Applied Active Control for a Nonlinear Aeroelastic Structure

Linear and nonlinear aeroelasticresponseisexamined using a uniquetest apparatusthat allowsforexperiments of plunge and pitch motion of a wing with prescribed stiffness characteristics. The addition of a control surface, combined with an active control system, extends the stable e ight region. Unsteady aerodynamics are modeled with an approximation to Theodorsen’ s theory appropriate for the low reduced frequencies associated with the experiment. Incorporated with a full-state feedback control law, an optimal observer is utilized to stabilize the system above the open-loop e utter velocity. Coulomb damping and hardening of the pitch stiffness are included to examine nonlinear control behavior. The nonlinear model is tested using the control laws developed from an extensionoflineartheory.EachmodelissimulatedusingMATLAB ® andcomparedwithexperimentalresultsofthe active control system. Excellent correlation between theory and experiment isachieved. Using an optimal observer and full-state feedback, the linear and nonlinear systems are stabilized at velocities that exceed the open-loop e utter velocity. Limited control is achieved when the system is undergoing limit cycle oscillations.