基于电容边缘效应的叉指式微加速度计性能分析

发布时间：2018-05-29 00:28

本文选题：叉指式微加速度计 + 电容边缘效应　；参考：《电子科技大学》2016年硕士论文

【摘要】：MEMS微加速度计广泛应用于汽车安全气囊、智能手机等日常生活的消费产品中。其中叉指式微加速度计凭借成本低、检测精度高、温度敏感性小、噪声特性好等优点已成为MEMS微加速度计中备受关注的研究对象。在叉指式微加速度计的设计过程中,电容值的计算大多采用理想电容计算公式,而忽略了由于电容极板的边缘效应的存在而产生的附加电容,这会导致电容值在理论计算与实际使用过程之间存在差异。这种由电容边缘效应产生的实际电容值与理论结果间的误差将影响叉指式微加速度计的输出精度。所以,研究电容极板的边缘效应对微加速度计电容值的影响对于提高其精度具有重要帮助。目前,国内外对于电容边缘效应的研究主要集中在对电容值计算公式的理论推导上,而电容的边缘效应对叉指式微加速度计输出性能的影响很少被人提及。因此,本文推导了考虑电容边缘效应的电容值计算公式,由此分析了电容边缘效应对叉指式微加速度计的非线性度、静电刚度和灵敏度性能方面的影响,并利用仿真进行验证。首先对现有考虑电容边缘效应的电容值计算公式进行对比与总结,并在此基础上推导出考虑电容边缘效应情况下微加速度计中叉指电容的电容值计算公式;然后分析电容边缘效应对叉指电容的电容值的影响,并分析能够减小该影响的叉指电容的结构参数;最后基于本文中推导所得叉指电容的电容值计算公式,推导出叉指式微加速度计相应的静电刚度、灵敏度和非线性度关于电容的表达式,并分析电容的边缘效应对这些参数产生的影响。经过有限元仿真的验证,结果表明本文推导的叉指电容的电容值公式可以很准确的计算出叉指电容在考虑边缘效应情况下的电容值;理论分析表明,在叉指电容的结构参数中,极板宽度的增加、极板间距的减小、极板厚度的减小以及极板对数的增加都会减小电容边缘效应对叉指电容的电容值的影响;在叉指式微加速度计的理论推导中,电容的边缘效应会使得敏感质量块所受的静电力增大,静电刚度变大,降低微加速度计输出的灵敏度,增大微加速度计输出的非线性度。
[Abstract]:MEMS microaccelerometers are widely used in automotive airbags, smartphones and other everyday consumer products. Due to the advantages of low cost, high detection accuracy, low temperature sensitivity and good noise characteristics, InterDigital accelerometers have become the focus of research in MEMS microaccelerometers. In the design process of cross-finger accelerometer, the calculation of capacitance is mostly based on the formula of ideal capacitance, but the additional capacitance is neglected because of the edge effect of capacitor plate. This will result in a difference between the theoretical calculation and the actual use of the capacitance. The error between the actual capacitance value and the theoretical results generated by the capacitance edge effect will affect the output accuracy of the cross-finger micro-accelerometer. Therefore, it is important to study the effect of the edge effect of the capacitor plate on the capacitance value of the micro accelerometer. At present, the research on the capacitance edge effect is mainly focused on the theoretical derivation of the capacitance calculation formula, but the influence of the capacitance edge effect on the output performance of the cross-finger micro-accelerometer is seldom mentioned. Therefore, the calculation formula of capacitance value considering capacitance edge effect is derived in this paper. The influence of capacitance edge effect on the nonlinearity, static stiffness and sensitivity performance of cross finger micro-accelerometer is analyzed and verified by simulation. Firstly, the current calculation formulas of capacitance value considering capacitance edge effect are compared and summarized, and the calculation formula of capacitance value of interDigital capacitance in micro-accelerometer considering capacitance edge effect is deduced. Then the influence of capacitance edge effect on the capacitance value of the interDigital capacitance is analyzed, and the structural parameters of the cross-finger capacitance which can reduce the influence are analyzed. Finally, the formula for calculating the capacitance value of the cross-finger capacitance is derived based on this paper. The expressions of the electrostatic stiffness, sensitivity and nonlinearity of the micro-accelerometer are derived, and the influence of the edge effect of the capacitance on these parameters is analyzed. The results of finite element simulation show that the capacitance formula derived in this paper can accurately calculate the capacitance value of the interDigital capacitance under the consideration of the edge effect, and the theoretical analysis shows that, in the structural parameters of the cross-finger capacitance, The increase of plate width, the decrease of plate spacing, the decrease of plate thickness and the increase of plate logarithm will reduce the effect of capacitance edge effect on the capacitance value of cross finger capacitance. The edge effect of capacitance will increase the static power of the sensitive mass block, increase the electrostatic stiffness, reduce the sensitivity of the micro-accelerometer output, and increase the nonlinearity of the micro-accelerometer output.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TH824.4

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