Research On Reusable Structure Knowledge Discovery Of 3D Assembly Model

With Computer-aided design(CAD)Systems implemented widely in industrial field,there have been plenty of three-dimensional(3D)CAD assembly models in enterprises,which can be used for reference and reuse when developing new products.3D assembly model is the carrier of product functions that can not only embody the overall design structure of product,but also implicate lots of function semantics,design intent and design experience knowledge,etc.How to discover actively the potential and reusabe design structure knowledge from 3D CAD assembly model is one of the effective ways for improving level of assembly retrieval and reuse.Function runs through the whole process of product design,which reflects the specific purpose and requirements of product.Content-based CAD assembly model retrieval focusing on similarity measure of bottom-level geometry and topology information can hardly meet design reuse demand of engineering designers in the product scheme design.Semantic-based CAD assembly model retrieval can provide effective support for demand of assembly model reuse in the process of product structure scheme.Aiming at above problems,the thoery,methods and key techonogies for reusable structure knowledge discovery of 3D CAD assembly model are studied and explored in the paper.The main research contents are shown as follows:1)An approach for structure-function correlations analysis and functional semantics annotation of CAD assembly model is proposed.First,a functional semantic ontology of 3D CAD assembly model is constructed as an instruction to guide the standardized labeling of function on CAD model.Then,CAD assembly model is represented by part attributed adjacency graph and partitioned into multiple function regions.Assembly region and flow-activity region are defined to analyze conveniently structures of CAD assembly model.Meanwhile,the extraction process of assembly region and flow-activity region is given in detail.Furthermore,on the basis of the function region,a method for functional semamtic annotation of CAD assembly model is put forword,where sample CAD model is labeld and potential functional semantic annotation based on structure similarity is built.Finally,a structure-function relation model is established based on polychromatic sets for expressing explicitly and formally relationships between functional structures,assembled parts and functional semantics.2)Key assembly structure identification in CAD assembly model based on complex network is proposed.First,complex network centrality is employed to analyze the network topology characteristics of assembly model.Then,a two-level evaluation model is given for evaluating importance of parts assembled from aspects of assembly network topology and multi-source attributes.Thus,the key function parts in assembly can be obtained.After that,on the basis of the key function parts,a heuristic algorithm upon breadth first searching is given to identify key assembly structures.3)Module partition for CAD assembly model based on community detection is proposed.Firstly,the correlation strength between assembled parts is analyzed and evaluated based on multi-source correlation information from the point of view of assembly structure,function and flows.Then,the weighted network is constructed for expressing correlation relationships between assembled parts in the assembly model.After that,a Fast Newman-based community detection algorithm upon greedy thought is given to discover communities in weighted network,thereby realizing the modularization of mechanical CAD assembly model.4)An approach for function-driven CAD assembly model retrieval using multi-source semantics information is proposed.First,the semantic ontology for mechanical assembly model is constructed considering multi-source semantics information including part semantics,assembly constraint semantics and functional semantics.The query text is parsed into standerd terms by ontology rules.Subsequently,semantic similarity between concepts is evaluated comprehensively with HowNet and domain ontology,and a semantic matching model is built based on weighted bipartite graph(WBG)for solving the many-to-many semantics matching problem of semantic retrieval for CAD assembly models.The CAD assembly models in mechanical field are taken for example,which are employed to verify the effectiveness and feasibility of the proposed approaches for functional semantic annotation in assembly model,key assembly identification in assembly model,module partition of assembly model,and semantics retrieval of assembly model.Based on that,a prototype system for reusable structure knowledge discovery of CAD assembly model is designed and developed,where the key techonolgies and mehods in the paper is achived and tested.