Flapping wing actuation using resonant compliant mechanisms

Abstract

The realization of a wing actuation mechanism for a flapping wing micro air vehicle requires a move away from traditional designs based on gears and links. An approach inspired by nature’s flyers is better suited. For flapping flight two wing motions are important: the sweeping and the pitching motion. The current design is set up to exploit resonant properties, as exhibited by flying insects, to reduce the energy expenditure and to provide amplitude amplification for the wing sweeping motion. In order to achieve resonance, a significantly compliant structure has to be incorporated into the design. The structure used for elastic storage is a ring-type structure which is combined with a compliant amplification mechanism to realize the wing sweeping motion. After initial sizing, prototype structures are analyzed. Based on the initial analysis, the structures are realized to be tested later. For lift production, timing of the wing pitching motion is of paramount importance. A compliant pitching hinge is introduced to obtain passive pitching motion. The wings are analyzed independent of the structure and consequently tuned. The objective is to reproduce a reference motion based on insect kinematics by using a coupled quasi-steady aerodynamic and mechanical model. The wings are realized and consequently tested to judge if manufactured wings reflect the predicted performance. The wings are coupled to the ring-based thorax to test the performance of the assembled structure. Significant lift is produced, in the order of the weight of the structure, while kinematic patterns present during resonant actuation show accurate reproduction of predicted wing motion. The combination of the ring-based structure and compliant wing pitching mechanism shows that simple lightweight structures can be used to obtain both large amplitude wing sweeping motion and passive pitching motion in an energy efficient manner.