Research On The Vehicle Fusion Positioning Strategy Based On UWB/IMU In GNSS Denied Environment

Accurate and reliable vehicle position is the key foundation of Intelligent Transportation System(ITS)and other applications.The fusion of Global Navigation Satellite System(GNSS)and Inertial Navigation System(INS)has been widely used in the field of vehicle positioning and can meet the needs of reliable vehicle positioning in open environment.However,in GNSSdenied environments(such as tunnels,indoor parking lots,urban canyons,etc.),the Global Navigation Satellite System(GNSS)fails due to the occlusion of satellite signals,resulting in reduced positioning accuracy.How to achieve precise positioning of vehicles in GNSS-denied environments is a very important and challenging issue.To solve the above problems,this paper develops the research of vehicle fusion positioning technology based on Ultra-Wide Band(UWB)and Inertial Measurement Unit(IMU)in GNSS-denied environment.The main research work of this paper are summarized as follows:(1)Aiming at the vehicle positioning requirements in GNSS-denied environment,a UWB/IMU vehicle fusion strategy based on adaptive factor graph has been designed,and the corresponding experimental hardware platform was built according to the designed scheme,the experimental hardware platform has been built,and the multi-sensor collection software has been designed to realize the synchronous acquisition and processing of multi-sensor information.(2)According to the transmission characteristics of UWB distance signal,a factor graph model based on UWB distance information under line-of-sight(LOS)and non-line-of-sight(NLOS)is established.Then an improved interactive multi-model distance smoothing algorithm is proposed to correct the deviation of UWB signals due to non-line-of-sight effects.(3)A UWB/IMU fusion location model based on factor graph is proposed.Considering the non-Gaussian property of observation noise,an adaptive factor graph algorithm based on Variational Bayesian is proposed to adjust the observation noise matrix of UWB adaptively during the fusion process,which provided a secondary guarantee for mitigating NLOS errors.(4)To verify the reliability of the proposed fusion positioning scheme,a real vehicle experiment was carried out and the experimental data were analyzed and processed,and the positioning accuracy of different fusion algorithms was compared.The results of real vehicle experiments show that the vehicle fusion positioning algorithm based on adaptive factor graph designed in this paper can effectively mitigate the NLOS effect of UWB signals,improve the positioning accuracy,and achieve reliable and continuous positioning of vehicles in GNSSdenied environment.