Modeling dynamics of agile fixed-wing UAVs for real-time applications

A special class of fixed-wing UAVs called agile UAVs have emerged recently, that are lightweight with control surfaces as big as 50% chord capable of deflecting up to 50 deg., and are characterized by high thrust-to-weight ratios of around 2-3, and a strong propwash. Such configuration allows agile UAVs to perform extreme aerobatic maneuvers that expand the conventional flight envelope to cover the full angle of attack and sideslip range. The desire to automate these aerobatic capabilities has led to a renewed interest in fixed-wing UAVs with a focus on understanding and modeling their dynamics for the full flight envelope. This paper presents a six degree-of-freedom dynamics model for agile UAVs obtained through first principles. Simple but accurate techniques are presented to model the aerodynamics, thruster dynamics and propeller slipstream effects, which are embedded into the overall UAV simulation that is setup to run both offline as well as in real-time with the pilot-in-loop. Static bench tests are performed for validation of the presented six-dof agile UAV model and underlying modeling techniques. As well, qualitative validation shows the model to successfully capture well-known RC maneuvers flown by an experienced pilot in real-time simulation.