低频压电加速度传感器的噪声特性及信号处理方法研究

发布时间：2018-03-07 20:39

本文选题：压电效应　切入点：噪声测试　出处：《燕山大学》2016年博士论文　论文类型：学位论文

【摘要】：压电加速度计作为测量振动信号的传感器,在汽车制造、航天工程等诸多领域得到广泛应用。随着科技的发展,对振动信号、尤其是对低频振动信号的精确获取及处理的精度要求越来越高。由于传统的压电加速度计应用范围窄,响应时间长,无法对低频、微弱振动信号进行高精度的测量,目前对低频、微弱振动信号的高精度测量仍然是国内外研究人员所面临的难题。本文通过对压电加速度计本底噪声的研究,分析测试实验数据,并采取相应降噪措施,研制出IEPE(Integrated Electronics Piezoelectric)压电加速度计。其具有频率响应范围宽、灵敏度高等特点,可应用于微弱信号的测量领域。该研究对于确保被测信号不被加速度计的本底噪声所淹没,从而对提高压电加速度计的精度和灵敏度具有十分重要的意义。论文针对压电加速度计在不同领域的应用实例,以IEPE加速度计为代表,研究了压电加速度计的本底噪声特性,通过建立噪声模型,设计出压电加速度计的低噪声系统。主要完成了以下工作:(1)基于压电效应,推导出圆柱型陶瓷材料的压电方程,研究压电加速度计的工作机理。基于压电材料的种类,研究表征压电材料的性能参数。根据压电元件的结构和位置,分析各种类型的压电加速度计(即:压缩型、剪切型和弯曲型)的特点。通过对IEPE加速度计的组成结构及供电方式的研究,发现封装的结构形式具有很高的抗电磁感应和抗高温能力。其两线制的工作方式由于不受热电偶的影响,因此温漂小,易于分散采集,便于集中控制,从而提高了加速度计的抗干扰性和测量精度。(2)基于噪声基本理论和特性,研究压电加速度计的噪声来源。压电变换器内部噪声包括机械谐振系统产生的机械热噪声和压电元件产生的电热噪声。为分析压电变换器内部的噪声种类,研制IEPE加速度计的电荷放大器,建立各种噪声模型。在对T型偏置网络的噪声的分析中,运用-Y?变换原理,从而减小了建模难度。同时基于该噪声模型推导出本底噪声谱密度表达式,为压电加速度计低噪声设计提供了理论依据。(3)对研制的低噪声IEPE加速度计电荷放大器进行实验研究,对电路的幅频特性和低频截止频率进行性能测试。通过对电路的噪声特性的实验研究,将实验测试结果与噪声谱密度表达式的理论值相比较,验证了理论公式的有效性。对实验样机进行测试,并采集样机输出的噪声波形,分析噪声的功率谱。通过对实验测试结果和噪声谱密度公式的对照结合,总结出低噪声加速度计的技术要求。(4)基于小波分析理论,对加速度计输出的信号进行去噪处理。针对传统小波变换的不足,研究基于小波形态学的加速度传感器信号去噪方法,并采用Matlab进行仿真测试,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.
【学位授予单位】：燕山大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TP212

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