Wind-Tunnel Tests for Active Flutter Control and Closed-Loop Flutter Identification

In this study, active flutter control and closed-loop flutter identification were experimentally studied for a low-aspect-ratio wing model in an Nanhang-2 subsonic wind tunnel. To actively suppress the flutter of the wing model in wind-tunnel tests, a real-time digital control system was developed so as to complete the data acquisition, digital signal processing, computation of the control strategy, and servo control of the actuator. Using the digital control system, wind-tunnel tests were conducted to examine the flutter control of the wing model. The experimental results showed that the linear feedback controller designed via the optimization of pole assignment can effectively suppress the flutter instability. Moreover, for the high-dimensional aeroservoelastic system, the online estimation of closed-loop flutter modes is a challenging problem because the flutter identification from closed-loop measurements may lead to biased estimates, and the identification efficiency must be improved. Therefore, as the second task of this study, the online closed-loop flutter identification of the wing model was explored. To efficiently identify the flutter modes, a fast recursive subspace identification method was used. The experimental results show that the natural frequencies and modal damping ratios of the closed-loop flutter modes could be accurately tracked over a wide range of flow speeds.