Research And Design Of Tram Positioning System Based On GPS

With the development of urban railway transit, tram is becoming very important public transport, and modern tram based on car-car communication walking in the forefront of tram. In order to realize the tram control system, the tram need precise positioning to run and schedule. So, the paper propose a method of integrated positioning based GPS/INS/RFID. Through information fusion algorithm, the system can output positioning data that can satisfy the system error range, which can lay the foundation for the tram.The system consist of six parts:master control module, GPS module, INS module, RFID module, information module, and GPRS module. The master control chip is ARM CPU with FPU based on Cortex M4, and design the clock circuit, reset circuit, JTAG interface circuit. The GPS module choose NEO-6M receive module which designed by U-BLOX. We can get date, velocity, latitude and longitude, speed and heading angle by parsing the navigation message from GPS receiver. The INS module choose inertial components, include three-axis accelerometer ADXL345, three-axis gyroscope ITG3205, and magnetometer HMC5883L. The data from inertial components can update attitude matrix through quaternion algorithms. Then compute the velocity, latitude and longitude by attitude matrix. RFID module can get electronic tag’s number beside the railway through ultra-high frequency read/write device. Then query the corresponding location information in database. The data can replace the GPS data and update INS’initial position. In order to reduce the error of INS, information module can fuse the GPS and INS’data to modify the INS through Kalman filter algorithm. GPRS module choose SIM900A as data delivery module, it can connect the server by AT instruction. The data include date, velocity, latitude and longitude, speed and so on. The data send by GPRS can be shown on the map of server. The position accuracy can be limited in the error range after testing, and realize the function of integrated positioning system.The integrated positioning system is the foundation of train supervision and computing the protective curve to monitor the tram on real-time. The test result shows that the system can locate the tram when the GPS’signal is lost. This can lay the foundation for tram’s monitoring and control.