Active flutter suppression of a two-dimensional airfoil section using μ synthesis

This paper presents how to use the ultrasonic motor as an actuator in the flutter suppression of a two-dimensional airfoil section with a control surface. The study begins with the combined theoretical and experimental modeling for the aeroservoelastic system with the damping uncertainty in plunge direction and the modeling error of the ultrasonic motor taken into consideration. Then, it focuses on the design of a controller by using μ synthesis at a given flow speed. The numerical simulations and wind tunnel tests show that the μ controller is able to suppress the flutter effectively and the critical flutter speed of controlled system is increased by 23.4%. In addition, a comparison of μ controller and H_∞ controller shows that the former is superior to the latter in the flutter suppression and in the robustness with respect to the time delay in the control loop.