Modal studies on a truck frame and suspension

This paper presents a comparative study of conventional Experimental Modal Analysis (EMA) and output-only Operational Modal Analysis (OMA) techniques for estimating the modal parameters of a moderately damped truck chassis. The OMA, without its need to measure input forces, would serve as a convenient methodology to test vehicle structures when response data alone is available. Data has been acquired from the test structure with different excitation techniques, namely, shaker and impact hammer for the EMA tests, and, shaker and random impact using hammer for the OMA tests. Re sponse powerspectral data has been processed for output-only OMA and the estimates obtained have been validated against those based on processing frequency response function (FRF) data based on conventional EMA methods. The results indicate a fairly consistent estimation of modal parameters for the test structure using both OMA and EMA methods.