Research On Post Logistical Vehicle Routing Problems

Post logistics is one of the important applications of operational researches and logistics studies. Post logistics vehicle routing problem (VRP) is a multi-restricted conditions and multi-objective problem that strongly correlates the theoretical research and the production practice in complicated conditions. The main restricted conditions and influencing factors include time windows, vehicle loading capacity, road traffic, stochastic demand, round-trip collection, mixed loading, natural conditions, and so on. The study on the VRP has been doing in depth, and further researches are still needed in some particular contents. For instance, a simple and effective calculation method as well as the way to resolve the stochastic demand, time windows and unpredicted conditions. According to the relevant existing reports, based on the systematic ideology of modern logistics,abstracted actual problem from the post logistics practice,this dissertation constructs the mathematical models including post VRP with hard time windows, multi-objective post logistics mixed VRP and dynamic post logistics mixed VRP with soft time windows. The multi-objective genetic algorithm and adaptive polymorphic ant colony algorithm are designed, and have been presented for the solution to the post logistics VRP by taking YaFang integrated post with logistics delivery services in 11 cities in May 2008 by Sichuan post as the example. The optimal strategies also have been raised. Further analysis about implications on post freight costs and vehicle numbers in use under different optimal strategies also has been done.The main contents of this dissertation are listed as the following.In chapter1, the literature and theoretical achievements of post network, post logistics, domestic and foreign research achievements on VRP and algorithms have been summarized and sort out. The main research content and technological practices have been presented, based on the analysis of the latent fields of the multi-restricted conditions and multi-objective post logistics VRP.Chapter 2 is concentrated on the analysis of post transportation problem. The characteristic, classification and main influencing factors have been described for post transportation. The influence of transportation and delivery on post distribution press has also been analyzed. The monthly practical freight cost also has been calculated by taking Sichuan post in 11 cities as an example. The general model has also been put forward.In chapter 3, the model of post VRP with time windows has been constructed based on the analysis of restricted conditions like time windows and round-trip collection. The multi-objective genetic algorithm is designed to solute the post VRP with time windows in comparative analysis of post route optimization in 11 city post offices of Sichuan province. The influence of uncontrollable factors, such as emergency and earthquake, on post VRP also has been analyzed.In chapter 4, according to the characteristics of post logistic services, the vehicle scheduling and routing optimization problem has been analyzed on basis of the post transportation as well as the integration post logistical project. The adaptive polymorphic ant colony algorithm has been used to solve the multi-objective post logistic mixed VRP by which takes YaFang integrated post with logistics services in May 2008 by Sichuan post as an example. The influence of different type postal matter on post logistic mixed VRP also has been analyzed.In chapter 5, the model of minimum freight cost with time windows penalty has been built for the dynamic post logistic mixed VRP with soft time windows. It has been computed and comparatively analyzed by using of genetic algorithm, which takes care of the restrict conditions such as vehicle loading capacity, time windows, round-trip collection, mixed loading, time windows penalty and so on.In chapter 6, this dissertation comparatively analyses the total freight cost, vehicle numbers and optimal strategies, based on the theories, the post actual transportation problem, post VRP with time windows, multi-objective post logistic mixed VRP and dynamic post logistic mixed VRP through practical examples. Four optimal measures with practice have also been submitted.To sum up, the conclusion points out the main innovation of this dissertation and prospect the future research direction, which may be focused on the problem of post logistic mixed loading with multi-variety, multi-priority and multi-time limited.