Vibration measurements using continuous scanning laser vibrometry: advanced aspects in rotor applications
Ben Halkon
Steve Rothberg
2134/3321
https://repository.lboro.ac.uk/articles/journal_contribution/Vibration_measurements_using_continuous_scanning_laser_vibrometry_advanced_aspects_in_rotor_applications/9563930
This paper builds on previous work concerned with the development of a
comprehensive velocity sensitivity model for continuous scanning Laser Vibrometry.
This versatile model predicts the measured velocity for arbitrary mirror scan angles and
arbitrary target motion and it has been especially valuable in revealing the sources of
additional components seen in continuous scanning and tracking measurements on
rotors.
The application to vibration measurements on rotors is the particular focus of this paper
which includes, for the first time, a three dimensional consideration of the incident point
on the target and validation of the DC component of measured velocity leading to
evaluation of the individual components of the small but inevitable misalignments
between the rotor and optical axes. This has not previously been possible.
Misalignments in the region 0.5mm and 0.5° were found and the model shows how
additional components of the order 10-20mm/s result for typical measurements. Such
levels are significant as they are comparable with vibration levels likely in real
applications and, if unexpected, may lead to data misinterpretation.
The first thorough analysis of laser speckle effects in scanning Laser Vibrometer
measurements on rotors is presented in the form of a speckle repeat map, together with
experimental data quantifying the dramatic reduction in speckle noise found in tracking
measurements. Finally, the velocity sensitivity model and the description of laser
speckle effects are used to enable confident interpretation of data from a series of
measurements on a rotating bladed disc.
2008-05-02 13:40:30
Laser Doppler Vibrometry
Scanning
Tracking
Vibration measurement
Rotating machinery
Laser speckle
Mechanical Engineering not elsewhere classified
Mechanical Engineering