Research On Positioning Algorithm Of Beidou Pseudolites Network

In some areas with complex environment,such as city,field,underground and so on,the global satellite navigation system(GNSS)cannot provide accurate positioning services because of the occlusion of signals,and the same problem exists in Beidou Satellite Navigation System in China.Therefore,the establishment of a pseudo-satellite system to provide navigation signals in a specific area has become one of the effective ways to overcome such problems.Many key technical problems such as time synchronization between pseudo-satellites,anti-multipath effect and far-near effect have been solved in foreign Locata system,and now it has become an effective ground reinforcement system for GPS in specific areas.Referring to some methods and technologies adopted by Locata system,this paper studies the positioning system of ground pseudolites network supporting Beidou system from the following aspects:Firstly,the research status of pseudolites at home and abroad has been analyzed,and the research significance has been clarified.The composition of the system,including transceiver,receiver and positioning network,is introduced.At the same time,the positioning principle of Beidou pseudolites network and some key technical problems are studied,and the corresponding solutions are given.Secondly,the on-The-Fly(OTF)algorithm of carrier phase integer ambiguity is studied,and the mathematical model of single frequency integer ambiguity is established.The integer ambiguity is solved by using weighted least squares algorithm and LAMBDA algorithm.Aiming at the poor positioning accuracy caused by poor pseudo-satellite layout,the Tikhonov Regularization algorithm is proposed to optimize it.At the same time,based on the ambiguity resolution of single frequency,a dual-frequency localization algorithm with double antenna is proposed,the solution model is established,and the detailed solution process is given.The experimental results show that the Tikhonov regularization can improve the positioning accuracy caused by the poor distribution of pseudolites,and the ambiguity resolution algorithm of dual-frequency has higher positioning accuracy than single-frequency algorithm.Thirdly,the combined positioning algorithm of Beidou navigation system and pseudolites is studied.From the aspect of satellite layout,the impact of the addition of pseudolites on the DOP of beidou satellite system is studied.At the same time,the experiment simulation is completed from two aspects: the positioning of Beidou satellite system assisted by pseudolites and the positioning of pseudolites System assisted by Beidou satellite system,and the effectiveness of the combined positioning algorithm is verified Finally,the research contents and work carried out in this paper are summarized comprehensively,and the direction for further research is pointed out.