Flapping-flight (I): development of a DC motor-based resonant flapping mechanism for large wing strokes

Abstract

Three elastic coupling mechanisms have been designed to improve the efficiency of a flapping mechanism directly powered by a DC motor run with an alternating signal for oscillating rotation. The mechanisms were designed to oscillate at natural frequency where little or no energy is wasted to accelerate the mass of the system, while most of the energy provided is used to generate lift. One of the mechanisms was a torsional pendulum, which was found to have the highest natural frequency of the three. A second mechanism involved tensile force on an elastic string to provide torque to the motor to support oscillation. This mechanism was found to be nonlinear and a third mechanism was developed. The third mechanism stretched an elastic string wrapped around a cylinder which was rotating. The three mechanisms were tested and compared. It was shown that all the tested mechanisms improved flapping efficiency.