METHOD AND SYSTEM FOR DETECTING AND MEASURING THE DISTURBANCES IN TERMS OF FREQUENCY OF THE RATE OF ROTATION OF A ROTOR

• US 20070090961A1
• Filed: 10/20/2006
• Published: 04/26/2007
• Est. Priority Date: 10/21/2005
• Status: Active Grant

• Current Assignee: Safran Aircraft Engine Company
• Original Assignee: Snecma (Safran SA)
• Inventors: GEREZ, Valerio
• Granted Patent: US 7,583,200 B2
• Time in Patent Office: Days
• US Class Current: 340/670
• CPC Class Codes: F02D 41/1497 With detection of the mechanical response of the engine
• CPC Class Codes: G01M 15/046 by monitoring revolutions for detecting misfire G01M15/11
• CPC Class Codes: G01P 3/489 Digital circuits therefor

Abstract

The invention pertains to a method of detecting the variations of speed (R) of a rotor characterized by the fact that it consists, in real time, in: measuring signals representative of the march-past of the teeth of a phonic wheel or of an equivalent means secured to the rotor for a determined duration (T), sampling, digitizing and storing the measurements performed to obtain an initial digital vector (B), extracting from the initial vector (B) a detection signal around a known disturbing frequency (F), comparing the detection signal with a predetermined threshold (SO) and delivering an alert message in the event of overshoot. The invention also pertains to a system for detecting such variations.

Claims

1. - Method of detecting the variations of speed (R) of a rotor characterized by the fact that it consists, in real time, in:

measuring signals representative of the march-past of the teeth of a phonic wheel or of an equivalent means secured to the rotor for a determined duration (T),

sampling, digitizing and storing the measurements performed to obtain an initial digital vector (B),

extracting from the initial vector (B) a detection signal around a known disturbing frequency (F),

comparing the detection signal with a predetermined threshold (SO) and

delivering an alert message in the event of overshoot.

2. - Method according to claim 1, in which, to extract a signal of detection of the disturbing frequency:

the initial vector (B) is filtered and a filtered vector (H) is obtained,

peaks (S) of alternation of the signals are detected,

the peaks (S) are dated, the time intervals (Δ

T) separating the adjacent peaks are calculated, the temporal evolution R(t) of the speed (R) is established on the basis of these intervals, and

the said evolution is filtered around the known disturbing frequency (F).

3. - Method according to claim 2, in which the vectors (B, . . . , S) are tagged in relation to a time base (A) of dimension N determined from the speed (R), the characteristics of the measurement means (1, n) and the disturbing frequency (F).

4. - Method according to claim 1, in which the said signals are sampled at a frequency (Fe) at least twice as high as those of the transient disturbances present in the signals.

5. - Method according to claim 2, in which the vector operations applied to the vectors comprise exclusively sums, differences, tests and coordinate shifts.

6. - System for detecting the variations of speed (R) of a rotor, comprising measurement means comprising a sensor delivering in real time signals representative of the rate of rotation of the rotor, characterized by the fact that it comprises means of signals processing comprising a calculation block calculating in real time the rate of rotation so as, if appropriate, to instantaneously emit a message of disturbance of the speed (R) and delivering a message of abnormal appearance of a disturbance of frequency (F) lower than the frequency of rotation of the rotor.

7. - System according to claim 6, in which the measurement means comprise a phonic wheel secured to the rotor delivering signals representative of the march-past of the teeth of the phonic wheel, and in which the processing means sample the said signals before digitizing them and storing them in digital form.

8. - System according to claim 7, in which the processing means sample the signals at a frequency (Fe) at least twice higher than the maximal frequency of the transient disturbances which may be present therein.

9. - System according to claim 6, in which the calculation block comprises a filtering module eliminating any spurious noise that might be present in the signals.

10. - System according to claim 6, in which the calculation block comprises a module for detecting peaks in the signals, corresponding to the transits of the crests of the teeth in front of the sensor.

11. - System according to claim 10, in which the calculation block dates the peaks, and deduces therefrom the time intervals (Δ

T) separating them.