The Research On Train Carrying Capacity Estimation Of CBTC Based Urban Rail Transit

In recent years, the capacity of urban rail transit system is facing the pressure of the continuous expansion of urban scale and the rapid growth of people's travel demands.As an important index to examine whether the capacity meets the demands, the carrying capacity is greatly influenced by factors such as the characteristics of the signal system,complex line conditions and the trains' running variations. Accurate estimation method of the carrying capacity can provide important technical support for capacity assessment and transit operation.Headway is the core of the carrying capacity. In this paper, from the angle of the headway,the carrying capacity research is divided into the carrying capacity estimation when the train runs regularly and the operation adjustment when the train delays. The influencing factors and characteristics of CBTC system are summarized and the basic model of headway is established which is based on the blocking time of urban rail transit. Based on this, first of all,the wireless communication delay which is an important factor in CBTC system that affects the headway of urban rail transit is indicated, the wireless communication theory and the train positioning method are introduced to establish the constraint relation between the communication delay and the train speed, and the headway model under the condition of communication delay is constructed, therefore the estimation accuracy of the carrying capacity in the CBTC system is improved. Secondly, the headway model is expanded and the estimation method of urban rail transit complex line -- reversal carrying capacity is proposed,according to the complexity of the reversal line, path rules and reversal mode, the complex line is described as the clique model with the objective function of maximizing the number of paths. Furthermore, the Linear Programming model of the headway under the condition of complex line is constructed, the ability of estimating the carrying capacity on the complex line of urban rail transit is improved. In the end, the adjustment problem of the headway is studied when the train delays, the real-time headway control model is established to minimize headway variance, which reduces the delay propagation effectively and improves the carrying capacity of the line.The innovations of the thesis are as follows:1. A carrying capacity model under the condition of communication delay is proposed. The constraints relation between train speed and wireless communication delay is deduced by using the wireless communication theory and train safety profile calculation. Then, the headway under the condition of communication delay is modeled into a Non-Linear Programming problem,based on this, a method of carrying capacity is proposed. Simulation is carried out to analysis the relation between communication delay and carrying capacity.2. A maximum clique method is introduced to solve the problem of calculate the number of paths of complex lines. The number of paths is the indicator of headway and carrying capacity of complex lines. An undirected graph is built to deal with the diversity of complex lines and constraints between paths. On this basis, the maximum clique method is used to solve the problem of paths.This method can be used in any kind of station layouts and train reversal types and is suitable for applying in different scale of lines.3. The carrying capacity estimation method of complex lines is proposed.According to maximum method and train types, the headway problem of complex line is transformed into Linear Programming problem and the carrying capacity estimation method is proposed,the simplex algorithm is used to solve the model. In addition, the extremum theorem is used to analyze the convergence of algorithm and the stability of the algorithm is proved.4. In order to deal with the train delay, a real-time train control method is proposed to reduce the delay and delay propagation. The objective function of this method is minimizing the headway variance. For the purpose of absorbing delay and making the train return to the regular running status, the running time in the line section is adjusted through optimizing the train running profile. This method can not only satisfy real-time requirements but also guide the train running under the irregular situation.