Research On Subway Train Positioning System Based On Inertial Navigation/geomagnetism

With the rapid development of urban rail transit,subway travel has become the most convenient and important mode of transportation for common urban residents.In recent years,many subway train rear-end collisions have also exposed the safety problems are still existing in urban rail transit.At present,Communication Based Train Control(CBTC)system is widely used in most metro safety control systems in China,and the train positioning technology is the basis for the stable operation of the system.The railway positioning technology of domestic mainstream,such as track circuit and inter-track cable,has the problems of complicated equipment laying,high cost and tedious later maintenance.Therefore,in order to provide a low-cost and effective solution for train positioning,this paper proposes a subway train positioning system based on strapdown inertial navigation and geomagnetic.Firstly,this paper introduces the working principle of strapdown inertial navigation system and the basic principle of geomagnetic attitude measurement,including the establishment of coordinate system,the calculation flow of strapdown inertial navigation,the installation of magnetic sensors and the principle of attitude measurement.In particular,the error source and compensation method of geomagnetic measurement are analyzed.Then the data of the two types of sensors are fused and combined,and the real-time attitude information of the train is solved by the complementary filtering method.Then,according to the attitude angle,the output of accelerometer is decomposed and a Kalman filter for train positioning is designed.Especially considering the known characteristics of track fixing in Metro operation,this paper studies how to extract the characteristic information of track,and adds this priori information to the state equation of the system.It also constrains the state vector,and deduces the Kalman filter equation with constraints.Next,the development platform of Metro positioning system is built,including hardware platform and software program design.In the aspect of hardware,the device selection and performance of each module of the hardware are explained.In the software part,the driver program is designed according to the hardware platform.On this basis,the sub-programs of other functional modules of the system are designed,including communication subroutine and train positioning subroutine.Finally,the train positioning system is debugged and verified for its communication performance,calculation speed and positioning effect.The accuracy and stability of the proposed algorithm using the track constraints of strapdown inertial navigation and geomagnetic combination is verified by experiments and comparisons with the SINS location solution.This paper is a pioneering exploration for the method of metro train positioning.