Test with two twin rotor damper units

The video demonstrates a method to prevent re-excitation of the system. When the vibrations come to rest due to active damping by the twin rotor damper (TRD), the TRD can re-excite the system. One method to prevent this outcome is the use of a second identical TRD unit to neutralize the control force or the control moment of the first one. This is illustrated in the video with torsional vibrations. The system that oscillates after an initial displacement (rotation) is first actively damped by both TRD units (TRD unit on the left side and on the ride side are in the same phase). In the video only the left TRD unit can be seen, the TRD unit on the right-hand side is hidden by the wind tunnel. Once the amplitude falls below a certain value, the phasing between the left TRD unit and the right TRD unit is set in a way that the resultant moments neutralize each other (left TRD unit and right TRD unit are in counterphase). Re-excitation of the system is thus prevented.