Research On Design Method Of Assembly Tolerance Specification Based On Ontology

Assembly tolerance specification design is to study how to reasonably select the basis,specify the geometric elements,determine the tolerance type and select the tolerance principle under the premise of ensuring product functional requirements and assembly constraints,mainly including indicators such as tolerance type,tolerance value and tolerance principle the design of.In view of the uncertainty of the design parameters of geometric product tolerance specifications and the difficulty of intelligentization,this paper introduces the ontology into the design of assembly tolerance specifications by taking advantage of the ontology at the conceptual level,semantic expression,knowledge reasoning,knowledge sharing,and knowledge reuse.In order to provide a feasible method for the automated and intelligent design of assembly tolerance specifications.The main contents of this article are as follows:First,a hierarchical representation model of assembly tolerance specifications is constructed.According to the new generation product geometric technical specification system,the concept classes and topological relationships involved in the assembly tolerance specification design process are analyzed.Starting from the requirement of the semantic representation of the tolerance specification information,a part layer,feature surface layer,spatial relationship layer and tolerance are established.Representation model of assembly tolerance specification composed of seven levels including principle level,reference level,tolerance type level and tolerance zone level.Using the adjacency matrix as a description tool,an abstract representation of the assembly tolerance specification information representing the mapping relationship of each level of the model is given.Each tolerance element level represents the tolerance specification information of that layer,and the mapping relationship between the elements is used to represent geometric products The connection between various parts and characteristic elements provides a prerequisite for building a knowledge base system for assembly tolerance specification design.Then,a knowledge base of assembly tolerance specification design is constructed.According to the constructed hierarchical representation model of assembly tolerance specification,OWL DL language is used to computerize the conceptual classes,attributes and topological relations of assembly tolerance specification design,and define the definition domain and value range of attributes involved in tolerance specification design.Complete the construction of the ontology model of assembly tolerance specification information.Then,it analyzes and refines the basic involved standards,expert knowledge and design manual knowledge involved in the assembly tolerance specification,and usesthe Semantic Web Rule Language(SWRL)to construct an inference rule base for assembly tolerance design.Secondly,the tolerance knowledge acquired in the field is converted into Jess-facts;the constrained knowledge used for inference is converted into Jess-rules,and on the basis of this,a knowledge base system for ontology-based assembly tolerance specification design is developed to achieve geometry Intelligent design of product assembly tolerance specifications,knowledge sharing and knowledge transfer among heterogeneous CAX software.Finally,using Matlab GUI platform,a prototype system for intelligent design of assembly tolerance specifications based on ontology was developed.Based on the research on assembly tolerance design in this paper,the ontology editing tool Protégé is used to complete the definition of the ontology model classes,attributes and relationships of assembly tolerance specifications.Then,based on the functional requirements of the prototype system,Matlab was used to develop the design of the human-computer interaction visual interface for assembly tolerance specification design.Secondly,the Matlab GUI,the ontology editing tool Protégé and the Jess inference engine are combined to complete the development of the prototype system for assembly tolerance specification design.Finally,a gear reducer is used as an engineering example to verify the feasibility and effectiveness of the prototype system.