Research On High Precision Positioning Key Technologies Of Beidou/Inertial System In Multipath Environment

With the development of Beidou satellite navigation system,its application has penetrated into various fields.So higher requirements for its accuracy and stability is needed.In the actual application environment,frequent multipath will interfere with the receiver's operation and reduce its positioning accuracy.The accuracy of positioning using the carrier phase measurement value is higher than pseudorange measurement.However,there exists integer ambiguity in the carrier phase measurement.Therefore,the speed and accuracy of solving integer ambiguity is important for improving the positioning accuracy.This paper studies the multipath elimination algorithm and the solution of the integer ambiguity,and proposes improved wavelet transform,EMD algorithm and improved MEDLL algorithm to eliminate multipath effect,improved LAMBDA algorithm,carrier smoothing pseudorange and inertiaassisted method to solve integer ambiguity.And these algorithms are verified in the Beidou/inertial tight combination system.Firstly,the inertial navigation system,satellite navigation system and satellite/inertial combination system are introduced.The advantages and disadvantages of satellite/inertial integrated navigation system and different combinations are analyzed.The sources of error are discussed.A multipath signal model is established based on the characteristics and causes of the multipath signal.A multipath Simulator is introduced to analyze the characteristics of multipath signals and their influencing factors,which provides an important idea for the research of multipath elimination algorithm.Then according to the characteristics of multipath effect,this paper classifies the principle of multipath elimination algorithm from 4 aspects: satellite signal design,receiving antenna design and location,digital signal processing method,and navigation and positioning.This paper focuses on the latter two methods,and deeply studies the narrow correlation technique,wavelet denoising,EMD,MEDLL technology,and proposes a semi-soft threshold wavelet and improved MEDLL technology,and simulation verification.In order to further improve the positioning accuracy,this paper discusses the solution method of the integer ambiguity,aiming at the most widely used LAMBDA and carrier smoothing pseudo.The method of distance and inertia assisting is deeply studied.It is proposed and verified that the improved LAMBDA method,the carrier smoothing pseudorange and the inertial aid method of tri-frequency measurement combination can significantly improve the positioning accuracy.Finally,3 groups of comparative experiments were carried out,including the presence/absence of multipath interference experiments,RTK/IF sampler experiments in multipath environments,and BDSim/IGS comparison experiments.Experimental results show that the proposed algorithm can effectively improve the positioning accuracy of BDS/inertial system in multipath environment.