First experimental results on enhancing hovering performance of unmanned helicopters by using a tethered setup

• The hover performance of small-size helicopters can be seriously affected by wind disturbances.
• The mechanical model of a tethered setup is analyzed to show its benefits in stabilizing translational dynamics.
• A control strategy for the tethered helicopter based on model inversions and PI-D laws is developed.
• The proposed approach is tested in successful field experiments.

The hovering capabilities of helicopters can be seriously affected by wind. This could be even more significant in the small-size platforms used for developing unmanned aerial vehicles. One possible solution for improving performance under such circumstances is the use of a tethered setup. This approach takes advantage of the tension exerted on the cable linking the helicopter to the ground. This paper analyzes the mechanical model of this augmented setup to show its benefits in stabilizing translational dynamics. Control guidelines to exploit these potentialities are also highlighted. The latter allows the definition of a model-based control strategy consisting of a combination of classical PID laws together with model inversion blocks. Tether tension feed-forward is also included to take into account the side effects of tether tension in rotational dynamics. Experiments performed with the real platform confirm the validity of the proposed approach.