Method of monitoring a transmission assembly of a vehicle equipped with acceleration sensors, in particular a helicopter

• US 6,016,993 A
• Filed: 07/06/1998
• Issued: 01/25/2000
• Est. Priority Date: 07/04/1997
• Status: Expired due to Term

• Current Assignee: Agusta SPA (Finmeccanica SPA)
• Original Assignee: Finmeccanica SPA
• Inventors: Maino, Bruno, Bellazzi, Alberto
• Primary Examiner(s): ELDRED, JOHN W
• Application Number:
  US09/110,305
• Time in Patent Office: 568 Days
• Field of Search: 244/60, 244/17.13, 180/337, 180/338
• US Class Current: 244/17.13
• CPC Class Codes: B64C 27/14 Direct drive between power plant and rotor hub
• CPC Class Codes: F16H 57/00 General details of gearing of screw-and-nut gearing F16H25/00; of fluid gearing F16H39/00 - F16H43/00
• CPC Class Codes: G01M 13/028 Acoustic or vibration analysis

Abstract

The method includes the steps of: acquiring a signal from an acceleration sensor; calculating the Hilbert transform of the signal filtered and sampled beforehand; defining a complex signal having the filtered and sampled signal as the real part and the Hilbert transform of the filtered and sampled signal as the imaginary part; calculating a phase signal given by the difference between the phase of the complex signal and a reference phase; calculating the variance of the phase signal; comparing the variance with at least one predetermined threshold; and generating an alarm signal if the variance exceeds the threshold value.

Claims

1. A method of monitoring a transmission assembly of a vehicle equipped with acceleration sensors, comprising the steps of:

a) acquiring a signal from an acceleration sensor mounted on the transmission assembly for detecting the acceleration of a moving member of the transmission assembly;

b) calculating the Hilbert transform of said signal;

c) defining a complex signal having said signal as the real part and said Hilbert transform of said signal as the imaginary part;

d) calculating the difference between the phase of said complex signal and a reference phase to obtain a phase signal;

e) calculating the variability of said phase signal to obtain a variability signal;

f) comparing said variability signal with at least a first predetermined threshold; and

g) generating an alarm signal if said variability signal exceeds said at least a first predetermined threshold.

2. A method as claimed in claim 1, characterized in that said variability signal is the variance of said phase signal.

3. A method as claimed in claim 1, characterized by repeating said steps a) to f) for a number of iterations.

4. A method as claimed in claim 1, characterized in that said step of calculating said Hilbert transform is preceded by a step of sampling and filtering said signal.

5. A method as claimed in claim 4, characterized in that said step of sampling and filtering comprises the steps of:

acquiring a number of synchronous samples T₁ (i) for each revolution of a shaft associated with said acceleration sensor; and

calculating an average time series T_1m (i) according to the equation;

##EQU5## where T₁ (i) is said synchronous samples, and 1 is a counter for counting the number of revolutions of said shaft.

6. A method as claimed in claim 5, characterized in that said step of sampling and filtering also comprises the step of filtering said average time series (T_1m (i)) with a band-pass filter centered at a predetermined frequency, to obtain a filtered mean signal (T'"'"'_1m (i)).

7. A method as claimed in claim 5, characterized in that said step of calculating an average time series is preceded by a step of determining the presence of significant signal values.

8. A method as claimed in claim 5, characterized in that said step of calculating an average time series is followed by a step of determining convergence of said average time series.

9. A method as claimed in claim 1, characterized in that said step of comparing said variability signal also comprises the step of comparing said variability signal with a second threshold.