Active control of the hinge of a flapping wing with electrostatic sticking to modify the passive pitching motion

Wing designs for Flapping Wing Micro Air Vehicles (FWMAVs) might use a properly tuned elastic hinge at the wing root to obtain the required passive pitching motion to achieve enough lift production to stay aloft. Practical use of this type of FWMAVs requires some form of control which can be achieved by actively adjusting the elastic hinge stiffness and, thus, the pitching motion and lift production of the wing. This paper studies an elastic hinge design consisting of stacked layers which can be sticked together using electrostatics. This sticking changes the bending stiffness of the hinge. The voltage-dependent behavior of this elastic hinge during the large pitching motion are described in detail. The passive pitching motion is governed by the equation of motion which is a function of the elastic hinge stiffness and the applied control voltage. The lift generated by the passive pitching wings is predicted by a quasi-steady aerodynamic model. Numerical simulations show significant changes of the passive pitching motion and, consequently, of the lift production, if slipping stacked layers stick together. Experiments are conducted to study the practical applicability of this method on FWMAVs. The experiments show similar trends as the numerical simulations in modifying the pitching motion although the effect is less significant which is mainly due to manufacturing difficulties. This approach is, in conclusion, promising to control FWMAV flight.