Study On Virtual Cell Dynamic Scheduling Problem Considering The Resources Constraints And Lot Splitting

Virtual manufacturing cells (VMCS) have attracted some researchers’ close attentionas they provide greater flexibility and avoid some shortages of the cellular manufacturingsystems (CMS) without incurring much additional system cost, becouse VCMS dosen’tneed to change the physical position of mashines. Although there has been some researchesabout virtual cell manufacturing system, the existing literature lack of discussion about thedynamic scheduling model that considering with bottleneck machines in the virtual cells. Inview of this deficiency and the new characteristics of the batch splitting problem, this paperconsidered the batch splitting (or lot splitting) problem in scheduling of virtualmanufacturing cells with bottlenecks.On one hand, this paper aimed at improving the throughoput of the whole systemthrough bottleneck resources management and batch splitting. On the other hand, this paperconsidered the random disturbance events in the system, because there are many randomdisturbance events, constant schedule strategy will make the performance of themanufacturing system deteriorate slowly. So, this paper provided a dynamic schedulingmethod for the manufacturing companies which facing dynamic internal and externalenvironment, it has important theoretical and practical significance.Considering the complexity of the problem, this paper is divided into two steps. Thefirst step researches the batch splitting (or lot splitting) problem in scheduling of virtualmanufacturing cells where there are bottlenecks exist, and there are multiple machine types,each of which has several identical machines under the stable internal and externalenvironment. In consideration of the hierarchical decision structure of the problem, wedevelop a bi-level multi-objective mathematical model to decompose and simplify theproblem based on the existing researches, and design the method to solve the schedulingstrategy. In this model, additional scheduling objectives are improved in the second modellevel, while maintaining the maximum use of the bottleneck machine ability. The resultsshow that, in consideration of the system bottlenecks, model with batch splitting can obtainmore satisfactory results. Scheduling solution given by this method is more authentic. Withthe above research foundation, the second step studies the multi-stage scheduling problemof the VCMS considering lots of the uncertain factors in the manufacturing system, at thesame time considering the machine group, resource bottleneck, lot splitting, and the time that the virtual cells were formed or dissolved. This paper constructs a model to solve thisproblem. The goal of the model is to minimize the total traveling distance and delay time ofall the jobs. The model is solved with the age based genetic algorithm, which wasdeveloped from the traditional genetic algorithm. Difference between this new algorithmand the traditional genetic algorithm is that each individual in a population of candidatesolutions has different age structure, and each individual’s birth and death rates aredetermined by the initial age structure, to ensure that the population size is stable, so as toachieve better effects.In order to validate the application effect of the proposed method when applied in theactual manufacturing enterprise, this paper analyzes the existing production organizingproblems of a ship manufacturing enterprises in Nantong detailedly, and applies the virtualcell dynamic scheduling method in the outfitting production provess, proposes thecorresponding improving program. And compares the results before and after improvement,the results show the feasibility and effectiveness of the proposed program.