Reducing measurement time for a Laser Doppler Vibrometer using a spatial regressive techniqueReducing measurement time for a Laser Doppler Vibrometer using a spatial regressive technique
Faculty of Applied Engineering Sciences
Engineering sciences. Technology
7th International Conference on Vibration Measurements by Laser, Techniques, June 19-22, 2006, Ancona, Italy
In the last decade the laser Doppler vibrometer (LDV) has become a widely spread instrument for measuring vibrations. It often offers accurate measurements with a high spatial resolution. However, the measurement time of the LDV and especially for the scanning LDV is long. Therefore reducing the measurement time is an attractive objective. A way to achieve this is to use a single sine excitation (on a resonance frequency). However this technique has two major drawbacks: the inability to provide accurate information on the damping and an operational deflection shape that can differ from the true mode shape. In this article a method will be introduced to reduce measurement time for scanning LDV measurements without these defaults. This is done by using a narrow band multisine excitation signal. Now for uncoupled normal modes the obtained time domain sequences for each scan point are in direct linear relation with each other. Therefore it is possible to estimate the full time domain sequence from the current scan point by using the previous scan point and a limited number of time samples from the current scan point, hence reducing the measurement time. This method is a key benefit for in-line quality control, which can have upwards of 1000 spatial measurement locations. The proposed technique will be validated on both simulations and experiments of varying complexity.