Wind Disturbance Rejection and Fault Recovery for Quadplane Trajectory Tracking Using a Supertwisting Observer

This paper presents a combined wind disturbance rejection and actuator fault compensation control strategy for the longitudinal quadplane trajectory tracking. A super twisting sliding mode observer is formulated to estimate lumped uncertainties, consisting of wind disturbances on all longitudinal gust channels and an additive elevator fault. A Dryden continuous gust model is used for the simulation analysis. The estimated perturbations are compensated in the control loop to ensure robust trajectory tracking across the vertical takeoff and landing, forward flight modes and the transitioning modes between them. The super twisting sliding mode observer algorithm provides finite time convergence with smooth flight mode transitions. Simulation results demonstrate accurate trajectory tracking under moderate wind conditions in the presence of an additive actuator fault. The super twisting observer-based compensation is combined with two benchmark controllers, a linear quadratic regulator and a H∞ controller, without loss of generality. The observer-based corrections improve the tracking accuracy-energy trade-off in both cases. The super twisting observer-based H∞ controller outperforms the observer-compensated linear quadratic regulator in terms of tracking accuracy for similar energy consumption, which is attributed to increased robustness to observer estimation errors. Simultaneous fault and wind disturbance compensation presents benefits for safety-critical unmanned aerial vehicle operations under windy conditions.