A laser-based automated mechanical mobility measurement system has been developed
that can obtain a very high spatial resolution of frequency response functions (FRFs) for
experimental modal analysis where one-dimensional structural motion predominates. With
this system FRFs are measured and recorded in a format that is readily imported into a
popular modal analysis software. A scanning laser Doppler velocimeter is coupled to a
multi-channel FFf analyzer system for efficient data collection and management of
spatially distributed FRFs. The objectives in designing this measurement system is to
take advantage of the laser's non-contacting nature, its high spatial resolution, and its fast
point-to-point movement. By using the scanning capabilities of the laser, experimental
mobility FRF data can be collected in those structures that have dominant response in one
direction at up to 16,000,000 positions. Moreover, the laser does not mass load the
structure thus making the structure time invariant unlike "roving" accelerometers. The design and implementation of this automated mechanical mobility measurement system
is presented. Instrumentation interfacing and control issues as well as software
development issues are addressed in this thesis. Procedures required to implement the
laser-based measurement system are presented. The performance of the laser-based
system is presented along with an illustrative example of its use on a free-free rectangular
plate where the vibration response is primarily in one direction.
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