Research On Integrated Optimization Of Intelligent Virtual Cell Formation And Scheduling

Intelligent manufacturing is aiming at the most advanced production mode at present.On the one hand,through the implementation of intelligent transformation of workshop,it is expected to solve two major uncertain problems of uncertain customer demand and uncertain manufacturing process,so as to realize the optimal allocation of workshop resources and maximize the comprehensive value of manufacturing system.On the other hand,intelligent manufacturing has also made profound changes in workshop manufacturing.Modern manufacturing enterprises urgently need to use the corresponding advanced manufacturing mode and production scheduling technology.With the advancement of digital workshop construction,virtual cell manufacturing system has a better matching degree to digital workshop.In order to make the manufacturing system adapt to the market changes quickly,further improve the comprehensive performance of the workshop production,this paper studies the integrated optimization problem of virtual cell construction and scheduling.A nonlinear integer programming model is established based on the comprehensive consideration of the influencing factors and optimization objectives,and designs an improved NSGA-II algorithm based on four-level coding,the validity and superiority of the model and algorithm are proved in the application of semiconductor workshop.The main work of the thesis is divided into the following aspects:Firstly,this paper expounds the characteristics of digital workshop under intelligent manufacturing and the concept of smart manufacturing unit production,and summarizes the current situation and difficulties of the cell and virtual cell formation and scheduling problems,analyses the adaptability of flexible reconfigurable virtual cell manufacturing system to efficient and fast intelligent manufacturing,discusses the significance and advantages of integrated optimization,then the integrated optimization of intelligent virtual cell formation and scheduling is proposed in this paper.Secondly,the integration optimization is a complex problem.This paper comprehensively analyses the factors that influence the integration optimization of virtual cell formation and scheduling,puts forward several optimization objectives covering reasonable system resource allocation,short scheduling time and equipment load balancing,and then describes the problem from the perspective of system platform and workshop site.Finally,the mathematical model of multi-objective non-linear integer programming are established.Thirdly,in order to achieve multi-objective optimization simultaneously,this paper designs an improved NSGA-II algorithm based on four-level coding.The algorithm adopts an improved tournament selection strategy based on shared fitness value,implements a cell-based multi-point crossover operator,and designs a variable neighborhood search algorithm to make up for the deficiency of genetic algorithm in local search.This algorithm is used to solve the semiconductor workshop case,so that the factory can get the optimal virtual cell formation and scheduling scheme according to the current order step by step.The effectiveness and superiority of the integrated optimization algorithm are proved by comparing the algorithm with the original workshop processing,the non-improved NSGA-II algorithm and the staged optimization algorithm.The influence of two decision factors,the number of building units and the capacity of unit equipment,on the objective optimization is discussed.Finally,the multiplier index weighting method is used to select the optimal scheme,which provides a reference for enterprise decision-making.