Automotive components vibration measurements by tracking laser Doppler vibrometry: advances in signal processing

This paper describes the application of a tracking laser Doppler vibrometer (TLDV) for vibration measurements on automotive components and the advances in data processing. A Lagrangian approach is adopted: the target point moves continuously and it is tracked by the measurement laser spot, thus no relative velocity between the target and the laser spot exists. By eliminating the relative motion of the laser beam on the surface, speckle noise is drastically reduced. Measuring on a moving reference frame opens an innovative way to look at automotive component vibrations, because the space-time evolution of the vibration can be measured under simulated operative conditions. After a presentation and discussion of the measurement technique, attention is focused on three different applications in the automotive field: the side-wall vibration of a rolling tyre, the out-of-plane vibration of a timing belt and the rubber blade vibration of complex motion windscreen wipers. The development of optimized TLDV measurement systems for each specific application is shown and some results are presented. Vibration data have been analysed in both the time and frequency domains. Moreover, in order to point out time-dependent frequency features in signals, vibration data have been further processed by means of joint time-frequency algorithms.