高温环境下MEMS微构件动态特性测试技术研究

基于放电激励方法建立了高温环境下MEMS微构件动态特性测试系统,该系统主要由激励装置、激光多普勒测振仪、微构件温度控制系统组成.激励装置利用尖端放电产生的激波激励微构件,通过进给机构调节电极间距以改变激励能量.激励底座是用高温胶粘接而构成的多层结构,包括微构件安装板、十字载台、陶瓷绝缘片和板电极.微构件胶粘在底座上,其振动响应信号由多普勒测振仪测量,计算机对测量数据频谱分析后得到谐振频率.编写了基于LabVIEW的微构件温度控制软件,控制测试时温度.利用该测试系统,测试了微构件在室温~500℃环境下的谐振频率,得到了谐振频率随温度变化规律.     

MEMS微构件动态特性测试的激励技术和方法

在微机电系统(MEMS)微构件动态特性的测试中,激励是基本环节,通过激励使微构件振动,并测量和分析振动响应信号,实现对微构件动态特性的测试.由于MEMS微构件的尺寸小、谐振频率较高,限制了传统的激励技术和方法在其动态特性测试中的应用.目前应用在MEMS微构件动态特性测试中的激励技术和方法,根据实现激励的方式不同,归纳为三类:利用外部场能的激励方法、内部集成激励元件的方法和基于底座激励的方法.具体介绍了声波激励、超声激励、静电激励、磁激励、电热激励、光热激励和压电激励等具体激励方式的原理及其特点,并对各种激励方法的特点进行了比较和分析.     

振动作用对MEMS微结构湿汽吸附的影响

为了提高检测微机电系统（micro-electro-mechanical systems, MEMS）结构谐振频率的准确性，笔者针对湿汽对MEMS微结构影响的问题，进行了实验设计，并分析了MEMS微结构在振动载荷下谐振频率的变化特性．结果表明，振动初期谐振频率的变化是由于MEMS微结构吸附及解吸附湿汽的作用造成的，而并非是由结构刚度的变化引起的．因此，利用谐振频率检测结构参数变化的实验中，考虑环境湿度的影响十分必要．     

基于亚像素综合定位匹配算法的MEMS平面运动测量

动态测试对MEMS的设计、制造和可靠性具有非常重要的意义．提出了快速高精度的综合亚像素定位匹配算法，应用于MEMS平面运动测量．该综合算法把标准化协方差相关法、亚像素步长相关法、曲面拟合法、序惯相似性检测算法和单纯形法有机结合，综合运用各算法的优点，达到了提高亚像素定位速度和精度的目的．通过位移测量实验和对硅微陀螺仪质量块面内振动及谐振频率的测量，验证了该综合算法的可行性和有效性．     

新型的激光多普勒信号检波系统

为解决超低频、微小振动的高精度测量与装调间的矛盾,提出了一种新型的激光多普勒信号检波系统。该系统通过一运动光栅的衍射,得到约40.5%的测量光强,用另一光栅的衍射消除两束差动光间的夹角以及光波长对测量精度的影响;频移﹑混频分开进行,保证系统装调更方便准确;用1/4波片﹑渥拉斯顿棱镜等得到相位差90°的正余弦信号,实现位移方向识别。实验得出,该系统振动频率和振幅测量精度均为1%,可测频率范围可达到0.5-500Hz,可测振幅范围:1μm-5mm。     

CCD图象传感器在桥梁动态位移测量系统中的应用

CCD (charge coupled device)图象传感器是近年来发展起来的新型固体图象传感器件,具有光电转换、信号存储和信号传输等功能,在图象传感、信息处理和信息存储等方面得到广泛的应用。本文介绍了 CCD 图象传感器的结构、原理、特点和用途,并具体介绍 CCD 在桥梁动态位移测试系统研制中的应用。该系统采用TCD142D 作为传感器件,由桥跨位移测量子系统、桥础位移测量子系统和数据处理子系统组成。在系统测试软件的支持下,可以测量桥梁动态位移的时域曲线,强迫振动的频谱和桥梁的自振频率,冲击系数,横向两测点间倾角和阻尼值。该系统成功地解决了军用桥梁二维、动态、大位移和多参数的远距离非接触测试问题。     

