Design of terminal sliding mode controller for a quadrotor UAV with disturbance observer

In this paper, a novel sliding mode control scheme has been proposed to solve the trajectory tracking problem of the quadrotor UAV subjected to external disturbances based on a double closed-loop control strategy. Firstly, a dynamic model of the quadrotor based on Newton-Euler laws is given, the integral terminal sliding mode method is adopted to the outer loop to ensure the robustness and accuracy of tracking. Furthermore, in order to attenuate external disturbances accurately, a nonsingular terminal sliding mode control combining sliding mode disturbance observer with the scheme has been applied to the inner loop to realize the stability of the attitude. The stability of system is proved by Lyapunov theory. Finally, simulation results are provided to demonstrate effectiveness of the proposed scheme.