Transverse gust mitigation via closed-loop control*

Unsteady flow conditions present significant challenges to stable flight, and gust rejection remains a concern for stability and control in many modern flight environments. Examples of gust-dominated environments include stormy conditions, aircraft takeoffs and landings in strong crosswinds or ship air wakes, and micro air vehicle flight in urban settings. In this work, we present lift mitigation experiments in large-amplitude transverse wing-gust encounters using simple proportional closed-loop control based on pitch actuation. The chosen control law was found to mitigate the lift transient peaks by 75 % for gusts inducing up to 35° effective angles of attack without a priori knowledge of the gust onset time or strength. The physics behind the success of simple control in a highly unsteady nonlinear environment is discussed. In addition, we present time-resolved lift, pitching moment, and flowfield measurements to bring about a deeper understanding of the unsteady flow physics for wings maneuvering in strong transverse gusts. Highlights of these findings include the effect of the wing’s maneuver on the gust’s structure, the evolution of the leading- and trailing-edge vortices, and the integral contribution of added mass in gust mitigation.