Study On Transportation Management Of Cold Chain Logistics For Fruits And Vegetables

China is a large agricultural country, in which produce logistics plays an important role in the development of national economy. Fruit and vegetable account for a large share in agricultural products. Fruit and vegetable have the characteristics such as high liquid water content, shorter shelf-life, easy to be rotten, etc. There will be losses in the stages of production, processing, storage, and sale. Therefore, one of key points in produce logistics for fruit and vegetable is to effectively improve distribution efficiency and reduce the cost of distribution. Important parts in distribution of fruit and vegetable include rational organization of distribution process, standard distribution channels, and determining reasonable distribution routes with scientific method.Vehicle routing problem (VRP) is a typical combinatorial optimization problem. It has not only theoretical significance in theory of computation, but also important practical values. This problem is a widely used in many areas. On the other hand, ant colony algorithm is a random searching method, which simulated the behavior of ant in nature. Its main characteristics are stronger robustness, better distributed computation mechanism, and being easy to be combined with other approaches. This algorithm has been widely using in vehicle routing optimizations.In this thesis, VRP and ant colony algorithm are analyzed. VRPs are classified, and different optimization methods for VRP are described. Basic principle of ant colony algorithm is discussed. Its mathematic model is set up, including transfer probability calculation, pheromone update rules, and ranges of parameters and so on. On the other hand, the characteristics of cold chain logistics for fruit and vegetable are analyzed. Accordingly, a time window for shelf-life of fruit and vegetable is proposed to meet the demand of tight service time requirement for their distribution. A function of customer satisfaction is established as a constraint on optimal route selection. Sometimes, there may be special situations occurring when transporting fruit and vegetable. In these cases, the planned routes are needed to be changed in time. Hence, route re-planning is studied in this thesis in order to let transportation routes be in accordance with real situations.Ant colony algorithm is adopted in this thesis to resolve problems of optimizing vehicle routes of transporting fruit and vegetable for distribution. Some improvement are made, including status transfer probability, pheromone update, and local optimum search strategy to optimize search capabilities and avoid premature convergence and stagnation, etc. Simulation experiments are performed with satisfied results.