Benchmark Evaluation of Hybrid Fixed-Flapping Wing Aerial Robot with Autopilot Architecture for Autonomous Outdoor Flight Operations

This letter is focused on the benchmark evaluation and comparison of the flapping and fixed wing flight modes on an hybrid platform developed for the realization of autonomous inspection operations outdoors. The platform combines the high range and endurance of fixed-wing UAVs (unmanned aerial vehicles), with the higher maneuverability and intrinsic safety of flapping wing in the interaction with humans during the hand launch and capture. A unified model of the hybrid platform is derived for both configurations following the Lagrange formulation to express the multi-body dynamics and aerodynamic forces of the flapping wing and the propellers. The proposed control scheme exploits the similarities of both flight modes in the tail actuation and in the generation of thrust either with the flapping wings or the propellers, in such a way that it can be implemented on conventional autopilots, facilitating in this way the adoption of this type of aerial platforms. To evaluate and compare the performance of both modes, a set of benchmark tests and metrics are defined, including the energy efficiency in forward flight, trajectory tracking, hand launch and capture, and accuracy in visual inspection. Experimental results in outdoors validate the developed prototype, identifying the fixed/flapping transitions, and evidencing the higher energy efficiency of the flapping wing mode compared to the fixed wing.