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

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