Fixed-Time Command Filtered Attitude Fault-Tolerant Tracking Control for a TTUAV with Input Saturation

To address the attitude tracking fault-tolerant control problem of a tilt trirotor unmanned aerial vehicles (TTUAV) under input saturation, modeling uncertainties and external disturbances, a fixed-time command filtered attitude fault-tolerant tracking control scheme based on a fixed-time disturbance observer (FTDO) is proposed. First, taking into consideration the effects of modeling uncertainties and external, the attitude dynamics model of the TTUAV is developed. A new FTDO is designed to eliminate the effects of lumped disturbances. Next, a fixed-time command filter (FTCF) is introduced to reduce the computational complexity and overcome the complexity explosion (CE) problem. To eliminate the impact of filtering errors, a fixed-time filtering error compensation strategy is designed. Then, to tackle the input saturation problem of the TTUAV, a fixedtime auxiliary system (FTAS) is introduced to mitigate the effects of input saturation. By combining the fixed-time filtering error compensation strategy and the FTAS, a new fixed-time attitude tracking controller (FTATC) is designed. Moreover, The stability of the attitude system is examined and confirmed through the Lyapunov method. Finally, numerical simulations are conducted to verify the excellent performance of the proposed FTATC for attitude tracking control of the TTUAV.