| The pick-up train in the single-track railway undertakes the task of transporting the traffic flow in the section.In order to make full use of the cargo resources and improve the efficiency of transportation,the optimization of the pick-up train diagram of the single-track railway is particularly important.This thesis mainly studies the daily operation of a pair of and two pairs of pick-up train diagram optimization,aiming at improving the transportation speed of the single-track railway intermediate station traffic flow and reducing the residence time of freight trains in the intermediate station.Firstly,the basic theory of the train diagram of the single-track railway is analyzed,and the basic concepts of the pick-up train and the pick-up train diagram are introduced.The running time,stop time,cargo operation time,departure interval time and their characteristics during the operation of the pick-up train are analyzed,and the influencing factors and stop plan of the pick-up train diagram are described,which lays a foundation for the subsequent model establishment,solution and optimization.Secondly,according to the three drawing situations of the upper opening,the lower opening and the cross formed by the daily operation of a pair of pick-and-hang train diagram,a solution to convert the three drawing situations into one is proposed.On this basis,considering the constraints of the cross station constraints of a pair of pick-up and trailer trains,the total stay time of the reverse traffic flow in each intermediate station,the cargo operation time and the stop time,a nonlinear programming mathematical optimization model is established to minimize the residence time of the pick-up and trailer flow in each intermediate station.The large M method is used to convert it into a linear programming model,and the CPLEX software is used to solve it.The correctness of the solution method and the feasibility of the model are verified by an example.Then,according to the seven drawing situations formed by the daily operation of two pairs of pick-up and pull-up train diagrams,it is transformed into three types of drawing situations: upper opening,lower opening and crossover,and a two-pair pickup and pull-up train diagram optimization model for single-track railways is constructed.The model comprehensively considers the constraints of crossing stations,stop time constraints,stop car minute calculation and cargo operation time constraints during train operation,and takes the shortest stop time of forward and reverse traffic flows at each intermediate station as the objective function.The correctness of the solution method and the feasibility of the model are also verified by examples.Finally,according to the analysis of the results of the optimization model of one pair and two pairs of pick-up and drop-off trains,the reasons for the long stop time of pick-up and drop-off trains at a certain station in the train diagram are pointed out,and the regularity of the optimization of the train diagram of a pair of pick-up and drop-off trains is summarized. |
