Research On Airborne Integrity Monitoring Of DGNSS/INS Integrated Precision Relative Positioning For Shipboard Landing

Taking shipboard landing applications as the research background,aiming to meet the strict navigation quality requirement for precise approach and landing of aircraft,this dissertation has emphatically developed a DGNSS/INS integrated precise relative positioning method with high output rate and low broadcast rate,integrity monitoring method for carrier-phase-based precise relative positioning,integrity monitoring method for DGNSS/INS integrated precise relative positioning and carried out the research on verification of navigation quality requirement.Besides,numerical simulation experiments and ex-post simulation experiments of real-time process based on the data from field tests have also been carried out.On one hand,GNSS/INS numerical simulation experiment system for shipboard landing is developed mainly for the verification of integrity risk,continuity risk and avalibility based on supercomputer and parallel computing technology.On the other hand,vehicle-to-vehicle,UAV-to-boat field tests and ex-post simulation experiments of real-time process have been carried out for evaluating accuracy,real-time performance and applicability of the proposed methods.The main research results and conclusions are as follows:（1）A DGNSS/INS integrated precise relative positioning method with high output rate and low broadcast rate has been studied.Firstly,to solve the problem of high broadcast rate,poor real-time performance and heavy computation burden in high-output-rate carrier-phase-based precise relative positioning,the DGNSS/INS integrated precise relative positioning method is proposed,which combining the advantages of high accuracy of carrier-phase-based relative positioning and high output rate of tightly coupled GNSS/INS positioning.And then,the influence of broadcast rate and sampling rate of moving base on the prediction of position increments is analyzed based on two types of field tests with simple straight movements and complex turning movements respectively.The results show that as for moving base with frequently turning movements,under the condition of fixed sampling rate of GNSS measurements,increasing the broadcast rate of position increments of moving base can improve the prediction accuracy obviously.Fortunately,as the amount of position increment data is relatively small,appropriately increasing the broadcast rate will not increase data broadcast volume in unit time obviously,which is named bit rate.Finally,the results of vehicle-to-vehicle and UAV-to-boat field test show that compared to the method that obtaining 10-Hz-output-rate relative positions by solely carrier-pahsed-based precise relative positioning,the proposed method can not only provide 125-Hz-output-rate relative positions with centimeter-level accuracy but decrease bit rate and sampling rate of GNSS measurements largely,which can reduce data communication pressure,computation burden and device power consumption greatly.In vehicle-to-vehicle and UAV-to-boat field test,the maximum reduction of bit rate can reach 83.12%and 97.61%respectively and the sampling rate of GNSS measurementsof rover and moving base can also be reduced from 10 Hz to 1 Hz.Besides,the proposed method can also overcome the adverse impact of latency well and can tolerate the packet drops.（2）An integrity monitoring method for carrier-phase-based precise relative positioning has been studied.In carrier-phase-based precise relative positioning under fix-and-hold mode,if ambiguities are fixed correctly,cycle slips of carrier phase will be the main object of integrity monitoring.Firstly,a cycle slip detection and elimination method is proposed for double-differenced cycle slip between satellites and receivers.Next,a analytical method for posterior variance of carrier phase of single channel based on expected acceptable region is proposed.The methods to obtain integrity risk of inside and outside expected acceptable region under least squares projection with multiple carrier phase channels and comprehensive integrity risk of relative positioning are deduced further afterwards.In the end,a analytical method for continuity risk based on given false alarm rate is proposed.The results from numerical simulation experiment of shipboard landing show that the proposed method can not only effectively ensure the conservatism of integrity risk but ensure that all of accuracy,integrity risk and continuity risk of single epoch in the process of approach and landing can meet strict navigation quality requirement which only needs to know the whole probability of cycle slip or the probability of small cycle slip.At the same time,105000 independent repeated simulation experiment of shipboard landing under bad environment parameters are carried out based on parallel computing technology to validate the conservatism of theoretical integrity risk of single epoch.Combing with the results of simulation experiment of shipboard landing under normal environment parameters,it can be proved that the proposed method can meet the integrity risk requirement.The results from comparison with standard RAIM and advanced RAIM show that both of integrity and continuity of the proposed method are better than that of standard RAIM and advanced RAIM in single simulation experiment under normal environment parameters;the proposed method can reach 100%avalibility under BDS,GPS and BDS+GPS joint system and has excellent real-time performance in the 1000 simulation experiments covering all day at the same beginning position,especially when there are a large number of visible satellites the advantage of real-time performance will be more obvious.Compared with advance RAIM,the proposed method can decrease the mean computation time by 58.50%under BDS+GPS joint system.In the comparison of avalibility of the world during all day,SRAIM is unavalible and the region which can can reach the requirement of avalibility at 99.7%under BDS or GPS conditions of the proposed method is larger than that of ARAIM at 17.06%and 19.95%respectively.