Research On Improvement Of Receiver Autonomous Integrity Monitoring Algorithm For GNSS Airborne Augmentation System

In recent years,with the widespread use and development of GNSS in various fields,the high accuracy and global reach of the GNSS system has brought great promise for both military and civil applications.When GNSS is the only means of navigation for the user,the reliability of the system needs to be improved to guarantee the required navigation performance.This thesis therefore presents an improved research and validation analysis of the autonomous integrity monitoring technology for airborne enhanced user-side receivers in integrity,as follows.(1)Firstly,the research background of the autonomous integrity monitoring technology(RAIM)for satellite-based navigation and positioning airborne receivers and the current status of domestic and international optimisation research on RAIM algorithms are introduced,and the principle of satellite-based navigation pseudo-range positioning and the error sources and correction theory of satellite-based navigation and positioning are briefly explained.Then the autonomous integrity algorithm for airborne augmentation receivers is studied,and the indicators and four accuracy parameters for algorithm performance evaluation are given.The traditional least-squares residual-based RAIM algorithm,parity vector-based RAIM algorithm and ARAIM algorithm are also introduced,and the advantages and disadvantages of these algorithms are analysed theoretically,leading to the goal of improvement: the weighted leastsquares RAIM algorithm.(2)The factors affecting the least squares RAIM algorithm are analyzed by simulation.The influence of visible stars and cut-off altitude angle factors on the horizontal protection level of RAIM algorithm is verified.The characteristic slope factor of the satellite corresponding to the satellite altitude angle is studied,and the influence of the satellite characteristic slope factor on the positioning is explored through simulation,which illustrates the rationality of the satellite characteristic slope factor participating in the weighting improvement of the least squares RAIM algorithm.(3)The fault detection situation before and after the improvement of the weighting method of the least squares RAIM algorithm is compared through experiments.After the satellite altitude angle factor participates in the weighted improvement,a new test statistic is constructed.The fault detection of the algorithm before and after the improvement in 600 epochs is compared,and it is preliminarily proved that the improved algorithm is better than the traditional algorithm.(4)The performance of the algorithm before and after the improvement is compared and verified by using the fault detection rate and availability parameters.The simulation results show that the improved algorithm improves the performance of the RAIM algorithm compared with the conventional algorithm.In this paper,an improved research on the autonomous integrity monitoring algorithm of the airborne augmentation system receiver is carried out.Aiming at the shortcomings of the existing least squares RAIM algorithm,an improved weighted least squares RAIM algorithm is proposed by introducing the satellite altitude angle as a consideration factor,and compared the fault detection effect,fault detection rate and the performance of the availability level protection level before and after the algorithm improvement through the measured data,and concluded that the performance improvement effect of the new algorithm is more obvious.