Modeling And Security Analysis Of Speed And Position Determination System In Metro Train Based On SCADE

In the urban rail transit, the speed and position determination system is the key subsystem of on-board equipments in train control system. It detects train speed and current position in real-time, and the data detected is used for the calculation of train movement authority. The safety and efficiency of train operation is affected directly by the accuracy and reliability of the speed and position determination system. Recently, model-based software development is gradually approved in safety-critical system. Safety critical application development environment (SCADE) provides certification and solutions for safety-critical system and software developers. The model-based software development mode, built-in simulator and design verifier of SCADE ensure the functionality and safety of the system. This paper analyzed the speed and position determination system, and on the platform of SCADE, the models are established and verified.The main work of this paper is as follows:1、The safety critical system and related developement methods of the urban rail traffic control system is researched. An analysis on the advantages of model-based developement method is given. And a detail description of safety critical application development environment (SCADE) is shown.2、According to the function features of the speed and position determination system, the paper divides the speed and position determination system into four subsystems. They are wheel diameter correction subsystem, initialization subsystem, train location calculation subsystem and train failure management subsystem. Then a detail analysis and modeling methods of each subsystem is given.3、In order to improve the safety of the speed and position determination system, according to the rail specification 1474.3, the paper uses the data flow diagram and secure state machine modeling mechanism of SCADE to model the four subsystems of the speed and position determination system based on clear and unambiguous theoretical. And through the subsystem interface, the whole speed and position determination system is established.4、According to the build-in logical operation formulas and the intermediate data generated by model running, the paper uses the simulation and verification tools of SCADE to verify the function and safety of the model. And through verifying the results of logical operation, it is proved that the model meets the functionality and security requirements of speed and position determination system.5、After the model security is verified, the paper uses Deductive Cause-Consequence Analysis (DCCA) to analyze the failure modes which cause damage to the speed and position determination system. In order to provide the basis for the design of high-security systems, based on the verifier tools of SCADE, the paper finds the minimal critical set which causes damage to the speed and position determination system.6、Because of the advantages that SCADE KCG passed the rail EN 50128 SIL 3\4 class certification and embeded source code can be automatically generated from requirements specification in SCADE, the paper uses KCG to generate high quality and safety C code so that the module established in this paper can be applied directly to the engineering products.