豚鼠耳蜗基底膜响应特性的实验测试与分析

为探究耳蜗基底膜的动态特性,利用激光多普勒测振仪(Laser Doppler Vibrometer,LDV)测试了豚鼠耳蜗基底膜在纯音激励下的动态响应。实验时,选取了14只新鲜的豚鼠耳蜗离体标本,分别测试了70 dB、80 dB、90 dB三种声激励下耳蜗基底膜的速度响应和位移响应,并改变输入声音信号的频率,研究了基底膜的振动特性。实验结果表明:纯音激励下基底膜的振动是正弦振动;在大小相同、频率不同的纯音激励下,基底膜同一位置处振动速度和振动位移大小不同,基底膜具有频率选择特性,在最佳频率处振动响应最大;基底膜在不同大小声压激励下相位响应趋势接近,超过最佳频率后相位滞后迅速增加;基底膜的运动具有行波特征。实验方法和测试结果可为人耳耳蜗听觉机制的研究提供指导。     

豚鼠耳蜗基底膜响应特性的实验测试与分析EI北大核心CSCD

为探究耳蜗基底膜的动态特性,利用激光多普勒测振仪(Laser Doppler Vibrometer,LDV)测试了豚鼠耳蜗基底膜在纯音激励下的动态响应。实验时,选取了14只新鲜的豚鼠耳蜗离体标本,分别测试了70 dB、80 dB、90 dB三种声激励下耳蜗基底膜的速度响应和位移响应,并改变输入声音信号的频率,研究了基底膜的振动特性。实验结果表明:纯音激励下基底膜的振动是正弦振动;在大小相同、频率不同的纯音激励下,基底膜同一位置处振动速度和振动位移大小不同,基底膜具有频率选择特性,在最佳频率处振动响应最大;基底膜在不同大小声压激励下相位响应趋势接近,超过最佳频率后相位滞后迅速增加;基底膜的运动具有行波特征。实验方法和测试结果可为人耳耳蜗听觉机制的研究提供指导。     

1 550 nm全光纤激光多普勒测振系统研制

针对目前国内激光测振系统价格昂贵、使用不便的问题,采用1 550 nm波段成熟的窄线宽光源和光纤元器件研制了一套低成本的全光纤激光测振系统原理样机。此原理样机光路部分采用马赫?泽德干涉仪结构,搭建了外差式激光干涉光路,参考光被40 MHz的声光调制器调制,与测量光在光电探测器表面发生干涉,产生原始的激光多普勒信号;信号解调部分采用相位解调法对原始激光多普勒信号进行解调,得到振动目标的运动特性,包括位移、速度和加速度信息。采用本单位的振动标准装置对其性能进行了测试,实验结果表明：在10 ~ 2 000 Hz的中低频振动范围内,1 550 nm全光纤激光多普勒测振系统峰值位移、速度和加速度的测量误差在-0.6% ~ 0.7%内。该系统在中低频段具有较高的测量准确度,且成本相对较低、操作便捷,具有技术借鉴价值。     

基于磁悬浮技术惯性式振动测量方法研究

磁悬浮球作为质量块实现惯性式振动测量,测量磁悬浮球与测振系统壳体的相对位移即可得到被测振动体的振动参数。由于磁悬浮球不与任何物体接触、无机械摩擦、无机械间隙误差,与传统惯性式振动测量方法相比具有灵敏度高、测量上限频率高,直接输出振动位移信号,通过微加工技术可实现体积小等优点,控制电路还可提供各类所需阻尼函数,但低于10 H z测量频率时需加大测试装置尺寸。在构建磁悬浮球模型及控制系统的基础上,通过对系统的结构和运行参数分析,推导了磁悬浮测振系统动力学方程,并将其等效成表征质量-弹簧测振系统的常系数二阶微分方程,使等效阻尼系数和刚度系数与质量-弹簧系统的参数有一定的对应关系。通过标准激振器产生不同的振动信号,测量结果验证了该方法正确。测试系统灵敏度:986 mV/g,测量频率范围:20 H z~5 kH z。该方法无需粘贴传感器、性价比高、操作方便。     

Accurate velocity measurements of AFM-cantilever vibrations by Doppler interferometry

Doppler velocimetry is widely used in the measurement of nanometre resonance vibrations of micro-electromechanical systems (MEMS). It has excellent sensitivity and precision, but typical engineering applications do not require traceability of these velocity measurements to the SI system. While Doppler velocimetry is, in principle, easy to make traceable to the velocity of light, in practice a frequency-to-voltage conversion in common commercial instruments breaks this traceability unless calibrated. Typically, though, calibration is performed at a much lower frequency than those typical of MEMS devices, without the guarantee that the calibration is applicable in this higher frequency regime.

