Implementation and Real-Time Validation of a European Remain Well Clear Function for Unmanned Vehicles

The full integration of Remotely Piloted unmanned vehicles into civil airspace requires first and foremost the integration of a traffic Detect and Avoid (DAA) system into the vehicle. The DAA system supports remote pilots in performing their task of remaining Well Clear from other aircraft and avoiding collisions. Several studies related to the design of a Remain Well Clear function have been performed that served as input for the development of technical standards applicable to non-European countries. In this paper, a Remain Well Clear implementation is proposed that, using the results of past international projects, fits European airspace needs and specificities and can be acceptable to both remote pilots and air traffic controllers, with only minimal impact on the standard operating procedures used for manned aircraft. The proposed Remain Well Clear software has been successfully validated through real-time simulations with pilots and controllers in the loop considering traffic encounters and mission scenarios typically found in European airspace. The achieved results highlight the appropriate situational awareness provided by the proposed RWC function and its effective support to the remote pilot in making adequate decisions in conflict solving. Real-time simulation tests showed that, in almost all cases, an RWC maneuver is successfully performed, giving the RP sufficient time to assess the conflict, coordinate with the controller, if needed, and execute the maneuver. The fundamental role of the proposed RWC function has been especially evident in uncontrolled airspace classes where the controller does not provide any separation provision. Moreover, its effectiveness has also been tested in encounters with aircraft flying under visual flight rules in controlled airspace, where the controller is not informed or has less information regarding these aircraft. The results from validation tests imply two key potential safety benefits, namely: the mitigation of performing a collision avoidance maneuver and the prevention of potential conflict while not disrupting the traffic flow with possible further consequences of generating other potentially hazardous situations

Full–Envelope Robust Control of a Shrouded–Fan Unmanned Vehicle

The development is described of a rate-command system for the control of a novel unmanned vehicle, the baseline model of which is highly nonlinear and presents fast and unstable open-loop modes. Structured singular-value design methodology is used to achieve the desired command response characteristics under specified uncertainties taking into consideration typical problems of small-size helicopters and ducted-fan vehicles such as rate-limited servos and significant time delays. Two robust linear controllers are designed for the low- and high-speed subsets of the operating envelope, and full-envelope flight control is achieved by switching between controllers as the threshold airspeed is traversed. Following an analysis of scaling effects, controller performance is evaluated against rotorcraft handling-qualities specifications. Flight control system development is assessed by piloted, hardware-in-the-loop simulation in the full range of operating conditions, with the controller implemented in the flight computer and pilot commands transmitted to the vehicle via radio link. Simulation testing also shows that the control system has good turbulence gust rejection performance and is robust to significant variations of c.g. position

Full–Envelope Robust Control of a Shrouded–Fan Unmanned Vehicle

The development is described of a rate-command system for the control of a novel unmanned vehicle, the baseline model of which is highly nonlinear and presents fast and unstable open-loop modes. Structured singular-value design methodology is used to achieve the desired command response characteristics under specified uncertainties taking into consideration typical problems of small-size helicopters and ducted-fan vehicles such as rate-limited servos and significant time delays. Two robust linear controllers are designed for the low- and high-speed subsets of the operating envelope, and full-envelope flight control is achieved by switching between controllers as the threshold airspeed is traversed. Following an analysis of scaling effects, controller performance is evaluated against rotorcraft handling-qualities specifications. Flight control system development is assessed by piloted, hardware-in-the-loop simulation in the full range of operating conditions, with the controller implemented in the flight computer and pilot commands transmitted to the vehicle via radio link. Simulation testing also shows that the control system has good turbulence gust rejection performance and is robust to significant variations of c.g. position

Differences between URClearED Remain Well Clear and DO-365

In 2017, RTCA published the first release of the Minimum Operational Performance Standards for UAS Detect and Avoid systems, DO-365. In 2019, EUROCAE published the Operational Services and Environment Definition for Detect and Avoid in airspace classes D-G in Europe, and in 2020 RTCA published the first update to DO-365. In 2021 the URClearED project was started to develop the requirements and capabilities for the Remain Well Clear function to be integrated in RPAS flying under instrument flight rules in airspace classes D-G. This paper discusses differences between the URClearED and DO- 365A Remain Well Clear quantification and associated alerting and guidance function requirements. Fast-Time and Real-Time Simulation campaigns have been carried out to motivate and assess the introduced differences

Fast Time and Real Time Validation of a Remain Well Clear Function for Airspace Classes D to G

A relevant step in the full seamless integration of Remotely Piloted Aircraft Systems (RPAS) in unsegregated airspace is the development of a Detect-And-Avoid (DAA) system that supports their insertion in airspace classes D to G, where the interaction of RPAS with aircraft flying Visual Flight Rules, possibly not transponder equipped, poses major challenges. These challenges mainly arise from the need to assure a level of safety, specifically against the risk of Mid-Air Collision events, as high as that currently characterizing manned civil and commercial aviation. While a DAA system last resort is represented by the Collision Avoidance component, the Remain-Well-Clear (RWC) component acts as a Decision Support System to assist the Remote Pilot in preventing collision hazards. This paper discusses the results of fast-time and real-time simulations performed to validate a prototype RWC system for RPAS integration in European airspace classes D to G. The RWC functional and operational context was defined. Fast-time simulations were used to tune RWC system parameters such as the quantification of the well-clear volume and the time-to-alert. Real-time simulations evaluated how acceptable RWC functionality was for remote pilots and air traffic controllers. Future research activities are also proposed