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23 August 1996 Laser torquemeter: effects of axial shaft vibration
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Proceedings Volume 2868, Second International Conference on Vibration Measurements by Laser Techniques: Advances and Applications; (1996) https://doi.org/10.1117/12.248668
Event: Second International Conference on Vibration Measurements by Laser Techniques: Advances and Applications, 1996, Ancona, Italy
Abstract
Laser speckle produced from a diffuse object may be used in determining the angular position of a rotating object. When the object rotates the backscattered speckle patterns are sampled by a suitably positioned photodetector. The photodetector output signal is periodic and one period is stored in memory as a reference. Shaft position is then determined by cross-correlating this stored reference signal with the current photodetector output signal. When the shift is axially displaced the back scattered speckle patterns change and the cross-correlation between the reference signal and the current signal is reduced. The Laser Torquemeter is an instrument designed to measure the time- resolved torque transmitted in a rotating shaft and uses two probe laser beams, axially separated on a shaft of known mechanical properties. In order to design a robust Laser Torquemeter it is necessary to determine the cross- correlation of the current photodetector output signal and the stored reference signal as a function of axial shift position because the reduced cross-correlation due to axial motion results in a loss of tracking which is determined to the performance of the Torquemeter. Experiments conducted to measure the photodetector output cross-correlation show that the ratio of decorrelation displacement to beam diameter can achieve a maximum value of 0.7. For a typical axial shaft vibration of 0.6 mm peak to peak, a minimum beam diameter of 1 mm is recommended and further details of the optical configuration necessary to achieve this optimum resistance to decorrelation are suggested.
© (1996) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Iain D. C. Tullis, Neil A. Halliwell, and Steve J. Rothberg "Laser torquemeter: effects of axial shaft vibration", Proc. SPIE 2868, Second International Conference on Vibration Measurements by Laser Techniques: Advances and Applications, (23 August 1996); https://doi.org/10.1117/12.248668
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