Fault-Tolerant Position Tracking Control Design for a Tilt Tri-Rotor Unmanned Aerial Vehicle

In this article, a new nonlinear robust fault-tolerant position tracking control law is proposed for a tilt tri-rotor unmanned aerial vehicle (UAV) under unknown rear servo's stuck fault together with parametric uncertainties and unknown external disturbances. The immersion and invariance approach is employed to design the adaptive controller for the position loop of the UAV. For the attitude loop of the UAV, a sliding-mode-based adaptive observer is utilized to estimate the unknown stuck fault associated with the rear servo, and then the robust integral of the signum of the error method is utilized to formulate the robust attitude controller to compensate for the estimation mismatch and unknown disturbances. The stability of the closed-loop system and asymptotic tracking of the desired position trajectory are proved via Lyapunov-based stability analysis. To validate the performance of the proposed fault-tolerant control design, real-time experiments are implemented on a self-built hard-ware-in-loop UAV testbed. Comparing the results with the proportional-integral-differential (PID) controller shows that the proposed control scheme has achieved better control performance.