Research On GPS/AHRS Integrated Navigation Positioning Method Based On PPP

Precise Point Positioning(PPP)is a precise absolute positioning technology.PPP technology uses a single receiver to receive satellite data,and makes use of International GNSS Service(IGS)to provide precise satellite products to accurately correct various observation errors,so as to obtain afterwards cm-mm and real-time sub-minute-level navigation and positioning results.However,the positioning accuracy and reliability of PPP are affected by navigation environments such as urban canyons.Therefore,ins-based assisted PPP technology has become a research hotspot at home and abroad.At present,INS assisted PPP based loose combination technology has been widely used due to its advantages of simple structure and easy engineering implementation.However,at present,the problem of long PPP convergence time is still not effectively solved in loose combination,which obviously cannot meet the application demand of real-time high-precision navigation and positioning.Attitude and Heading Reference System(AHRS)can provide highprecision autonomous Heading information,which can be used as a constraint condition for INS assisted PPP and provides a new idea for AHRS assisted PPP real-time high-precision positioning.This paper aims to improve the convergence time of the AHRS assisted PPP loose combination technology,and studies the PPP processing method,PPP error correction,combined system design with additional course constraint,combined system design with additional course constraint and speed constraint,so as to meet the demand of real-time highprecision navigation and positioning.The main research contents of this paper are as follows:(1)Firstly,three typical functional models commonly used in PPP are introduced,including traditional ionospheric model,Uof C model and fuzzy-free model,and the random model and parameter estimation method of PPP are introduced.By analyzing the advantages and disadvantages of various PPP models,the basic treatment methods of PPP in this paper are summarized.(2)In the PPP error handling,considering the mathematical model for error correction is the basis of realization PPP precise positioning,this paper,according to the theory of observation error sources are classified,and analyzes the effect of the error magnitude,model were taken respectively for different types of error correction or parameter estimation method for processing,in order to reduce its influence on positioning accuracy.(3)Aiming at the problem of slow convergence of traditional PPP,an AHRS auxiliary PPP method is proposed.The filtering model of the combined system with additional course constraint was designed,including the state model and measurement model of the system,and the combined system with additional course constraint was verified by dynamic experimental simulation test,so as to improve the convergence time based on AHRS auxiliary PPP.(4)In order to increase the redundancy of the model and improve the stability of the filtering model,the filtering state model and measurement model of the combined system with additional course constraint and speed constraint are designed.In this model,the doppler frequency shift observed by the receiver is expressed as a velocity function,which ACTS as a velocity constraint.The combined system of additional course constraint and speed constraint is verified by dynamic experimental simulation test in order to improve the stability of the filter model.