A Novel GNSS Integrity Augmentation System for Autonomous Airport Ground Operations

Abstract

In recent years, the degree of vehicle automation is continuously increasing in all modes of transport. Automated Guided Transport (AGT) systems, which were conceptualised a couple of decades ago are now being realised as unmanned aircraft systems and autonomous ground/sea vehicles. Autonomous ground vehicles are an emerging tool that provide a safer, more cost-effective and sustainable alternative to traditional methods. Furthermore, they offer the capability to detect, alert and compensate for any deviations from the required system performance. In this paper, the system architecture and mathematical modeling of a Global Navigation Satellite System (GNSS) based Navigation and Guidance System (NGS) for autonomous airport surface vehicle operations is presented. Specifically, an integrity augmentation system is implemented in the NGS by modeling the key GNSS error sources (including masking, multipath and signal attenuation). The GNSS based integrity augmentation system is designed to be capable of monitoring the Required Navigation Performance (RNP) and providing usable and timely alerts (by the generation of caution and warning flags). The system is also capable of issuing suitable steering commands to an on-board trajectory re-optimization module; in the event of GNSS signal degradations or losses. One of the key focuses is on modelling the multipath error, which is determined using a ray tracing algorithm. The vehicle position error is obtained as a function of relative geometry between the satellites, receiver antenna and reflectors in realistic airport ground operation environment. Additionally, the airside surface vehicle dynamics and reflective surfaces of buildings located in the airport premises are modelled in order to simulate a 2D trajectory (assuming a flat surface) in a representative airport scenario. Simulation results corroborate the validity of the mathematical models developed for the GNSS based integrity augmentation system, as well as the capability of the system to generate predictive and reactive alerts. Keywords: Airside Operations, Global Navigation Satellite System, Integrity Monitoring and Augmentation, Avionics Based Integrity Augmentation, Model-Predictive, Integrity Flags.