FAST-Hex -- A Morphing Hexarotor: Design, Mechanical Implementation, Control and Experimental Validation
This work addresses the trade-off between efficiency and control in aerial robotics, offering a practical solution for applications requiring adaptable flight modes, though it builds incrementally on prior configurable vehicle designs.
The authors tackled the problem of transitioning between efficient under-actuated and full-pose-tracking configurations in micro aerial vehicles by designing FAST-Hex, a hexarotor that uses one additional motor to tilt propellers, achieving seamless transitions and full pose tracking with experimental validation.
We present FAST-Hex, a micro aerial hexarotor platform that allows to seamlessly transit from an under-actuated to a fully-actuated configuration with only one additional control input, a motor that synchronously tilts all propellers. The FAST-Hex adapts its configuration between the more efficient but under-actuated, collinear multi-rotors and the less efficient, but full-pose-tracking, which is attained by non-collinear multi-rotors. On the basis of prior work on minimal input configurable micro aerial vehicle we mainly stress three aspects: mechanical design, motion control and experimental validation. Specifically, we present the lightweight mechanical structure of the FAST-Hex that allows it to only use one additional input to achieve configurability and full actuation in a vast state space. The motion controller receives as input any reference pose in $\mathbb{R}^3\times \mathrm{SO}(3)$ (3D position + 3D orientation). Full pose tracking is achieved if the reference pose is feasible with respect to actuator constraints. In case of unfeasibility a new feasible desired trajectory is generated online giving priority to the position tracking over the orientation tracking. Finally we present a large set of experimental results shading light on all aspects of the control and pose tracking of FAST-Hex.