ROBUST ADAPTIVE BACKSTEPPING CONTROLLER DESIGN FOR REJECTING EXTERNAL WIND GUSTS EFFECT IN AN UNMANNED AUTONOMOUS VEHICLE

In this paper, a nonlinear robust adaptive backstepping controller to reject the external wind gusts effect in an unmanned autonomous helicopter (UAH) is proposed. The proposed controller is designed based on a recuirsive backstepping technique to control the hover and vertically takeoff/landing flight of an UAH. The vertical and yaw dynamics of an UAH are considered to derive the proposed controller in order to take into detention the dynamic variations of main rotor and tail rotor thrusts due to any external uncertainties. The proposed controller is designed in such a way that it is adaptive to unknown external disturbances which are estimated through the adaptation laws and the convergences of these adaptation laws are obtained through the negative semi-definiteness of control Lyapunov functions (CLFs). Finally, effectiveness of the designed controller is tested using a high-fidelity MATLAB simulation model by considering the external wind gusts effect into the UAH system for a hover flight and compared the performances of the proposed controller with an existing PD controller. Simulation results demonstrate the robustness of the proposed controller over the existing PD controller in terms of rejecting external wind gusts