052 - Robust navigation of airborne autonomous systems with carrier phase of ARNS signals
As the Unmanned Aerial Vehicle (UAV) regulatory framework continues to evolve towards autonomous flight and operations beyond visual line-of-sight (BVLOS), it drives the need for reliable navigation services to complement or act as a back-up to existing ones. Trusted PNT solutions have to be developed to help tackle the many challenges that a congested airspace brings such as the safety of autonomous flight in populated areas or in-flight collision avoidance. Moreover, it is paramount to support future UAV Traffic Management (UTM) systems with the tools for safe operations. Regulating bodies will require reliable trajectory information in the decision making process and for conveying information, such as changes in the flight route to the UAV, in a timely manner with sufficient reliability.
In the search for robust and resilient positioning alternatives, users have already looked at signal-of-opportunity (SOOP) techniques that make use of radiofrequency signals broadcasted for different purposes (e.g. wireless, TV, etc.). These signals are more robust against interference and spoofing and can contribute to Position, Navigation and Timing (PNT) determination. So far, SOOP-based positioning solutions have not achieved targeted accuracy levels for UAV operation, nor have they proven to be suitable for integration in safety-critical processes. Nevertheless, in recent studies, the feasibility of using carrier phase positioning techniques has been demonstrated over the cellular networks. Therefore, it is envisaged that similar techniques could also enable high-accuracy alternative PNT solutions for UAV, if they are based on reliable and certifiable signals-of-opportunities such as the Aeronautical Radionavigation Service (ARNS) signals.
In order to use ARNS signals in safety-critical UAV operations such as autonomous landing, take-off and BVLOS navigation, one would also have to be guaranteed on a certain level of trust in the PNT solution and be provided with timely alerts when the criticality threshold is exceeded. Although the consolidated knowledge on safety cases and feared events for UAV operations is not yet mature, the precise characterisation (e.g. position and clock parameters) of ARNS transmitters could facilitate the definition of integrity, integrity risks, and integrity monitoring concepts.
The objectives of the proposed activity are to:
- define and implement robust and reliable PNT concepts for autonomous navigation of UAVs, relying on carrier phase of ARNS signals further hybridized with dead-reckoning (e.g. inertial measurements) and vision (e.g. terrain mapping). The foreseen SOOP in ARNS bands would primarily be VOR and ADS-B signals;
- develop a SDR-based proof-of-concept to demonstrate feasibility of the proposed techniques on real signals,
- validate several related hypotheses in specific beyond visual line of sight (BVLOS) operation conditions.
The tasks to be performed will include:
- identification of regulations and technical challenges of BVLOS operations of UAVs;
- derivation of performance targets for accuracy, integrity, continuity, availability and latency;
- Development of reliable PNT concepts and algorithms based on SOOPs and similar technologies, hybridised with dead-reckoning, in support of integrity protection in UAV operations;
- Implementation of a SDR platform for receiving and processing terrestrial ARNS signals suitable for UAV platforms and for deriving the raw observables for PNT;
- Demonstration of the concept with real signals representative for connected drones operating in BVLOS conditions;
- benchmarking with state-of-the-art and assessment of the improvements of ARNS carrier phase solutions, in particular for BVLOS operations.
The main results of the activity will provide:
- a preliminary assessment of integrity concept and safety aspects for the purpose of reliable navigation with ARNS signals, as a complementary radio-based positioning technique, for UAVs operating under BVLOS;.
- Design and implementation of ultra-reliable overall PNT concept and algorithms in support of safety in UAV operations;
- SDR receiver platform for processing ARNS signals;
- Implementation of processing algorithms used to derive the raw observables, a PNT solution, and for triggering alerts;
- Test reports, including achievable performance, for both synthetic (laboratory) and real signals conclusions.