Nonlinear Robust Trajectory Tracking Control for a Three-rotor UAV with Unknown Time-varying External Disturbances

In this paper, the accurate dynamics of three-rotor unmanned aerial vehicle (UAV) are detailedly analyzed and a nonlinear robust tracking control strategy is proposed considering unknown time-varying external disturbances. Aiming at the tracking control of the typical underactuated system, the dynamic model of the three-rotor UAV is divided into outer-loop position subsystem and inner-loop attitude subsystem. The feedback linearization algorithm is employed to design the outer-loop controller for the trajectory tracking of the UAV. For the inner-loop control of the UAV, the robust integral of the signum of the error (RISE) method is utilized to formulate the robust attitude controller to deal with the external disturbances. The stability of the closed loop system and the asymptotical tracking of the desired trajectory are proved via Lyapunov based stability analysis. Real-time experiments are implemented to validate the performance of the proposed control strategy.