Nonlinear robust attitude tracking control of a table-mount experimental helicopter using output feedback

This paper proposes a robust attitude tracking controller for a table-mounted experimental helicopter that has three rotational degrees-of-freedom and only equips angular position sensors. The proposed controller can achieve output-feedback attitude tracking of the pitch and elevation channels of the helicopter. The experimental platform is subjected to model uncertainties, coupling effects, and equips with an independent active disturbance system, which have effectively examined the robustness of proposed controller. The control law includes a second-order auxiliary system to generate filtered error signals, and a discontinuous uncertainty and disturbance estimation (UDE) term to compensate the model uncertainties and external disturbances. A Lyapunov-based stability analysis shows the semiglobal asymptotic tracking ability of the proposed controller. The experimental results further demonstrate that the proposed method can achieve equivalent dynamic and static performance compared to other high-performance state-feedback methods, and even when the initial position is away from design point, it also gives more consistent responses than other linear methods.