Operational modal analysis of a rotating tyre subject to cleat excitation

Structure-borne tyre/road noise is an important component of the perceived noise annoyance of passenger cars. More in particular, it was observed that crossing road surface discontinuities (e.g. concrete road surface joints, railroad crossing, potholes, ...) causes a significant increase in instantaneous exterior noise level. In addition, it has an adverse effect on the interior vehicle NVH in the sense that the passengers experience high-amplitude transient noise and vibrations. Therefore, an extensive research programme was established at the Department of Mechanical Engineering, K.U.Leuven, to study structure-borne tyre/road noise due to road surface discontinuities. As part of the research activities, an original test setup for impact tyre/road noise was developed so that rolling tyre vibrations, radiated noise and dynamic spindle forces could be measured at different rolling speeds. The test setup is based on the tyre-on-tyre principle and a cleat is used to reproduce a road surface discontinuity. This paper concentrates on the data processing techniques used to experimentally obtain the modes of a rolling tyre. Since the forces introduced by the cleat cannot me measured, Operational Modal Analysis was selected as processing technique. A major challenge is the requirement to obtain spatial information on the tire from a single-point measurement device. Therefore, a dedicated triggering and time-domain averaging procedure was elaborated. The purpose of averaging is obviously to reduce random noise whereas triggering is required to be able to correlate different tyre locations that have not been measured at the same time (a single-point Laser Doppler Vibrometer was used). ©2010 Society for Experimental Mechanics Inc.