Adaptive Fault-Tolerant Control for Quadrotor Based on the Second-Order Fast Nonsingular Terminal Sliding Mode Control

In this article, a novel adaptive fault-tolerant controller (FTC) based on the second-order fast nonsingular terminal sliding mode control (AFT-SOFNTSM) is developed to guarantee flight stabilization and a smooth landing at the designated location for the event of a single rotor failure in the quadrotor. The proposed controller employs a second-order sliding mode control (SOSMC) method as a reaching law, which can effectively eliminate chattering behaviors and smooth the control output while retaining the speed and accuracy of tracking the rotation axis. In addition, the influences of the desired rotation axis and angular velocity norm are discussed in relation to the dynamic tracking performance of the FTC. Based on the above, a strategy is presented to improve the tracking performance with a large moment of inertia. Finally, the high-speed response and accuracy tracking error properties of the closed-loop control system under the AFT-SOFNTSM controller are theoretically analyzed. The flight experiments demonstrate the feasibility and tracking performance of the proposed control strategy. Comparative studies, involving different rotation axes and angular velocity norms, are also conducted. The results of these studies validate our theoretical analysis.