Wind tunnel testing of an adaptive control system for vibration suppression on aircraft

Recently, it has been shown that adaptive feed-forward control is a very efficient means for the reduction of atmospheric turbulence induced structural vibrations on large transport aircraft. However, the real-time behavior of such an adaptive control system has not been investigated yet. In order to ease the step towards flight testing, an adaptive wing bending control system has been investigated in wind tunnel experiments. Testing of feed-forward vibration control in a wind tunnel poses many technical challenges. The most important of which is to generate locally correlated disturbances in order to provide a proper reference signal for feed forward control. This problem has been solved by designing a gust generator which is mounted right in front of an elastic wind tunnel model of a four-engine transport aircraft, while keeping wind tunnel turbulence low at the same time. Despite the fact that the wind tunnel environment is more difficult for proper feed-forward control of aircraft vibrations than the real atmosphere would be, the adaptive controller showed excellent performance. The successful wind tunnel tests represent a major step towards flight testing of the adaptive aircraft vibration control system.