Control and cable deployment of a tethered PVTOL aircraft

This paper deals with the development of a strategy to stabilize a Planar Vertical TakeOff and Landing Aerial Vehicle powered by a tether system. The tether system consists of a ground station which provides power through a suspended cable to the aerial vehicle. Giving a position reference, the ground station computes the optimal cable length reference, which minimizes the tension force acting on the vehicle due to the cable weight. The optimal cable length is commanded by an automatic winch that retracts/releases the cable forming a catenary curve shape between the ground station and the aerial vehicle. This automatic procedure allows to reduce the disturbances in the vehicle since over-tensions in the cable are avoided. We used a state feedback controller with a tension compensator to control the vehicle altitude as well as its horizontal position, while the vehicle attitude and the winch dynamics are controlled by local state feedback controllers. Finally, in order to demonstrate the effectiveness of the proposed strategy we conducted simulation tests.