Experimental gust mitigation using model based feedforward and feedback control

Wing-gust encounters arising from flight over complex terrain or adverse weather are unavoidable and cause large lift transients that may result in structural damage due to extreme loads and/or fatigue. With the potential to extend the lifetime and improve the safety of air vehicles, gust mitigation through control is challenged by sensor noise, time-delays, and short response-time requirements. In this study, we build and deploy a closed-loop controller on an airfoil equipped with an actuated trailing-edge flap in a wind tunnel experiment. The control objective is the regulation of the lift coefficient, measured in real-time along the mid-section using fast-response pressure sensors. The onset and magnitude of gust disturbances, which are generated upstream by a pitching airfoil, are fed through using a two-component cross-wire located upstream of the leading edge. Feedback and feedforward controllers are designed based on reduced-order models for the lift response to flap actuation and perturbations in the cross-wire signals identified from open-loop experiments. The combined control setup proves to be an effective strategy for lift regulation during gust encounters, rejecting disturbances, attenuating noise, and compensating for model uncertainty.