Train Timetable Optimization For Y-Type Metro Lines Considering Virtual Coupling Technology

In the face of the increasing pressure of subway passenger flow,the contradiction between line capacity and passenger demand is becoming more and more prominent.Especially in the peak period,some subway lines are already in the state of overload operation,and it is difficult to increase the traffic density by increasing the number of trains.In the virtual marshalling scenario,the unit train in the coupled formation has the characteristics of speed convergence and small driving interval,which can effectively improve the line capacity.In addition,with the help of train coupling and decoupling,the use of vehicle bottom in virtual marshalling scene is more flexible,which can better adapt to the time-varying passenger demand.Firstly,considering the requirements of train operation behavior and safety interval,this paper analyzes the relevant time scale of coupling and decoupling of virtual marshalling trains in different scenarios.On this basis,the Y-shaped subway line in the morning rush hour is selected as the research object,the train diagram optimization model is constructed and the solution algorithm is designed to minimize the passenger travel cost and train operation cost.The main research contents and conclusions are as follows:(1)Based on the safety braking model of virtual coupled formation train,the minimum safety interval of coupled formation unit train is calculated.The results show that the minimum safety interval of the virtual coupling formation unit train is far less than that of the traditional mode at the same operating speed,and the difference between the two will become larger and larger with the increase of the train speed.When the train speed is 60 km / h,the minimum safety interval of trains in the coupled formation can be shortened by about 71.7 % compared with that in the traditional mode.(2)For the transformation process of train operation state in virtual marshalling,considering the characteristics of train operation behavior,the time scale of train coupling and decoupling time,area length and required minimum interval operation distance under time-saving mode are analyzed.At the same time,three parameters of initial time difference,interval speed limit and train traction braking performance are selected for sensitivity analysis.The results show that the initial time difference of vehicle-vehicle communication establishment has a great influence on train interval coupling.Within the range of 30 – 60 s of initial time difference of vehicle-vehicle communication establishment,the fluctuation amplitude of train coupling time and distance can reach 210 s and 4478 m,respectively.(3)The Y-shaped subway line connecting suburbs and urban areas is taken as the research object,and the minimum passenger travel cost and train operation cost are taken as the objectives.The departure frequency of the feeder train,the departure time of the first station,the running time of the coupling interval,and the coupling state and stop state of the train on the main line are selected as the decision variables.Considering the tracking interval constraint,state transition constraint,and the scale constraint and passenger riding constraint in the process of virtual marshalling train operation,the optimization model of train diagram for the Y-shaped subway line in the morning and peak hours is constructed,and the genetic algorithm and particle swarm optimization algorithm are designed to solve the problem.(4)The case analysis shows that the optimization scheme based on virtual marshalling technology reduces the train operation cost by 7.1 %,the passenger time cost by 23.6 %,and the total cost by 16.7 % compared with the fixed 6 marshalling scheme.When the number of vehicles on the line is the same between the optimization scheme and the fixed marshalling scheme,the optimization scheme can save 26.7 % of the passenger time cost.This is because the train can shorten the train tracking interval by establishing a coupling formation in the virtual marshalling mode,and realize the small marshalling high-density driving.In addition,considering the time-varying characteristics of passenger flow,the optimization scheme optimizes the driving interval of different periods,which is more suitable for the imbalance of passenger flow time distribution than the virtual marshalling and equal interval departure scheme.The waiting time cost is saved by 19.9 %,the passenger travel time cost is reduced by 5.8 %,and the total cost of the system is reduced by 1.5 %.