Nonlinear hovering control laws for small vectored-thrust tail-sitter UAVs

In this paper, we develop hovering control laws for a small vectored-thrust tail-sitter unmanned aerial vehicle (UAV). The UAV is equipped with propellers in a pusher configuration. The magnitude and direction of the thrust generated by the propellers are regarded as the control input. Since the state equation is not in an input-affine form, a state and an input transformation are introduced. Then, three control laws including the inverse optimal controller are derived based on the backstepping control method. Numerical simulations confirm that all the control laws successfully realize the hovering. Comparison of the performance of these control laws is also conducted.