Integration of Onboard Sensors and Local Area DGNSS to Support High Integrity Unmanned Aerial Vehicles (UAV) Navigation

Abstract

A Local-Area Differential GNSS (LAD-GNSS) provides high integrity and accuracy for Unmanned Aerial Vehicles (UAVs). The integration of onboard sensors to the LAD-GNSS can support continuous and reliable navigation by overcoming GNSS signal vulnerability. This paper proposes the concept of a high integrity navigation architecture into which the LAD-GNSS and onboard sensors are integrated using an extended Kalman filter (EKF). Key components of the integrated system developed in this work, include its integrity/continuity requirement design, fault-monitoring strategies, and the corresponding protection level (PL) computation formulations. In this paper, the total integrity requirements are divided into mainly the following four hypotheses: a fault-free condition, a reference receiver failure, all other failures of LAD-GNSS, and an onboard sensor failure. According to the integrity allocation, fault monitoring strategies and PL computation formulations were proposed. The ground monitor of the LAD-GNSS and the onboard Receiver Autonomous Integrity Monitoring (RAIM) are utilized to monitor a single satellite failure sequentially, and an innovation-based fault-monitoring method is applied to monitor onboard sensor failures. To evaluate the performance of the integrated system, the VPLs under the four hypotheses were calculated using data collected from flight experiments which used an Inertial Navigation Sensor (INS) as an onboard sensor. The results show that the PL for the INS failure hypothesis has the largest vertical protection level (VPL) for the most of the operation time and it suitably bounds vertical position errors during a flight test.