三维MEMS加速度计的性能测试方法与分析

文章针对一种三维MEMS加速度计,提出了三维加速度计的测试方法,并根据测试结果对此加速度计进行了性能分析。通过对其设计原理和内部结构的描述,指出该型MEMS加速度计的结构优点及性能特点。针对该加速度计,作者设计了测试装置,制作了测试电路,并在文章中详细描述了测试原理及整个测试过程。分别在三个方向上,对此三维MEMS加速度计进行了多次对比测试,同时采集包括标准加速度计输出和MEMS加速度计三向输出在内的四路信号,以便进行冲击方向上两加速度计的横向对比和三向MEMS加速度计的轴间耦合分析。测试结果表明,此测试方法和装置是可靠有效的,且具有一定的通用性可用于其它类似传感器的测试分析中。     

微加速度计固有频率的推导及验证

为了解决压阻式加速度计的动态特性欠佳的共性,避免微加速度计在工作过程中因为共振导致结构损坏,在结构设计过程中选择合理固有频率是至关重要的。本文就针对一种四边八梁结构的高gn值压阻式加速度计,通过力学知识,简化结构并推导出其固有频率的理论计算公式,并利用有限元仿真软件和测试高gn值加速度计频率特性的方法,对此理论公式进行了仿真和实验验证,证明此理论公式的正确性和可用性。这样,在加速度计结构的设计过程中,可以直接利用此公式计算出结构的固有频率,从而减化加速度计的结构设计和优化过程,设计出最合理的固有频率结构。     

基于介观压阻效应的硅微加速度计研究

为了突破传统机电转换局限,提高加速度计灵敏度,提出以介观压阻效应为工作原理制作高灵敏度的硅微加速度计,基于这种原理设计并制备了GaAs基加速度计,通过理论分析计算与试验测试,得出该结构在0.1 gn输入下的输出,并对介观压阻灵敏度和压阻灵敏度的量级作出了比较,验证了采用介观压阻效应制作高灵敏度传感器的可行性,为此类加速度计的设计提供参考.     

基于高冲击激励的加速度计参数辨识的研究

加速度计的动态校准在国内外计量领域越来越受到重视,参考国内外最新的加速度计动态校准方法,主要阐述了基于高冲击激励下加速度计动态特性参数辨识的问题。该方法根据加速度计的物理结构建立了其状态空间模型,利用外差式激光干涉仪测量并经过相应处理得到了输入加速度计的激励信号。利用得到的输入-输出数据,通过最小化其状态空间模型的预测误差序列得到了被校加速度计的动态特性的参数,通过在不同的冲加速度峰值下进行了试验并比较表明该方法的有效性。     

介观压阻效应在硅微加速度计中的应用

为了突破传统机电转换局限，提高加速度计灵敏度，提出以介观压阻效应为工作原理制作高灵敏度的硅微加速度计，基于这种原理设计一种四梁岛结构，通过理论分析与仿真计算，得出该结构在lgn输入下的输出，并对介观压阻灵敏度和压阻灵敏度的量级作出了比较，从理论上验证了采用介观压阻效应制作高灵敏度传感器的可行性，为此类加速度计的设计提供参考。     

基于电容模型的多层栅FFET研究

通过SILCAVO软件仿真了铁电场效应晶体管漏极电流Id特性。在研究了单层栅极的结构铁电场效应管的Id与铁电参数(ε,Ec,Pr,Ps/Pr)的关系基础上,提出了一种新型结构—电容模型多层栅极结构的铁电场效应管研究,发现具有多层栅极结构的铁电场效应晶体管的工作电压较高,具有抗干扰的优点;在栅极电压介于3~4V之间容易饱和极化,器件输出特性稳定,对材料性能不敏感,易于制造和便于电路设计;其极化前后输出的漏极电流差较大,有利于信号的分辨,提高电路工作效率。仿真结果为人们研究高性能铁电场效应晶体管提出了一个新的思路。     

基于介观压阻效应的高g值加速度计设计

依据介观压阻效应原理,设计出一种以超晶格量子阱薄膜为敏感单元的高g值纳机电加速度计,期望利用超晶格量子阱薄膜的高灵敏特性,提高加速度计的灵敏度。结合GaAs基表面微机械加工工艺和控制孔技术完成了加速度计的加工。采用马歇特冲击的方法完成了加速度计的测试,并利用冲击响应谱分析了微加速度计在有外部冲击情况下的响应,研究结果表明:依据介观压阻效应原理和MEMS技术制作高g值纳机电加速度计具有可行性,从测试结果可以看出该微加速度计不但冲击响应信号与标准加速度计所测信号很接近,而且它们的响应一致性较好。     

dsPIC芯片的单相正弦波逆变器设计

选择Microchip的dsPIC33F系列芯片作为系统的控制器,通过比较分析最终选取交错反激式的拓扑结构进行微逆变器的设计,选用具有电流源特性的DCM工作模式.该设计采用双级式的拓扑结构,前级将交错反激变换器输出的直流电流调制为正弦半波波形,后级再全桥逆变对前级输出的正弦半波电流进行翻转得到正弦波波形的电流.主开关和从开关之间通过非互补导通的有源箝位技术来解决由变压器漏感所引起的主开关的关断电压尖峰和功率耗损问题,漏感能量通过该技术得到回收,该技术实现了主开关的零电压(ZVS)开通,并且主开关两端的尖峰电压也得到了降低.     

