Finite-Time Observer-Based Robust Continuous Twisting Control for the Attitude of an Uncertain Quadrotor UAV Subjected to Disturbances

This paper deals with robust attitude control problem of the quadrotor UAV in the presence of model uncertainties and external disturbances such as wind gusts. A Disturbance Observer-Based Control (DOBC) method is proposed by combining an Improved Twisting Control (ITC) algorithm and a Finite-Time Observer (FTO). Within the ITC scheme, the chattering problem of discontinuous Sliding Mode Control (SMC) techniques can be reduced due to the continuous control signal. Besides, finite-time convergence of the system states can be ensured to achieve accurate control. On the other hand, to reject external disturbances, the FTO observer is incorporated into the control framework. Stability analysis of the closed-loop system is rigorously investigated by using a homogeneous Lyapunov Function (LF). Experimental tests are conducted to validate the theoretical findings. A comparative study is made involving the proposed ITC-FTO strategy and three other controllers, including Continuous Twisting Controller (TC), Integral Backstepping Sliding Mode Controller (IBSMC), and a Nominal Backstepping Controller (NBSC). Overall, the obtained results show that the suggested control system yields performance improvement regarding accuracy and robustness. Meanwhile, the chattering effect of conventional SMC is remarkably alleviated.