Active Control and Closed-Loop Identification of Flutter Instability in Typical Section Airfoil

This research used the technique ofQ parameterization to identify an unstable model of an airfoil above its flutter boundary. A nominal, stabilizing controller was designed and implemented on a typical section airfoil with an articulated trailing-edge flap. Although stabilized by the nominal controller, the open-loop, unstable plant was identified from closed-loop signals at increasing flow speeds. The plant model identified at the highest flow speed was then used to design a new controller using theEvans root-locus technique. In a series ofwind tunnel tests, the nominal controller increased the flutter boundary by 30 % above the open-loop flutter speed, and the redesigned controller increased the boundary by 52%. Nomenclature A = state transition matrix B = input matrix C = output matrix D = feedthrough matrix d = disturbance G = actual plant G0 = nominal plant model H = disturbance shaping filter j = 1p K1 = nominal feedback controller K2 = redesigned feedback controller M0 = left coprime factor of G0 N0 = left coprime factor of G0 r = reference input s = Laplace transform variable U1 = flow speed u = plant input X = left coprime factor of K Y = left coprime factor of K y = plant output = input of = output of = plant Q parameter = plant pole = damping ratio of pole! = radian frequency!n = natural frequency of pole