数控直流电流源设计

介绍了一种数控直流电流源的硬件电路和工作原理以及软件设计。该电流源通过输出电流反馈构成了闭环控制系统。其输出电流精度高、稳定性好,具有良好的负载特性。     

一种新结构硅微机械压阻加速度计

设计、制造并测试了一种新结构硅微机械压阻加速度计.器件结构是悬臂梁-质量块结构的一种变形.比较硬的主悬臂梁提供了一定的机械强度,并且提供了高谐振频率.微梁很细,检测时微梁沿轴向直拉直压.力敏电阻就扩散在微梁上,质量块很小的挠动就能在微梁上产生很大的应力,输出很大的信号.5 V条件下,灵敏度为14.80 mV/g,谐振频率为994 Hz,分别是传统结构压阻加速度计的2.487倍和2.485倍.加速度计用普通的N型硅片制造,为了刻蚀高深宽比的结构,使用了深反应离子刻蚀(DRIE)工艺.     

PHEMT电离辐照效应研究

对PHEMT的电离辐照效应进行了研究,通过测量辐照前后器件的I-V特性和低频噪声,发现辐照对PHEMT的性能影响并不明显.分析了PHEMT漏电流退化的机理以及其低频噪声的来源,发现异质结界面态是引起漏电流退化和产生较大低频噪声的主要原因,但辐照不会在异质结界面处引入大量的界面态,从而在微观上解释了实验结果.     

微悬臂梁谐振式气体传感器研究进展

微机械谐振式传感器已经成为微型机电系统(MEMS)领域的研究热点。讨论了微悬臂梁谐振式气体传感器的工作原理,介绍微悬臂梁表面修饰的关键技术、主要方法和基于微悬臂梁的谐振式气体传感器领域的研究状况以及近五年以来该领域的研究进展,并对基于微悬臂梁的谐振式气体传感器的发展方向和应用前景做了展望。     

ANN modeling approach for designing low noise phemt amplifier in wireless communication systems

Future efficient wireless communication systems require, for high quality performance a Broadband Amplifier in the frequency range under consideration. This could be plugged into the measuring path so that it enables the system to perceive even the weakest signals. For this a new Scattering-parameter model for the microwave analysis of a PHEMT (Pseudomorphic High Electron Mobility Transistor) has been developed, which is valid for a wide frequency range. The developed neural network model is used in designing the PHEMT power amplifier. The calculated S-parameters, gain and minimum noise figure from the ANN (Artificial Neural Networks) model are the parameters which are used to design the low noise PHEMT power amplifier. The various gains so obtained from the S-parameters are plotted with the frequency and yield a closer fit to the simulated model. The neural network training has been done using Levenberg-Marqaurdt back propagation algorithm implemented in ANN toolbox of MATLAB software. All the results have been compared with the experimental data and show a close agreement and the validity of our model.     

The mechanics of polymer swelling on microcantilever sensors

This paper investigates the swelling mechanics of polymer capture layers integrated into piezoresistive cantilever biochemical sensors. A finite element model investigates mechanical deformations in a polymer layer affixed to a silicon microcantilever. The polymer swells during analyte absorption, inducing deformations in the silicon cantilever which are sensed by a piezoresistive sensor integrated into the cantilever. The highest sensitivity is predicted for short and wide cantilevers that are coated with stiff polymer whose thickness is twice that of the cantilever. While the polymer swelling induces the deformations, the silicon carries most of the load. When portions of the silicon beam are removed to introduce stress concentrations, the system sensitivity can increase by 18% compared to the cantilever without stress concentrations. This study of stress distributions in the cantilever system allows sensor optimization that considers the full 3D effects of polymer swelling mechanics.     

