一种微机械加速度计的自检测特性研究

采用静电力驱动质量块产生等效加速度信号实现了微机械加速度计的自检测功能。分析了平板驱动电极的静电驱动力、吸合电压以及稳定驱动位移条件。采用光学测试技术测试了驱动电压和驱动位移的关系,吸合电压,证实了理论分析。利用理论分析公式计算了低驱动电压情况下的驱动位移。结果表明在10～15V的直流驱动电压下能产生等效于1g加速度的输出。     

一种高灵敏度硅微机械陀螺的设计与制造

设计与制造了一种高灵敏度的硅微机械陀螺。陀螺用静电来驱动,用连接成惠斯顿电桥的压阻式力敏电阻应变计来检测。主梁、微梁 质量块结构实现了高灵敏度。比较硬的主梁提供了一定的机械强度,并且提供了高共振频率。微梁很细,检测时微梁沿轴向直拉直压。力敏电阻应变计就扩散在微梁上,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。5V条件下,陀螺检测部分的理论灵敏度达到27.45mV/gn。压阻式四端器件用来监测驱动振幅,可以反馈补偿压阻的温度系数。检测模态的Q值达260使陀螺能在大气下工作。陀螺利用普通的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。     

三框架电容式硅微机械陀螺动力学分析

为了解决双框架陀螺在加工中不可避免的误差,提出了三框架电容式微机械陀螺系统。该系统由3个框架(即3个质量块)组成。采用静电差分驱动方式,梳状叉指电容,多个柔性杆设计使得该结构从理论分析和加工误差上解决了耦合现象。同时,通过提高中间框架的质量,使得陀螺的灵敏度大大提高。介绍了该三框架电容式微机械陀螺仪的工作原理,给出了所设计陀螺动力学方程的详尽推导和MAT-LAB仿真分析。     

一种双轴电容式微机械加速度计

提出一种双轴电容式微机械加速度计的结构形式.采用一个质量块敏感两个正交方向的加速度,设计的弹性支撑结构巧妙地实现了正交方向的解耦,且结构稳定性好,以梳齿电容实现差动的静电驱动、电容检测.利用MATLAB软件对敏感结构参数、性能参数进行了计算、分析,用ANSYS仿真软件对敏感结构进行了静态和模态分析,从理论上验证了所提出的双轴电容式微机械加速度计整体结构的可行性.     

基于复合静电驱动结构的硅微机械扭转微镜

为了改善硅微机械扭转微镜的机电耦合特性,降低器件的驱动电压并提高其工作可靠性,提出了几种新颖的基于复合静电驱动结构的硅微机械扭转微镜.提出的硅微机械扭转微镜将垂直扭转梳齿静电驱动结构、侧壁平行板电容静电驱动结构有机结合,实现了两种静电驱动方式的复合驱动,同时设计了内外双镜面结构,通过内外双镜面结构,实现了微镜的差动复合驱动,理论分析、模拟仿真与测试结果表明,通过上述两个方面新颖的设计,新结构显著降低了器件的驱动电压.同时为了提高器件的工作可靠性,在设计折叠梁柔性支撑结构时,将梁的不同位置设计成不同的厚度,对于硅微机械扭转微镜扭转过程中容易疲劳的梁部分加大了其厚度,从而在不影响器件扭转性能的前提下,明显提高了器件的可靠性.利用有限元方法对器件的力学特性和机电耦合特性进行了系统的仿真,获得了影响器件机电特性的关键结构参数.器件基于SOI晶片,采用表面硅工艺与体硅工艺相结合的方式加工制造,采用SOI晶片显著降低了微镜镜面的表面粗糙度,提高了其光反射能力.最后利用原子力显微镜对微镜镜面的表面粗糙度进行了测量和分析,实验结果表面微镜表面具有16nm的表面粗糙度,完全可以满足光学应用的需要.     

