Research On Relative Positioning Algorithm For Indoor Pseudolite And Software Implementation

The Global Navigation Satellite System(GNSS)has global coverage,high precision and all-weather features.It has been widely used in various industries since its inception and regarded as the most perfect positioning and navigation technology outdoors.However,in special environments,such as urban canyons,underground or tunnel precision engineering and all indoor environments,no matter which kind of GNSS positioning method cannot meet the high-precision positioning requirements or even provide services.How to ensure relatively stable high-precision positioning results in the indoor environment will become an important research focus for indoor precision industrial applications.This paper pays attention to study the relative positioning algorithm of indoor pseudolites,including the establishment of mathematical model,error source resolution,carrier phase ambiguity resolution and integrity monitoring theory.In view of the drawbacks of the existing pseudolite indoor positioning algorithm in applications,this paper makes a series of improvements to satisfy the actual scene and provides better technical methods for indoor high-precision positioning.The research contents and innovations can be summarized as below:(1)An indoor pseudolite location algorithm without known point initialization is proposed.The existing indoor pseudolite positioning algorithms are mainly based on KPI(Known Point Initialization),but there are many drawbacks in the practical application of this method.It is shown that fixed known points are generally difficult to obtain,and it is not easy to operate in dynamic observation.In addition,carrier phase ambiguity may not be fixed accurately even if there are known points with decimeter initial accuracy in indoor environment(classical LAMBDA method/Ratio test).In view of these drawbacks,this paper proposes an indoor pseudolite positioning method(DAFV)which does not need initialization at fixed points and can satisfy the initial accuracy requirements of LAMBDA.In order to ensure the efficiency of solution,the LAMBDA method and Ratio test are still used for ambiguity search and fixing.DAFV mainly provides high-precision initial values.The results of some experiments show that the positioning accuracy can reach the centimeter level in dynamic tests and the millimeter level for static ones.Moreover,when the KPI method is unable to locate accurately,the high-precision positioning can still be achieved when the proposed method is used.(2)A strategy to exclude wrong peaks is carried out.In the DAFV algorithm,the ambiguity function method(AFM)is needed.However,the ambiguity function method has the disadvantage of multiple peaks.In this paper,a processing strategy for removing false peaks is proposed in combination with the actual situation,that is,through linear disturbance.Tracking the coordinates corresponding to each peak and only the coordinates corresponding to the correct peak will move in the correct straight line direction.At the same time,the feasibility of the strategy has also been verified by experiments.(3)A method of integrity monitoring for pseudolite system is proposed.In the actual indoor pseudolite positioning,some cases may happen,such as the insufficient accuracy of the fixed point,the poor quality of the observations or the faulty on the pseudolite.The occurrence of this situation will lead to a large excess of the priori residuals,thus cannot guarantee the correct fixed resolution of the ambiguity.Even using the new algorithm of this paper,the problem of AFM multi-peak will become more serious.In order to ensure the reliability and availability of pseudolite positioning,the quality of indoor pseudolite data is evaluated and test statistics is built based on innovation information in Extended Kalman Filter(EKF).In combination with the characteristics of indoor pseudolites,a complete indoor Pseudolite Receiver Autonomous Integrity Monitoring(PLRAIM)is proposed.Through some experiments,the horizontal alarm limit(HAL)is summarized.Under the premise that the horizontal protection level(HPL)is less than HAL,the algorithm can accurately identify faulty satellites or observations.After reasonable decentralization or isolation,the reliability and stability of the positioning result can be guaranteed.According to some tests,the accuracy of positioning is effectively improved by PLRAIM and the ambiguity fixed rate can also be improved.In addition,this method also provides an indicator for evaluating the positioning accuracy.(4)Based on the above research contents,VS2010 is used as the tool to realize the program and software..The proposed high-precision relative positioning algorithm for indoor pseudosatellite is realized,which provides a basic software platform for the research of indoor pseudosatellite positioning technology.