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Contribution à l'estimation paramétrique de signaux à variation sinusoïdale de la fréquence instantanée et à amplitude variable : application à l'anémométrie laser à effet Doppler pour l'acoustique

Abstract : Laser Doppler Anemometry (LDA), which is widely used in fluid mechanics, can also be used in order to measure acoustic particle velocity. The knowledge of this vector quantity could be especially useful to characterize a complex acoustic field, allowing for example the study of phenomena close to vibrating surfaces or around duct discontinuities. In addition, LDA ensures, for this kind of problem, theoretically non-invasive velocity measurements with an excellent spatial resolution.
The Laboratoire d'Acoustique de l'Université du Maine is equipped with a system designed for acoustic velocity measurement. For nearly eight years, research has been directed towards the experimental assessment of this technique and the development of signal processing methods based on post-processing techniques, with the assumption of a constant amplitude Doppler signal.
However, in order to design a more integrated set-up, furthermore easy to manipulate, it is essential to design a system providing real-time measurements of acoustic velocity and taking into account the varying amplitude of the Doppler signal.
This research work offers signal processing methods adapted to the estimation of acoustic particle velocity, for a sine-wave excitation, and defines hardware and software architectures suited to this measurement. The latter is performed with the help of the in-phase and the quadrature components of the Doppler signal, which is downshifted thanks to an analog quadrature demodulation technique especially designed for this application. Three estimators are then proposed: the first is based on the Doppler phase derivation, and is the starting point of a second method based on maximum likelihood estimation. The extended Kalman filter is the third method explored . Finally , the approximated, though accurate, analytical forms of the Cramer-Rao bounds show the influence of the parameters on the quality of the estimations. Estimator performance is then illustrated by means of statistical Monte-Carlo simulations. An assessment of the complexity of these algorithms also supplements this evaluation.
Finally, the assessment of the estimation technique is obtained thanks to two experiments. Firstly, the measurement of the sinusoidal velocity of the displacement of a needle assembled in a vibration exciter allows the comparison of the results obtained by LDA with those obtained with a laser vibrometer. Then, the measurement of the acoustic particle velocity field radiated by a loudspeaker, is proposed. The measurements obtained in free field by LDA are then compared with the reference velocities obtained using a sound intensity probe.
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https://tel.archives-ouvertes.fr/tel-00004877
Contributor : Alain Le Duff <>
Submitted on : Thursday, February 19, 2004 - 2:08:26 PM
Last modification on : Tuesday, March 31, 2020 - 3:21:02 PM
Long-term archiving on: : Friday, April 2, 2010 - 7:28:44 PM

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  • HAL Id : tel-00004877, version 1

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Alain Le Duff. Contribution à l'estimation paramétrique de signaux à variation sinusoïdale de la fréquence instantanée et à amplitude variable : application à l'anémométrie laser à effet Doppler pour l'acoustique. Autre. Université du Maine, 2003. Français. ⟨tel-00004877⟩

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