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A Robust Graph Optimization Realization of Tightly Coupled GNSS/INS Integrated Navigation System for Urban Vehicles
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Abstract
This paper describes a robust integrated positioning method to provide ground vehicles in urbanenvironments with accurate and reliable localization results. The localization problem is formulated as a maximum a posteriori probability estimation and solved using graph optimization instead of Bayesian filter. Graph optimization exploits the inherent sparsity of the observation process to satisfy the real-time requirement and only updates the incremental portion of the variables with each new incoming measurement. Unlike the Extended Kalman Filter (EKF) in a typical tightly coupled Global Navigation Satellite System/Inertial Navigation System (GNSS/INS) integrated system, optimization iterates the solution for the entire trajectory. Thus, previous INS measurements may provide redundant motion constraints for satellite fault detection. With the help of data redundancy, we add a new variable that presents reliability of GNSS measurement to the original state vector for adjusting the weight of corresponding pseudorange residual and exclude faulty measurements. The proposed method is demonstrated on datasets with artificial noise, simulating a moving vehicle equipped with GNSS receiver and inertial measurement unit. Compared with the solutions obtained by the EKF with innovation filtering, the new reliability factor can indicate the satellite faults effectively and provide successful positioning despite contaminated observations.
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Wei Li received the BS degree from Tsinghua University, China, in 2014. She is currently pursuing the PhD degree in electronic engineering at Tsinghua University. Her major research focuses on robust and accurate algorithms for GNSS/INS integrated navigation.
Xiaowei Cui is an associate professor at the Department of Electronic Engineering, Tsinghua University, Beijing, China. He is a member of the Expert Group of China BeiDou Navigation Satellite System. His research interests include robust GNSS signal processing, multipath mitigation techniques, and high-precision positioning. He obtained both the BS and PhD degrees in electronic engineering from Tsinghua University, in 1999 and 2005, respectively.
Mingquan Lu is a professor of the Department of Electronic Engineering, Tsinghua University, Beijing, China. He is the director of Tsinghua Position, Navigation, and Timing Center, and a member of the Expert Group of China BeiDou Navigation Satellite System. His current research interests include GNSS signal design and analysis, GNSS signal processing and receiver development, and GNSS system modeling and simulation. He received the ME and PhD degrees in electronic engineering from University of Electronic Science and Technology, Chengdu, China, in 1993 and 1999, respectively.