A bio-inspired membrane wing for passive aerodynamic control

We present a novel, lightweight design of an adaptive membrane wing for flapping wing systems. The wing holder is equipped with variable leading and trailing edges which allow for passive cambering of the wing and to align both edges with the surrounding flow. To evaluate the performance of the new design, we conduct experimental optimizations to find the wing kinematics yielding highest aerodynamic lift and efficiency in hovering flight, both for the adaptive membrane wings and for a rigid reference case. The results of the optimization show that the flexible wings reaches higher lift coefficients without increasing the aerodynamic power of the system. This leads to an overall better efficiency of the flexible wings compared to the rigid reference case. The adaptive holder is able to produce the same amount of lift at lower average angles of attack due to the passive cambering of the membrane. We perform additional deformation and velocity flow field measurements for the optimal kinematics and find that the adaptive cambering and lower angles of attack keep the flow attached to the wing longer for the membrane wings promoting the efficiency of the system relative to stiff wings.