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Analysis of a Pot-Like Ultrasonic Sensor with an Anisotropic Beam Pattern

Published online by Cambridge University Press:  05 May 2011

C.-C. Cheng*
Affiliation:
Institute of Applied Mechanics, National Taiwan University, Taipei, Taiwan 10617, R.O.C.
C.-Y. Lin*
Affiliation:
Institute of Applied Mechanics, National Taiwan University, Taipei, Taiwan 10617, R.O.C.
J.-H. Ho*
Affiliation:
Engineering Science and Ocean Engineering, National Taiwan University, Taipei, Taiwan 10617, R.O.C.
C.-S. Chen*
Affiliation:
Civil Engineering, National Taiwan University, Taipei, Taiwan 10617, R.O.C.
J. Shieh*
Affiliation:
Material Science, National Taiwan University, Taipei, Taiwan 10617, R. O. C
W.-J. Wu*
Affiliation:
Engineering Science and Ocean Engineering, National Taiwan University, Taipei, Taiwan 10617, R.O.C.
K.-C. Wu*
Affiliation:
Institute of Applied Mechanics, National Taiwan University, Taipei, Taiwan 10617, R.O.C. National Applied Research Laboratories (NARL), Taipei, Taiwan 10622, R.O.C.
C.-K. Lee*
Affiliation:
Institute of Applied Mechanics, National Taiwan University, Taipei, Taiwan 10617, R.O.C. Engineering Science and Ocean Engineering, National Taiwan University, Taipei, Taiwan 10617, R.O.C. Industrial Technology Research Institute (ITRI), Hsinchu, Taiwan 30011 and 31040, R.O.C.
*
*Ph.D. candidate
**Master
**Master
***Associate Professor
****Assistant Professor
**Master
*****Professor, corresponding author
*****Professor, corresponding author
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Abstract

We investigated the design parameters of a compact pot-like ultrasonic sensor which possesses a highly anisotropic beam pattern. As the sensor size is small due to its application constraint, the parameters are thus highly coupled to one another. We analyzed the respective effects of the parameters in the case where there is a vertical beam width reduction. The parameters investigated include resonant frequency, vibrating plate width-expanded angle, and ratio of thickness discontinuity of the vibrating plate. Numerical models developed by combining finite-element analysis and spatial Fourier transforms were adopted to predict the far-field radiating beam pattern of the various design configurations. The displacement distribution of the vibrating plate was measured using a microscopic laser Doppler vibrometer and the far-field pressure beam patterns were measured using a standard microphone in a semianechoic environment. The three configurations we used to validate the simulation model resulted in an H-V ratio of 2.67, 2.68 and 3.13, respectively which all agreed well with the numerical calculations. We found that by increasing the operating resonant frequency from 40kHz to 58kHz, the vertical far-field beam width of an ultrasonic sensor can be reduced by 31.62%. We found that the vertical beam width can be significantly reduced when the ratio of the thickness discontinuity of the vibrating plate decreases from 1 to 0.4 and is incorporated with its optimal width-expanded angle of the vibrating plate. It appears that an ultrasonic sensor with this type of anisotropic beam pattern can be ideally adopted for today's automotive applications.

Type
Articles
Copyright
Copyright © The Society of Theoretical and Applied Mechanics, R.O.C. 2010

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