Fixed time output feedback control for quadrotor unmanned aerial vehicle under disturbances

Abstract

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.

Unknown Input Observer-Based Fixed-Time Trajectory Tracking Control for QUAV with Actuator Saturation and Faults

“…The simulation results show that the high-accuracy estimation of the lumped disturbance can be obtained in fixed time, employing the proposed fixed-time UIO. Compared with other observers, such as the observers in [20][21][22][23][24][25][26], the advantages of proposed fixed-time UIO can be summarized as follows: (a) there is no chattering in the estimation of lumped disturbance and the estimation precision is better; (b) prior knowledge of the boundary of the disturbance or its derivative is not required; (c) the lumped disturbance can be observed accurately and quickly when it changes suddenly due to actuator faults. The fixed-time tracking controllers for translational and rotational subsystems could drive the tracking error into a small region in fixed time regardless of the initial values with the help of the proposed fixed-time UIO.…”

“…Remark 2. Compared with ESO in [21,22] and STDO in [25,26], the proposed fixed-time UIO in Equation ( 26) does not include the sign function and the prior knowledge of the disturbance, so the observer is simple to design and there is no chattering when estimating the disturbance.…”

“…To verify the performance of the proposed fixed-time UIO (FUIO), simulations using the fixed-time extend state observer (FESO) in [22] and the fixed-time integral sliding mode disturbance observer (FISMDO) in [25] are carried out for comparison.…”

“…The most efficient strategy for dealing with external disturbances, inertia uncertainties, and actuator faults is to compensate for their negative impacts on the system via exact estimation. As a result, numerous disturbance observer-based control approaches, such as those based on the extended state observer (ESO) [21,22], the super-twisting disturbance observer (STDO) [20,23,24], and the sliding mode disturbance observer (SMDO) [25,26], have been developed. Nonetheless, the observers mentioned above all require that disturbance is continuously differentiable and its derivative is bounded or known beforehand.…”

“…The fixed-time UIOs are designed to estimate the lumped disturbance for translational and rotational subsystems, with the estimation error able to converge to zero in fixed time. The proposed observer has three advantages and can overcome the limitations described in [20][21][22][23][24][25][26]. Firstly, it does not require prior knowledge of the upper bound of disturbance or its derivative.…”