Laser Doppler Vibration Research Articles

Laser Doppler vibration measuring system using bispectral analysis

A new laser Doppler vibration measuring method, which operates correctly even in fairly large disturbing Gaussian noise, is developed. In this method the amplitude and phase of vibration are extracted by bispectral analysis between the detected and reference signals so that the significant bispectral characteristics of the detected signal, which reflects the frequency modulation by the vibration, is used. Application of the bispectral analysis excludes disturbing Gaussian noise, resulting in realization of a measuring system effective even under noisy circumstances. The experimental results show clearly the usefulness of the proposed method.

Flexible gear for ship propulsion: L. R. Emmet. ( General Electric Review, vol. xx, No. 3, p. 238, March, 1917.)

The application of laser Doppler vibration measurements is a powerful technique for monitoring and analysing mechanical systems. Frequently experiments in operative conditions may be a useful tool for analysing the real behaviour of an object. However, in several applications we may find that the object is rotating during its work and in these conditions the measurement with traditional techniques becomes difficult. For these reasons a system for the tracking of rotating objects has been developed in order to perform vibration measurements.In the present work the application of the tracking laser scanning vibrometer on an operative condition problem is shown. A tracking laser scanning vibrometer has been used for measuring the vibration of a map of points on the object surface during a complete circular motion. The analysed object was a model of a naval propeller working in water. A comparison has been found with the static analysis, in water and air, of the same propeller. Some results are shown.