Research On The Optimization Of Dynamic Location-Routing Under Constraints Of Soft Time Windows

With the rapid development of global economy, the logistics enterprises are faced with a complicated dynamic decision-making environment, the market increasingly competitive and many decision factors will change over time. In the logistics system planning, between site selection of distribution center and routing arrangement have exists interdependent relationship, integrated optimization of these two elements, is the core issue of the integration of logistics system planning. There have been many scholars focus on the research of the two elements of the integrated optimization, but these studies are mostly static, do not conform to the actual dynamic decision-making environment, result in the decision belongs to the "short-sighted" of sub-optimal decisions. At the same time, considering the development of a variety of customer demands, customers are increasing for the response speed of the order, make enterprise in a market environment based on time competition. Therefore, the study on optimization of dynamic location-routing problem with constraints of soft time windows not only has theoretical value, also has a practical significance.This paper has optimize the two elements of site selection of distribution center and routing arrangement of the integrated logistics system and taking into account the dynamic characteristic of the logistics system change with time, established a dynamic location-routing model. Under the condition of one factory, multiple distribution center, multiple customers, multiple time periods, to determine the site selection of the number and location of distribution center and arrangement plan of routing at each time period, and to determine the optimal scheme of the whole planning period. On this basis, considering the limitation of customer soft time windows, established a dynamic location-routing under the restriction of soft time windows optimization model, and determined the site selection of the number and location of distribution center and arrangement plan of routing at each time period, and also determine the optimal scheme of the whole planning period.On the solving of model, for the two optimization model, this paper will be solved it by broken down into two sub-problems of static location-routing optimization problem and dynamic planning. For static location-routing optimization problem has design respectively of based on Greedy Algorithm of the improved PSO and PENALTY-PSO to solve, and got the site selection of the number and location of distribution center and arrangement plan of routing at each time period. Finally, use the Dynamic Programming method to find the optimal solution of the whole planning period.The experimental results show that the improved PSO based on Greedy Algorithm is better than PENALTY-PSO in the minimum average total cost, the stability of the solution, the optimal solution of shooting and search speed. Meanwhile, considering the limits of customer’s soft time windows also have certain influence to the minimum average total cost. A numerical example results show that the model and the algorithm are both effective and practical.Finally, briefly summarize the research of this paper, and point out the problems that need further study.