Image-based tracking laser Doppler vibrometer

Abstract

An innovative version of the tracking laser Doppler vibrometer based on image acquisition and processing (iTLDV) is proposed. The iTLDV is developed for tracking of arbitrary motions; the system is feedback controlled and allows measuring the vibrations of a moving target by driving moving mirrors via position signals of the target obtained from a charge-coupled-device camera and an image processing algorithm. The tracking system developed has been applied to an industrial test case subject to self-excited vibrations, in order to verify the performances and limits in the operating conditions. The system demonstrates its ability to measure vibration time histories on a windscreen wiper in operative conditions. This test case represents a challenging measurement problem, since no other measurement techniques are available that are able to extract such data. Some examples of obtained data are shown, which highlight the potential of iTLDV. In addition, position accuracy and measurement uncertainty are discussed. For the windscreen wiper, the worst position accuracy is estimate as ±1.2 mm along the wiper axis, while the measurement uncertainty mainly depends on the commercial vibrometer applied in the setup (about ±2% depending on operative conditions).