Rotating shaft damping with electro-rheological fluid

1. A method of damping vibrations in a rotorcraft rotating shaft, the method comprising:

surrounding at least a portion of a circumferential surface area of a portion of a rotorcraft rotating shaft with a plurality of hollow members, each hollow member including an electro-rheological fluid having a viscosity that changes based on an electric field applied to the electro-rheological fluid;

controlling a vibration of the rotorcraft rotating shaft by changing the viscosity of the electro-rheological fluid in response to the electric field applied to the electro-rheological fluid; and

controlling the vibration of the rotorcraft rotating shaft by controlling a stiffness of an electromagnetic bearing positioned between the rotorcraft rotating shaft and the plurality of follow members.

2. The method of claim 1 , wherein the plurality of hollow members include two substantially U-shaped hollow members.

3. The method of claim 2 , wherein the two U-shaped hollow members surround all of the circumferential surface area of the portion of the rotorcraft rotating shaft.

4. The method of claim 1 , wherein each hollow member is an elastomeric member.

5. The method of claim 1 , wherein controlling the vibration of the rotorcraft rotating shaft comprises:

monitoring the vibration of the rotorcraft rotating shaft;

determining a quantity of damping to counter the vibration; and

applying a quantity of the electric field to the electro-rheological fluid, the quantity of the electric field to change the viscosity of the electro-rheological fluid to provide the determined quantity of damping.

6. The method of claim 5 , further comprising positioning a network of wires in the electro-rheological fluid, wherein applying the quantity of the electric field to the electro-rheological fluid comprises applying the quantity of the electric field to the network of wires.

7. The method of claim 1 , wherein controlling the vibration of the rotorcraft rotating shaft comprises:

determining that the vibration of the rotorcraft rotating shaft is greater than an upper vibrational limit; and

increasing the electric field applied to the electro-rheological fluid, wherein the electric field increases the viscosity of the electro-rheological fluid to counter the vibration.

8. The method of claim 7 , further comprising:

determining that the vibration of the rotating shaft is less than the upper vibrational limit; and

decreasing the electric field applied to the electro-rheological fluid, wherein the electric field decreases the viscosity of the electro-rheological fluid.

9. A radial damper assembly comprising:

a ring-shaped outer housing;

a plurality of hollow members positioned within the outer housing to surround at least a portion of a circumferential surface area of a portion of a rotorcraft rotating shaft, each hollow member including an electro-rheological fluid having a viscosity that changes based on an electric field applied to the electro-rheological fluid;

a network of wires arranged in columns or rows of alternating polarity that are positioned in and distributed throughout the electro-rheological fluid; and

an electromagnetic bearing having a variable stiffness positioned between the plurality of hollow members and the rotorcraft rotating shaft.

10. The assembly of claim 9 , wherein the plurality of hollow members include two substantially U-shaped hollow members.

11. The assembly of claim 10 , wherein the two U-shaped hollow members surround all of the circumferential surface area of the portion of the rotorcraft rotating shaft.

12. The assembly of claim 9 , wherein each hollow member is an elastomeric member.

13. The assembly of claim 9 , further comprising an inner race positioned between the plurality of hollow members and the rotorcraft rotating shaft.

14. A radial damper system comprising:

a radial damper assembly comprising a plurality of hollow members surrounding at least a portion of a circumferential surface area of a portion of a rotorcraft rotating shaft, each hollow member including an electro-rheological fluid having a viscosity that changes based on an electric field applied to the electro-rheological fluid;

an electromagnetic bearing positioned between the plurality of hollow members and the portion of the rotorcraft rotating shaft, the electromagnetic bearing having a variable stiffness; and

a vibration control system to control a vibration of the rotating shaft by changing at least one of the viscosity of the electro-rheological fluid in response to the electric field applied to the electro-rheological fluid or the stiffness of the electromagnetic bearing.

15. The system of claim 14 , wherein the vibration control system comprises:

a vibration monitoring system to monitor the vibration of the rotorcraft rotating shaft; and

an electric field generation system to apply a quantity of electric field to the electro-rheological fluid, the quantity of the electric field to change the viscosity of the electro-rheological fluid to damp the vibration.

16. The system of claim 14 , wherein the plurality of hollow members include two substantially U-shaped elastomeric hollow members which surround all of the circumferential surface area of the portion of the rotorcraft rotating shaft.

17. The assembly of claim 9 , wherein the network of wires positioned in the electro-rheological fluid comprises at least one of straight wires, crooked wires, or a matrix arrangement of wires.

18. The system of claim 14 , further comprising a network of wires positioned in and distributed throughout the electro-rheological fluid.

19. A radial damper assembly comprising:

a ring-shaped outer housing; and

a plurality of hollow members positioned within the outer housing to surround at least a portion of a circumferential surface area of a portion of a rotorcraft rotating shaft, each hollow member including an electro-rheological fluid having a viscosity that changes based on an electric field applied to the electro-rheological fluid;

a network of wires positioned in the electro-rheological fluid;

a bearing positioned between the plurality of hollow members and the rotorcraft rotating shaft, wherein the bearing is an electromagnetic bearing having a variable stiffness.

20. The assembly of claim 19 , wherein the plurality of hollow members include two substantially U-shaped hollow members that surround all of the circumferential surface area of the portion of the rotorcraft rotating shaft.

21. The assembly of claim 19 , wherein each hollow member is an elastomeric member.

22. The assembly of claim 19 , further comprising an inner race positioned between the plurality of hollow members and the rotorcraft rotating shaft.