Research On Integrity Monitoring Technology Of Multi-GNSS Receiver

With the rapid development of Global Navigation Satellite System(GNSS),the research on satellite navigation technology has made great progress,and it has been used in many fields,such as transportation and navigation,etc.and it can meet the precision requirements of most users.However,GNSS positioning accuracy,usability and integrity have been put forward higher requirements in some areas involving life safety,such as navigation and aviation,It makes the research of GNSS integrity important.In recent years,the number of GNSS satellites has increased significantly,which provides favorable conditions for the study of integrity.Therefore,multi-GNSS receiver navigation technology has become a research hotspot.In order to make the positioning accuracy,usability and integrity of satellite navigation meet the application requirement of special industries involving life safety,this paper has carried out research on the multi-GNSS Receiver Autonomous Integrity Monitoring(RAIM)technology.This paper mainly analyzes the basic principles of the RAIM algorithm and introduces the processing flow of RAIM algorithm for multiple constellations satellites detection and identification,The availability of RAIM algorithm is analyzed by using horizontal protection level(HPL).Under the condition of satisfying the availability of RAIM algorithm,the detection and identification of multi-constellation single-fault and multi-fault are realized.In this paper,the robustness of M estimation is used,and the RAIM algorithm based on M estimation is designed to realize the detection and identification of faulty satellites.Aiming at the characteristics of M estimation are susceptible to initial value error,an improved RAIM algorithm based on M estimation is proposed.According to the residual theory,the algorithm first removes some satellites with large gross errors,and then calculates the initial value,which reduces the influence of the gross error on the initial value.The Huber method and the Danish method are used as the weight function to verify the simulation.The results show that the improved algorithm is better than the original algorithm in multiple faulty satellites detection.In addition,the RAIM method of random search is studied.Aiming at the high complexity of the binary code search method in this algorithm,an algorithm to improve its search mode is proposed.It can be seen from the simulation comparison that the computation of improved algorithm is reduced by about 10%compared with the computation of original algorithm;when the gross error is less than 50 meters,the fault recognition rate and positioning accuracy are also significantly better than the original algorithm.In order to verify the effect of RAIM in the actual software platform application,according to the requirements of multi-GNSS integrity monitoring,the GPS/BDS dual-mode receiver integrity monitoring software is designed and implemented.The software has the functions of baseband signal processing,positioning solution and integrity monitoring.It can effectively monitor and eliminate faulty satellites and solve reliable positioning results under the condition of satisfying the availability of RAIM algorithm.The software implements three RAIM algorithm integrity monitoring functions,which are controlled by human-computer interaction interface.The least square residual RAIM algorithm can be used to detect and identify single-fault respectively,and the improved RAIM algorithm based on M estimation is used to detect and identify Multi-fault,and the improved random search RAIM algorithm is used to detect and identify Multi-fault.