Laser Doppler Vibrometry is now a well-established and commercially viable technique
enabling non-contact vibration measurements in the most challenging of environments.
Rotating target vibration measurements are often highlighted as a major application of
Laser Vibrometers due to their non-contact operation and illherent immunity to shaft
run-out. This thesis describes advances in the application and interpretation of such
measurements using Laser Vibrometers.
It is readily accepted that a Laser Vibrometer measures target velocity in the direction of
the incident laser beam but this measured velocity must be considered in terms of the
various components of the target velocity. A previously derived theoretical description
of the velocity sensed by an arbitrarily orientated laser beam on a rotating structure
undergoing arbitrary six degree-of-freedom vibration provides the mathematical basis
for the investigations contained herein. This comprehensive velocity sensitivity model
presents the measured velocity as the sum of six terms, each the product of a
combination of geometric parameters, relating to the laser beam orientation, and an
inseparable combination of motion parameters, referred to as the vibration "sets".
Resolution of the individual axial and torsional motion components is possible via
particular arrangement of the laser beam(s) and by assuming that the effects of the
cross-sensitivity terms within those particular vibration sets are negligible. It is not
possible, however, to resolve the radial or pitch/yaw motion components in a similar
manner; this can only be achieved by post-processing the outputs from simultaneous
orthogonal measurements. In the study described in this thesis, a Lab VIEW software
based solution has been developed enabling, for the first time, real-time frequency
domain post-processing of the outputs from standard commercially available
instrumentation. The resulting measurement system is rigorously examined in terms of
performance and error sensitivity and implemented in several example measurement
situations thereby demonstrating the potentially powerful vibration information that is
available to the vibration engineer...cont'd
A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.