Factor Graph Fusion Localization Method with Tight and Loose Coupling of GNSS/IMU and Odometry
Objectives:We investigate the impact of information fusion at different depths on the accuracy of navigation systems composed of micro inertial navigation systems(M-INS)and global navigation satel-lite systems(GNSS),as well as indoor and outdoor integrated positioning.Methods:First,based on the factor graph optimization(FGO)algorithm,a loosely coupled system of M-INS/single-point GNSS and a tightly coupled system of M-INS/pseudorange/Doppler velocity are established respectively,and the ad-vantages of the tightly coupled design are verified by experiments.Then,the visual inertial odometry(VIO)factor is inserted into the factor structure of the tightly coupled M-INS/GNSS system in a loosely coupled manner,and a tight-loosely coupled multi-source fusion algorithm model based on FGO is proposed.Fi-nally,the positioning accuracy and indoor and outdoor integrated positioning capability of the system are verified by experiments.Results:The experimental results show that:(1)When four satellites cannot be ob-served and the single-point positioning solution cannot be obtained,the positioning accuracy of the M-INS/GNSS tightly coupled system can reach twice that of the M-INS/GNSS loosely coupled system.(2)In the case of the sudden failure of either GNSS or VIO,the FGO-based M-INS/GNSS/VIO tight-loosely cou-pled system can continue to provide reliable positioning,and the average errors of the east and north direc-tions are improved by 53.98％ and 54.74％ respectively compared with the M-INS/GNSS/VIO system based on the filtering method.Conclusions:Compared with the loosely coupled M-INS/GNSS system,the M-INS/GNSS tightly coupled system effectively reduces the impact of GNSS signal instability on the system,and has higher accuracy and robustness.The proposed tightly-loosely coupled system can seam-lessly respond to changes between indoor and outdoor environments.
万方数据
维普
