Vehicle Scheduling Optimization Research For Plants Under Line-Pickup Mode

Manufacturing industry promotes economic development in china,at the same time,it also causes high logistics costs.In addition to poor management,the main reason lies in high storage and transportation cost.With development of business,large-scale manufactuding enterprises build more factories,and take measures such as simplifying the layout of plants,using assembly line production,building regional logistics center instead of finished goods warehouse in plant and so on,to maximum promote the production efficiency and reduce storage land use.The finished products from assembly line production,standard palletized,are directly shipped to the temporary shipping area with limited space.It is known as line-pickup mode.In this mode,the previous sent-directly way needs more vehicles to wait in the shipping area to avoid overflow.It will obviously cause the waste of vehicle resources.So the companies choose to integrate vehicle resources and adapt milk-run transport way,to improve the efficiency of transportation and reduce the logistics cost.The traditional vehicle routing problem theories can't be directly applied to the vehicle scheduling problem under line-pickup mode.This article choose to split the continuous production of a plant into a sequence of discrete packed tasks for pickup,so the problem can be converted to multiple trip vehicle routing problem with time window.Then according to the characteristics of the problem,the modified Particle Swarm Optimization(PSO)algorithm and Tabu Search(TS)algorithm are used to solve.In modified PSO,the clustering and task level method are applied,and it improves the quality of the generation of initial population.In modified TS,inserting method and the neighborhood structure are also improved to make them available between continuous routes.In addition,it can also improve the flexibility of the neighborhood structure operation by adopting the methods of “vhicle capacity relaxation”.Finally,a real industry case is studied to verify the effectiveness of the two algorithms.It can optimize the number of vehicles used to its theoretical lower bound.During the experiment,it also indicates that,to some extent,modified TS algorithm is better than modified PSO algorithm.