Research On Simultaneous Pickup And Delivery Problem With Time Windows Considering Routing And Three-Dimensional Loading Joint Optimization

In recent years,reducing the number of vehicles and increasing vehicle loading capacity has become an important means for logistics enterprises to reduce operating costs in order to improve the quality and efficiency.Joint optimization of vehicle routing and loading has increasingly received attention in the industry.Considering the widespread nature of logistics distribution with pickup and delivery characteristics,this thesis studies vehicle routing problem with simultaneous pickup and delivery with time windows and three-dimensional loading(3L-VRPSPDTW),and designs an algorithm to achieve cost reduction and efficiency enhancement for logistics systems with pickup and delivery.This thesis analyzed the literatures related to vehicle routing problem with simultaneous pickup and delivery with time windows and three-dimensional loading,and extends the 3L-VRPSPDTW problem.For the problem of mutual obstruction in the problem,the thesis proposes two modes: X-Vertical Space Partition(XVSP)and ZVertical Space Partition(ZVSP).A 3L-VRPSPDTW-H optimization model,which considers handling costs and time windows,is established with the objective of minimizing operating costs,including constraints such as time windows,threedimensional loading,Last-In-First-Out for delivery space,and reprocessing for pickup space.Due to the complexity of the problem,the one-dimensional VRPSPDTW mathematical model was solved using the gurobi solver for testing.A routing-packing mixed algorithm applicable to 3L-VRPSPDTW is designed based on the idea of routing first packing second and embedding a loading heuristic in an adaptive large neighborhood search algorithm.The results of the numerical experiments show that the adaptive large neighborhood search algorithm has good performance in solving VRPSPDTW.The routing-packing mixed algorithm with an embedded open space heuristic performs better in solving 3L-VRPSPDTW,and the First In Last Out constraint significantly reduces the loading rate of vehicles.XVSP mode is better than ZVSP mode,and the space selection strategy select the items based on the space is more computationally efficient.When solving 3L-VRPSPDTW-H using the mixed algorithm,the reprocessing operation improves the average loading rate by 46.67%,10.53%,and 24.14% on small,medium,and large-scale examples,respectively.Sensitivity analysis shows that for an equal proportion of pickup and delivery items,XVSP mode with a space division ratio of 0.6-0.7 is better;the minimum support area parameter is directly proportional to the space utilization rate.This thesis provides theoretical support and practical guidance for the joint optimization study of the simultaneous pickup and delivery with time windows considering vehicle routing and three-dimensional loading.