Lift generation of hummingbird wing models with flexible loosened membranes

Hummingbirds are promising reference for small flying robots in terms of their excellent ability to hover. Wing kinematics and shape of a hovering hummingbird were measured with four high-speed video cameras. Four types of wing models consisting of carbon fiber rods and polymer membranes with the same planform as the hummingbird wing were fabricated. 1-degree-of-freedom (DOF) flapping experiments with the wing models were performed, where the wing deformation and vertical force (hereafter called `lift´) were measured. The model wings demonstrated similar feathering deformation as that of the hummingbird in the upstroke. In addition, the model wing with a loosened membrane which caused larger feathering deformation produced lift enough to support the weight of the hummingbird. The results suggest that hovering hummingbirds could be modeled as a pair of 1-DOF flapping wings with a thin membrane which passively feathers.