Disturbance Observers based Fixed-Time Backstepping Control for Quadrotors with Input Saturation and Actuator Failure

This paper investigates the fixed-time tracking control of the quadrotor unmanned aerial vehicles considering the disturbance, input saturation and actuator failure. According to the hierarchical control principle, the quadrotor dynamics is decomposed into position and attitude loops to accommodate the controller design. To achieve fast convergence of system tracking error with fixed time, a novel non-singular fixed-time backstepping controller based on switching variables is proposed. To overcome the disturbance and the actuator failure, two fixed-time disturbance observers are designed in two loops, respectively. By integrating the fixed-time auxiliary variables into the dynamic controllers, the input saturation can be solved. In addition, the tracking errors of the closed-loop system can converge to the small region of the origin in fixed time. Finally, simulation results show the validity of the proposed control framework for the quadrotor.