Air-to-Air Automatic Landing of Unmanned Aerial Vehicles: A Quasi Time-Optimal Hybrid Strategy

It is well known that small electric Unmanned Aerial Vehicles (UAVs) suffer from low endurance problems. A possibility to extend the range of UAV missions could be to have a carrier drone with several lightweight multirotors aboard, which can take-off from and land on it. In this letter the challenging problem of Air-to-Air Automatic Landing (AAAL) of UAVs is solved by developing a strategy that combines a quasi-time optimal feedback and a hybrid logic to ensure a safe and fast landing. Eventually, the proposed algorithm is validated through experimental activities involving the landing of a small quadcopter on a bigger octocopter used as a carrier.