Robust Velocity Tracking Control with an Observer for Four-rotor Mini Helicopter

Focusing on the unmatched uncertainties with respect to the aero dynamic coefficients which characterize the thrust and torques developed on the airframe, a change of state variables with the unknown true model parameters is firstly proposed so as to transform the unmatched uncertainties to matched. Then a sliding mode observer is employed to estimate the new state variables robustly. Using the estimates, a sliding mode controller is effectively employed for the matched uncertainties. Numerical simulation illustrates the robustness of the proposed controller together with the author's previous controller designed by the backstepping method.