MEMS石英振梁高增益谐振电路的设计与分析

介绍了一种基于新型高阻抗QVBA的高增益谐振电路设计和谐振电路的分析测试实验。利用阻抗分析仪4294A测得石英振梁的等效参数,对石英振梁的电气特性进行分析,发现高阻抗石英振梁起振比普通晶振需要更高增益。基于双门振荡电路,利用运算放大器在开环系统中具有无限增益的理论,提高谐振电路的驱动能力。同时采用谐波抑制网络,指出谐波抑制网络可以抑制无用的频率避免传感器输出信号出现泛音频率,并提高谐振电路的稳频速度。考虑电噪声对输出波形质量的影响,在电路的输入部分采用滤波电容,并在电路的输出部分采用反向器整形,使电路输出标准的方波信号。最后利用安捷伦DSO5012A型号示波器和频率计对高增益谐振电路和石英振梁组成的谐振系统进行测试,测试结果表明本文设计的谐振电路与石英振梁组成的谐振系统可以输出标准的方波信号,输出频率精度达到10-5 kHz,在振动稳定以后频率变化小于0.1 Hz,无泛音频率出现,对研究高精度MEMS加速度计传感器具有重要意义。     

一种新型解耦陀螺的结构及电路设计

提出了一种新型的静电驱动微机械陀螺结构,采用两组对称的梳齿结构作为驱动电极,同时采用中央质量块栅格和另外一组梳齿两种结构检测感应模态的振动.该结构阻尼系数小,可达到较高的测量分辨率和准确率.本文采用解析方法和有限元法分析了该结构的振动阻尼特性、机械解耦和噪声特性以及梳齿结构的电磁学特性.提出了该结构的驱动电路和信号检测电路,并对电路特性进行了仿真分析.     

静电刚度式谐振微加速度计设计

运用梁的横向振动特性分析了梁振动频率与平行板电容形成的静电刚度的关系,并以此设计了静电刚度式谐振微加速度计。在加速度作用下,检测质量产生的惯性力使电容器极板发生位移来改变电容结构的间隙大小,从而使谐振频率发生变化,通过检测频率变化量来测量输入加速度的大小。根据加速度计的工作原理说明检测过程中梁的机械刚度保持不变,只与产生静电刚度的电容间隙变化相关,减小了检测信号对机械误差与残余应力的依赖性。运用加工参数进行理论计算得出加速度计的灵敏度为21．17Hz／gn,在CoventorWare2005中进行仿真表明：加速度计的固有频率为23．94kHz,灵敏度约为20Hz／gn,与理论设计值相近。     

静电刚度谐振式微加速度计及其接口电路分析

根据静电加载在平板电容器上产生等效静电负刚度原理,分析了基于静电刚度的谐振式微加速度计的敏感过程.针对有效信号检测中存在的同频干扰问题,建立了接口电路的等效模型,并根据干扰源提出在信号处理电路采用方波调制、开关解调的抑制方法.仿真和实验表明制造的加速度计检测端静态电容约为0.4pF,实验条件下变化的检测电容为3.1fF...     

基于静电纺丝法制备P(VDF-TRFE) /石墨烯(GR)薄膜的柔性复合压电纳米发电机

提出了一种利用静电纺丝工艺制备P(VDF-TRFE)/石墨烯(Graphene,以下简称GR)复合纳米纤维薄膜的方法并对其压电性能进行了研究。首先,以复合薄膜为功能层设计并制备了柔性压电纳米发电机。使用扫描电镜(SEM)表征了复合纤维薄膜表面的微观形貌。其次,对各纳米发电机样品进行了压电响应对比实验,含0.2%石墨烯的P(VDF-TRFE)/GR纳米发电机的开路输出电压、短路输出电流峰值分别为12.3 V、1.41 μA,比纯P(VDF-TRFE)样品分别增加了大约2.0倍、2.2倍。此外,通过理论分析和周期激振测试探究了纳米发电机电响应输出的影响因素和规律,证实在激振器驱动信号150 mV^300 mV振幅、10 Hz^30 Hz频率的范围内,其开路输出电压随着其振幅和振动频率增大而增大,电容充电效率随其振幅增大而增大。     

变截面粘弹性旋转梁非线性参数振动研究

研究了变截面粘弹性旋转梁的非线性参数振动.基于Kelvin-Voigt粘弹性本构关系,考虑几何非线性建立了变截面粘弹性旋转梁的非线性振动方程,用Galerkin法将其转化为常微分方程.运用多重尺度法得到其幅频响应.用数值方法讨论了转速和轮毂半径对梁固有频率和幅频响应的影响.研究表明:不稳定域随轮毂半径、转速的增大而增大,随锥度的增大而减小.     

DDS信号源的幅频特性补偿方法研究

在对DDS输出信号经D/A转换后的频谱特性进行分析的基础上,提出了一种幅频特性补偿方法.该方法利用LC并联电路在谐振点能够对信号进行放大的特点来补偿D/A转换引起的信号幅度衰减,从而提高DDS输出信号的幅度特性.实验结果表明此方法在0 Hz～40 MHz频率范围内可提高输出信号平坦度2 dB左右.     

