Emulating a Fully Actuated Aerial Vehicle Using Two Actuators

Abstract

Micro air vehicles exemplified by quadrotors generate downward thrust in their body fixed frame and may only maneuver spatially by changing their orientation. As a result of this underactuation they are fundamentally incapable of simultaneously regulating orientation and position. Furthermore, their feasible maneuvers are limited to spatial trajectories with continuously differentiable acceleration. We present a coaxial helicopter which emulates full actuation over forces and torques (six degrees of freedom) using only two actuators. The orientation of the thrust vector from each rotor is governed by the drive motor by exciting a cyclic flapping response in special articulated blades. The useful separation of orientation and translation dynamics is demonstrated in flight experiments by tracking spatial trajectories while maintaining flat body attitude as well as tracking desired orientations near hover while station keeping.