Sliding mode attitude control for a quadrotor micro unmanned aircraft vehicle using disturbance observer

In this paper, a sliding mode attitude controller with a two-cascaded loop structure is designed for the attitude control of a quadrotor micro unmanned aircraft vehicle. Considering that the quadrotor systems usually suffer external disturbances in the practical flight, a nonlinear disturbance observer is introduced to improve the robustness of the attitude controller. Extensive simulations show that the developed sliding mode attitude controller compensated by the nonlinear disturbance observer is insensitive to the external disturbances, which demonstrates the effectiveness of the designed attitude controller.