Research On Techniques Of Assembly Sequence Rapid Planning In Digital Pre-assembly Environment

Optimal product assembly sequence has great influence on the improvement ofassembly efficiency, the reduction of assembly cost and the upgrading of assembly quality.Nowadays, with the increasing complexity and shorter development cycle of products,rapidly getting optimal product assembly sequence will effectively help enterprises to winmarket competition with shorter time, higher quality, lower cost and better service. On theother hand, the progress of some related technique, including computer simulation,artificial intelligence and information process, lays the foundation for the digitalization andintelligentization of assembly sequence planning. Therefore, research and development ofassembly sequence rapid planning for complex product in digital pre-assemblyenvironment is very important in both theory study and engineering application.Based on the all-sided summary of previous assembly sequence planning methods andthe analysis of the difficulty and deficiency of these methods, a human-computercollaborative two-level design theory and method is presented in the dissertation forassembly sequence planning of complex products. Some key techniques of assemblysequence planning, such as structure-level assembly sequence rapid planning,reorganizable assembly model and its reorganizing algorithms, and operation-levelassembly sequence planning, are further researched and implemented. The abovetechniques and approaches have integrated interactive planning with automatic planning ofassembly sequence, to ensure the goodness and efficiency of assembly sequence planning.The structure-level assembly sequence rapid planning method, which is based on thereorganization of product hierarchy structure tree, is presented. With the support of digitalpre-assembly environment and product assembly model, technologists can reorganizedirectly and conveniently the product hierarchy structure tree built in the design stage.Through the above reorganization, they can perform subassembly repartition to satisfy thedemand of assembly process, and rapidly create the product assembly structure treemeeting production requirement. The validating method is given to ensure the correctnessand rationality of reorganization. Furthermore, the calculation method of degree ofseparation freedom of subassembly is expatiated on. The rules and algorithm of selectingclamped part among unstable subassembly are given to assist designing clamping scheme.The information and structure of assembly model are presented. On the basis of analysisof the basic requirements for supporting reorganization, a representation method for product assembly relationship model using assembly relationship element, is proposed toprovide a flexible maintenance mechanism for dynamic reorganizing the hierarchicalstructure tree of product. Moreover, the detailed maintenance algorithm for assemblyrelationship change and the method for assembly pose maintenance are given, which areresponsible for automatically maintaining the consistency, integrality and correctness ofassembly model during reorganizing the structure tree.The operation-level assembly sequence planning method based on rapid fuzzyevaluation is researched. Firstly an open evaluating index system is proposed. Then a rapidcalculation method of the similarity degree between activity sequences based on directedgraph is put forward. The calculation method of goodness membership grade of feasibleoperation-level assembly sequence is introduced as well. Applying the above two methods,the fuzzy evaluation result for every feasible operation-level assembly sequence can berapidly achieved. On the basis of the above study, an optimization model foroperation-level assembly sequences planning using simulated annealing algorithm isproposed.The architecture of digital pre-assembly system (DPAS) is presented. The keyimplementation technologies, such as the information integration between CAD and DPASsystem and the collision detection, are researched. At the end of this dissertation, theapplication of the DPAS system, which is developed by COM techniques, is introduced.