Research On Inter-cell Scheduling Optimization Based On Transportation Vehicle Sharing Strategy

In cellular manufacturing,parts with similar operations are placed in same part families,which are processed in one manufacturing cell.However,in actual processing process,as for the acceleration of product renewal and replacement,exceptional parts cannot complete all operations in one manufacturing cell,so it is necessary to adopt inter-cell processing method to complete exceptional operations.Transferences of exceptional parts between different manufacturing cells,which results in inter-cell scheduling optimization problem.In reality,due to the number of transportation vehicles are limited,that is,the transportation capacity is limited in inter-cell scheduling,in order to optimize the production efficiency and reduce the costs of cellular manufacturing system,it is necessary to coordinate machines processing process and transportation process of vehicles.For the inter-cell scheduling optimization problem with similar processing function between different manufacturing cells and flexible routes for inter-cell processing of exceptional parts,an inter-cell scheduling optimization model is established with the objective of makespan and total costs.In current research on inter-cell scheduling with limited transportation capacity,it is assumed that a manufacturing cell uses a fixed vehicle.When a vehicle transports its parts from one manufacturing cell to another manufacturing cell and unloads them,vehicle must return to original manufacturing cell without load.This kind of transportation strategy has a large number of unloaded routes.In order to reduce unloaded routes,transportation vehicle sharing strategy is proposed.In transportation vehicle sharing strategy,manufacturing cell can use any vehicle to transport part.After a part is transported to destination cell,vehicle does not need to return emptily,vehicle can continue to transport other part that need to be transported nearby,which reduces unloaded routes of vehicle.As for the model involves the optimization of parts processing sequence,cell and machine selection,and transportation vehicle allocation,a four-segment coding method is proposed.In order to solve the problem that shuffled frog leaping algorithm is easy to fall into local optimum solution,the random grouping strategy is adopted when each individual frog is put into each memeplexes and the sub-optimal frog in each memeplexes mutates at the same time.A case study is solved by the improved shuffled frog leaping algorithm and the shuffled frog leaping algorithm,it is found that the improved shuffled frog leaping algorithm can avoid the algorithm falling into the local optimal solution to a certain extent.At the same time,the improved shuffled frog leaping algorithm is compared with the NSGA-II algorithm,which verifies the superiority of the improved shuffled frog leaping algorithm in solving the inter-cell scheduling problem with limited transportation capacity.Results of the proposed transportation vehicle sharing strategy are compared with those of current transportation strategy.Results show that the transportation vehicle sharing strategy has obvious advantages in reducing makespan and total costs.Among the above results obtained by different transportation strategies,the scheduling schemes of parts are different except difference of transportation strategies.To show differences of the two transportation strategies,optimization results of the two transportation strategies are compared under a same scheduling scheme.Results show that the proposed transportation vehicle sharing strategy can reduce unloaded routes of vehicles and reduce makespan and total costs.As for the situation that number of vehicles cannot be properly selected according to processing tasks,number of vehicles can be regarded as one of the optimization objectives,to complete an inter-cell scheduling optimization with makespan and total costs.The relationship between makespan and number of vehicles,total costs and number of vehicles are all analyzed when number of vehicles changes.With the increase of vehicles,makespan begins to decline rapidly,then decline speed decreases,and eventually stabilizes.The total costs increases slowly at first,then increases gradually,and finally increases linearly.