Active flutter suppression for a 2-D supersonic airfoil with nonlinear stiffness

A 3-DOF dynamic model is used for a 2-D airfoil with a control surface. The cubic nonlinear structural stiffness is considered in this model, and the aerodynamic load in the supersonic airflow is obtained by 3rd order Piston Theory. Nonlinear flutter happens with a phenomenon of limit cycle oscillations (LCOs) when the flight speed reaches the critical speed. The LQR approach is employed to design a control law to increase the critical speed of aerodynamic flutter. And then a combined control law is proposed in order to reduce the amplitude of LCOs by adding the cubic nonlinear feedback control. The dynamic responses of controlled system are given and used to compare with those of the uncontrolled system. Results of simulation show that the active flutter suppression method proposed here is effective.