Attitude tracking control for quadrotor based on time-varying gain extended state observer

Considering the problems of unknown external disturbances and parametric uncertainties in attitude tracking of a quadrotor, a backstepping sliding mode control method based on the time-varying gain extended state observer is proposed in this article. First, the mathematical model of the attitude system of the quadrotor is introduced. Second, a time-varying gain extended state observer is proposed to observe the unmeasurable states, total disturbance, and reduce the “peaking value” phenomenon, which often occurs in traditional linear extended state observers. It is proved that the observation errors are bounded. Third, a novel controller synthesized by backstepping sliding mode control method and the time-varying gain extended state observer is proposed for the attitude system of the quadrotor. Moreover, the designed controller can ensure that all signals of the closed-loop system are bounded. Finally, the effectiveness and superiority of the proposed control method are verified by simulation.