Robust antiwindup for manual flight control of an unstable aircraft

A result on robust-in-the-large antiwindup compensation obtained for the case of asymptotically stable systems is extended to deal with unstable plants with asymptotically null references. The use of a weakened formulation of the antiwindup problem is crucial in the achievement of robustness to large parameter variations. The proposed design approach results in an antiwindup compensator that works as an add-on for any a priori given, high-performance controller, synthesized without taking saturation or robustness issues into account. The technique is applied to a reduced, short-period dynamic model of a highly unstable fighter aircraft, a case in which the issues of control saturation during aggressive maneuvering and robustness with respect to large parameter variations are of paramount importance. Simulations in low- and high-speed regimes demonstrate that the weakened antiwindup compensator outperforms previous antiwindup techniques in providing robust stability to the closed-loop system while exploiting the available control power in all of the considered maneuvers.