| In the traditional logistics and transportation industry of China,the problems of low transportation scheduling efficiency and high transportation cost need to be solved urgently.As a classic combinatorial optimization problem,the vehicle routing problem has a wide range of application scenarios and research value in improving logistics efficiency and reducing transportation costs.In actual distribution,some goods cannot be stacked during transportation due to their shape and fragile characteristics.It is necessary to consider the feasibility of the two-dimensional layout of the rectangle corresponding to the goods on the loading surface of vehicles,which leads to the vehicle routing problem with two-dimensional loading constraints.In addition,according to the type and quantity of the customer’s demand,the problem can be extended to the vehicle routing problem with simultaneous pickup and delivery and two-dimensional loading constraints and the split delivery vehicle routing problem with two-dimensional loading constraints,respectively.The main research contents and innovative achievements of this thesis are as follows:(1)A mixed integer linear programming model for the vehicle routing problem with two-dimensional loading constraints is constructed,and the validity of the model is verified by example tests.(2)A branch-and-price based algorithm with packing heuristic is proposed to solve the vehicle routing problem with two-dimensional loading constraints.The validity of the algorithm and acceleration strategy is verified through the test and comparison of numerical examples,which provides a new idea for solving the vehicle routing problem under loading constraints.(3)A branch-and-price based algorithm is proposed to solve the vehicle routing problem with simultaneous pickup and delivery and two-dimensional loading constraints.In addition,the same set of examples is regarded as the vehicle routing problem with simultaneous pickup and delivery and vehicle routing problem with mixed pickup and delivery under two-dimensional loading constraints,both of which are solved by the proposed algorithm.it is compared and analyzed that the cost cannot be saved by splitting the customer’s pickup and delivery demands in the scenario set in this thesis.(4)The mathematical model of the split delivery vehicle routing problem with two-dimensional loading constraints is studied,and an enhanced neighborhood search algorithm is proposed to solve the problem.The effectiveness of the algorithm is analyzed by the simulation test of the numerical instance and the comparison of the results.Meanwhile,it is compared and analyzed that in the case of large customer demand and large total area of goods,more significant economic benefits can be obtained by distribution of splitting demand.This thesis comprehensively uses intelligent optimization,operations research,simulation experiments and other theories and methods to systematically study the vehicle routing problems with two-dimensional loading constraints,the vehicle routing problem with simultaneous picking and delivery and two-dimensional loading constraints,and the split delivery vehicle routing problem with two-dimensional loading constraints.The theoretical system in related fields provides a reference for the distribution decision of logistics enterprises.Figure 18,table 9,reference 88... |
