Robust attitude control for quadrotor UAV system with two kinds of disturbances

This paper develops a robust attitude control method for a quadrotor unmanned aerial vehicle (UAV), which considers two kinds of disturbances. Firstly, a nonsingular terminal sliding mode observer is presented, which is aimed to observe the derivative of three attitude angles of the UAV system. At the same time, the compensation and suppression of the matched disturbance are included in this observer. Secondly, a sliding mode controller based on the observer results is designed as the control strategy. Thirdly, considering the influence of mismatched disturbance, a disturbance observer based on sliding mode control method is given to deal with the problem of the mismatched disturbance. Finally, the feasibility and stability of the proposed method are verified by simulation.