（3）An integrity monitoring method for DGNSS/INS integrated precise relative positioning has been studied.Firstly,in order to reduce difficulties to analyze integrity risk,the specific positioning algorithms of DGNSS/INS integrated precise relative positioning are selected and optimized as follows:1)adopting continuous mode for carrier-phase-based relative positioning;2)adopting the combination of integer Bootstrapping method and consistency test of multiple epochs for ambiguity resolution;3)adopting optimization strategy between float position solution and fixed position solution for the output position;4)analyzing integrity risk of carrier-phase-based relative positioning based on error characteristics of float position solutions.Next,analytical method of comprehensive integrity risk in DGNSS/INS integrated relative positioning is deduced based on error equations of integrated relative positioning and definition of integrity risk.The comprehensive integrity risk is divided into two parts conservatively which is integrity risk of carrier-phase-based relative positioning and tightly coupled GNSS/INS positioning.On this foundation,analytical methods for integrity risk of two independent parts are developed based on the characteristics of relative positioning under continuous mode and the analytical method for posterior variance of carrier phase of single channel based on expected acceptable region.Besides,on the basis of the analytical method of continuity risk based on fixed false alarm rate,a novel analytical method of continuity risk based on the varation of GDOP is proposed,which can effectively decrease the computation time.Finally,in order to compare with the required integrity risk and continuity risk in total period,the integrity and continuity risk in standard approach time（150 s）is predicted based on the method of moving window,which can ensure to carry out the integrity monitoring all the time.The results from numerical simulation experiment of shipboard landing show that accuracy,integrity risk and continuity risk during approach and landing can meet the strict navigation quality requirement and real error of carrier-phase-based relative positioning and tightly coupled GNSS/INS positioning can be enveloped by 3-times theoritical posterior standard deviation,which directly reflects the conservatism of theoritical posterior variance of positioning error.In order to validate the conservatism of theoretical integrity risk,105000 independent repeated simulation experiment of shipboard landing under bad environment parameters are carried out based on parallel computing technology.Combing with the results of simulation experiment of shipboard landing under normal environment parameters,it can be proved that the proposed method can meet the integrity risk requirement of10^-7/150s.In order to validate requirement of continuity risk,1040000 independent repeated simulation experiments of shipboard landing under normal environment parameters are carried out,which proves that the requirement of continuity risk of2×10^-5/150scan also be met.In order to reflect the influence of satellite geometry,1000 numerical simulation experiments are carried out at every grid point（8×10,latitude multiply longtitude）of global grids covering 24h of all day to obtain avalibility and provide global avalibility map.The results show that under the condition of single system,the region which meet avalibility requirement of 99.7%is relatively small and scattered under GPS while relatively large and concentrated under BDS;Most of regions around China can meet avalibility requirement of 99.7%under BDS;All regions of the world can meet avalibility requirement of 99.7%under joint system of GNSS.In order to evaluate accuracy,real-time performance and applicability of the proposed methods under real-time data,ex-post simulation experiments of real-time process based on the data from vehicle-to-vehicle and UAV-to-boat field tests are carried out.The results show that centimeter-level relative positioning accuracy can be achieved in two kinematic-to-kinematic field tests;integrity risk and continuity risk can meet the strict requirement;real error of carrier-phase-based relative positioning and tightly coupled GNSS/INS positioning can be enveloped by 3-times theoritical posterior standard deviation;the proposed mehod has excellent real-time performance and applicability.（4）A verification method for high integrity requirement is studied,while numerical simulation experiments and ex-post simulation experiments of real-time process based on the data from field tests have been carried out to evaluate the performance and validate the navigation quality requirement of the proposed methods.DGNSS/INS numerical simulation experiment system for shipboard landing is developed.The system can not only carry out simulation experiments for GNSS or GNSS/INS integrated positioning,but also can be applied in parallel computation and ex-post simulation experiments of real-time process.The requirements of integrity,continuity and availability are validated mainly by a large number of numerical simulation experiments based on the system.A novel validation method based on the invariance of conservatism is proposed for high integrity validation.The method can effectively decrease times of simulation experiments from10⁸ to10⁵.In ex-post simulation experiments based on data from field tests,reference for relative positioning under kinematic-to-kinematic conditions is easy to be obtained and multiple times of experiments can be carried out based on the data from one field test.Focusing on the validation of accuracy,real-time performance and applicability of the proposed method,vehicle-to-vehicle and UAV-to-boat field tests have been carried out based on DGNSS/INS integrated relative positioning system and the process of shipboard landing is simulated in ex-post simulation experiments.