Performance Monitoring Software Design Of Satellite Navigation Base Station For Railway Safety Application

As an important technical means of CTCS-4 train control system,satellite navigation and positioning can provide the information of train position and speed.In order to realize the active monitoring and evaluation of positioning performance in transit and further improve the accuracy and reliability of train positioning,China is gradually launching the research on the local reinforcement technology of train positioning,and developing a Ground-based Augmentation System(GBAS)composed of differential reference station and an enhanced service control center.In the face of complex railway scenarios,the integrity of satellite positioning system along the railway needs to be monitored.The difference correction information sent by the base station to the user may cause some deviation due to the satellite navigation system itself and the randomness of signal transmission,which will affect the final train positioning results,so it is particularly important to monitor the performance of the base station receiver.In this paper,the performance monitoring method of satellite navigation base station for railway safety application is proposed and the monitoring software is designed,which can detect and remove the faulty base station to ensure the accuracy of train positioning and the safety of train running.This method can be divided into single base station and multi base stations from the system point of view.The single base station performance monitoring consisting of signal power and ephemeris integrity link and the multi base station performance monitoring consisting of message monitoring and multi reference consistency detection are designed.From the receiving signal and data content of the receiver,the base station receiver is monitored and realized by building a visual software platform.The main contents of this paper are as follows:(1)This paper investigates the current situation of the Ground-based Augmentation System for railway and its integrity monitoring and base station performance monitoring,summarizes the performance monitoring indicators of the receiver,and determines that the main purpose of the base station performance monitoring is to detect the receiver fault.(2)The performance monitoring method based on single base station is designed.In this paper,the receiver fault detection is implemented from two aspects of signal power and ephemeris integrity.Different monitoring processes are made for different monitoring processes,and the threshold value of each monitoring index is calculated based on the Gauss overbounding method.For the signal power monitoring,according to different satellites and different normal distribution principles,the thresholds are injected into different sizes of faults in different time periods,experiments show that the threshold value of C/N and the threshold value calculated by 3? principle can effectively improve the detection ability.The detection ability is improved from two aspects: the classification of different satellite data and the use of different normal distribution principles in different time periods.Aiming at the integrity monitoring of ephemeris,the effective time of deriving satellite coordinates with old ephemeris is analyzed,and the monitoring methods for different situations of ephemeris not updated or incorrect updating are designed for software design.(3)The performance monitoring method based on multi base station is designed.In this paper,multi receiver fault detection is implemented from two aspects: message monitoring and multi reference consistency check(MRCC).Message monitoring mainly judges whether the output differential correction number of receivers exceed the preset limit value.At the same time,for multi base station redundancy,the feasibility of the algorithm based on Delaunay triangulation is verified.For multi reference consistency detection,the B-value is taken as the standard to detect the consistency of pseudo-range correction amount among receivers.The pseudo-range correction value data in RTCM protocol is obtained through simulation,according to the principle of multi base station network,different types of faults are injected based on different receiver layout.Experiments show that the detection algorithm for the layout of base stations with different network structure can effectively achieve fault detection.(4)Performance monitoring software suitable for single base station and multi base station is designed.Based on the Android Studio development environment,analyze the software requirements,build the software framework,and complete the software design based on the implemented performance monitoring algorithm of single base station and multi base station.The base station performance monitoring software designed in this paper realizes a complete monitoring system from single base station to multi base stations,a single base station monitoring subsystem from signal power to ephemeris data monitoring,and a multi base station monitoring subsystem from message monitoring to multi reference consistency check.The base station comprehensive monitoring system consists of two subsystems,which effectively detects the receiver fault.There are 89 pictures,17 tables and 66 references in this paper.