Quadrotor UAV flight control via a novel saturation integral backstepping controller

In this paper, in order to reduce the influence on quadrotor flight from different external disturbances, a novel nonlinear robust controller is designed and used in the quadrotor system. At first, a nonlinear dynamic model of the quadrotor is formulated mathematically. Then, a quadrotor flight controller is designed with the method of classical backstepping control (CBC) and the nonlinear system using this controller is proved to be asymptotically stabilized by the Lyapunov stability theory when there is no external disturbance. At last, a new nonlinear robust controller established by the introduction of both the saturation function and the integral of error into CBC is designed and named as saturation integral backstepping control (SIBC). The boundedness of the nonlinear system under external disturbances is verified by the uniformly ultimately bounded theorem of the nonvanishing perturbation. The numerical simulations of hovering and trajectory tracking are carried out using MATLAB/SIMULINK taking the external disturbances into consideration. In addition, a series of outdoor flight experiments were completed on the actual experimental equipments of quadrotor UAV under the time-varying disturbance from wind. According to the simulation and flight experiment results, the proposed SIBC strategy shows a superior robustness than CBC and integral backstepping control (IBC) strategy.