the design knowledge interacting among various design platforms and directly utilized by them). With the goal of solving these problems, combining the Internet enabling technologies with CAD platforms, a scheme, the IPDP, is proposed. The problems of representation, storage, transference, search and implementation of knowledge in IPDP are discussed in detail later. The ultimate objective of this paper is to present a rational scheme used to integrate the knowledge resources and design platforms over Internet so as to support the designer in developing a high quality product quickly and efficiently. 2. The structure of IPDP The framework of IPDP is shown as Fig. 1. It is S. Zhou et al. / Knowledge-Based Systems 16 (2003) 7–15 Fig. 1. Framework of Internet-based intensive product design platform. composed of three layers: traditional design platform, middle-ware, and knowledge repositories. The IPDP apart design platforms (e.g. SolidWorks) from knowledge repositories, and links them via middle-ware. The design platforms are independent of knowledge repositories. And the outside knowledge repositories are distributed in the servers of knowledge (product) vendors, it is also independent of the design platform. The design platforms communicate with knowledge repositories via Internet control, and the knowledge is translated between them via pre/post processor. As Fig. 1 states, obviously, the IPDP is a system with a Client/Server mechanism. Common repositories are useropened, and can be expanded by any user according to the specifications of the knowledge definition. The knowledge in IPDP repositories is represented with certain standard (e.g. the standard for the exchange of product model data, STEP). All product designers may use these repositories. Furthermore, the designers can also add their knowledge to the repositories or construct their own repositories according to the standard. Hence, the structure of repositories in IPDP is distributed, flat and net-like. The knowledge store style of the IPDP with the distributed, user-opened and userexpanded feature breaks through the limitations of the traditional style of commercial CAD (i.e. the single stiffness closeness feature). Considering the Internet networks can integrate distributive repositories with an opened network style, in IPDP, the knowledge (outside design platform) acquisition, organization, construction and utilization all are implemented through the Internet. All common repositories of IPDP are constructed and integrated over the Internet. By this mechanism, product designer can retrieve and download the knowledge from common repositories of IPDP via Internet control if the knowledge inside the repository of his design platforms does not meet what he needs. In IPDP, the product designer still depends on traditional design platform (commercial CAD system) to develop product. Intensively,
Table 1 EXPRESS information model of rolling bearing STEP information model SCHEMA rolling_bearing_support_schema: ENTITY bearing: style: STRING; static_load: REAL; dynamic_load: REAL; weight: REAL; limited_speed_with_oil: REAL; limited_speed_with_grease: REAL; external_diameter: REAL; inner_diameter: REAL; width: REAL; install_damin: REAL; install_damax: REAL; install_rasmax: REAL; other_d2_inner: REAL; other_d2_external: REAL; other_rsmin: REAL; END_ENTITY: END_SCHEMA: he can use not only the repositories inside the commercial CAD system, but also the common outside repositories via Internet control. Due to the common repositories are maintained by knowledge (products) providers, they can quickly be updated and kept up to date. Since knowledge providers are distributed in all kinds of disciplines and to various sites, the knowledge in the repositories of the IPDP can abundantly contain distributive, various discipline knowledge resources. Consequently, a robust intensive product design platform is formed. To achieve this IPDP framework successfully, there are server all-important issues need to be solved. Firstly, the common repositories of IPDP are distributed at various locations, domains and disciplines. And the knowledge stored in them should be utilized with various design platforms. So the knowledge must be represented with a neutral form independent of design platforms, meanwhile, it should be understood by them via knowledge processor. Secondly, because the IPDP is constructed over the Internet and its knowledge repositories is a dynamic league of knowledge sites, an efficient method of knowledge search within Internet environment must be provided to assure the running performance of IPDP. The following content then will discuss these issues in detail. 3. Knowledge representation As stated in Section 2, a key issue of the IPDP is that the knowledge retrieved from the repositories of IPDP should be directly utilized for various design platforms. So, if the knowledge is still represented in a traditional handbook with such things as data, tables and, diagrams, the user must translate the knowledge into a format that his design platform can understand. For example, a product designer S. Zhou et al. / Knowledge-Based Systems 16 (2003) 7–15 9 needs a rolling bearing when he designs the structure of a product with a Solidworks platform. If the product designer gains the detailed structure of the rolling bearing from a traditional format such as a handbook, table or diagram, it cannot be directly understood in a Solidworks platform. As a result, the designer must draw a rolling bearing with Solidworks using the rolling bearing information as represented in traditional handbook form. This indicates that the traditional handbook representation limits the level of knowledge utilization and the speed of product development. Since the repositories of the IPDP are independent of the application platform, and the knowledge acquired by the designer requires that it directly utilize the application platform, the knowledge representation must be standardized. The standard for the exchange of product model data (STEP) [8,9], released by ISO, can implement the information expression depending on various application platforms. It is a standard based on the EXPRESS language [10], which can grow and can be extended to any industry and will not be outdated as soon as it is published. The EXPRESS language describes constraints as well as data structure. The formal rules of the STEP standard will prevent conflicting interpretations. The knowledge represented in the STEP standard can felicitously meet the requirements of the IPDP system on the knowledge representation form. Since STEP provides a mechanism for describing product data models and EXPRESS featureneutral and independent of any application platform. Besides the traditional form, in this paper, the knowledge in common repositories of the IPDP is also represented with EXPRESS language based on the STEP standard. Hence, the designer can acquire not only the traditional handbook form but also the STEP information model of knowledge from repositories of the IPDP. The STEP contains all information of this knowledge as expressed in traditional handbook form in data, table and diagram style. When a designer retrieves knowledge from repositories of the IPDP, he first downloads the STEP information model of knowledge and, then employs the STEP pre/post processor, translating the STEP information into a form understood by the application platform. By this mean, the knowledge can be quickly and directly utilized in various product design platforms. Taking the rolling bearing as an example, we note in Table 1 that the representation form of knowledge (rolling bearing) in the repositories of IPDP is described with EXPRESS language. This knowledge model then is translated into a data dictionary model using the EXPRESS compiler (e.g. ST-Deeloper8.0 [11]). The data dictionary is a knowledge model that is not populated (e.g. a class of rolling bearing), meaning that the model attributions are not endued with exact values. The bearing’s code is in a binary format, which can be directly read by machine (for example, after being compiled, the data dictionary of the information model rolling_bearing_support_schema
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Page 5 and 6: Fig. 4. The flowchart of searching
Page 7 and 8: the BP network is shown as Fig. 5.
Page 9: Acknowledgments This research was p

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