Method and apparatus for sensing preload in a tilt rotor downstop

• US 6,220,545 B1
• Filed: 08/06/1999
• Issued: 04/24/2001
• Est. Priority Date: 08/06/1999
• Status: Expired due to Term

• Current Assignee: Bell Helicopter Textron Incorporated (Textron Inc)
• Original Assignee: Bell Helicopter Textron Incorporated (Textron Inc)
• Inventors: Darden, Paul Eugene, Fenny, Carlos Alexander, Builta, Kenneth Eugene
• Primary Examiner(s): Barefoot, Galen L.
• Application Number:
  US09/369,820
• Time in Patent Office: 627 Days
• Field of Search: 244/7.R, 244/7.A, 244/7.B, 244/7.C, 244/75.R, 738/625.41, 738/625.42, 915/12, 914/47, 702/41-44, 318/566, 604/36, 604/41, 604/42
• US Class Current: 244/7.00R
• CPC Class Codes: B64C 29/0033 the propellers being tiltable relative to the fuselage
• CPC Class Codes: B64D 35/04 characterised by the transmission driving a plurality of propellers or rotors

Abstract

A improved tilt rotor aircraft comprising an airframe, at least one wing member coupled to the airframe, and at least one tilt rotor assembly carried by the at least one wing member. The tilt rotor assembly is actuated by a conversion actuator. The improved tilt rotor aircraft includes a low-height tunable downstop assembly for absorbing oscillatory vibration loads, such as pitch loads and yaw loads. The low-height tunable downstop assembly comprises a pivotable striker assembly having an adjustable stiffness, and a cradle assembly adapted to releasably receive the striker assembly. The striker assembly is attached to the tilt rotor assembly and the cradle assembly is attached to the wing member. A plurality of sensor modules are bonded to the cradle assembly. The sensor modules include a plurality of strain gages arranged to sense shear strain in the cradle assembly. The sensor modules are electrically coupled to sensor circuits and flight control computers. As the conversion actuator pivots the tilt rotor assembly into the airplane mode, the conversion actuator forces the striker assembly into contact with the cradle assembly at a selected preload. The sensor modules directly sense preload induced strain in the cradle assembly and send corresponding signals to the flight control computers via the sensor circuits. If the signals from the sensor modules indicate that the preload is insufficient to maintain stability in the aircraft mode, then a warning signal is sent to the pilot and a control signal is sent to the conversion actuator to increase the preload. Likewise, if the signals from the sensor modules indicate that the preload is too high, a warning signal is sent to the pilot and a control signal is sent to the conversion actuator to decrease the preload.

Claims

1. An apparatus for maintaining a selected preload between members movable relative to one another, the apparatus comprising:

at least one actuator for creating a force between the members such that at least one of the members is strained, the force generating the selected preload between the members;

at least one sensor module coupled to at least one of the members to sense the strain therein and generate a corresponding signal; and

at least one microprocessor coupled to the at least one strain gage to interpret the signal;

wherein the microprocessor processes the signal and sends a control signal to the at least one actuator causing the at least one actuator to increase the force if the force is less than the selected preload, or decrease the force if the force is greater than the selected preload.

2. The apparatus according to claim 1, wherein the at least one sensor module is a plurality of sensor modules aligned in a parallel arrangement, each sensor module comprising a plurality of strain gages.

3. The apparatus according to claim 1, wherein the members movable relative to one another comprise:

an airframe of an aircraft; and

a wing member.

4. The apparatus according to claim 1, wherein the members movable relative to one another comprise:

an airframe of an aircraft; and

a radar assembly.

5. The apparatus according to claim 1, wherein the members movable relative to one another comprise:

a watercraft; and

a sensor assembly.

6. The apparatus according to claim 1, wherein the members movable relative to one another comprise:

an airframe of a tilt rotor aircraft; and

a tilt rotor assembly.

7. An improved tilt rotor aircraft comprising:

an airframe;

at least one wing member coupled to the airframe;

a tilt rotor assembly pivotally coupled to the at least one wing member;

a downstop assembly disposed between the tilt rotor assembly and the at least one wing member;

at least one actuator for pivoting the tilt rotor assembly relative to the at least one wing member and for creating a force between the tilt rotor assembly and the at least one wing member such that the downstop assembly is strained and a selected preload is induced between the tilt rotor assembly and the at least one wing member;

at least one sensor module coupled to the downstop assembly to sense the strain therein and generate a corresponding signal; and

at least one microprocessor coupled to the at least one sensor module to interpret the signal;

wherein the microprocessor processes the signal and sends a control signal to the at least one actuator causing the at least one actuator to increase the force if the force is less than the selected preload or decrease the force if the force is greater than the selected preload.

8. The apparatus according to claim 7, wherein the force is increased and decreased by dynamic loads generated during flight.

9. The apparatus according to claim 7, wherein the at least one sensor module is a plurality of redundant sensor modules aligned in a parallel arrangement, each sensor module comprising a plurality of strain gages.

10. The apparatus according to claim 7, wherein the downstop assembly comprises:

a first portion coupled to the tilt rotor assembly; and

a second portion coupled to the at least one wing member, the second portion being configured to releasably receive the first portion.

11. The apparatus according to claim 10, wherein the at least one sensor module is coupled to the second portion.

12. The apparatus according to claim 10, wherein the second portion comprises:

a cantilevered portion adapted to receive the at least one sensor module; and

a V-shaped block carried by the cantilevered portion, the V-shaped block being adapted to releasably receive the first portion;

wherein the cantilevered portion is strained by the force.

13. The apparatus according to claim 7, wherein the downstop assembly isolates and absorbs oscillatory loads generated by the tilt rotor assembly.

14. The apparatus according to claim 13, wherein the oscillatory loads are pitch loads and yaw loads.

15. The apparatus according to claim 7, wherein the pitch loads are isolated and absorbed by the first portion and the yaw loads are isolated and absorbed by the V-block.

16. In a tilt rotor aircraft having an airframe, at least one wing member coupled to the airframe, and a tilt rotor assembly pivotally coupled to the at least one wing member, a method of maintaining a selected preload between the tilt rotor assembly and the at least wing member comprising the steps of:

providing at least one actuator for pivoting the tilt rotor assembly relative to the at least one wing member;

disposing a downstop assembly between the tilt rotor assembly and the at least one wing member;

coupling at least one sensor module to the downstop assembly;

electrically coupling at least one microprocessor to the at least one sensor module;

pivoting the tilt rotor assembly relative to the at least one wing member with the actuator;

creating a force between the tilt rotor assembly and the at least one wing member;

straining the downstop assembly with the force;

sensing the strain in the downstop assembly with the at least one sensor module and generating a corresponding signal;

interpreting the signal with the microprocessor;

sending a control signal from the microprocessor to the at least one actuator in response to the signal;

increasing the force with the actuator if the force is less than the selected preload; and

decreasing the force with the actuator if the force is greater than the selected preload.

17. The method according to claim 16, wherein the force is increased and decreased by dynamic loads generated during flight.

18. The method according to claim 16, wherein the step of coupling at least one sensor module to the downstop assembly is achieved by coupling a plurality of redundant sensor modules to the downstop assembly in a parallel arrangement, each sensor module comprising a plurality of strain gages.

19. The method according to claim 16, wherein the step of disposing a downstop assembly between the tilt rotor assembly and the at least one wing member is achieved by disposing a first portion on the tilt rotor assembly and disposing a second portion on the at least one wing member.