Research On Optimized Algorithm Of BD Satellite GBAS Integrity Monitoring

The precision approach landing in the civil aviation approach phase is a critical phase throughout the flight process and requires a reliable navigation system to provide tighter positioning performance requirements.The Ground-Based Augmentation System(GBAS)is a satellite navigation augmentation system that provides real-time and reliable high-precision positioning services for aviation users.It is the future development direction of civil aviation navigation systems.GBAS integrity indicates the ability of the system to alert in time when the navigation system fails or the system error exceeds the maximum allowable limit.It is an important indicator for verifying and evaluating the reliability of the navigation system.At present,China's Beidou satellite GBAS system only meets the precision approach class I(CAT I)navigation performance service,and there is still a big gap between the US LAAS and the high-precision navigation service for the precision approach phase.Therefore,in order to improve BDGBAS to meet the precision approach CAT II/III navigation performance,this thesis studies and improves the integrity monitoring performance of the BDGBAS.The main research contents and innovations are as follows:1.The characteristics of BDGBAS carrier phase smoothing pseudorange correction technology are analyzed in detail.The influence of ionosphere gradient on GBAS smoothing pseudorange error is deeply explored.It is proposed to suppress the ionosphere delay to smooth the pseudorange band by calculating the optimal smoothing time constant.The discrete effects came from and the data simulation analysis was carried out.2.The multi-reference consistency monitoring and ionosphere gradient anomaly monitoring of the BDGBAS ground end integrity monitoring system are discussed and studied.The detection algorithms of the traditional corresponding monitoring modules are discussed in detail and their defects are analyzed.The adaptive Kalman filter is the core monitoring algorithm,which can detect ionosphere anomalies in time,solve the correlation problem of traditional multi-reference consistency monitoring,and more accurately judge and eliminate response faults.3.The calculation of vertical protection level under the condition of non-ideal error distribution on the airborne end is studied.The influence of non-Gaussian distribution error on vertical protection level and user positioning accuracy is analyzed,which makes the vertical protection level more in line with the actual monitoring level of the system.