Research On Quick Positioning And Robust Velocity Estimation Technology Of Satellite Navigation Receivers In The Challenging Environment

Currently,the constellation deployment mission of the BDS-3 basic system has been completed.By the end of 2018,it will officially provide navigation services to those countries and regions alongside the “Belt and Road”.With the rapid development of satellite navigation systems represented by BeiDou,for users of satellite navigation receivers,there are increasing requirements for the quality of positioning and velocity estimation services.However,in challenging environments such as weak signals and frequent occlusions,incomplete broadcast ephemeris and incomplete observations can increase the time taken for the satellite navigation receiver to complete positioning.Moreover,in challenging environments such as weak signals and high dynamics,the observations with gross errors and large deviations can reduce the robustness of the navigation receiver's velocity estimation.In order to improve the user experience of satellite navigation receivers in challenging environments,this thesis focuses on the quick positioning and robust velocity estimation technology of satellite navigation receivers in challenging environments.The contents and the potential innovations of this thesis are as follows:(1)To solve the incomplete reception of the navigation message and extented time to first-fix(TTFF)of the BeiDou terminal in the weak signal environment,and to propose a self-assisted first-fix method for the BeiDou terminal based on the mediumand long-term ephemeris extension.For the self-assisted first-fix method proposed in this paper,the medium-and long-term extended ephemeris of the BeiDou MEO/IGSO satellite is used in the first-fix,and the real-time broadcast ephemeris of the BeiDou GEO satellite is also used.The simulation results show that the self-assisted first-fix method based on the medium-and long-term extended ephemeris of BeiDou navigation satellite has a positioning error of about 12 meters in the two-dimensional horizontal direction and a positioning error of about 25 meters in the three-dimensional direction,the corresponding time to first-fix is about 8?14 seconds.Besides,compared to the BeiDou terminal based on the real-time broadcast ephemeris,the time to first-fix is reduced by about 20 seconds,which increases the speed of the standalone positioning in the weak signal environment.(2)To reduce the dependence of the coarse-position-free coarse-time positioning algorithm based on the elevation information assisted 3 satellites' code phase ambiguity resolution on the elevation information,and the extended time of coarse-time positioning,a coarse-position-free coarse-time positioning algorithm based on 4 satellites' mixed-type code phase ambiguity resolution is proposed.In the proposed coarse-time positioning method,a coarse position estimation method based on 4 satellites' mixed-type code phase ambiguity search is used.This method does not require any external auxiliary position information to complete the coarse position estimation.Based on real observation data and dynamic simulation observation data,the experimental results show that,under the condition of no external elevation information assistance,when the coarse time deviation is within 30 s,the success rate of the coarse-position-free coarse-time positioning is over 97%.When the coarse time deviation is within 5 s,the coarse-time positioning success rate is 100%.The experimental results also show that,for some BeiDou satellites' navigation signals are completely occluded,the proposed coarse-time positioning method can be used to resolve the correct code phase ambiguity and still maintain a high success rate of coarse-time positioning.(3)In the terrestrial navigation application,problems such as frequent occlusion of navigation signals and signal attenuation are frequently happened,causing the number of visible satellites to change drastically and the corresponding observation noise being non-Gaussian,and the occurrence of gross error within the observation.The velocity domain selective-fusion adaptive robust UKF standalone velocity estimation method is proposed.The actual experimental results show that the proposed method can cocurrently solve the problem of numerical instability of UKF filtering algorithm with positioning and velocity estimation.Moreover,the influence of cycle slip and gross error on carrier phase derived Doppler observation can be suppressed by robust filtering.The fusion of filtering results can improve the robustness of the standalone velocity estimation filtering solution.(4)For the navigation terminal,the large velocity estimation deviation error will occur,using the carrier phase derived Doppler standalone velocity estimation method under high dynamic conditions.To solve this problem,a method improving the robustness of navigation filtering based velocity estimation under high dynamic conditions is proposed.This method uses the raw Doppler robust least square method to assist sequentially robust IMM-STF standalone velocity estimation method.The algorithm can improve the robustness of the carrier phase derived Doppler standalone velocity estimation.Based on the high dynamic real experiment of BeiDou terminal,the evaluation of the performance of the standalone velocity estimation method is carried out.The experimental results show that the horizontal velocity estimation error of this standalone velocity estimation method is about 0.05 m/s under high dynamic conditions and the three-dimensional velocity estimation error is about 0.09 m/s.Under high dynamic conditions,the standalone velocity estimation error of the proposed method can be kept on the order of several cm/s or lower.Finally,the key findings of the thesis are summarized,the application of the research results in engineering is listed,and the work to be carried out in the future is prospected.