Robust adaptive nonsingular fast terminal sliding-mode tracking control for an uncertain quadrotor UAV subjected to disturbances

Abstract

This paper investigates the design of a robust controller for the trajectory tracking problem of an under-actuated quadrotor UAV subject to the modeling uncertainties and unknown external disturbances. A new robust nonlinear adaptive controller is proposed for orientation and translation tracking by using the Adaptive Nonsingular Fast Terminal Sliding-Mode Control (ANFTSMC) algorithms. The ANFTSM control law: (i) ensures fast convergence, i.e. the quadrotor outputs achieve to the original values in a short finite-time; (ii) avoids singularities; (iii) solves the chattering effect; (iv) offers robustness against the unknown external disturbances and uncertainties. Furthermore, the system unknown uncertainty and external disturbances upper bound are coped by the proposed control approach. Online estimation of these upper bounds is only introduced by velocity and position measurements. In addition, the control law applies the Lyapunov theory, guarantees the closed-loop stability of the quadrotor system. Finally, various simulations under different scenarios in terms of external disturbances and parametric uncertainties are carried out to evaluate/emphasize the effectiveness of the ANFTSMC strategy proposed in this work. Moreover, a comparative study is accomplished at the end of the present paper and shows clearly the outperformance of the proposed control scheme.