Fixed-Time Observer Based Safety Control for a Quadrotor UAV

This article presents a fixed-time observer-based safety control strategy for quadrotor unmanned aerial vehicles (UAVs) against multiple actuator faults and unknown disturbances. The fixed-time sliding mode observer is designed to estimate the state residual and the unknown actuator fault. Unlike most of the existing safety control strategies, the estimation time of the fault parameters is independent of initial condition, which can be strictly ensured within a fixed upper bound. Besides, the transient estimation error is regarded as a disturbance. In this article, a retrofit control mechanism with integration of the fixed-time estimator and an integral sliding mode controller is devised against multiple actuator faults and disturbances. Finally, both simulation and experimental tests demonstrate the effectiveness of the proposed UAV safety control.