Upward Wing Elevation Stabilizes Descending Flight of a Tailless Flapping Wing Micro Air Vehicle

This paper investigates the effect of wing elevation on the passive stability of a flapping wing micro air vehicle. Flapping wing fliers generally have one unstable longitudinal eigenmode and one unstable lateral eigenmode. This unstable character gives natural fliers a capacity for great aerial acro-batics, but it also poses a challenge for researchers developing flapping wing drone flight controllers. Simulation results indicate that upward wing elevation stabilizes the descending flight of a flapping wing system at a moderate rate of descent. Wing elevation counteracts lateral or longitudinal disturbances by a mechanism similar to the dihedral effect that stabilizes the lateral motion of dragonflies and large aircraft. Stability in descent guarantees that the system recovers from collision or wind gusts. This relaxes the requirements on the potential flight controller, since a disturbance is less likely to result in a crash. The system converges towards an upright descent from which the flight controller can return to the desired flight condition. Climbing flight remains unstable, so the system theoretically remains capable of the agile maneuvering seen in natural fliers.