On the need for bump event correction in vibration test profiles representing road excitations in automobiles

This paper presents an approach to the synthesis of compressed vibration test proŽ les representing much longer time histories obtained in road testing of ground vehicles. Vibration test proŽ les are deŽ ned as those related directly to operational testing on speciŽ c road surfaces and which summarize the input to the vehicle in the given conditions. The method extends the classical Fourier transform technique by means of bump event correction in the background Fourier signal where the bump event term implies a high amplitude transient event of the shock type. The orthogonal wavelet decomposition was used as a speciŽ c Ž ltering tool facilitating bump event identiŽ cation. Examples of seat guide vertical acceleration have been considered. Calculated probability density functions suggest the ability of the bump correction method to improve the statistical accuracy of the Ž nal vibration test proŽ le with respect to the original road data. Test proŽ les obtained by means of Fourier transform synthesis with subsequent re-insertion of bump events from separated frequency bands were more accurate than those obtained by Fourier synthesis alone. Further developments led to advanced bump re-insertion with synchronization of events occurring in diVerent frequency bands at the same moment of time. Test proŽ les generated in this way have provided better accuracy compared with the non-synchronized algorithm.