Output Feedback Control Design for Quadrotors in the Presence of Uncertainties

This paper proposes an output feedback control design for quadrotor Unmanned Aerial Vehicles (UAVs) to deal with unmeasured system states, system uncertainties, and external disturbances. Extended High-Gain Observers (EHGOs) are used to estimate the uncertainties and unmeasured system states. Dynamic inversion utilizes the estimates from EHGOs in the second and third fastest time scales in order to deal with input uncertainties and a form of non-affine control inputs. In plant dynamics, rotational dynamics in the fourth fastest time scale, is forced to be faster than translational dynamics in the slowest time scale to overcome the lack of the number of control inputs in this underactuated mechanical system. Using the singular perturbation method, stability of the closed-loop system is conducted. Throughout numerical simulations, the proposed control algorithm is verified.