Device for indicating a beat level

• US 20060029499A1
• Filed: 06/10/2005
• Published: 02/09/2006
• Est. Priority Date: 06/10/2004
• Status: Active Grant

• Current Assignee: Airbus Helicopters
• Original Assignee: Eurocopter
• Inventors: Aubourg, Pierre-Antoine
• Granted Patent: US 7,331,235 B2
• Time in Patent Office: Days
• US Class Current: 416/190
• CPC Class Codes: B64C 27/001 Vibration damping devices

Abstract

The present invention relates to a device for indicating a beat level L, the device comprising analyzer means which respond to a reference frequency Ω and a harmonic coefficient B to extract the following from an evaluation signal E:

• • a first acceleration signal γ_B at a frequency equal to the product of said reference frequency Ω multiplied by said harmonic coefficient B; and
  • a second acceleration signal γ_B -1 at a frequency equal to the product of said reference frequency Ω multiplied by said harmonic coefficient minus one;
  • and it further comprises a control circuit CC which receives said acceleration signal γ_B′γ_B-1 to produce said beat level L.

Claims

1. A device for indicating a beat level L, the device comprising analyzer means FT which, in response to a reference frequency Ω

and to a harmonic coefficient B extracts the following from an evaluation signal E;

a first acceleration signal γ

_B at a frequency equal to the product of said reference frequency Ω

multiplied by said harmonic coefficient B; and

a second acceleration signal γ

_B-1 at a frequency equal to the product of said reference frequency Ω

multiplied by said harmonic coefficient minus one;

and the device further comprising a control circuit CC which receives said acceleration signal γ

_B′

γ

_B-1 to produce said beat level L.

2. A device according to claim 1, further comprising a comparator COMP which produces a warning signal AL if said beat level L exceeds a predetermined threshold TH.

3. A device according to claim 1, wherein said beat level L is a function of the exact difference between firstly the n^th power of one of said acceleration signals γ

_B′

and secondly the other acceleration signal γ

_B .

4. A device according to claim 3, wherein said beat level is equal to the ratio of the n^th power of one of said acceleration signals γ

_B-1 divided by the other acceleration signal γ

_B .

5. A device according to claim 3, wherein the value of n is equal to 2.

6. A device according to claim 1, wherein said evaluation signal E comes from a vibration sensor.

7. A device according to claim 1, including a concentrator member MM for producing said evaluation signal E in response to a plurality of measurement signals C1, C2, and C3, each coming from a distinct vibration sensor S1, S2, S3.

8. A device according to claim 7, wherein said evaluation signal E is equal to the sum of said measurement signals C1, C2, C3.

9. A device according to claim 7, wherein said evaluation signal E is the greatest of said measurement signals C1, C2, C3.

10. A device according to claim 1, wherein said reference frequency Ω

is derived from a tachometer T.

11. A device for indicating a beat level L of a rotary wing aircraft having a rotor with a plurality of blades, the device comprising:

a vibration sensor S1, S2, S3 for measuring vibration on board the aircraft;

a speed sensor T for measuring the speed of rotation of the rotor, the speed sensor providing a reference signal having a reference frequency Ω

;

a synchronous analysis means FT for synchronously analysing harmonic components of a vibration signal E derived from the vibration sensor, the synchronous analysis means FT being connected to the vibration sensor and to the speed sensor, the synchronous analysis means FT being arranged to extract from the vibration signal E;

i) a first harmonic component γ

_B of frequency BΩ

equal to the product of said reference frequency Ω

multiplied by a harmonic coefficient B equal to the number of blades of the rotor, and

ii) a second harmonic component γ

_B-1 of frequency (B-1)Ω

equal to the product of said reference frequency Ω

multiplied by said harmonic coefficient B minus one;

a control circuit DC connected to the synchronous analysis means FT, the control circuit receiving said first and second harmonic components and outputting a beat level L.

12. A device according to claim 11, further comprising a comparator which produces a warning signal AL if said beat level L exceeds a predetermined threshold TH.

13. A device according to claim 11, wherein said beat level L is a function of the exact difference between firstly the n^th power of one of said harmonic components γ

_B′

and secondly the other harmonic component γ

_B .

14. A device according to claim 13, wherein said beat level is equal to the ratio of the n^th power of one of said harmonic components γ

_B-1 divided by the other harmonic component γ

_B .

15. A device according to claim 14, wherein the value of n is equal to 2.

16. A device according to claim 11, including a concentrator member for producing said vibration signal E in response to a plurality of measurement signals C1, C2, and C3, each coming from a distinct vibration sensor.

17. A device according to claim 16, wherein said vibration signal E is equal to the sum of said measurement signals C1, C2, C3.

18. A device according to claim 16, wherein said vibration signal E is the greatest of said measurement signals C1, C2, C3.