The Position System Based On Scade Design And Validation

In recent years, with the progress of urbanization construction in our country, the population in cities is growing faster and faster, and following the increasing of the private cars, the traffic jam phenomenon is becoming more and more serious. Practice has proved that the construction of urban rail transit has very effected to the traffic congestion, and new railway traffic control technologies are needed to meet the need of the faster and more intensive operation of urban rail transit.The train position determination system which is an important part of urban rail transit train automatic control system is one of key equipments of train-borne ATP, its safety and accuracy are two key parameters for the speed and position determination technology, which directly affect the safety and efficiency of train operation. According to the characteristics of the urban rail transit, this paper adopts the pulse speed sensor and acceleration sensor to design the train localization algorithm. This algorithm determines the rain current operation state by comparing the speed data obtained respectively from speed sensors and acceleration sensor, and then the train travel distance is calculated, meanwhile the balise is setted to revise the train location information and measuring error. The measuring error of speed and acceleration sensors, calculation error when slide and spin occurred, abrasion of wheels are the main errors of train speed and position determination system. This paper designed the wheel diameter adjusting module and analyzed the detection and error compensation of spin and slide states based on fail-safe concept.Safety-Critical Application Development Environment (SCADE) is suitable for the development of embedded software with high safety requirements. SCADE have data flow graph and safety state machine two modeling mechanisms, which provides modeling, test and formal verification methods for continuous and discrete systems and can improve highly the quality and efficiency. Speed and position determination system is a typically safety-critical system.This paper established the speed and position determination model based on SCADE, and the coverage analysis is done using masking MC/DC to improve the simulation test of the model. According to the safety requirements of train speed and position determination system, safety properties model has been established in SCADE and the model checking of formal verification technology is used to verify the safety properties of the model, and the result shows the model fully meet the safety requirements.