Research On Assembly Tolerance Modeling Based On Feature Variation

Based on the Feature and TTRS theory, this dissertation presents a new theory and method of Assembly tolerance error stack-up analysis for aircraft assembly. Research of the key techniques includes the representation, building of 3-D tolerance zone and foundation, retrieving of Assembly tolerance model. On the basis of the theoretical research, a supporting sub-system is developed, which can support tolerance design and research. The dissertation is organized as followed:In chapter 1, the important role of modeling and representation of tolerance information in computer aided tolerancing (CAT) is analyzed. On the basis of investigating the status of internal and overseas research about tolerance, the main questions for study and contents of this dissertation are put forward.In chapter 2, the feature in geometrical product specifications (GPS) and the theory of technologically and topologically related surface (TTRS) is analyzed. Then a 3-D method of tolerance representation based on degree of freedom (DOF) variation is purposed, and all of the tolerance zones are build in CATIA according to the method.In chapter 3,I discuss the structure of aviation product, the feature classification of assembly, the b-rep representation of 3-D model and the constrain relationship between minimum geometric datum elements (MGDE). Then a unified tolerance method for assembly comes into being.The assembly dimension-chain is created in chapter 4. The automatic formalization of the dimension/tolerance link for parts and its integration with CAD system are studied systematically. Visualized tolerance analysis is put forward and studied and the steps for visualized tolerance analysis are also given.In chapter 5, the sub-system for the assembly tolerance modeling is introduced. At first, I present system structure, implementing flow, and function modules. Then the sub-system is developed based on CATIA V5 using its development tool CAA API. An example about subassembly of certain aircraft is studied to demonstrate the theory of this dissertation.Finally, conclusions are given along with recommendations for future research in...