Research On Communication Subsystem Of Distributed Object Controller In Train Control System

The rapid development of high-speed railway and urban rail transit has put forward higher requirements on train control system.The development of communication technology and the improvement of computer processing capability provide technical foundation for further reducing the operation interval,simplifying ground equipment and saving the cost of construction and maintenance.The object controllers in train control system are the important ground equipment in the next generation of train control system.They are the execution units of trackside signal equipment,controlling the signal equipment switching and transforming,meanwhile,they undertake the task that is executing command information and getting status of signal device.The correct communication of them plays an important role in the safe operation of train.Therefore,aiming at the characteristics of distributed object controller in the next generation of train control system and its demand,a design method of communication subsystem for distributed object controller was proposed.First of all,the structure of the next generation of train control system was analyzed.Then the communication requirements of distributed object controller were confirmed.Based on those requirements and the design principle of train control system,two architectures of distributed object controller communication subsystem were designed,which were,pure wireless structure and stratified architecture of internal and external networks.Then,the theoretical analysis of these two architecture were carried out by using deterministic and stochastic Petri nets theory,thus the reliability and real-time parameters of the two solutions were obtained.And combined with other aspects of stability,safety and other considerations,the internal and external network hierarchical architecture was taken as the structure of distributed object controller communication subsystem.Secondly,a distributed communication bus with time triggered architecture was designed for the internal network of distributed object controller communication subsystem.Based on the OSI model,the bus was designed hierarchically and the OC management and link layer protocols were designed.Based on the study of Precision Timing Protocol,an improved clock synchronization algorithm was proposed to adjust the network delay online.In the aspect of real-time scheduling,combining with the segmentation and priority algorithms,an improved scheduling algorithm based on the round robin scheduling was proposed to realize the deterministic transmission of event information under the time-triggered structure.At the same time,the scheduling table was adjusted online to satisfy the requirements of the network communication.Finally,an experimental platform was set up for the designed internal network.The performance of the internal network communication delay was tested and verified in the environment of simulating the external network.The test results showed that the internal bus can send and receive data within the scheduling cycle.At the same time,it was indicated that in a scheduling cycle of the internal bus,when the number of object controllers which communication at the same time increases,the increase of the total communication delay of the communication subsystem is mainly affected by the communication delay of external network.Meanwhile,the function of the internal network was tested,the test results showed that the time-trigger bus meet the requirements of the design.