Method and apparatus for normalizing condition indicators

• US 20030045976A1
• Filed: 12/04/2001
• Published: 03/06/2003
• Est. Priority Date: 05/24/2001
• Status: Active Grant

• Current Assignee: Simmonds Precision Products, Inc. (Rtx Corporation)
• Original Assignee: Simmonds Precision Products, Inc. (Rtx Corporation)
• Inventors: Bechhoefer, Eric Robert
• Granted Patent: US 6,754,569 B2
• Time in Patent Office: Days
• US Class Current: 701/29
• CPC Class Codes: G01H 1/003 of rotating machines G01H1/10 takes precedence
• CPC Class Codes: G01M 5/0033 by determining damage, crack or wear
• CPC Class Codes: G01M 5/0066 by exciting or detecting vibration or acceleration vibration testing of structures G01M7/00
• CPC Class Codes: G01M 7/00 Vibration-testing of structures; Shock-testing of structures G01M9/00 takes precedence
• CPC Class Codes: G01N 2291/2693 Rotor or turbine parts
• CPC Class Codes: G01N 2291/2696 Wheels, Gears, Bearings
• CPC Class Codes: G01N 29/11 by measuring attenuation of acoustic waves
• CPC Class Codes: G01N 29/12 by measuring frequency or resonance of acoustic waves measuring frequency or resonant frequency of mechanical vibrations or acoustic waves in general G01H1/06, G01H3/04, G01H13/00; acoustic resonators G10K11/04; vibration or shock testing of structures G01M7/00
• CPC Class Codes: G01N 29/4445 Classification of defects
• CPC Class Codes: G01N 29/449 Statistical methods not provided for in G01N29/4409, e.g. averaging, smoothing and interpolation
• CPC Class Codes: G01N 29/46 by spectral analysis, e.g. Fourier analysis or wavelet analysis spectral signal processing per se G06F17/14
• CPC Class Codes: G05B 23/0248 Causal models, e.g. fault tree; digraphs; qualitative physics

Abstract

Disclosed are techniques used in connection with determining a health indicator (HI) of a component, such as that of an aircraft component. The HI is determined using condition indicators (CIs) which parameterize characteristics about a component minimizing possibility of a false alarm. Different algorithms are disclosed which may be used in determining one or more CIs. The HI may be determined using a normalized CI value. Techniques are also described in connection with selecting particular CIs that provide for maximizing separation between HI classifications. Given a particular HI at a point in time for a component, techniques are described for predicting a future state or health of the component using the Kalman filter. Techniques are described for estimating data values as an alternative to performing data acquisitions, as may be used when there is no pre-existing data.

Claims

1. A method for normalizing a set of at least one observed condition indicator comprising:

determining a plurality of conditional indicators and at least one associated factor in accordance with previous data acquisitions;

determining a mean and at least one model coefficient corresponding to said at least one associated factor; and

adjusting said set of observed condition indicators in accordance with model coefficients and said at least one associated factor producing a normalized set of condition indicators.

2. The method of claim 1, wherein said relevant factors include at least one of:

torque, airspeed, and rotor speed.

3. The method of claim 2, wherein said relevant factors include torque, airspeed and rotor speed (Nr), and the method further comprising:

solving for B using the equation form y=B x for the following;

$y=\left[\begin{array}{c}{\mathrm{CI}}_1\\ {\mathrm{CI}}_{\mathrm{\dots <br><br>}}\\ {\mathrm{CI}}_n\end{array}\right]<br><br>\text{\hspace{1em}<br><br>}<br><br>B=\left[\begin{array}{cc}{B}_0& B_1<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\dots <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>B_n\end{array}\right]<br><br>\text{\hspace{1em}<br><br>}<br><br>\text{and}<br><br>\text{\hspace{1em}<br><br>}<br><br>x=\hspace{1em}<br><br>\left[\begin{array}{cccc}1& t_1& N_{R_1}& \mathrm{Airspeed1}\\ 1& t<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\dots <br><br>}& N_{R<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\dots <br><br>}}& \mathrm{Airspeed}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\dots <br><br>}\\ 1& t_n& N_R<br><br>n& \mathrm{Airspeedn}\end{array}\right]$

 

wherein the vector y includes condition indicator values and the matrix x includes relevant factors corresponding to one of said condition indicators included in y, and B includes coefficients.

4. The method of claim 3, wherein a normalized CI is determined at a later point in time by determining:

CInormalized=CIobs−

(B*x)

where CIobs is an actual observed value corresponding to a normalized CI value CInormalized.

5. The method of claim 4, further comprising:

storing said values for B and x in a database; and

retrieving said values for B and x in connection with determining CInormalized.

6. A computer program product for normalizing a set of at least one observed condition indicator comprising machine executable code for:

determining a plurality of conditional indicators and at least one associated factor in accordance with previous data acquisitions;

determining a mean and at least one model coefficient corresponding to said at least one associated factor; and

adjusting said set of observed condition indicators in accordance with model coefficients and said at least one associated factor producing a normalized set of condition indicators.

7. The computer program product of claim 6, wherein said relevant factors include at least one of:

torque, airspeed, and rotor speed.

8. The computer program product of claim 7, wherein said relevant factors include torque, airspeed and rotor speed (Nr), and the computer program product further comprising machine executable code for:

solving for B using the equation form y=B x for the following;

$y=\left[\begin{array}{c}{\mathrm{CI}}_1\\ {\mathrm{CI}}_{\mathrm{\dots <br><br>}}\\ {\mathrm{CI}}_n\end{array}\right]<br><br>\text{\hspace{1em}<br><br>}<br><br>B=\left[\begin{array}{cc}{B}_0& B_1<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\dots <br><br>}<br><br>\text{\hspace{1em}<br><br>}<br><br>B_n\end{array}\right]<br><br>\text{\hspace{1em}<br><br>}<br><br>\text{and}<br><br>\text{\hspace{1em}<br><br>}<br><br>x=\hspace{1em}<br><br>\left[\begin{array}{cccc}1& t_1& N_{R_1}& \mathrm{Airspeed1}\\ 1& t<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\dots <br><br>}& N_{R<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\dots <br><br>}}& \mathrm{Airspeed}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\dots <br><br>}\\ 1& t_n& N_R<br><br>n& \mathrm{Airspeedn}\end{array}\right]$

 

wherein the vector y includes condition indicator values and the matrix x includes relevant factors corresponding to one of said condition indicators included in y, and B includes coefficients.

9. The computer program product of claim 8, wherein a normalized CI is determined at a later point in time, and the computer program product further comprising machine executable code for determining:

CInormalized=CIobs−

(B*x)

where CIobs is an actual observed value corresponding to a normalized CI value CInormalized.

10. The computer program product of claim 9, further comprising machine executable code for:

storing said values for B and x in a database; and

retrieving said values for B and x in connection with determining CInormalized.