Autonomous Landing of Fixed-Wing UAV in Net suspended by Multirotor UAVs - A Fixed-Wing Landing System

Abstract

This thesis presents an autonomous landing system designed for an fixed-wing unmanned aerial vehicle (UAV) to land in a net suspended by multirotor UAVs. Ordinary landing of an fixed-wing UAV usually involves landing on a long runway, but by landing in a net suspended below multirotor UAVs, operations with fixed-wing UAV can be performed from ships or other platforms with confined space where no runway is available. The focus in this thesis is placed on the fixed-wing UAV part of the landing, and involves design and implementation of a guidance and control system, together with a system for coordinating a landing path between the fixed-wing UAV and the multirotor UAVs. The autonomous landing system uses the Pixhawk autopilot for low-level control, and a software toolchain from Underwater Systems and Technology Laboratory (LSTS), Porto, for high-level guidance and control, mission review and communication. The guidance and control system developed in this thesis is implemented in the LSTS toolchain, and consist of a decoupled lateral and longitudinal line-of-sight (LOS) guidance scheme for pitch and roll angle commands, and a speed controller for throttle command. The system is tested both in software-in-the-loop (SITL) simulations and flight experiments at Agdenes airfield, where successful tests demonstrated both the feasibility and the good performance of the system using a Skywalker X8 fixed-wing UAV.