Fixed-Time Fault-Tolerant Attitude Tracking Control for a TTUAV with Prescribed Performance

To address the issues of underactuation, model uncertainty, external disturbances and time-varying actuator faults in the tilt trirotor UAV (TTUAV) system, in this paper, a novel fixed-time fault-tolerant attitude tracking control scheme based on a fixed-time disturbance observer is proposed. First, a new prescribed performance function (PPF) is designed and by combining the error transformation method, the original attitude error dynamic model with constrained performance is transformed into an unconstrained equivalent attitude error dynamic model, ensuring both transient and steady-state performance of the TTUAV control system. Secondly, a fresh fixed-time disturbance observer (FTDO) is introduced to eliminate the effects of the composite disturbances consist of model uncertainty, external disturbances and time-varying actuator faults. Then, by combining the PPF and the FTDO, a fixed-time fault-tolerant attitude tracking control strategy based on the backstepping method is derived. Furthermore, the stability of the closed-loop system is analyzed by utilizing Lyapunov stability theory and it is verified that the TTUAV’s attitude tracking errors can converge to zero in fixed time. Finally, numerical simulations are performed, the results validate that the proposed fixed-time fault-tolerant attitude tracking control scheme can effectively enhance the robustness of the TTUAV system against the composite disturbances.