Towards efficient flight: insights on proper morphing-wing modulation in a bat-like robot

In this article, we address the question of how the flight efficiency of Micro Aerial Vehicles with variable wing geometry can be inspired by the biomechanics of bats. We use a bat-like drone with highly articulated wings using shape memory alloys (SMA) as artificial muscle-like actuators. The possibility of actively changing the wing shape by controlling the SMA actuators, let us study the effects of different wing modulation patterns on lift generation, drag reduction, and the energy cost of a wingbeat cycle. To this purpose, we present an energy-model for estimating the energy cost required by the wings during a wingbeat cycle, using experimental aerodynamic and inertial force data as inputs to the energy-model. Results allowed us determining that faster contraction of the wings during the upstroke, and slower extension during the downstroke enables to reduce the energy cost of flapping in our prototype.