Using High-Speed Stereophotogrammetry Techniques to Extract Shape Information from Wind Turbine/Rotor Operating Data
Stereophotogrammetry techniques used in concert with 3D point tracking (dynamic photogrammetry) software are advantageous for the collection of operating data on large wind turbines (or helicopter rotors) over conventional accelerometer-data acquisition systems (DAQ) for several reasons. First, this is a non-contacting technique that doesn’t require the use of mounted accelerometers and electrically noisy slip rings. Second, the optical targets (measurement points) that are mounted to the blade surfaces can remain in place for long periods of time and be used for subsequent measurements without extended/overly complicated setup time. Third, deflection data can be collected on many more points on a turbine/rotor surface beyond what is capable of a conventional multi-channel data acquisition system and accelerometer setup. Operating data has previously been collected on a 1.17 m Southwest Windpower Air BreezeTM wind turbine  using Stereophotogrammetry and this data has been used to extract operating deflection shapes from the structure. The purpose of this work is to improve upon the experimental methods used on the 1.17 turbine by Warren  and apply these improved methods to a larger, 2.56 m diameter turbine/rotor analog, and collect operating data on the structure. This data was collected outdoors and shape information was extracted from this operating data and compared to that taken with a standard, impact test.
KeywordsWind Turbine Mode Shape Electronic Speckle Pattern Interferometry Modal Assurance Criterion Crosspower Spectrum
The authors gratefully appreciate the financial support for this work provided by the U.S. Army Research Office Nanomanufacturing of Multifunctional Sensors Ref. Award Number: W911NF-07-2-0081 and the National Science Foundation under Grant No. 0900534, entitled “Dynamic Stress–strain Prediction of Vibrating Structures in Operation”. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation or Army Research Office.
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