Continuous Nonsingular Terminal Sliding-Mode Control With Integral-Type Sliding Surface for Disturbed Systems: Application to Attitude Control for Quadrotor UAVs Under External Disturbances

This paper proposes a continuous nonsingular terminal sliding mode control with integral-type sliding surface (CNTSMC-ISS) framework for disturbed systems, in which we consider two types of finite-time controller: the state feedback CNTSMC-ISS and the disturbance observer-based CNTSMCISS. Compared with the existing sliding mode controllers, the noteworthy contributions of two finite-time controllers in the proposed CNTSMC-ISS framework are the alleviation of the chattering phenomenon, the fast finite-time stability, the singularity-free, and the ease-of-implementation characteristics. In the proposed CNTSMC-ISS framework, we first introduce a nonsingular integral terminal sliding mode surface (NITSMS) such that the finite-time convergence of the system state to zero in the sliding phase is ensured and the singularity problem is avoided. Besides, a finite-time observer is developed to recover the external disturbance. Then, based on the constructed NITSMS with the super-twisting-like algorithm, the state feedback CNTSMC-ISS and the disturbance observer-based CNTSMC-ISS are proposed, which generate the continuous control signals and guarantee the fast finite-time convergence of the system state to the designed sliding surface. Rigorous finite-time stability of the closed-loop system under two proposed controllers is provided. Lastly, we apply two finite-time controllers in the proposed CNTSMC-ISS framework to the attitude control for quadrotor UAVs under external disturbances. Extensive simulation and experimental results are illustrated to prove the effectiveness of the proposed attitude controllers.