Research On The Key Technologies Of Communication Based Train Control System In Urban Rail Transit

As the nerve center of urban rail transit system, train operation control system takes on heavy responsibilities for safe train running with great efficiency and short running intervals and plays an important role in promoting modern management and improving comprehensive transport capacity and service. With the development of communication technology and especially the widespread application of wireless communication technology, the traditional mode of train operation control based on TBTC (Track-circuit Based Train Control) has evolved into the one based on CBTC (Communication Based Train Control).CBTC systems with full duplex, high capacity, bidirectional and continuous data communications between trains and wayside equipment can bring more accurate train operation control into effect for greater efficiency of train operation and have considerably diminished wayside equipment to save the cost and enhance transport capacity and safety. In recent years, CBTC systems have been a solution to train operation control system in many metro or light rail projects. Some existing metro and light rail lines in some major cities abroad have already been reconstructed by CBTC technology and CBTC systems have also been designed and adopted in urban rail transit in China. So the research and development of CBTC systems with our own intellectual property rights is urgently needed according to the development and application of train operation control system in urban rail transit in China, which is of practical significance for higher transport capacity and lower operation cost.This dissertation studies train operation control system in urban rail transit and focuses on CBTC systems and their critical technologies in order to provide the theoretical basis for CBTC systems developed by our country. The main contents of research are as follows:Firstly, a general analysis of CBTC systems is presented including the definition, composition, structure, advantages, IEEE Standards, principle, communication mode of the systems. The technologies of moving block, train positioning and bidirectional communications between trains and wayside equipment are regarded as critical technologies. The development trend of train control system in urban rail transit is also showed.Secondly, based on formalization modeling language Petri net, CBTC systems are modeled and simulated with CPN Tools. The simulation models of CBTC systems are created with Petri net in the aspects of the ground communication subsystem model of Data Communication System, model of on-board subsystem of Data Communication System(DCS), model of on-board subsystem of Automatic Train Protection etc. The simulation results of maximum delay of data transmission, relationship between standard deviation of mean delay and length of data frame and the speed control curve of ATP are showed in wired network on the ground of CBTC systems in urban rail transit. Thirdly, the modeling and simulation of the technology of moving block in urban rail transit is considered. On the basis of comparison among fixed block, quasi moving block and moving block, the problem of intervals control of train tracing has emphatically studied in the condition of moving block. The model of train tracing in stations and sections is created under the circumstances of moving block and quasi moving block and the calculation method of train tracing intervals with different signaling systems is provided and the determination of minimum intervals of train return is discussed. According to the fundamental characteristics of running vehicles in urban rail transit, the simulation for train tracing intervals is performed by MATLAB for further explanation for advantages of moving block.Fourthly, the method of train positioning based on wireless spread-spectrum technology is studied. Compared with various methods of train positioning used at present, the method of train positioning based on wireless spread-spectrum technology has many advantages. The fundamental theory of wireless spread-spectrum technology and positioning based on spread-spectrum technology is expounded and the configuration of positioning system based on spread-spectrum technology is given. The receiver of positioning system based on wireless spread-spectrum technology is designed in detail.Finally, the availability and safety of WLAN in CBTC systems is included. After the analysis of composition, features, transmission mode and related standards of WLAN, the security requirements and the model of wireless transmission system of WLAN in CBTC systems are provided and then the availability is analyzed. Under the discussion of the safety of WLAN, protocol of IPsec, implementation of IPsec in wireless network of CBTC, the safe design of data communication system of CBTC based on IPSec is presented, which has been tested and simulated. The result shows that WLAN based on the transmission medium of free space waves is completely available and it is feasible to adopt the protocol of IPsec for greater security of wireless DCS in urban rail transit.