We present a method of traceable measurement of velocity in terms of the velocity of light, valid for the range of frequency and nanometre amplitudes typical of MEMS devices driven to resonance vibration. This is achieved by analysis of sideband amplitudes in the interference spectrum before demodulation of the Doppler signal. These sideband amplitudes can conveniently be measured using a benchtop spectrum analyser, a piece of widely available electrical test equipment. We illustrate the method with measurements on individual AFM cantilevers. In combination with cantilever calibration methods based on MEMS devices this method enables traceable calibration of those cantilevers employed for the measurement of pico- and nanonewton forces between individual biomolecules.     

A new adaptive mean frequency estimator: application to constant variance color flow mapping

A class of adapted mean frequency estimators is proposed for color flow mapping. These estimators can be fitted to the specific characteristics of a given Doppler signal to optimize the compromise between the range of analysable frequencies and the variance of mean frequency estimation. A sub-optimal estimator is derived for real-time applications, and an adaptive criterion based on the Doppler signal variance is developed for color flow mapping applications. Its performance is compared to that of the usual correlation phase estimator on simulated Doppler signals and on synthetic Doppler images. An improvement in image quality is achieved, mainly for low signal-to-noise ratio Doppler signals.     

基于峰值检测的MEMS器件微弱电容检测电路

针对MEMS器件研制中微弱信号的检测问题,提出了一种适用于电容式MEMS器件的微弱电容检测电路.此电路采用峰值检测技术,原理及结构简单;只检测待测电容的变化量,既可用于差分式检测,也可应用于单一待测电容的情况.首先利用正弦载波信号和微分电路对电容量进行载波调制,再通过减法电路得到幅值与电容变化量成比例的正弦信号,最后采用峰值检测方法解调信号,得到直流量输出.利用微小可调电容进行标定,结果表明检测电路的线性度良好,灵敏度约为3.631V/pF,精度达到0.2%.利用该检测电路检测MEMS陀螺上振动频率为2.85kHz的梳齿驱动器的电容量变化,输出信号频率为（2.85±0.02）kHz,误差低于0.7%,说明该电路能够应用于MEMS器件的微弱电容检测.     

一种新的相位编码信号多普勒补偿算法研究

相位编码信号是一种多普勒频率敏感信号,而且码长越大,对多普勒频率越敏感,严重影响了雷达对高径向速度目标和远距离目标探测的能力。该文在分析伪码序列与多普勒容限关系的基础上,提出一种新的伪码调相准连续波雷达的多普勒补偿算法。该算法将回波信号取平方后送到动目标检测(MTD)滤波器中,通过提取回波信号中的多普勒频率信息,进行多普勒补偿。从仿真结果可以看出,该算法能够有效地降低多普勒频率对脉冲压缩结果的影响,验证了方法的可行性。     

水声通信Doppler扩展估计的实验研究

发射机和接收机之间的相对运动引起Doppler扩展,即时间选择性衰落,它导致发射信号频率扩展。Doppler扩展是动态通信时导致误码率上升的主要原因之一,所以通信接收机首先需要估计Doppler扩展,然后才能补偿Doppler扩展,从而够降低动态情况下的误码率。单频信号是频率敏感信号,根据相对发射机的频率偏移量可以估计Doppler扩展。由于声传播速率相对较低,Doppler扩展导致接收信号相对发射信号产生时间上的伸缩变化,这样也可以采用测量伸缩量的办法估计Doppler扩展。通过水声通信湖上试验,验证了这两种方法的可行性,为未来的水声通信研究提供借鉴和参考。     

