LAUSR

This paper designs the double closed-loop control system combining nonlinear disturbances observers (NDOB) and an adaptive fast nonsingular terminal sliding mode (AFNTSM) for the tracking control problem of quadrotor under external disturbances, actuator saturation and unmodeled dynamics. The NDOB-AFNTSM method avoids the singularity problem. To compensate for disturbances, an adaptive strategy estimates the unknown bound of NDOB errors and the unknown bound of disturbances. Besides, new fast reaching law shortens convergence times. The dead zone method is chosen to avoid over-estimation and system divergence. Considering actuator saturation, this paper uses an anti-saturation auxiliary compensator to compensate for unknown saturation errors. System stability is confirmed by the Lyapunov direct method. The simulation results reveal that the proposed method improves convergence speed and accuracy, which is more robuster than similar methods. Finally, two comparative studies for performance indexes in simulation demonstrate the preferable performance of the proposed method.