Study On Data Hierarchical Representation And Reuse Technologies For Heterogeneous CAD Product Models

With the increasingly need from multi-disciplinary and distributed collaborative design and data management, reusing and collaboration of design resources within and between companies becomes a trend in concurrent product design. The heterogeneousness of knowledge representation and data storage formats of design resources between different design systems makes it very difficult in product design reuse. This paper probes into product knowledge representation and reuse of heterogeneous CAD models, with its main researches being as follows:(1) An ontology-based hierarchical expression mechanism for product data is proposed.Regarding to design reuse of heterogeneous CAD models, the problem of a uniform representation for product data must be solved urgently. Existing product data models lacked high-level CAD semantics such as modeling features, parameters, constraints, modeling history and etc. This deficiency poses a difficulty for the designers in undertaking product variant design from existing available design resources. In this thesis, a hierarchical representation mechanism for product data based on the CAD feature models is proposed. By adopting the ontology technology, the uniform representation of different knowledge (such as high design semantic features and management data features) of CAD feature models is realized. In comparison with other similar researches, our proposed product data model has an advantage of good expansibility and can support representation and reuse of all kinds of design resources between heterogeneous CAD systems.(2) A method for semantic exchange of heterogeneous 3D CAD feature models is presented based on the hierarchical representation mechanism for product model data.Based on the hierarchical representation mechanism for product model data from heterogeneous 3D CAD features, a method for exchange of product semantics between heterogeneous CAD systems is presented. Using semantic equivalence and simulation, mappings between legacy ontology and uniform representation ontology of product model data are built. The semantic exchange method not only retains its original modeling features and history, but also supports real-time exchange of product model data.(3) A multi-layer retrieval technology based on the semantic knowledge representation is presented under the hierarchical representation mechanism for product model data.Towards the uniform knowledge presentation of heterogeneous CAD models, how to search useful design resources from product models quickly is another key to design reuse. Existing case-based methods and semantics-based methods are hard to be applied to hierarchical representation mechanism for product model retrieval. To solve this problem, this paper proposes a multi-layer semantic retrieval technology integrating form features and design knowledge. The retrieval technology captures design intent using form features that are automatically extracted. By using semantic annotations, the mappings between form features and application features are built, and the uniform modeling of case-based methods and semantic-based methods is realized. So it could meet all kinds of retrieval requirements.(4) A CAD/PDM integration technology is proposed based on the hierarchical representation mechanism for product data.PDM has become an important platform for product data storage and management. Based on the hierarchical representation mechanism, the CAD/PDM semantic integration technology is proposed. The technology can not only resolve problems of data storage and management of the uniform knowledge representation, but also support product knowledge sharing, reuse and communication among heterogeneous systems. Finally, based on above theory framework architecture and application programming interfaces of digital systems, a prototype system for product design reuse is implemented.