This brief focuses on the problem of fixed-time adaptive trajectory tracking control for a quadrotor unmanned aerial vehicle (QUAV) subject to error constraints. By virtue of the fixed-time command filter, the phenomenon of “explosion of complexity” (EOC) existing in the conventional backstepping method is successfully eliminated, meanwhile the effect of filtered error is skillfully removed via a new fractional power error compensation mechanism. By combining the prescribed performance control and backstepping design method together with command filter technique, a fixed-time adaptive control strategy is established. It is proved that all signals of the closed-loop system are fixed-time bounded, and the position and attitude tracking errors of the QUAV approach to an arbitrarily small region of the original point within the predefined performance bounds in a fixed time. Finally, simulation results are given to show the availability of the presented fixed-time control algorithm.

This paper considers the distributed fixed-time formation control problem of multiple quad-rotor unmanned aerial vehicles (QUAVs) subject to input constraints. With an emphasis on resolving the “explosion of complexity” problem, the fixed time command filter is constructed. Aiming at eliminating the impact of filtering errors, the error compensation signals based on fractional-power are designed. Additionally, the problem of singularity is skillfully addressed with the help of the piecewise function. To compensate for the influence of input constraints, the auxiliary signal with fixed-time convergence is devised. By incorporating the event-triggered control mechanism into the command filtered backstepping design process, an event-triggered distributed adaptive fixed-time formation control algorithm for multiple QUAVs is developed. It is strictly proved that all closed loop signals are fixed-time bounded and the formation tracking errors are driven into a small neighborhood of the origin within a fixed time. Finally, two simulation examples demonstrate the effectiveness of the proposed fixed-time formation control scheme

In this brief, the problem of fixed-time distributed formation control for multiple quadrotor unmanned aerial vehicles (QUAVs) suffering from external disturbances is investigated. Resorting to the fixed-time disturbance observer (FTDO), the unknown disturbances are accurately estimated without requiring the information of initial observer errors. Based on the fusion of command filter technique, nonsmooth error compensation mechanism and backstepping design method, the proposed singularity-free distributed formation controllers ensure that the whole closed-loop system is practical fixed-time stable, and the formation tracking errors converge to a small neighbourhood of the zero in a fixed time. Finally, a numerical simulation reveals the validity of the devised distributed formation control scheme.

In this brief, the problem of finite-time heading tracking control for surface vehicles with controller faults and full state constraints is studied. The fuzzy logical systems and command filtered backstepping method are utilized to approximate the unknown nonlinear dynamics and construct an adaptive controller, respectively. The Nussbaum function is employed to solve the unknown control direction arising in the system. The new control scheme is proposed based on barrier Lyapunov functions and finite-time control strategy. It is proved that the error between the actual heading angle and the expected one can converge to the region near the origin in a finite time without violating the full state constraints. Finally, the simulation results are presented to show the effectiveness of the proposed finite-time control scheme.