Analysis Of Two-dimensional Wing Active Flutter Suppression System With Time-delayand Free Play Nonlinearity

In wing flutter control system, time delay is inevitable during signal transducing and processing, and the control surface free-play cannot be completely eliminated because of manufacturing errors. This dissertation devotes to the effects of time delay and control surface free-play on wing flutter control system using an airfoil with an ultrasonic motor actuated control surface. The main contribution of the dissertation can be summarized as follows:Firstly, the ultrasonic motor control system, whose core component is a DSP board, is constructed and tested using PID controller. The test result demonstrates that the control system works well and the control surface can rotate tracing the control command efficiently.Secondly, the aeroelastic model of the two-dimensional airfoil is established based on Theodorsen unsteady aerodynamics. The flutter speed of the airfoil model is 15.45m/s. Two sub-optimal controllers are designed with the wind speed of 17.8 m/s and 22m/s respectively. Numerical simulations and wind tunnel tests show that the sub-optimal controllers are able to suppress the flutter effectively. Using the first controller, the flutter speed of controlled system can be increased by 36%, and by switching to the second controller when the flow speed is about 19 m/s, the flutter speed can be increased by 84%.Then, the effect of time-delay on the control system is studied. The result shows that time-delay will reduce the stability of flutter suppression system. In order to eliminate the negative effects, time-delay optical controllers are designed. Numerical simulations and wind tunnel experiments demonstrate that the time-delay optical controllers are efficient.Finally, the effects of control surface free-play on open and closed loop of the aero-elastic system are investigated. Numerical simulations show that control surface free-play will reduce wing flutter speed and cause the flutter control system instable. If time delay and control surface free-play are both incorporated, the flutter control system will be more inclined to be instable and its behavior will be more complicated.