| With the global development of logistics industry, the importance of distribution in the whole logistics system is more progressively. The rationalization of the vehicle routing in distribution will make more influence on the speed, cost and benefit. Choosing the appropriate routing can accelerate the response of the client requirement, upgrade the quality of service, improve the client’s satisfaction degree.To achieve the basic aim of minimum cost and maximum benefit, considering the activities of simultaneous pickup and delivery will be the trend. In addition, The diversified demand also makes a high demand on the time of goods’value, time windows becomes more and more important in goods’distribution, so time window constraint becomes more and more important.This paper studies the pickup and delivery vehicle routing problem with time windows, there are four main parts in this paper:Firstly, this paper bases on reading a lot of literatures about the vehicle routing problem with simultaneous pickup and delivery, and analyses the problems in existence; Furthermore, the paper compares and summarizes all algorithms for the vehicle routing problem, and this will be the basis for the research.Secondly, by analysis of the problem, this paper establishes a basic mathematical model of the vehicle routing problem with simultaneous pickup and delivery, and adds the time window constraint which accords with the fact to the model to increase the practicability.Thirdly, this paper analyses the complication of solving the mathematical model, and chooses genetic algorithm to solve the problem. This paper selects better selection operator, crossover operator and mutation operator, and make an improved design on the load constraint’s penalty function to improve the capability of genetic algorithm.Fourthly, the paper uses VC++6.0software to design a programming of the designed genetic algorithm which is proved a better method to solve VRP problem by instance. |
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