Robust full degree-of-freedom tracking control of a helicopter

We consider the problem of controlling the vertical, lateral, longitudinal and yaw attitude motion of a helicopter along desired arbitrary trajectories with only restrictions on the time derivatives imposed by the functional controllability of the system. To this purpose we design a nonlinear controller, obtained by suitably combining feedforward control actions and high-gain and nested saturation feedback laws, which succeeds in enforcing the desired trajectories robustly with respect to uncertainties characterizing the physical and aerodynamical parameters of the helicopter. Experimental results are also given to show the effectiveness of the method to accomplish aggressive maneuvers.