Research On Realtime Airborne ARAIM For Precision Approach Of Civil Aviation

In recent years,with the rapid development of GNSS(Global Navigation Satellite System),satellite-based navigation has been widely used in civil aviation and other fields related to human life safety.In civil aviation,as the reliability of the navigation solution is directly related to the safety of the passengers and the flight crew,ICAO(International Civil Aviation Organization)demands strict performance requirements for the navigation system.PBN(Performance Based Navigation)of ICAO specifies the navigation performance requirements with accuracy,continuity,integrity,and availability.Integrity is the ability of the navigation system to alarm the users in time when the performance of the navigation system fails to meet the demanding performance requirements,which represents the reliability of the navigation system.For the GNSS navigation system,integrity is the most difficult to meet,which is also an important factor hindering its further extensive application.As the GNSS navigation system is not always able to meet the integrity requirements of the precision approach in civil aviation,it is necessary to study the integrity monitoring method of the navigation system.Integrity is an important indicator of the reliability or correctness of positioning results obtained by the navigation system.GNSS RAIM(Receiver Autonomous Integrity Monitoring)and ARAIM(Advanced RAIM)algorithms are widely used to evaluate the integrity of the civil aviation GNSS navigation system.With the support of the project "C919 aircraft internal data communication network,satellite navigation application and EWIS airworthiness certification technology" of Airworthiness Certification Center and the project “Research on integrity monitoring of multi-constellation satellite navigation” of Honeywell,this dissertation focused research on the integrity monitoring technology to meet the precision approach requirements of civil aviation.In this dissertation,we conduct research on GNSS ARAIM and GNSS/INS ARAIM.We lay emphasis on the study of the methods to improve the performance of GNSS ARAIM and the methods to reduce the computational load of GNSS/INS ARAIM.On this basis,a no-subset GNSS/INS ARAIM is proposed.The main contents include the following four aspects:1.As the integrity performance of GNSS alone ARAIM can not always meet the integrity requirements of LPV-200(for certain areas and time),this dissertation proposed a position estimator to improve the integrity and availability performance of GNSS ARAIM at the expense of a little positioning accuracy performance and presents the ARAIM based on this estimator and its performance.2.As GNSS alone ARAIM is not able to meet the integrity requirements of precision approach(like CAT-I),this dissertation conducted research of GNSS/INS ARAIM.After studying the current GNSS/INS ARAIM,we found that the nominal bias was not considered in the current GNSS/INS ARAIM,which will result in that the integrity risk obtained by the ARAIM can’t bound the real integrity risk.Based on this fact,the dissertation proposes a GNSS/INS ARAIM method with the nominal bias considered,in which the influence of the nominal bias on the integrity performance is evaluated.At the same time,with the increase of available satellites,the continuity risk of navigation system rises.Aiming at this problem,this dissertation proposed a fault exclusion method for the GNSS/INS ARAIM.After the fault detection test failing,the proposed fault exclusion method can find out and remove the failing satellite accurately and continue to provide navigation services,which improves the continuity of navigation system.In order to bound the real integrity risk,the integrity evaluating method divides the fault exclusion subsets into two groups:correct fault exclusion and wrong exclusion,which is able to make the integrity risk bound the real integrity risk.This dissertation presents an integrity evaluating method after fault exclusion.3.In order to reduce the computational load of GNSS/INS ARAIM,a subset-reduced GNSS/INS ARAIM is provided.As the GNSS/INS ARAIM is based on MHSS,its fault detection and fault exclusion method need a high computational load.Based on the analysis of the algorithm design of ARAIM and the subset-reduced method for GNSS alone ARAIM,combined with the information provided by INS,this dissertation proposes a subset-reduced GNSS/INS ARAIM algorithm.The purpose of this algorithm is to reduce the number of fault subsets and the computational load at the cost of a little integrity performance.To take full use of the data from INS,this dissertation redesigns the fault detection exclusion method of the ARAIM.In the fault detection method,a fault detection test with the residual statistics of predictive state estimation is added.In the fault exclusion test,the dissertation proposed subset-identified statistics as the fault exclusion statistics.At the same time,this dissertation also presents the integrity evaluating method based on this fault detection and exclusion test.4.In order to further reduce the computational load of GNSS/INS ARAIM,a no-subset GNSS/INS ARAIM algorithm is proposed.The computational load of RAIM based on pseudorange residuals is low,while the fault detection area of the MHSS-based ARAIM is much closer to the optimal integrity fault detection area for most fault models.After analyzing the characters of these two methods,with the aid of aviation-class INS,a non-subset GNSS/INS ARAIM is proposed.At the cost of a little integrity performance,the nonsubset GNSS/INS ARAIM reduces the computational load greatly.With the help of aviation-glass INS,the integrity performance of the no-subset GNSS/INS ARAIM can still meet the integrity requirements of CAT-I precision approach.The key technologies and innovations of this paper are as follows:1.Aiming at the problem that the performance of GNSS ARAIM is not always able to meet the integrity requirements of the precision approach in civil aviation,this paper provides a position estimator that is able to improve the integrity performance of GNSS ARAIM.Based on this position estimator,the GNSS ARAIM can obtain better integrity and availability performance.2.Aiming at the continuity risk increase of multiple constellations GNSS navigation system,a fault exclusion method is proposed for the GNSS/INS ARAIM.The proposed method can reduce the continuity risk by identifying and excluding failing satellite accurately.A integrity evaluating method on the above fault exclusion method is also proposed.3.To cope with the high computational load of the GNSS/INS ARAIM,a subset-reduced GNSS/INS ARAIM and a no-subset GNSS/INS ARAIM are proposed.With the aid of aviation-glass INS,these two methods are able to reduce the computational load greatly while holding the ability to meet the integrity requirements of precision approach.