Vibration attenuator

A vibration attenuator for a rotor of an aircraft, the attenuator comprising:

• a housing adapted for rotation with the rotor about an axis;
• a lower weight coupled to a lower ring rotatably carried by a housing for rotation about the axis;
• an upper weight coupled to an upper ring rotatably carried by the lower ring for rotation about the axis;
• a stop member located on one of the rings and configured for abutting a corresponding feature of the other ring for limiting the relative rotation of the rings between positions corresponding to a minimum-force configuration, in which the weights are positioned 180 degrees apart;
• a first motor configured for rotating the first ring relative to the housing;
• and
• a second motor configured for rotating the second ring relative to the housing and to the first ring;
• wherein the first and second motors are operated to rotate the weights within the housing and position the weights relative to each other for attenuating vibrations.

An aircraft having a rotor, the rotor comprising:

• a hub;
• a plurality of blades coupled to the hub;
• a vibration attenuator, comprising:
• a housing coupled to the hub for rotation with the rotor about an axis;
• a first ring rotatably carried within the housing on a first bearing, a first weight being coupled to the first ring for rotation therewith relative to the housing about the axis;
• a second ring rotatably carried by the first ring on a second bearing, a second weight being coupled to the second ring for rotation therewith relative to the housing and to the first ring;
• a stop member located on the first ring and configured for abutting a corresponding feature of the second ring for limiting the relative rotation of the rings between positions corresponding to a minimum-force configuration, in which the weights are positioned 180 degrees apart;
• a first motor configured for rotating the first ring relative to the housing;
• and
• a second motor configured for rotating the second ring relative to the housing and to the first ring;
• wherein the first and second motors are operated to rotate the weights within the housing and position the weights relative to each other for attenuating vibrations.