| Today, with the rapid development of the society, the increase of the economy nowadays, the quality of people’s living standard improving ceaselessly. The requirement for perishable products such as quick-frozen food, vegetables and seafood has been improved a lot, which cause that people pay more and more attention on the quality and safety of cold chain products. The cold chain logistics which can guarantee the quality of perishable products and decrease the waste of perishable products has rise rapidly. The cold chain logistics have the characteristics of fresh, perishable and easy to loss, so it’s difficult to transport the cold chain product from one place to another place. The choice of the route is facing severe test.This paper based on the review of relevant research both at home and abroad, combining the characteristics of cold-chain logistics and solving the vehicle routing problem (VRP) of cold chain. Firstly, the paper analyzes the present research situation of the VRP and pointed out the current study trend. Secondly, the paper gives the basic introduction of vehicle routing problem with time windows (VRPTW), expounds the general description and the basic model of VRPTW and summarizes the several kind of algorithms to solve VRPTW, including the accurate algorithm heuristic algorithm and intelligent optimization algorithm, especially focused on Genetic Algorithm and Nondominated Sorting Genetic Algorithm (NSGA-II), which will be used in this paper. Thirdly, the paper establishes a multi-objective VRPTW model combining the characteristics of cold chain logistics. This model has two goals: minimum total cost of distribution and maximum punctuality of distribution. The model considers a number constrains such as vehicle capacity, time windows, fuzzy driving time and so on. After simplifying the model, used the NSGA-Ⅱ to compute the model. Finally, using a practical example, choosing the Xiao Dian distribution of fresh fruits and vegetables in Meet all supermarket in Taiyuan, Shanxi as background, using the model and algorithm to design more cost-effective route for the delivery of cold-chain products distribution center. It can be proved that the model and algorithm are rationality and validity.The cold-chain logistics multi-objective VRPTW model established in this paper and the nondominated sorting algorithm for the model design can be applied into the actual distribution of cold chain products work. And it has the reference meaning to other similar cold-chain distribution centers. |
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