Nonlinear Robust Fault-Tolerant Control of the Tilt Trirotor UAV Under Rear Servo's Stuck Fault: Theory and Experiments

This paper presents a fault-tolerant control strategy to deal with the rear servo's stuck fault together with unknown exogenous disturbances of a trirotor unmanned aerial vehicle. A supertwisting-based observer is utilized to estimate the rear servo's stuck fault which is unknown, and a robust integral of the signum of the error based fault-tolerant controller is designed to compensate for the observation errors and exogenous disturbances. To avoid the singularity associated with orientation representations, the unit quaternion is utilized to formulate the attitude controller. The composite stability is analyzed via the Lyapunov-based methodology. Real-time experiments are implemented on a self-built hardware-in-loop-simulation trirotor testbed and the contrast experimental results with the sliding-mode-based fault-tolerant controller show that the proposed control scheme has achieved better control performance under the rear servo's stuck fault.