Automatic Generation And Solution Of 3-D Assembly Tolerance Chain Considering Deviation Of Fitting

In the development of complex mechanical products such as spacecraft and military products,it is very important to establish a fast and accurate prediction system for assembly precision due to its complex structure,high precision and high cost of repeated design.In this dissertation,the automatic generation and solution of three-dimensional assembly tolerance chain with the deviation of fitting is explored considering the analytical demands of spacecraft,military products and other complex products.The main work of this dissertation is as follows:(1)The background of precision prediction and the current research situation of related technology are introduced.The main problems in the research of precision prediction are pointed out,and the sources and significance of the research are given.(2)A precision information model for precision prediction is proposed.Based on the analysis of the characteristics of complex structure,the existing tolerance modeling methods and the data structure of CAD software are compared,and information cells and the hierarchical assembly model are established.(3)The deviation of fitting in the assembly process is researched.Taking the fitting between planes and between axis and hole as examples,the deviation of the geometrical features under different kinds of constraints is analyzed and calculated.(4)The generation and solution of assembly dimension chain with the deviation of fitting are proposed.After pretreatment of the product assembly model,the dimension and tolerance transfer diagrams of parts and the transfer graph of assembly relations of product are established,and the generation of assembly dimension chain is realized.On the basis of completion of deviation transformation,solution of tolerance chains is proposed.(5)As the engineering practice of the above research results,the prototype system of automatic tolerance chain generation and solution is designed and developed.The background,architecture,function module and implementation method of the software are discussed.The related technologies and algorithms are verified with concrete examples.Finally,the summing-up of the whole dissertation is made,and the future research work and the development direction of related technologies are prospected.