Kinematic and aerodynamic enhancement of a robotic hummingbird

This paper reports a study aiming at improving the flight quality and aerodynamic performance of a robotic hummingbird. The first part of the paper addresses the issue of the parasitic roll and pitch bias moments resulting from the small asymmetry (left/right and front/back) in the wing trajectory. This is achieved with a new string-based mechanism that reduces by 90% the asymmetry associated with the previous mechanism of our robot (known as COLIBRI). The second part of the paper aims at increasing the lift and reducing the mechanical power. An experimental study is conducted with leading edge bars of various diameters and it is found that wing flexibility may contribute to smooth the transition at wing reversal (less twisting oscillations) and leads to a significant increase of the lift force and a significant reduction of the mechanical power. As a side effect, the wing compliance contributes to reducing the noise in the inertial sensor and the acoustic noise produced by the flying robot.