Robust Backstepping Controller for Inner and Outer Loops Control of a Small-Scale Helicopter

This paper presents an investigation into the design of a flight control system, using a robust backstepping control structure, designed using the two-time scale control procedure of the dynamic of a small-size autonomous helicopter in hover. The two-time scale controller takes advantage of the ‘decoupling’ of the translational and rotational dynamics of the rigid body, resulting in a two-level hierarchical control scheme. The inner loop controller (attitude control) tracks the attitude commands generated by the outer loop controller and sets the main rotor thrust vector, while the outer loop controller (position control) tracks the reference position. The controller is designed using the backstepping method based on Lyapunov function. Lyapunov function is used to show the robustness of the proposed control method under the consideration of wind gusts. Simulation results are finally given showing the effectiveness of the proposed control and its ability to cope with external wind gusts on the plant model.