Design and Finite Element Simulation of Closed Type Ultrasonic Sensor
Date Issued
2007
Date
2007
Author(s)
Hu, Chih-Kai
DOI
zh-TW
Abstract
Closed Type Ultrasonic Sensors have been used widely in cars to detect obstacles in close range. Despite theoretical and computational advances made recently in ultrasound, these sensors have been generally designed by trial and error. The objective of this work is to develop suitable computational strategies to support virtual prototyping design of closed type ultrasonic sensors. To this end, analysis capabilities from ANSYS, a commercially available finite element analysis package, are utilized. Resonance frequency, directivity, and source level of commercially available losed type ultrasonic sensors were simulated using ANSYS. The calculated results were in a good agreement with experimental measurements.
The primary design concern for closed type ultrasonic sensors used in cars is to avoid undesired response reflected from the ground in the vertical direction while maintain its covering range in the horizontal direction. Patents related to closed type ultrasonic sensors were reviewed to guide the design direction. Salient features associated with directivity and source level from these patents were analyzed. We then used two ways to improve their performance. The first design was to alter boundary conditions of vibrating plate. To this end, we designed a sensor with a circular hollow shape to verify this design. The side wall of vertical direction of vibration plate was dug in a pair of slots by mill. We found that when the length of the slots is 0.4 times of the diameter of cases and the position of the slots is about 2 mm away from the interior of the vibration plate, an optimal performance of source level and directivity was obtained. The second design was to shift the vertical direction of the transmitting ultrasound. We designed a sensor with a snowman hollow shape to verify this design. We found that in order to shift the transmission, the thickness of the hollow circle that contains the piezoelectric element should be thicker.
In this work, a computational framework to predict resonance frequency, directivity, and source level of ultrasonic sensors has been established for virtual prototyping. We have also successfully improved the performance of closed type ultrasonic sensor by changing the boundary condition of vibration plate and shifting the vertical direction of the transmitting ultrasound.
Subjects
超音波感測器
有限元素分析
虛擬原型
倒車雷達
共振頻率
指向性
半衰角
音源強度
ultrasonic sensor
finite element analysis
virtual prototyping
parking sensor
resonance frequency
directivity
half decay angle
source level
Type
thesis
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