Continuous Vector Fields for Precise Cable-Guided Landing of Tethered UAVs

This letter presents a method for the precise cable-guided landing of tethered drones. The proposed approach is based on a continuous velocity vector field that relies on the tether variables only. We assume that the vehicle is attached to a landing platform through a tensioned and free-of-collision cable whose length and angles are measured by a tether management system. We do not assume that the cable is taut. The method is suitable for highly degraded environments, where traditional landing strategies based on GNSS and vision are not feasible, such as dark underground mines and caves. This letter shows that, besides being easy to implement and adjust, the proposed vector field is proven to correctly guide the vehicle to its desired landing position. Experiments with a quad-rotor vehicle landing on static and moving platforms illustrate the precision, robustness, and efficacy of the method.