针对钢铁物流园堆场内由于区储位分配不合理导致的车辆长时间排队等货、堆区作业堵塞等问题,提出以优化出入场时间和均衡园区堆场总作业量的多目标优化模型.模型中综合考虑需求量和受订频次因素对货位分配位置的影响,构建了以缩短运输距离的单区货位布局优化子目标,同时为避免作业量过度集中,减少装卸作业堵塞,针对全堆场构建了基于出入库频率划分的货物堆场内作业均衡子目标.为高效求解该多目标模型,针对NSGA-Ⅱ算法存在的Pareto前沿分布不均匀及局部拥挤区域的分布性优化不佳,提出了自适应分层保留和区间种群扩张的改进策略,构建了改进多目标优化算法(Hierarchical Re-tention and Interval Population Expansion NSGA-Ⅱ,HRIPE-NSGA-Ⅱ).基于实际案例进行了模型和算法验证试验,结果表明该模型在HRIPE-NSGA-Ⅱ求解下能够获得比对比算法更优的解方案,缩短车辆在园区内作业停留时间,平衡各区作业量,提高堆场运作效率.
Multi-Objective Modeling and Optimization of Steel Park Storage Allocation Problem
In order to solve the problems such as long waiting time for vehicles loading and unloading,yard channel blocking et al.,which caused by the unreasonable allocation of storage space in a steel logistics yard,a multi-objective optimization model is proposed to improve the inbound and outbound time of steel and balance the workload among different sections of a yard.In the model,the first objective is to shorten the transportation distance for vehicles with the comprehensive consideration of the influence of the demand and or-der frequency of different steel on storage location assignment.Then in order to avoid the excessive concentration of workload and re-duce the congestion of loading and unloading operations,the second objective is constructed to balance the workload of the different storage areas of the yard based on the operation frequency.For solve the multi-objective problem efficiently,an improved algorithm(Hierarchical Retention and Interval Population Expansion NSGA-Ⅱ,HRIPE-NSGA-Ⅱ)is provided.In the algorithm,two im-provement strategies as adaptive hierarchical retention and interval population expansion are constructed to overcome the shortcoming of uneven distribution of Pareto front and poor distribution of local congestion area of NSGA-Ⅱ.Finally,a practical case is applied to verify the validity of the model and algorithm.The results show that a better solution can be gotten based on the model by HRIPE-NS-GA-Ⅱ than other selected algorithms,which can shorten the stay time of vehicles in the park,balance the workload,and improve the operation efficiency of the yard.
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