Efficient resonant drive of flapping-wing robots

Flapping-wing air vehicles can improve efficiency by running at resonance to reduce inertial costs of accelerating and decelerating the wings. For battery-powered, DC motor-driven systems with gears and cranks, the drive torque and velocity is a complicated function of battery voltage. Hence, resonant behavior is not as well defined as for flapping-wing systems with elastic actuators. In this paper, we analyze a resonant drive to reduce average battery power consumption for DC motor-driven flapping-wing robots. We derive a nondimensionalized analysis of the generic class of a motor-driven slider crank, considering motor and battery resistance. This analysis is used to demonstrate the benefits of efficient resonant drive on a 5.8 g flapping-wing robot and experiments showed a 30% average power reduction by integrating a tuned compliant element.