Aeroservoelastic unstability failure analysis in special wind tunnel test

In an already completed wind tunnel test where a flight control system was applied, the vibration divergence of the test model under big closed-loop gain has drawn our attention. To find the mechanism of this failure, the frequency analysis of the test data has been done and the servo stabilization under no wind condition has been examined. Also, we built a simplified structural mechanic model according to the real situation and investigated the problem by analyzing the related differential equation of motion. The main cause for this failure has been found: the unexpected elastic effect after the involving of support system is significant and thus the coupling of elastic structure, control system and aerodynamic force gives rise to the aeroservoelastic instability. In addition, a numerical simulation has been done and verified the above mechanism. To solve this divergence problem, two improvements/solutions for the control system have been brought up: adding a structure filter in the feedback loop or changing the gain parameters of different control surfaces. Also, both the solutions have been verified by numerical simulation. The solution of adding a structure filter has been applied in the real wind tunnel test and expected effect has been achieved.