Flapping wings via direct-driving by DC motors

In previous work, a proof-of-concept artificial flapper was devised by Campolo et al. to demonstrate that DC motors, in concert with compliant mechanisms, would be able to directly flap wings at relatively high frequencies and large angles without exceeding their operational limits. The prototype makes use of a pair of relatively long elastic strings as the compliant structures. In this article, we experimentally analyze the wing kinematics and efficiency of a more compact prototype, where small helical springs are implemented instead of elastic strings. Since the proof-of-concept prototype validated the quasi-sinusoidal assumption in spite of nonlinear aerodynamic damping, incorporating instantaneous wing kinematics into the analysis is not necessary, simplifying experiments and data processing. Along with wing kinematics and system efficiency, the possibility of controlling the wing pair to flap independently is evaluated as well.