Calculates the weighted coherence for a given set of FRF and Coherence
c = summary_coherence(f)
c = summary_coherence(f,freq_range,dof,'dof','freq','both','all','use_frf','silent')
Summary coherence is used to assess overall frequency response function quality for a given set of response degrees of freedom over a specified frequency range.
F is an imat_fn containing FRF or Autospectra, and Coherence.
FREQ_RANGE is a 1x2 vector containing the frequency range of interest. If not supplied, SUMMARY_COHERENCE will use the entire frequency range.
DOF is an imat_ctrace containing a list of response degrees of freedom to be used. If not supplied, SUMMARY_COHERENCE will use all of the DOF in the coherence functions.
Passing in the string 'silent' suppresses output.
The following strings select the various summary coherence summation options:
'freq' | Summary coherence for each test DOF over a range of frequencies. Gives an indication of sensor quality. |
'dof' | Summary coherence for each frequency over a set of test DOF. Gives an indication of overall FRF quality as a function of frequency. |
'both' | Summary coherence over a set of test DOF and over a set of frequencies gives a scalar value that can be used to assess overall test quality. |
'all' | Select all of the above options. |
The optional input string causes SUMMARY_COHERENCE to estimate response DOF autospectra by assuming white noise input. If not supplied, SUMMARY_COHERENCE will use the response DOF Autospectra directly.
C is a structure containing the summary coherence output. It contains the following fields:
.matrix | Coherence matrix (MxN) where M is number of frequencies and N is number of DOF. |
.coherence | imat_fn containing coherence functions. |
.freq | Vector of evaluation frequencies. |
.dof | imat_ctrace containing DOF evaluated. |
.summary_freq | 'freq' option only. Vector of length N containing summed coherences. Values are also stored in column N+1 of .matrix. |
.summary_dof | 'dof' option only. imat_fn containing summed coherences. Values are also stored in row M+1 of .matrix. |
.summary_both | 'both' option only. Scalar summed coherences. Value is also stored in location M+1,N+1 of .matrix. |
Kevin L. Napolitano, Nathaniel C. Yoder, Ralph D. Brillhart, "A Comparison Of Multiple Impact Testing Methods", IMAC, 2012.
>> c = summary_coherence(f);
>> c = summary_coherence(f,[100 500],'all');
>> c = summary_coherence(f,ct,'freq','dof','silent','use_frf');