Research On Storage Allocation Of Port Steel Yard Based On Improved NSGA-Ⅱ

With the implementation of carbon peaking and carbon neutrality goals,our country’s steel industry has entered a stage of transformation and upgrading with high quality development as target,while steel enterprises have begun to devote themselves to optimization of steel logistics system.Water transportation of steel products is one of the most important links in steel logistics system.As the transfer hub of water transportation,port yard carries the storage and turnover function.The problem of storage allocation is an important subject of port yard.Traditional storage allocation scheme is compiled manually and usually only considers a single objective for optimization,which cannot meet various needs and is difficult to adapt to the current high quality development trend.Therefore,it is very important to study the steel storage allocation of port yard.This thesis will focus on improving the operation efficiency of yard,and design the storage allocation model from perspectives of reducing the travel distance of vehicles and balancing the work load among yard areas.This thesis aims at the challenges such as low storage resource utilization rate,long travel distance of vehicles during carrying work and unbalanced work load among yard areas in the scene of port steel yard,so as to provide a suitable storage allocation model for port steel yard.First of all,the optimization direction of storage allocation of steel yard at port is analyzed based on water transportation logistics of steel products.Secondly,on the premise of making full use of the storage capacity,considering reducing the travel distance of the vehicles and promoting the work load balance among yard areas,a multi-objective optimization model of storage allocation was constructed.Thirdly,based on Non-dominated Sorting Genetic Algorithm Ⅱ(NSGA-Ⅱ),Dynamic Crowding Distance and Adaptive Hierarchical Selection NSGA-Ⅱ(DCDAHS-NSGA-Ⅱ)was proposed.The algorithm performance test experiment is designed,and the standard test function and a variety of performance evaluation indexes are used to verify the effectiveness of the algorithm improvement strategy.Finally,based on a port case,DCDAHS-NSGA-Ⅱ and NSGA-Ⅱ were respectively used to solve the above model.Many aspects were compared and analyzed,which proved the application value of storage allocation model and the superior performance of DCDAHS-NSGA-Ⅱ.The main contribution of this thesis includes the following aspects:(1)Multi-objective optimization model of storage allocation for steel yard at port:Aiming at the storage allocation problem of steel yard at port,based on the principle of nearby stacking with high turnover rate,the optimization goal is to minimize the travel distance of vehicles during carrying work.Based on the principle of zonal work load balancing,the optimization objective was to minimize the stacking distribution distance of hot and cold steel groups.In order to reduce the complexity of solving the model,some constraints of model are approximated according to the high inventory.(2)Dynamic crowding distance strategy applicable to NSGA-Ⅱ: Aiming at the lack of diversity of crowding distance sorting mechanism in NSGA-Ⅱ,a dynamic crowding sorting strategy was introduced,and the concept of crowding correlation solution set was proposed.In this way,the problem of dense interval being overly sparse in crowding sorting process in non-dominated solution set was improved with relatively low time complexity cost.(3)Adaptive hierarchical selection strategy applicable to NSGA-Ⅱ: To solve the problem of insufficient global search ability of elite retention strategy of NSGA-Ⅱ,an adaptive hierarchical selection strategy was introduced to adjust the hierarchical selection mechanism according to evolutionary stage of population,so as to improve the problem of premature convergence caused by poor population diversity in early evolutionary stage under poor initial population conditions.In this thesis,the storage allocation scheme is designed for steel yard at port,and DCDAHS-NSGA-Ⅱ is designed based on the improvement of NSGA-Ⅱ.The performance of the improved algorithm is compared and verified by the algorithm performance test experiment and case application experiment.The results show that the storage allocation scheme proposed in this thesis can reduce the driving distance of vehicles and promote the work load balance among yard areas while making full use of the storage capacity of the yard.