Composite Nonlinear Extended State Observer-Based Trajectory Tracking Control for Quadrotor Under Input Constraints

In this paper, the trajectory tracking control problem of quadrotor subject to unknown external disturbance and input constraints is addressed. In order to achieve the active disturbance rejection, a composite nonlinear extended state observer (ESO) consisting of both linear and nonlinear functions is developed, and the rigorous convergence analysis is also presented. It is worth mentioning that the proposed composite nonlinear ESO brings together the advantages of both the linear and nonlinear ESOs. Furthermore, the position controller is proposed in the nested saturation control framework, and the disturbance estimate is incorporated in the controller to reject disturbances actively, which provides a composite disturbance rejection control strategy for systems with input constraints and unknown disturbances. The domain of attraction and the rigorous stability analysis of whole system are also presented. Finally, simulation and experiment are provided to show the efficiency of the proposed methods.