本文選題：壓電效應(yīng)　切入點(diǎn)：噪聲測試　出處：《燕山大學(xué)》2016年博士論文　論文類型：學(xué)位論文

【摘要】：壓電加速度計(jì)作為測量振動信號的傳感器,在汽車制造、航天工程等諸多領(lǐng)域得到廣泛應(yīng)用。隨著科技的發(fā)展,對振動信號、尤其是對低頻振動信號的精確獲取及處理的精度要求越來越高。由于傳統(tǒng)的壓電加速度計(jì)應(yīng)用范圍窄,響應(yīng)時(shí)間長,無法對低頻、微弱振動信號進(jìn)行高精度的測量,目前對低頻、微弱振動信號的高精度測量仍然是國內(nèi)外研究人員所面臨的難題。本文通過對壓電加速度計(jì)本底噪聲的研究,分析測試實(shí)驗(yàn)數(shù)據(jù),并采取相應(yīng)降噪措施,研制出IEPE(Integrated Electronics Piezoelectric)壓電加速度計(jì)。其具有頻率響應(yīng)范圍寬、靈敏度高等特點(diǎn),可應(yīng)用于微弱信號的測量領(lǐng)域。該研究對于確保被測信號不被加速度計(jì)的本底噪聲所淹沒,從而對提高壓電加速度計(jì)的精度和靈敏度具有十分重要的意義。論文針對壓電加速度計(jì)在不同領(lǐng)域的應(yīng)用實(shí)例,以IEPE加速度計(jì)為代表,研究了壓電加速度計(jì)的本底噪聲特性,通過建立噪聲模型,設(shè)計(jì)出壓電加速度計(jì)的低噪聲系統(tǒng)。主要完成了以下工作:(1)基于壓電效應(yīng),推導(dǎo)出圓柱型陶瓷材料的壓電方程,研究壓電加速度計(jì)的工作機(jī)理。基于壓電材料的種類,研究表征壓電材料的性能參數(shù)。根據(jù)壓電元件的結(jié)構(gòu)和位置,分析各種類型的壓電加速度計(jì)(即:壓縮型、剪切型和彎曲型)的特點(diǎn)。通過對IEPE加速度計(jì)的組成結(jié)構(gòu)及供電方式的研究,發(fā)現(xiàn)封裝的結(jié)構(gòu)形式具有很高的抗電磁感應(yīng)和抗高溫能力。其兩線制的工作方式由于不受熱電偶的影響,因此溫漂小,易于分散采集,便于集中控制,從而提高了加速度計(jì)的抗干擾性和測量精度。(2)基于噪聲基本理論和特性,研究壓電加速度計(jì)的噪聲來源。壓電變換器內(nèi)部噪聲包括機(jī)械諧振系統(tǒng)產(chǎn)生的機(jī)械熱噪聲和壓電元件產(chǎn)生的電熱噪聲。為分析壓電變換器內(nèi)部的噪聲種類,研制IEPE加速度計(jì)的電荷放大器,建立各種噪聲模型。在對T型偏置網(wǎng)絡(luò)的噪聲的分析中,運(yùn)用-Y?變換原理,從而減小了建模難度。同時(shí)基于該噪聲模型推導(dǎo)出本底噪聲譜密度表達(dá)式,為壓電加速度計(jì)低噪聲設(shè)計(jì)提供了理論依據(jù)。(3)對研制的低噪聲IEPE加速度計(jì)電荷放大器進(jìn)行實(shí)驗(yàn)研究,對電路的幅頻特性和低頻截止頻率進(jìn)行性能測試。通過對電路的噪聲特性的實(shí)驗(yàn)研究,將實(shí)驗(yàn)測試結(jié)果與噪聲譜密度表達(dá)式的理論值相比較,驗(yàn)證了理論公式的有效性。對實(shí)驗(yàn)樣機(jī)進(jìn)行測試,并采集樣機(jī)輸出的噪聲波形,分析噪聲的功率譜。通過對實(shí)驗(yàn)測試結(jié)果和噪聲譜密度公式的對照結(jié)合,總結(jié)出低噪聲加速度計(jì)的技術(shù)要求。(4)基于小波分析理論,對加速度計(jì)輸出的信號進(jìn)行去噪處理。針對傳統(tǒng)小波變換的不足,研究基于小波形態(tài)學(xué)的加速度傳感器信號去噪方法,并采用Matlab進(jìn)行仿真測試,取得了良好的效果。
[Abstract]:Piezoelectric accelerometers, as sensors for measuring vibration signals, have been widely used in many fields, such as automobile manufacturing, aerospace engineering, etc. With the development of science and technology, the vibration signals, Especially, the precision of obtaining and processing low frequency vibration signals is more and more high. Because of the narrow application range and long response time of traditional piezoelectric accelerometers, it is impossible to measure the low frequency and weak vibration signals with high precision. At present, the high accuracy measurement of low frequency and weak vibration signals is still a difficult problem for researchers at home and abroad. In this paper, the background noise of piezoelectric accelerometers is studied, the experimental data are analyzed and the corresponding noise reduction measures are taken. IEPE(Integrated Electronics Piezoelectricpiezoelectric accelerometer is developed. It has the characteristics of wide frequency response range, high sensitivity and so on. It can be used in the field of weak signal measurement. This research can ensure that the measured signal is not submerged by the background noise of the accelerometer. Therefore, it is of great significance to improve the precision and sensitivity of piezoelectric accelerometers. In this paper, the background noise characteristics of piezoelectric accelerometers are studied by using IEPE accelerometers as an example in different fields. The low noise system of the piezoelectric accelerometer is designed by establishing the noise model. The following work is accomplished: 1) based on the piezoelectric effect, the piezoelectric equation of the cylindrical ceramic material is derived. The working mechanism of piezoelectric accelerometers is studied. Based on the types of piezoelectric materials, the performance parameters of piezoelectric materials are studied. According to the structure and position of piezoelectric elements, various types of piezoelectric accelerometers are analyzed. The characteristics of shear type and bending type. Through the research of the structure and power supply mode of IEPE accelerometer, It is found that the structure of the package has high resistance to electromagnetic induction and high temperature. Because the two-wire working mode is not affected by thermocouple, the temperature drift is small, the collection is easy to disperse and the centralized control is easy. Therefore, the anti-interference and measurement accuracy of accelerometer are improved. (2) based on the basic theory and characteristics of noise, The noise source of piezoelectric accelerometer is studied. The internal noise of piezoelectric converter includes mechanical thermal noise generated by mechanical resonance system and electrothermal noise generated by piezoelectric element. The charge amplifier of IEPE accelerometer is developed, and various noise models are established. The transformation principle reduces the difficulty of modeling. Based on the noise model, the expression of background noise spectral density is derived. This paper provides a theoretical basis for the low noise design of piezoelectric accelerometers. The experimental study on the charge amplifier of low noise IEPE accelerometers is carried out. The amplitude-frequency characteristic and the low-frequency cutoff frequency of the circuit are tested, and the experimental results are compared with the theoretical values of the expression of the noise spectrum density through the experimental study of the noise characteristics of the circuit. The validity of the theoretical formula is verified. The experimental prototype is tested, and the output noise waveform is collected, and the power spectrum of noise is analyzed. The technical requirement of low noise accelerometer is summarized. Based on wavelet analysis theory, the signal of accelerometer output is de-noised. Aiming at the shortcomings of traditional wavelet transform, the signal de-noising method of accelerometer based on wavelet morphology is studied. The simulation test is carried out by Matlab, and good results are obtained.
【學(xué)位授予單位】：燕山大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：TP212

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