Study On The Knowledge Base System Of Function Tolerance Analysis With An Ontology-based Approach

Tolerance design is one of an important part in the process of design and manufacturing. In most cases, the assembly tolerance specification is specified manually. The same nominal geometry will be specified different assembly tolerance specification by different designers. The process will increase the uncertainty of product and the complexity of function tolerance analysis. In order to reduce the uncertainty in the product design and to solve the smoothly transferring tolerance information heterogeneous systems, ontology, one of the latest technologies in the field of artificial intelligence is introduced to the study of function tolerance analysis. A meta-ontology model is build, a generating algorithm is designed and the knowledge-base system is build. To be specific, the main contents and creative points are as follows.Firstly, an ontology-based methodology for automatically generating assembly tolerance specification is proposed. By means of extracting the concept, relation, constraint and design experience in the process of tolerance design, a concrete domain named Dts for representing assembly tolerance specification is defined by a description logic SHOIN(D) which in the underlying layer of Web Ontology Language(OWL). Based on the representation meta-ontology model, the classes, properties, relations and individuals are described by OWL. The meta-ontology is constructed by the seven-step approach. The constraint knowledge is described by Semantic Web Rule Language(SWRL). Then the automatically generating algorithm is proposed. The feasibility and effectiveness of the designed algorithm is verified by a practical example. The automatically generating tolerance specification can be a solid foundation for function tolerance analysis.Secondly, a description logic SHOIN(DTA) for function tolerance analysis is proposed. The geometric accumulation model, tolerance representation model and tolerance loop are build by the concrete domain named DTA. According to the ABox composed by the defined parts, feature surfaces and constraint relations, the TBox comprised by the given SHOIN(Dta) representations and the Tableau algorithm of SHOIN(Dta), the algorithm for function tolerance analysis based on description logic automatically is designed. The feasibility and effectiveness of the designed algorithm based on the description logic is verified by a practical example. This provides a theoretical basis for the tolerance analysis on ontology.Finally, a knowledge base system for function tolerance analysis is developed. The function tolerance analysis meta-ontology representation model is structured based on the SHOIN(DTA) model. The process of structuring the meta-ontology is also constructed by the seven-step approach. Base on that the OWL-based structure knowledge and SWRL-based constraint knowledge, the Jess inference engine transforms them into Jess fact and Jess rules, respectively. Based on that, the ontology-based on knowledge base system for the function tolerance analysis is developed. The prototype system is completed at last. The feasibility and effectiveness of the ontology-base knowledge base system is verified by a project case.