水下高速目标航行参数遥测技术研究

对于高速、强机动的水下目标来说,其航行参数信息的实时遥测具有重要意义。水声信号的多普勒频移估计与补偿是水声遥测的关键技术之一,它直接影响着水声遥测的效果与性能。针对双曲线调频信号及线性调频信号进行仿真分析,对比在相同情况下的多普勒频偏可补偿性,仿真实验证明双曲线调频信号具备较高的多普勒容限,其时延值估计精度可达到1μs。结合工程实际,采用双曲调频信号与单频信号组合的方式进行水声遥测,充分发挥双曲线调频信号的多普勒不变性和单频信号对多普勒频移的敏感性,在获得较高定位精度的同时,也具备高精度的水声遥测功能。该组合信标信号经过湖上试验验证,具有遥测精度高、误码率低、易于实现等优点,可直接应用于相关水声工程中。     

Real-time tracking of time-varying velocity using a self-mixing laser diode

A new method is proposed for estimating the time-varying velocity of a moving target with a low-cost laser sensor using optical feedback interferometry. A new algorithm is proposed to track velocity variations from real-time analysis of the output signal of a self-mixing laser diode. This signal is strongly corrupted by a multiplicative noise caused by the speckle effect, which occurs very often with noncooperative targets used in many industrial applications. The proposed signal processing method is based on a second order adaptive linear predictor filter, which enables us to track the digital instantaneous Doppler frequency, which is proportional to the velocity. A model of the laser diode output signal is proposed, and it is shown that the sensor and its associated algorithm have a global first-order lowpass transfer function with a cutoff frequency expressed as a function of the speckle perturbations, the signal to noise ratio and the mean Doppler frequency. Numerical as well as experimental results illustrate the properties of this sensor.     

Estimation of mean frequency and variance of ultrasonic Doppler signal by using second-order autoregressive model

In order to estimate the mean frequency and variance of the diagnostic ultrasound Doppler signal in the presence of clutter noise, a new estimator using a second-order autoregressive (AR) model, called the AR estimator, is proposed. The sampled signal that contains information of both the Doppler signal and clutter is described by the second-order AR model with two poles. The mean frequency and variance of a unidirectional Doppler signal can be estimated, respectively, from the phase and the magnitude of the pole, with larger phase between the two poles. If the clutter is not completely rejected, all conventional estimators, including the autocorrelation (AC) estimator, result in erroneous estimations for the mean frequency and variance of the Doppler signal, whereas the AR estimator gives an accurate estimation. In the absence of clutter, however, the performance of both the AC and AR estimators are similar. If the blood flows in both directions in a sample volume and the clutter is rejected to the extent that it no longer obscures the Doppler signal, the proposed method can estimate simultaneously the mean frequencies and variances of both the forward and reverse blood flows. The performance of the proposed AR estimator was compared with that of the AC estimator by computer simulations and experiments, and it was found that when the number of available sampled data is small, the AR estimator does not require the use of a clutter filter, which simplifies Doppler signal detection.     

基于FPGA的激光外差干涉仪反正切解调技术

针对高频声学应用中多普勒信号软件解调的局限,提出了一种基于FPGA的数字硬件信号解调方案。基于AD9467设计了高速ADC采集系统,以实现原始多普勒信号的奈奎斯特采样或带通采样;基于Xilinx Zynq-7000片上芯片系统设计数字信号处理系统,实现了DDS合成参考信号与多普勒信号混频、低通滤波产生I&Q基带信号对,采用CORDIC算法对I&Q基带信号对反正切解调得到待测振动位移,实现了多普勒信号的实时解调。50～500kHz范围的数值仿真和50～300kHz范围的初步实验结果验证了设计方案的可行性。     

Design of a MEMS acoustical beamforming sensor microarray

This paper describes the design methodology for a microelectromechanical systems (MEMS)-based acoustical beamforming sensor microarray. The proposed acoustical array offers the potential of controlled directional sensitivity with constant beamwidth when used in conjunction with the appropriate digital signal processor. The array has been designed for use in a hearing instrument with a digital beamsteering engine to provide controlled directional sensitivity and constant beamwidth over the audio frequency range to improve speech intelligibility in noisy and reverberant environments. A MEMS-based packaging solution that allows the sensor array to be mounted in the ear canal is also described. The MEMS sensor-package interface features microspring contacts that enable low impedance connectivity between the sensor array and the related microelectronics. This allows the array to be easily removed for cleaning or replacement purposes.