【作者】 张慧；

【导师】 靳世久；

【作者基本信息】 天津大学 ， 精密仪器及机械， 2010， 博士

【摘要】 超声波具有方向性好,穿透能力强,易于获得较集中的声能,会引起空化作用等特点,广泛的应用在工业无损检测,医学超声成像,军事声纳系统等领域。作为超声系统中的关键器件,超声传感器对系统性能具有很大影响,目前普遍使用的压电式超声传感器存在着压电材料与工作介质水、空气等阻抗不匹配,小尺寸二维阵列制作困难、工作温度范围小等问题。近年来,由于电容式微型超声传感器具有声阻抗低、体积小、灵敏度高、频带宽和易于集成等特点,在医学超声成像、流量测量和空气耦合式超声检测等方面具有潜在的优势,受到国内外研究人员的关注。本文以电容式微型超声传感器在声频定向技术中的应用为目标,开展了非平膜低频电容式微型超声传感器的基础研究工作,围绕传感器的理论模型分析、结构设计、力电耦合及声场特性有限元分析、实验测试等几个方面,论文的主要研究工作包括:1、以提高电容式微型超声传感器的机电耦合效率为目标,设计了两种非平膜传感器结构,即改变传感器振动膜的形状,使整个薄膜的厚度不一致,通过对传感器进行力电耦合有限元分析,表明两种非平膜传感器与传统结构的传感器相比,薄膜平均位移量增大,机电耦合效率提高。2、建立了非平膜传感器的声场有限元模型,研究了传感器的输出声压分布情况,对相同尺寸的平膜与非平膜传感器在振膜位移相同时的发射声压进行了对比分析,非平膜传感器的平均输出声压高于相同尺寸的平膜传感器。3、研究分析了非平膜传感器的主要结构参数如薄膜半径,厚度,空腔间隙,电极尺寸,凸台及凹槽尺寸等对其吸合电压、机电转换系数、发射声压及带宽等性能的影响规律,为传感器的设计及优化提供了理论依据。4、设计并制作了用于声频定向技术的电容式微型超声传感器,构建了实验测试系统,对传感器进行了机械、电学和声学性能测试。验证了非平膜电容式微型超声传感器设计理论与设计思想的正确性。更多还原

【Abstract】 Ultrasonic waves have characteristics such as good direction, penetrating ablility, sound energy concentrated and cavitation, which is commonly used in many applications including non-destructive testing, medical ultrasonic imaging and SONAR system in military. As a critical part of ultrasonic system, ultrasonic transducers determinate the system’s performance. Now, piezoelectric materials have dominated the ultrasonic transducer technology. However, the piezoelectric transducers exhibit disadvantages such as the impedance mismatch between the piezoceramic and the air or the fluid of interest, difficult of fabricating large 2D arrays, and unsuitable being used in high temperature environments. The capacitive subminiature ultrasonic transducers receive increasing acceptance as an alternative to conventional piezoelectric transducers, they offer performance advantages of wide bandwidth、low impedance、high sensitivity and small size,and they are ideally suitable for medical diagnostics、air-coupled inspection and micro-flow measurement.For the application in audio directional system, the capacitive subminiature ultrasonic transducers of non-flated membrane are studied deeply in this dissertation, which covers the aspects including theory model, structural designing, FEM simulations and characteristic testing.The major research works in this dissertation can be summarized as follows:1. Aimming at increasing the electromechanical coupling efficiency of transducers, two improved structures with non-flat membrane are proposed, one is a boss on the membrane and another is trench on the membrane. Finite element analysis results demonstrated that both improved structures achieved more uniform membrane deformation, and larger average membrane displacement, and higher effective electromechanical coupling efficiency.2. The acoustic finite element models of transducers are developed to demonstrate the distributing characteristic of sound field. The FEA simulations have illustrated that the output pressure comparision between flat membrane and non-flated membrane by same size and same displacement, the non-flated membranes can radiate larger sound pressure.3. The behaviors of the transducers with non-flated membrane in terms of collapse voltage, frequency, bandwidth and transformer ratio are investigated by varying the critical structural parameters such as membrane radius, membrane thickness, gap thickness, boss size and trench size. The detailed analysis results have been presented in this paper, which are beneficial for the design and optimization of capacitive ultrasonic transducers.4. The capacitive transducers of non-flated membrane for audio directional system have been fabricated, and the experiment setups for transducers are established. The electrical, mechanical and acoustical characteristic performances of transducers have been tested. The results of finite element analysis in this paper are successfully verified by those experiments.更多还原