Study On The Models And Algorithms Of Combined Location Routing And Inventory Problems

In this dissertation, the location-routing problems in integrated logistics are investigated. It is an important problem in logistical system optimization. This paper analyzed the relation among locating, routing and inventory. The main purposes are to research the models of location routing problem and combined location routing and inventory problem to minimize the cost of logistics system, and to find some heuristic algorithms to solve these problems.This paper tests the mathematic model of the mult-depot location routing problem by Lingo program when the points number is small. Because of its NP-hard property, it is difficult to get the optimal solution when the points number is more, so this paper designs tabu search heuristic algorithm to solve this problem. Firstly, the initial solution of location allocation problem is constructed by space filling curves, then this paper solves the vehicle routing problem with tabu algorithms, and thirdly solves the location allocation problem with the same algorithms, at last, by a large number of iterative from location to routing phases, the optimize solution of location routing problem can be obtained. The computing result by C++ language programming shows the validity of designed algorithm by comparing with the related literature.This paper sets up the mathematic model of the combined location routing and inventory problem when demand of client is stochastic, aims to min the sum of depot establishing cost, transportation cost and inventory cost. This paper designs a two-phase heuristic algorithm to solve this model. The first phase gains the initial solution by the first-route later-location. The second phase improves the solution by swap moves. The variables of inventory are gained by iterative method to minimize the cost of ordering goods, lack and transportation. At last, this paper compares the solution of this model with the solution that is abtained when location routing problem and inventory controlling problem are solved separately, it indicates that the combined location routing and inventory problem makes the logistics cost largely reduce. So it indicates that it's important to determine the inventory control method when optimize the logistics system, and the designed algorithm is practicable and effective to solve this problem.