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Analytical design studies, simulation, and a series of wind tunnel tests have led to the demonstration of a closed-loop vibration suppression system in the Baeing Vertol V/STOL Wlnd Tunnel. Using small amounts of oscillatory swashplate molion, this active ronlrol system simullsneously suppressed up to 90 percent of the fourper-rev vertical force, pitching moment, and rolling moment of a 3.05 m (10 fool)-diameter, four-bladed hingeless rotor. The system operated successfully in a large number of flight coaditions including trsnsition and autorotation. Response time to cancel sudden changes of vibration level was very short, about 1.25 rotor revolutions. Thus the system will be able to suppress vibration of a flight vehicle during maneuvers and gusty conditions. The system, although demonstrated on a hingeless rotor, is also applicable to arlieulated single and tandem rotor configurations. The wind tunnel testing included measurement of rotor fatigue loads, control loads, and performance. Based on the data, active control appears to be a practical approach to vibration suppression. The technology is now ready for full scale development.

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