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

Abstract This paper presents an approach to the synthesis of compressed vibration test profiles representing much longer time histories obtained in road testing of ground vehicles. Vibration test profiles are defined as those related directly to operational testing on specific 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 specific filtering tool facilitating bump event identification. 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 final vibration test profile with respect to the original road data. Test profiles 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 different frequency bands at the same moment of time. Test profiles generated in this way have provided better accuracy compared with the non-synchronized algorithm.

[1]  A. Baddeley.  Human Memory: Theory and Practice, Revised Edition , 1990 .

[2]  S K Lee,et al.  Application of wavelet analysis to the impact harshness of a vehicle , 2000 .

[3]  W. Staszewski.  WAVELET BASED COMPRESSION AND FEATURE SELECTION FOR VIBRATION ANALYSIS , 1998 .

[4]  W. J. Staszewski,et al.  A Vibration Mission Synthesis Algorithm for Mildly Nonstationary Road Data , 1999 .

[5]  W. J. Staszewski,et al.  Application of the Wavelet Based FRFs to the Analysis of Nonstationary Vehicle Data , 1997 .

[6]  H. Saunders,et al.  Book Reviews : AN INTRODUCTION TO RANDOM VIBRATION AND SPECTRAL ANALYSIS D.E. Newland Longman's Inc., New York, NY, 1978 , 1980 .

[7]  Charles K. Chui,et al.  An Introduction to Wavelets , 1992 .

[8]  M. Shinozuka,et al.  Digital simulation of random processes and its applications , 1972 .

[9]  C. K. Yuen,et al.  Digital Filters , 1979, IEEE Transactions on Systems, Man, and Cybernetics.

[10]  Lawrence Butler,et al.  'History: Theory and Practice' , 1997 .

[11]  S. Mallat.  A wavelet tour of signal processing , 1998 .

[12]  Alexander Steinwolf,et al.  Approximation and simulation of probability distributions with a variable kurtosis value , 1996 .

[13]  Joseph Giacomin,et al.  An algorithm for mildly nonstationary mission synthesis (MNMS) , 2000 .

[14]  David O. Smallwood.  Generation of Stationary Non-Gaussian Time Histories with a Specified Cross-spectral Density , 1997 .

[15]  I. Johnstone,et al.  Ideal denoising in an orthonormal basis chosen from a library of bases , 1994 .

[16]  D Charles.  DERIVATION OF ENVIRONMENT DESCRIPTIONS AND TEST SEVERITIES FROM MEASURED ROAD TRANSPORT DATA - PART 2 , 1993 .

[17]  F. Sherratt.  Current applications of frequency domain fatigue life estimation , 1996 .