CORA and ISO-18571

Use the HyperGraph 2D Curve Correlation dialog to find correlation metrics in the form of notes using different correlation algorithms. The CORA and ISO-18571 functions calculate the correlation metric between test and CAE data.

CORA
The Correlation Analysis (CORA) calculates the correlation metric between CAE and Test Data signals in the form of time history. Includes both corridor and cross correlation, which are calculated independently and then combined to give a comprehensive error. The error calculation can be biased toward either the measured time history (Test) or the computed (CAE) time history, with the former being the most common.
CORA(CORRIDOR)
The Corridor method (CR) calculates the correlation between two signals by corridor fitting. The error calculation can be biased toward either the measured time history (Test) or the computed (CAE) time history, with the former being the most common.
CORA(CROSS CORRELATION)
The cross correlation method (CRCR) calculates the correlation between two signals by calculating phase shift, size, and progression. The weighted sum of these three values gives the total cross correlation rating.
ISO-18571
The ISO metric combines different types of algorithms to a get reliable and robust assessment between CAE and Test Data signals in the form of time history. Includes corridor, phase, magnitude, and slope, which are calculated independently and then combined to give an overall ISO rating. The error calculation can be biased toward either the measured time history (Test) or the computed (CAE) time history, with the former being the most common.

Open the Curve Correlation Dialog

  1. From the File menu, click File > Open > Plot to open the Create Curves by File dialog.
  2. From the Open File dialog, navigate to your working directory and select a file to open and plot some curves.
  3. From the Plot Browser, select a reference curve, right-mouse click, and select Curve Correlation.
  4. From the Correlation Type drop-down menu, select a correlation method.
    Figure 1.


  5. Select Cora to display the following options.
    Figure 2.


  6. Retain the default settings or change the defaults per your requirements and click Plot.

    Notes are displayed with the correlation metrics in the plot window.

Input Options

Reference Curve
Select reference curves through the Plot Browser or enter a list of ID’s. For example, 1-4.
Correlation Curve IDs
An individual ID or list of IDs. For example, 5-7.
Correlation Type
Supported methods include:
  • SGCM
  • Wifac
  • Cora(cross correlation)
  • Cora(Corridor)
  • Cora
  • ISO-18571

Cora Parameters

Evaluation Interval Parameters
Description
A_THRES
Threshold to set the start of the interval of evaluation. Varies between 0 and 1.
B_THRES
Threshold to set the end of the interval of evaluation. Varies between 0 and 1.
A_EVAL
Automatically calculated interval of evaluation. Varies between 0 and 1.
B_DELTA_END
Shortens the end of the interval of evaluation if it is calculated automatically. Varies between 0 and 1.
Tmin/Tmax
Defines the start and the end time of the evaluation interval.
Corridor Parameters
Description
K
Exponent factor (progression) for the calculation of the corridor rating.
G-1
Weighting factor of the corridor rating.
a0
Width of the inner and outer corridor.
b0
Width of the inner and outer corridor.
a_sigma
Factors of the standard deviation to widen the inner corridor.
b_sigma
Factors of the standard deviation to widen the outer corridor.
Cross Correlation Parameters
Description
D_MIN
Calculates the interval of evaluation. Varies between 0 and 1.
D_MAX
Calculates the interval of evaluation. Varies between 0 and 1.
INT_MIN
Minimum overlap of the interval. Varies between 0 and 1.
K_V
Exponent factor (progression) of the calculation of the progression rating, V.
K_G
Exponent factor (progression) of the calculation of the size rating, G.
K_P
Exponent factor (progression) of the calculation of the phase shift rating, P.
G_V
Weighting factors of the progression rating.
G_G
Weighting factors of the size rating.
G_P
Weighting factors of the phase shift rating.
G_2
Weighting factors of the cross-correlation method.
Signal Parameters
Description
MIN_NORM
The limit to start the special treatment of the secondary axis. Varies between 0 and 1.
Y_NORM
Calculation type of Y_NORM; options include extremum or value.
WF_NORM
Normalization of the weighting factors; options include YES or NO.

Select ISO-18571 to display the following options:

Figure 3.


ISO-18571 Parameters

Evaluation Interval Parameters
A_THRES
Threshold to set the start of the interval of evaluation. Varies between 0 and 1.
B_THRES
Threshold to set the end of the interval of evaluation. Varies between 0 and 1.
A_EVAL
Automatically calculated interval of evaluation. Varies between 0 and 1.
B_DELTA_END
Shortens the end of the interval of evaluation if it is calculated automatically. Varies between 0 and 1.
Tmin/Tmax
Keyword that defines the start and end time of the interval of evaluation.
Corridor Parameters
K
Exponent factor (progression) for the calculation of the corridor rating.
W_Z
Weighting factor of the corridor rating.
a0
Width of the inner and outer corridor.
b0
Width of the inner and outer corridor.
a_sigma
Factors of the standard deviation to widen the inner corridor.
b_sigma
Factors of the standard deviation to widen the outer corridor.
Cross Correlation Parameters
W_P
Weighting factor of the phase score.
W_M
Weighting factor of the magnitude score.
W_S
Weighting factor of the slope curve.
Signal Parameters
MIN_NORM
The limit to start special treatment of a secondary axis. Varies between 0 and 1.
Y_NORM
Calculation type of Y_NORM; options include extremum or value.
WF_NORM
Normalization of the weighting factors; options include YES or NO.

Cora Display Options

Phase(P)
Display the phase value.
Progression(V)
Display the progression value.
Size(G)
Display the size value.
Total Correlation Rating(C2)
Display the total correlation rating value.
Total Cross Correlation Rating(C1)
Display the total cross correlation rating value.
Corridor Rating
Display the corridor rating value.
Reference Curve Label
Display the reference curve label.
Correlation Curve Label
Display the correlation curve label.

ISO-18571 Display Options

Total Correlation Rating(C2)
Display the total correlation rating value.
Phase Rating(EM)
Display the phase rating value.
Rank
Display the rank value.
Magnitude Rating(EP)
Display the magnitude rating value.
Corridor Rating
Display the corridor rating value.
Slope Rating(ES)
Display the slope rating value.
Reference Curve Label
Display the reference curve label.
Correlation Curve Label
Display the correlation curve label.