A Fault-Tolerant Tightly Coupled GNSS/INS/OVS Integration Vehicle Navigation System Based on an FDP Algorithm

This paper describes an adaptive fault-tolerant triple-integration vehicle navigation system. The proposed triple-integration system is based on a tightly coupled design, which fuses measurements from the Global Navigation Satellite System (GNSS), an Inertial Navigation System (INS), and optical velocity sensors (OVS). The difference between GNSS-measured and INS-derived pseudorange and pseudorange rate, and the difference between INS-derived and OVS-measured velocity are taken as the measurement inputs to the system filter, which uses them to obtain accurate and continuous navigation solutions. However, to ensure the optimality and to improve the robustness of the integration system in GNSS-challenging environments, a fault-tolerant fault detection and processing (FDP) algorithm is then applied to detect faults and further process the detected faults in fault-varying methods. The detected faults can be classified as Outliers and Biases according to the designed fault factor; Outliers are excluded and Biases are still utilized by adaptively adjusting the corresponding measurement noise covariance matrix. To evaluate the performance of the proposed triple-integration system, a road test was conducted under different scenarios, including GNSS open-sky, GNSS partly blocked, and GNSS-difficult conditions. The results indicate that the proposed integration system can generate more accurate position solutions than a loosely coupled system. To verify the fault-tolerant ability of the proposed FDP algorithm, typical types of GNSS faults are simulated. The results confirm that the proposed FDP algorithm can improve the system performance in terms of its fault-tolerant ability and accuracy as well.