單體雙源超音波測距感應器之指向性研究

Abstract

本研究之新型單體雙源超音波測距感應器，乃針對車用超音波感測器來進行研發與創新，一般來說，超音波發射器有幾個主要的設計目標，由於單一波源之倒車雷達所發射的超聲波於水平方向之角度不夠寬廣，因此需利用多顆倒車雷達進行干涉，才能獲得大範圍距離的監測；而在鉛直方向之角度卻又過大，限制了監測距離的長度。此外，監測距離的長度同時受限於超音波發射器本身的殘響以及接受電路的殘響。目前單體雙源超音波發射器的概念，用來改善上述倒車雷達之缺點，提高水平與鉛直之指向角比例，首先透過有限元素進行模擬的方法來確定超音波感測器之模態、共振頻率以及相關的資訊，再加以製作感測器之原型，並透過實驗來驗證其設計。在實驗中利用單一結構產生兩獨立波源，進而縮小發射器體積，並控制輸入訊號之相位，產生非對稱波形。此一方法增加超音波測距發射器之使用範圍，並可解決殘響問題、進而提供監測更短距離之方法。

Ultrasonic sensors have been used widely to generate higher directional radiating patterns where piezoelectric units are sparsely distributed in space. In this study, we present a novel design of a phase array ultrasonic sensor based on the concept of vibration decoupling. Decoupling is usually achieved by careful design of a source aperture, which allows piezoelectric discs to be tightly located in the same structure. Our novel design was based on a cylinder with a dumbbell shape groove to decouple the vibration. A finite element method was used to optimize the design. Two piezoelectric discs were adhered to the bottom plate of the sensor whereby a desirable wave generation and detection were controlled adaptively. By electrical steering, the sensor was thus able to operate with the specific fixed phase. Prototypes of the sensor were made and experimental work was conducted to verify the simulation results.