Robo Raven: A Flapping-Wing Air Vehicle with Highly Compliant and Independently Controlled Wings

Many current bird-inspired flapping-wing air vehicles (FWAVs) achieve their flight characteristics through deformations associated with compliant wings during the flapping cycle. Most FWAVs use a single actuator to flap both wings. This couples and synchronizes motions of the wings, which only provides variable rate flapping at constant amplitude to control wing deformations. Independent wing control has the potential to provide a greater flight envelope through the ability to program wing motions to achieve a desired wing shape and associated aerodynamic forces. This approach requires the use of at least two actuators with position and velocity control that can be programmed to drive the wings independently. Integration of two actuators in a flying platform significantly increases the weight and hence makes it challenging to achieve flight. Based on our previous designs with synchronized wing flapping, we developed a new FWAV platform using programmable digital servo motors and a compatible highly compliant wing design that enables shape control of the wings during the flapping cycle. The wings and flapping characteristics can generate the highest possible lift near the maximum power operating point for the servos. The servos were integrated into a wing drive subsystem consisting of 3D printed and laser-etched/cut structural components to reduce part count and weight. A servo-driven tail was also used to augment the steering control and lift of the FWAV. The platform reported in this article, known as Robo Raven, was the first demonstration of a bird-inspired platform doing outdoor aerobatics using independently actuated and controlled wings. This platform successfully performed dives, flips, and buttonhook turns, demonstrating the capability of bioinspired aerobatic maneuvers afforded by the new design.