Design Reuse Oriented 3D CAD Model Retrieval

The rapid development and extensive application of CAD technology provide an enormous wealth of digital resources for new product design. Reasonable reuse of these resources can effectively shorten the product development cycle, reduce the product cost and improve the product quality. However, 3D CAD models are often characterized with complicated geometry and topology, while the designer in the early design stage often has just an incomplete and fuzzy idea of the reusable object model; therefore, how to help the designers quickly and accurately find the reusable object models from the database containing massive amount of models using the relatively rough query instance is still a big challenge. To solve the problem, the design reuse oriented 3D CAD model retrieval is studied in this dissertation which includes both global retrieval and partial retrieval.The main contents of the dissertation are presented as follows:(1) A design reuse oriented hierarchical representation and matching method of 3D CAD models is presented, which supports the global retrieval for design reuse. Firstly, the hierarchical graph and hierarchical graph-matching are defined and the algorithm of generating the proper DBMS (Dilation Based Multiresolutional Skeleton) of a CAD model through multiresolutional dilation is described. Secondly, a novel representation of 3D CAD models using hierarchical graph is proposed, which can represents not only information in different levels but also their relationship, and then the algriothm of constructing the hierarchial graph of the CAD model based on its DBMS is given. Lastly, a matching algorithm and a similarity assessment method are proposed to obtain the similairty between two 3D CAD models based on the hierarchical graph representation, which are in a coarse-to-fine and layer-by-layer iterative manner. The advantage of the method is that it is very flexible to support both the retrieval of desired 3D CAD models through an incomplete and fuzzy query and the accurate global retrieval.(2) A design reuse oriented extraction and representation method of reusable regions in 3D CAD models is presented, which supports the partial retrieval for design reuse. Given a B-rep representation of a 3D CAD model, its design featrure based CAD model is constructed first, and then its reusable regions for design are extracted automatically based on design semantics and heuristics, and all the extracted reusable regions are represented by using hierarchical descriptors based on their local matching regions. The extracted reusable regions and their hierarchical descriptors provide the reasonable retrieval objects and their flexible representations for design reuse oriented partial retrieval.(3) A design reuse oriented multi-mode partial retrieval method of 3D CAD models is presented, which satisfies the various partial retrieval requirements on design reuse. According to the different design situations and different partial retrieval requirements on design reuse, three different partial retrieval modes are devised, and a multi-mode partial retrieval is realized based on multi-mode indexing, multi-mode matching and similarity assessment between the query and reusable regions in database.Based on the above researches, a prototype system ZD-DRCMRS is developed. Meanwhile, some tests including global retrieval, partial retrieval and the application of the retrieval results for design reuse are conducted to validate the main ideas of the proposed approaches and the prototype system.