【摘要】：超聲技術(shù)在醫(yī)療成像和無(wú)損探傷等領(lǐng)域具有廣泛應(yīng)用,而作為各種超聲應(yīng)用的核心器件,超聲傳感器一直是研究的熱點(diǎn)。其中,電容式微加工超聲傳感器(CMUT)克服了傳統(tǒng)壓電超聲傳感器阻抗失配的缺陷,同時(shí)還具有高帶寬、高靈敏度和易集成等優(yōu)點(diǎn),因此具有極大的應(yīng)用前景和研究?jī)r(jià)值。振動(dòng)薄膜是CMUT的核心結(jié)構(gòu)。通過(guò)薄膜的形變分布,既可以計(jì)算傳感器的電容變化量,又可以分析傳感器的穩(wěn)定性,因此薄膜的形變量是傳感器設(shè)計(jì)過(guò)程中需要考慮的一個(gè)重要因素。本文主要對(duì)CMUT的振動(dòng)薄膜(矩形薄膜和橢圓薄膜)在靜電力作用下的形變量進(jìn)行了研究。首先,本文根據(jù)CMUT的結(jié)構(gòu)特點(diǎn),利用有限元分析軟件ANSYS 15.0建立了CMUT的三維簡(jiǎn)化有限元模型,以CMUT的四分之一作為模型來(lái)分析整個(gè)傳感器,提高了運(yùn)算效率。對(duì)結(jié)構(gòu)進(jìn)行了靜力分析,并且以塌陷電壓為指標(biāo),驗(yàn)證了所建立的有限元模型及分析方法的有效性。為了更接近真實(shí)情況,本文還對(duì)模型進(jìn)行了改善,考慮了頂部電極對(duì)薄膜形變的影響,并且對(duì)改進(jìn)后的模型進(jìn)行了模態(tài)分析,研究了結(jié)構(gòu)的固有振動(dòng)頻率。其次,本文利用有限元分析的結(jié)果研究了直流偏壓和薄膜尺寸對(duì)薄膜形變影響的規(guī)律,選取和提出了能大致描繪薄膜形變曲線的基礎(chǔ)函數(shù)。在此基礎(chǔ)上,本文首次分別提出了CMUT矩形薄膜和橢圓薄膜在靜電力作用下的形變數(shù)學(xué)模型,并為模型提出了用來(lái)分析薄膜尺寸影響的二維函數(shù)。最后,本文利用新的形變數(shù)學(xué)模型,通過(guò)數(shù)值積分的方法計(jì)算了CMUT在薄膜發(fā)生形變后的電容值,并描繪了薄膜中心面的變形曲面,分析了模型對(duì)CMUT薄膜設(shè)計(jì)的指導(dǎo)意義。另外,本文在薄膜小形變和大形變的兩種情況下,分別從薄膜形變曲線的吻合度和傳感器電容值計(jì)算的精確度兩個(gè)方面,驗(yàn)證了形變模型的準(zhǔn)確性。特別地,隨機(jī)抽取一批不同規(guī)格的薄膜,通過(guò)與有限元法計(jì)算的電容值進(jìn)行比較,得到矩形薄膜形變模型計(jì)算的最大誤差為0.436%,而橢圓薄膜形變模型計(jì)算的最大誤差為2.920%。
[Abstract]:Ultrasonic technology is widely used in medical imaging and nondestructive testing. As the core device of various ultrasonic applications, ultrasonic sensor has always been the focus of research. Among them, capacitive micromachined ultrasonic sensor (CMUT) overcomes the defect of impedance mismatch of traditional piezoelectric ultrasonic sensor, and also has the advantages of high bandwidth, high sensitivity and easy integration, so it has great application prospect and research value. Vibrating thin film is the core structure of CMUT. Through the deformation distribution of the thin film, not only the capacitance change of the sensor can be calculated, but also the stability of the sensor can be analyzed. Therefore, the shape variable of the thin film is an important factor to be considered in the design process of the sensor. In this paper, the deformation of vibratory thin film (rectangular film and elliptical film) of CMUT under electrostatic force has been studied. Firstly, according to the structural characteristics of CMUT, the three-dimensional simplified finite element model of CMUT is established by using the finite element analysis software ANSYS 15.0, and the 1/4 of CMUT is used as the model to analyze the whole sensor, which improves the operation efficiency. The static analysis of the structure is carried out, and the validity of the established finite element model and analysis method is verified by taking the collapse voltage as the index. In order to get closer to the real situation, the model is improved, the influence of the top electrode on the film deformation is considered, and the modal analysis of the improved model is carried out, and the natural vibration frequency of the structure is studied. Secondly, the effects of DC bias and film size on the deformation of thin films are studied by using the results of finite element analysis, and the basic functions which can roughly describe the deformation curves of thin films are selected and put forward. On this basis, the deformation mathematical models of CMUT rectangular thin films and elliptical thin films under electrostatic force are proposed for the first time, and a two-dimensional function for analyzing the influence of thin film size is proposed for the model. Finally, by using the new deformation mathematical model, the capacitance of CMUT after thin film deformation is calculated by numerical integration method, and the deformation surface of the central surface of the film is described, and the guiding significance of the model to the design of CMUT thin film is analyzed. In addition, in the case of small deformation and large deformation of thin films, the accuracy of the deformation model is verified from two aspects: the coincidence of thin film deformation curves and the accuracy of sensor capacitance calculation, respectively. In particular, a batch of thin films of different specifications are randomly selected and compared with the capacitance values calculated by the finite element method. The maximum error of the rectangular thin film deformation model is 0.436%. The maximum error of elliptical thin film deformation model is 2.920%.
【學(xué)位授予單位】：華南理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：TB383.2;TP212

【參考文獻(xiàn)】

相關(guān)期刊論文 前3條

1 張慧;宋光德;靳世久;官志堅(jiān);劉娟;;電容式微超聲傳感器的電極參數(shù)優(yōu)化設(shè)計(jì)[J];傳感技術(shù)學(xué)報(bào);2010年07期

2 谷雨;;MEMS技術(shù)現(xiàn)狀與發(fā)展前景[J];電子工業(yè)專(zhuān)用設(shè)備;2013年08期

3 徐s，

本文編號(hào)：2475732