Method and apparatus for reducing vibration of a helicopter fuselage

• US 4,819,182 A
• Filed: 02/04/1987
• Issued: 04/04/1989
• Est. Priority Date: 06/21/1985
• Status: Expired due to Term

• Current Assignee: Westland PLC
• Original Assignee: Westland PLC
• Inventors: King, Stephen P., Hughes, Christopher I.
• Primary Examiner(s): Lall, Parshotam S.
• Assistant Examiner(s): Black, Thomas G.
• Application Number:
  US07/010,699
• Time in Patent Office: 790 Days
• Field of Search: 364/508, 244/17.27, 244/17.13, 244/17.11, 73/769, 73/772, 248/550, 248/560-563, 248/665, 248/669, 248/566
• US Class Current: 700/280
• CPC Class Codes: B64C 2027/002 mounted between the rotor drive and the fuselage
• CPC Class Codes: B64C 27/001 Vibration damping devices
• CPC Class Codes: F16F 7/10 using inertia effect F16F13/108, F16F13/22, F16F15/10, F16F15/22 take precedence; stabilising vehicle bodies by means of movable masses B62D37/04; protection of buildings against vibrations or shocks by mass dampers E04H9/0215; arrangements or devices for damping mechanical oscillations of power lines H02G7/14

Abstract

This invention relates to a method and apparatus for reducing vibration of a helicopter fuselage. The apparatus comprises a plurality of actuators interconnecting parts of the helicopter structure capable of relative motion at an exciting frequency, means to continuously oscillate the actuators at a frequency corresponding to the exciting frequency, a plurality of accelerometers attached to the fuselage for generating signals representative of fuselage dynamic accelerations, and processing means for processing said signals and providing output signals for controlling the phase and magnitude of operation of the actuators. In a described embodiment, one of the relatively movable parts comprises a raft structure carrying the gearbox and engines and attached to the fuselage by a resilient attachment adjacent each of its four corners.

Claims

1. A method of reducing vibration of a structure comprises the steps of connecting a plurality of actuators between parts of the structure capable of relative motion at an exciting frequency, continuously oscillating the plurality of actuators at a frequency substantially corresponding to the exciting frequency, generating signals representative of dynamic accelerations at a plurality of locations on the structure and feeding said signals to on board processing means providing output signals for controlling the phase and magnitude of applied forces generated by the actuators and for varying the phase and magnitude characteristics of said forces so as to compensate for changes in structure dynamics whereby the overall level of structural vibration is reduced.

2. A helicopter comprising a structure including a main sustaining rotor supporting a fuselage, a plurality of actuators connected between parts of the structure capable of relative motion at a frequency corresponding substantially with a frequency exciting the fuselage to vibrate, power source means continuously oscillating the actuators at a frequency corresponding substantially with the exciting frequency, a plurality of accelerometers attached to the fuselage at selected locations for generating signals representative of fuselage dynamic accelerations, and on board processing means for processing said signals and providing output signals for controlling phase and magnitude of the output forces generated by the actuators and for automatically adjusting the phase and magnitude of the actuator output forces to compensate for changing dynamic characteristics of the helicopter fuselage.

3. A helicopter as claimed in claim 2, wherein said exciting frequency corresponds substantially with the rotor blade passing frequency.

4. A helicopter as claimed in claim 2, wherein said exciting frequency comprises an instantaneous value from a pre-selected range of exciting frequencies.

5. A helicopter as claimed in claim 2, wherein one of said relatively movable parts comprises a raft structure carrying the gearbox and engines and attached to the fuselage by a resilient attachment adjacent each of its four corners.

6. A helicopter as claimed in claim 5, wherein each said resilient attachment comprises an elastomeric unit.

7. A helicopter as claimed in claim 6, wherein said resilient attachments and said actuators are equal in number.

8. A helicopter as claimed in claim 7, wherein each said resilient attachment and actuator are integrated in a single unit.

9. A helicopter as claimed in claim 2, said actuator comprises an electro-hydraulic actuator.

10. A helicopter as claimed in claim 2, wherein the number of accelerometers is not less than the number of actuators.

14. Apparatus as claimed in claim 2, wherein each said resilient attachment means comprise an elastomeric unit.

15. Apparatus as claimed in claim 2, wherein said resilient attachments and said actuators are equal in number.

16. Apparatus as claimed in claim 15, wherein each said resilient attachment and actuator are integrated in a single unit.

11. Apparatus for reducing vibration of a vehicle structure comprising a plurality of actuators interconnecting parts of the structure capable of relative motion at an exciting frequency, a power source adapted to continuously oscillate the actuators at a frequency corresponding substantially to the exciting frequency, a plurality of accelerometers attached to the structure for generating signals representative of structure dynamic accelerations, and processing means for processing said signals and providing output signals for controlling the phase and magnitude of output forces generated by the actuators and for automatically adjusting the phase and magnitude so as to compensate for changing structural dynamic characteristics.

12. Apparatus as claimed in claim 11, wherein each said actuator comprises an electro-hydraulic actuator.

13. Apparatus as claimed in claim 11, wherein said relatively movable parts of the structure are attached by resilient attachment means.

17. Apparatus as claimed in claim 11, wherein the number of accelerometers is not less than the number of actuators.