Random Vibration Analysis and Vehicle Development

General methods are described for the use of random vibration analysis techniques in vehicle development activities. The success in the application of the described techniques depends to a large extent on a thorough understanding of all factors controlling vibration measurements in an on-the-road vehicle environment. Basic philosophy as well as specific recommendations are given for design of test procedures in vehicle evaluation and problem diagnosis tasks.

The use of random vibration analysis techniques has already resulted in better understanding of vehicle vibration phenomenon encountered. In particular, in recent years very significant work has been done by Ford and elsewhere on fundamental vibration sources such as road profile perturbation and rotating tire inputs. Good understanding of the relative importance of a particular vibration source in a given problem is required before a successful test plan can be prepared.

The final and most important task facing the development engineer is an effective description of the mechanism by which his particular vibration problem comes about. Such a description includes identification of predominant vibration sources, determination of pertinent system parameters, and, for continuous elastic structures, the description of mode shapes.