Terminal Sliding Mode Controller Design Based on Barrier for UAVs With Mismatched Disturbances

A novel terminal sliding mode controller is proposed for the control problem of quad-rotor unmanned aerial vehicles (UAVs) with mismatched disturbances. Unlike previous disturbance observer strategies, a sliding mode surface based on exponential coefficients dependent on the time variable is designed to reject the mismatched disturbance. Since the disturbance observer is not required to track the unmatched disturbance in real time, the proposed strategy can not only reduce the amount of calculation but also improve the calculation speed. Furthermore, a novel barrier function is designed to mitigate the impact of disturbance while avoid the occurrence of infinite control gain. Applying Lyapunov theory and a fixed-time strategy, the proposed method ensures convergence of the quad-rotor UAVs in a fixed time. Finally, we validate the effectiveness of the proposed method by comparing it with existing methods through simulations.