STRUCTURAL INSTABILITY INDUCED BY ACTUATOR CONSTRAINTS IN CONTROLLED AEROELASTIC SYSTEM
In this paper, an active flutter control scheme
is investigated for a 2dof airfoil with nonlinear torsional stiffness. We use a simple graphical method to characterize
all possible system equilibria. With the help of this method we study how an active flutter suppression system can lead to "parasitic" steady states, which are different from the nominal zero-pitch, zero-plunge trim conditions. It appears that these equilibria can be induced by the presence of non-smooth saturation function, which describes amplitude constraints imposed on the system actuators. With control system built using only knowledge of "nominal" system dynamics, the closed-loop system becomes structurally unstable in the sense that a small change in its parameters
or the addition of infinitesimal unmodeled dynamics can lead to the "parasitic" steady states appearance or disappearance.