基于微悬臂梁的化学传感器的灵敏度研究

基于探测的原理,在动态模式下,首先对不同结构梁的本征频率偏移量进行了有限元分析,结果表明三角形梁的灵敏度最高。然后重点针对不同结构参数的三角形梁进行了动态计算,获得了其频率偏移量随结构参数变化的关系曲线。另外,通过静态模式下的有限元计算,发现各种梁自由端的偏移量相同,表明它们的静态灵敏度与形状无关。最后,对三角形梁在不同测量模式下结构参数的优化设计进行了分析。     

A trapezoidal cantilever density sensor based on MEMS technology

A trapezoidal cantilever density sensor is developed based on micro-electro-mechanical systems (MEMS) technology. The sensor measures fluid density through the relationship between the density and the resonant frequency of the cantilever immersed in the fluid. To improve the sensitivity of the sensor, the modal and harmonic response analyses of trapezoidal and rectangular cantilevers are simulated by ANSYS software. The higher the resonant frequency of the cantilever immersed in the fluid, the higher the sensitivity of the sensor; the higher the resonant strain value, the easier the detection of the output signal of the sensor. Based on the results of simulation, the trapezoidal cantilever is selected to measure the densities of dimethyl silicone and toluene at the temperature ranges of 30 to 55 °C and 26 to 34 °C, respectively. Experimental results show that the trapezoidal cantilever density sensor has a good performance.     

含几何缺陷的均质材料悬臂薄板的自由振动

以TC4钛合金均质材料悬臂薄板为研究对象.基于经典板壳理论,通过Rayleigh-Ritz法,根据悬臂板边界条件预设模态函数,求得包括全局、局部的函数型几何缺陷的悬臂板的前四阶固有频率.探究了悬臂板的缺陷类型、尺寸、位置等多种因素对自由振动的影响.     

Static and dynamic stabilities of a microbeam actuated by a piezoelectric voltage

In this paper, flutter and divergence instabilities of a cantilever, a clamped–clamped, and a cantilever with intermediate simply-support microbeam sandwiched by piezoelectric layers have been studied. By presenting a mathematical formulation and numerical solution, critical piezoelectric force for avoiding of the instability in a cantilever microbeam has been calculated and validated by known buckling capacity of Beck column. By applying a similar mathematical analysis it has been introduced a critical piezoelectric voltage for a clamped–clamped microbeam. It has been shown that for cantilever microbeams, increasing of the follower piezoelectric force leads to: first flutter and then divergence instabilities whereas in the clamped–clamped microbeams only divergence instability can be occurred. Also effects of the intermediate simply support position on the critical piezoelectric voltage of a cantilever microbeam have been investigated. It has been shown that for case when the intermediate simply support is near to the fixed end of the cantilever increasing of the follower piezoelectric force leads to flutter instability but for case when the intermediate simply support is near to the free end of the cantilever it leads to divergence instability.     

A comparative analyze of fundamental noise in cantilever sensors based on lateral and longitudinal displacement: case of thermal infrared detectors

The performance of novel cantilever-based sensors approaches the limit posed by thermo-mechanical fluctuations, which is the currently accepted fundamental detection barrier for micro- and nanomechanical sensors. At the same time, the sensitivity of a high-level measurement techniques used for readout of the cantilever displacement nears the value of 10^?14 m/Hz^½. However, the thermo-mechanical noise of some cantilever sensors based on bimaterial structures is considerably higher than imposed by the fundamental limit. Moreover, the signal-to-noise ratio of some sensors based on contemporary MEMS technologies falls behind the characteristics of older types of mechanical sensors, fabricated using macroscopic production technologies. To investigate the cause of this situation, we perform a comparative analysis of the performance limits for two classes of cantilever sensors: the bimaterial cantilevers where the output signal is the transversal (lateral) displacement of the cantilever tip and the simple cantilever sensors where the signal is the longitudinal displacement along the cantilever axis. As a starting point of our analysis we established a correspondence between the parameters of a bimaterial cantilever and the simple cantilever. In a general case these two structures are not directly comparable, since the deformation of the bimaterial cantilever depends on 14 variables, while the longitudinal elongation of the simple cantilever depends on seven parameters only. However, under certain conditions analyzed in this paper a partial correspondence between the parameters of these two structures can be established. Our analysis shows that in certain applications a cantilever with longitudinal elongation has potentially better performance than the corresponding bimaterial element.     

一种用于高密度信息存储中数据读取的新方法的 理论和实验研究

通过测量压电悬臂梁的等效电容来检测悬臂梁的振动信息,以应用于基于扫描探针技术的高密度信息存储中进行数据读取.在压电悬臂梁的PZT压电层上施加交流电场使其工作在共振状态,并使其自由端与存储介质进行周期性的接触.当悬臂梁的自由端扫描到数据点时,其自由端的振幅和所受到的外力将发生变化,进而引起PZT压电层的介电常数发生变化.因此,通过检测悬臂梁上压电层的等效电容变化,便可以得到悬臂梁的振幅改变量,从而实现了对存储介质上数据的读取.实验结果表明,该可以实现1nm的位移检测分辨率.