Quaternion-based backstepping control of a fixed-wing unmanned aerial vehicle

In this paper the problem of controlling a fixed-wing UAV is studied. With basis in Newton´s second law and Euler´s moment equation the translational and rotational dynamics is derived. Using the rotational dynamics a quaternion-based backstepping controller is designed which is able to track a trajectory and is shown to be uniformly asymptotically stable. Since a fixed-wing UAV contains six states and only four actuators, the velocity component in y^b and z^b directions are underactuated. A velocity controller is designed to make the velocity component in the thrust direction go to zero, while the underactuated states are shown to go to their desired values using a line-of-sight guidance scheme.