| Digital pre-assembly technology is a critical technology in digital design and manufacture technology, which make use of modern computer technology development achievements, to complete the assembly sequence planning, assembly analysis and assembly process simulation based on product entity model, and find problems in the design and assembly process. To make a conclusion, Digital pre-assembly technology can improve product design, optimize assembly process, and shorten product development cycle. As for the assembly of aero vehicle thermal structure segments, digital assembly modeling, assembly sequence planning and assembly sequence evaluation techniques are researched in detail, in order to provide a theoretical basis for aero vehicle digital assembly system and production line. So the thesis has important theoretical significance and practical engineering application value.The main content of this thesis includes four parts, as follows:(1) For the assembly complexity, high assembly accuracy and low stress of the assembly of the aero vehicle thermal structure segments, the overall digital assembly system architecture of the aero vehicle thermal structure segments. And six modules of the digital assembly software system are discussed in detail.(2) In order to meet the complex assembly relationship and provide better models for the subsequent assembly sequence planning, the hierarchical assembly model based on assembly planning has been determined. The assembly model information has been divided into low-level assembly information and high-level assembly information, which represents all the information needed by the assembly sequence planning.(3) The cut set of directed graph theory is used to plan the assembly sequence of aero vehicle thermal structure segments. Firstly, directed assembly connection graph is established to represent the connections among various parts. Secondly, through a combination of assembly knowledge reasoning and broad sub-assembly identification, the nodes of sub-assembly in the directed assembly connection graph have been compressed to be super nodes, which reduce the number of nodes in the directed assembly connection graph and diminish the solving difficulty of assembly cut sets.(4) Assembly sequence evaluation system is based on fuzzy theory. Through entropy weight method and AHP (The Analytic Hierarchy Process) method, comprehensive weight value of five evaluation indicators of the quality of the assembly sequence is determined. Then through the overall evaluation system, the evaluation value of each assembly sequence will be acquired and ranked, to provide a theoretical basis and technical guidance for digital assembly of the thermal structure segments. |
