Research On Assembly Modeling And Assemblability In Agile Development Of Product

Due to fierce market competition, diversity of customers' requirements and strict dateof delivery, enterprises are devoting more and more attention to promote the agile responsecapability, lower the production cost and meet the diversified demands. Exactly under thiskind of background, the theory of mass customization, design for assembly and otheradvanced manufacturing conception are applied aggressively by modem enterprises. In thisdissertation, the pattern of assembly design in agile product development is proposed, which centers on the assembly model for product family, takes serialization andassemblability as two realized purposes and considers agility as the ultimate expression.The correlative key technologies in this research are as follows:Firstly, module partition for mass customization is studied. According to theshortcoming of current research methods, the uniform mathematics model (for bothproduct innovative design and product re-design) about module partition is set up, which isgeneralized that how to obtain the optimal partition matrix given the fuzzy similitudematrix and adjacency matrix. On the above foundation, according to the adjacent relationsamong partition objects, the fitness function is constructed by internal clusting degree andexternal detached degree. Since the element of partition matrix only has two numbers suchas 0 or 1 and the column element of partition matrix only has uniquely 1, genetic algorithm(GA) is applied to search for optimal partition matrix. In order to avoid early convergenceof GA, a novel matrix cross means is also presented.Secondly, the assembly modeling technology for agile product development is studied.In order to support both the top-down and the bottom-up design processes, a hybridassembly model for product family is proposed, which contains the assembly frameworkmodel, the hierarchy model, the constraint relation model, the component attribute modeland the parametric design model. The high-level assembly framework model is introducedto implement the top-down design process, which can reflect the designers' intention andtransfer assembly constraints to the bottom phase. The basic constraint relation model isused to implement the bottom-up design process, which can check, modify and completethe reconstruction of the assembly model. The parametric design model is applied toaccomplish the product variant design, so as to realize the reuse of knowledge.Thirdly, the assembly sequences planning based on genetic simulated annealingalgorithm (GSAA) is researched. After the limitation of traditional representation of assembly sequences is analyzed, the edge sequence, which denotes the contacting relationsof assembly connection graph, is proposed. The geometry feasibility of edge sequences, the deoxidization of edge sequences, the reasoning of part feasible line assembly directionsand the predigestion of edge sequences are studied. Then the optimal fimess functionincluding number of conflicting edges, sub-assembly stability, grouping operations andnumber of line reodentations is set up. Furthermore, a modified GSAA is presented tooptimize assembly sequences. The near-optimal values of this algorithm's parameters areobtained by combining orthogonal experiment (which is used to sort out the rough values)with contrastive experiment (which is used to determine the precise values).Fourthly, the assemblability evaluation method based on entropy method and fuzzyoptimization is studied. After the deficiency of present assemblability evalutation methodis analyzed, a four layers' evaluating framework system including design scheme layer, symantic layer, part layer and process layer is built step by step, which is parallel withproduct design process. Then a comprehensive evaluation approach based on entropymethod (which is used to determine every layer' indexes' influencing weights), leastsquares (which is used to get the optimal membership degree) and fuzzy set is proposed toevaluate phase assemblability during product design process, at the same time the phaseevaluating results and suggestions are provided.Finally, the agile assembly design system is researched. After the system'srequirement is analyzed from the viewpoint of methodology, function target, organizationmode, the total technical solution, which centers on the assembly model, takes serializationand assemblability as realized purposes, considers agility as the ultimate expression, ispresented and planned. Then, the system framework based on project management andenterprise application integrated framework based on web services technology are built up.On the above foundation, the system prototype is developed, and the relative functioninterfaces are also displayed.