This paper designs a fixed time output feedback trajectory tracking control scheme for quadrotor Unmanned Aerial Vehicle with unmeasurable velocity and external disturbances. Firstly, a fixed time extend state observer (ESO) is devised to accurately observe the unknown velocity and estimate unknown total disturbances within a fixed time. Especially, the convergence time of system is independent of system initial states. Secondly, considering control accuracy and convergence rate, robust fixed time controllers are respectively designed for position and attitude system. Thirdly, the tracking errors of controller is capable of converging to zero according to homogeneous theory and Lyapunov theory, and superior results can be achieved under the proposed control scheme. Finally, simulations and comparison studies are verified to demonstrate the effectiveness of the designed fixed time output feedback control scheme.

针对具有不可测速度和外界干扰的四旋翼无人机，设计了一种固定时间输出反馈轨迹跟踪控制方案。首先，设计了一个固定时间扩展状态观测器（ESO）来准确地观察未知速度并估计固定时间内的未知总扰动。特别是系统的收敛时间与系统初始状态无关。其次，考虑控制精度和收敛速度，分别为位置和姿态系统设计了鲁棒的固定时间控制器。第三，根据齐次理论和李雅普诺夫理论，控制器的跟踪误差能够收敛到零，在所提出的控制方案下可以取得较好的效果。最后，