Application of an enhanced Coordinate Modal Assurance Criterion

This paper presents an extension of the Coordinate Modal Assurance Criterion (COMAC) for spatial comparison of mode shapes. As is the case for the original COMAC, this enhanced COMAC helps identify degrees of freedom differences between test and analysis modes, but also overcomes some of the limitations of the original COMAC. The original COMAC cannot identify errors caused by scaling or polarity mistakes in the test data. Such mistakes are easily made during modal tests and not always easily detected since they do not affect the subjective quality of a frequency response function.