Research On Heterogeneous Fixed Fleet Vehicle Routing Problem With Fuzzy Time Windows

With the advance of global economic integration, global manufacturing, global purchasing and global marketing have become a common objective and strategic behavior of the enterprises, and the importance of logistics is increasingly significant. To improve competitive advantage, logistics enterprises pay more and more attention to customer service levels in logistics distribution while emphasizing reducing the cost. Because of the paradox between the service level and the cost in logistics, tradeoff between the service level and the cost has been an important strategic work in logistics enterprise. Based on the above analysis, the vehicle routing problem with a fuzzy time window considering both the distribution cost and service level was researched.Firstly, on the basis of reviewing the relevant studies of vehicle routing problem with a time window, multi vehicle routing problem, as well as vehicle routing problem of fuzzy information, this paper analysis the standard vehicle routing problem and its mathematical model, as well as the constituent elements of the problem, expansion standard, expansion problem and the algorithm.Secondly, by introducing fuzzy membership function of the delivery service level, a bi-objective heterogeneous fixed fleet vehicle scheduling model with fuzzy time window was established, which was taking the smallest total distribution costs and the highest customer satisfaction as the goal.Thirdly, based on the algorithm design of generating an initial feasible solution, adopting the neighborhood operations of the four operators based on probability selection to enhance the searching solution space ability of simulated annealing algorithm. A two-phase algorithm was proposed for solving the model: at the first stage, controlling the service level over a certain level to get the corresponding acceptable time window, the second phase is to get optimal solution of the higher service level.At last, this paper illustrates the feasibility of the method by solving the design examples, and taking the heterogeneous fixed fleet vehicle routing optimizing problem of the Yiyang tobacco distribution lines as an example to validate the usefulness of the model. The simulation results also show that distribution costs can effectively be reduced and it has little effect on the overall service levels by controlling the vehicle service time and departure time, and appropriatly reducing the service level of a small number of customers.