Nonsingular terminal sliding mode control for a quadrotor UAV with a total rotor failure

Abstract

Based on nonsingular terminal sliding mode control (NTSMC), a flight controller is proposed in this paper for a quadrotor with a total rotor failure. The proposed method is a finite-time position and attitude tracking approach with strong robustness. At first, the fault-tolerant controller for the quadrotor with a total rotor failure is derived, and the model uncertainties and wind disturbances are considered. The dynamic model of the quadrotor is introduced and divided into two control loops: the inner control loop and the outer control loop. Based on the division of the control system, the NTSMC based inner controller is designed which makes the attitude dynamics converge to the desired attitude in finite-time. And the NTSMC based outer controller is derived which generates the desired attitude for the inner controller and makes the dynamics converge to the desired position in finite-time. The stability of the closed-loop system is analyzed by Lyapunov theory and the stability conditions are obtained. Then, in order to improve the practicability of the control algorithm, a flight controller for a fault-free quadrotor is proposed which has a similar structure compared with the fault-tolerant one. A fault detection and isolation method is applied to detect the fault and reconfigure the flight controllers. Moreover, two estimation methods for external disturbance and model uncertainties are applied to enhance the robustness of the proposed flight controller. The estimated wind disturbances results are introduced into the outer controller to compensate for the effect of disturbance while the model uncertainties estimator is applied in the inner control loop. Finally, numerical simulation results show the great performance of the proposed flight control method.