Hanson D., Randall B., Antoni J., Ford R.

This paper presents the application of a new technique for operational modal analysis to a high performance race-car. The technique combines two very powerful signal processing tools: cyclostationarity and the complex cepstrum. Cyclostationarity is employed to isolate the contribution to the responses of the engine combustion alone, effectively reducing a multiple-input-multiple-output system to single-input-multiple-output. The cepstrum is then employed to separate the source and transmission path, and curve fitted. The frequency response functions are thereby recovered up to an overall scaling constant, which can be readily obtained from a finite element model or a previous similar measurement, allowing the mode shapes to be correctly scaled. Unlike most other operational modal analysis techniques, the input need not be white, only frequentially smooth. The resonance frequencies, damping and mode shapes are compared with those obtained from a traditional impact hammer modal analysis.