Research On Joint Optimization Of Balancing And Scheduling Of Mixed-flow Assembly Line In L Company

With the implementation of a large number of policy support,the domestic new energy automobile industry has ushered in unprecedented opportunities.Many new players enter the market,bringing opportunities and challenges to auto OEM.In extreme cases,the OEM needs to carry out OEM production for multiple brands of multiple automobile companies,which makes it difficult for the original single assembly line to effectively meet the existing OEM demand.Companies have had to opt for new mixed-flow assembly line that is more flexible and agile.However,the balancing and scheduling problems of mixed-flow assembly line are both NP-hard problems.At the same time,considering various needs of existing enterprises,it is necessary to employ multi-objective optimization for mixed-flow assembly line.Besides,the random fluctuation of operation time can not be ignored,which makes the multi-objective optimization design of mixed-flow assembly line considering the random fluctuation of operation time more complicated.Taking the random type mixed-flow assembly line of L Company as the research object,this thesis regards minimization of workstation loss coefficient,assembly line equalization coefficient,the pace of production line,double cycle maximum completion time,double cycle total waiting overload time and double cycle total production line change times as the optimization objectives.Then the multi-objective serial optimization and joint optimization design model of mixed-flow assembly line without considering the random fluctuation of operation and the multi-objective serial optimization and joint optimization design model of mixed-flow assembly line considering the random fluctuation of operation are established respectively.The influence of considering the fluctuation of operation time and the connection of balancing and scheduling on the multi-objective optimization design of random type mixed-flow assembly line is mainly studied.In terms of multi-objective optimization algorithm,NSGA-Ⅲ algorithm with more diverse solutions is introduced.In view of the relatively weak local search ability of NSGA-Ⅲ algorithm,this thesis has improved it with variable neighborhood search algorithm.And the effectiveness of the improvement is verified.Afterwards,the improved NSGA-Ⅲ algorithm is used to solve the above model.Considering the random fluctuation of assembly line operation time in L company,this thesis implements FLEXSIM simulation analysis of deterministic joint optimization scheme based on improved NSGA-Ⅲ algorithm,random serial optimization scheme and joint optimization scheme based on improved NSGA-Ⅲ algorithm.Comprehensive analysis results show that we should pay attention to the relationship between the balancing and scheduling of mixed-flow assembly line and should adopt joint optimization instead of separate or serial optimization in the multi-objective optimization design of mixed model assembly line.In addition,it is significant to consider the random fluctuation of operation in the optimal design of random type mixed-flow assembly line.If the random fluctuation is ignored in the optimal design of random type mixed-flow assembly line,the optimization scheme may fail,resulting in waste of production resources and delivery risk.