Computational modeling and comparison of three co-laminar microfluidic mixing techniques

This study compares three common microfluidic mixing techniques: electroosmosis with patterned zeta potential, hydrodynamic focusing and physical constrictions. All three techniques provide a higher degree of mixing than a comparable channel without a mixer, but at the cost of higher power requirements. Of the three techniques, the electroosmotic mixer requires the greatest amount of power to produce a high degree of mixing, unless the channels are much smaller than those typical for microfluidic devices. The power requirement of the physical constriction mixer may be lowered by using multiple constrictions, with only a small loss in mixing effectiveness. The physical constriction mixer is recommended, since it has power requirements similar to the hydrodynamic focusing mixer but only requires the use of a single pump. However, if the mixing liquids contain particulates, a hydrodynamic focusing mixer may be preferred, because the physical constriction mixer may clog, depending on the particulate size.     

基于LabVIEW的幅频特性测试系统软件设计

针对幅频特性信息采集的专用仪器价格昂贵的问题，自主研制了基于通用信号源和频谱仪的幅频特性测试系统，运用LabVIEW编程语言设计了测试系统软件，实现了仪器的自动控制，数据的自动处理、分析、显示和存储等功能。对前置功率放大器进行了实际测试，将测试结果和Agilent N5230A矢量网络分析仪的测试结果进行了对比，验证了所开发的幅频特性测试系统的有效性。     

Quantification of the performance of chaotic micromixers on the basis of finite time Lyapunov exponents

Chaotic micromixers such as the staggered herringbone mixer developed by Stroock et?al. allow efficient mixing of fluids even at low Reynolds number by repeated stretching and folding of the fluid interfaces. The ability of the fluid to mix well depends on the rate at which ??chaotic advection?? occurs in the mixer. An optimization of mixer geometries is a non-trivial task which is often performed by time consuming and expensive trial and error experiments. In this paper an algorithm is presented that applies the concept of finite-time Lyapunov exponents to obtain a quantitative measure of the chaotic advection of the flow and hence the performance of micromixers. By performing lattice Boltzmann simulations of the flow inside a mixer geometry, introducing massless and non-interacting tracer particles and following their trajectories the finite time Lyapunov exponents can be calculated. The applicability of the method is demonstrated by a comparison of the improved geometrical structure of the staggered herringbone mixer with available literature data.     

一种cPCI任意波形发生器硬件模块的设计

作为一种重要的信号源模块,任意波形发生器被广泛地应用于cPCI测试系统中。介绍了一种单槽cPCI任意波形发生器硬件模块的设计,阐述了任意波形合成及数字调制的基本原理,并对滤波器设计、幅频校正以及cPCI热插拔接口等若干关键技术进行了分析。最后,对任意波形发生器输出频谱与输出波形进行了测试分析,结果表明,该任意波形发生器可根据用户的需求产生特定的波形,输出波形幅频特性平坦,谐波失真性能良好。     

Performance analysis of a folding flow micromixer

The performance of a folding flow micromixer in the Stokes flow regime is investigated computationally and experimentally. Consistency with a previously derived general scaling relation is demonstrated and the geometric parameters in the scaling relation are determined for this mixer. Measured data from a second similar mixer are correctly predicted using the scaling relation, thus showing that the approach allows quantitative prediction of mixing. This paper focuses on the errors associated with such predictions. Basic errors, expressed as variations in the standard deviation of the concentration profile, were estimated to be −10% for the computation and −30% for the experiment at the highest values of Péclet number considered. It is shown that this experimental error was mostly due to depth averaging of the spectroscopic technique used for concentration measurement at the high Péclet numbers. However, extra uncertainty is associated with chip fabrication tolerances and this was investigated further. Measurements at the outlet of nine different mixer chips of notionally identical design revealed variations in mixing of ±26%. This variation was attributed to misalignment of the glass layers determining the geometry of the mixer in the chip. Thus, the combination of measurement error and misalignment means predictions of the concentration standard deviation for the mixer may get non-uniformity wrong by up to 50%. Ensuring a required uniformity, however, simply requires adding a few further elements to the mixer to allow for this uncertainty. Application of the scaling relation to mixer design is highlighted by a discussion of the options available for improving the performance of the experimental mixer.     

基于双PI控制的水煤粉制备系统设计

针对传统的水煤粉制备系统产品质量不稳定的问题,设计了一套双PI控制的水煤粉制备系统,介绍了系统的工作原理、硬件组成和程序设计。该系统以OMRON C200HE PLC为核心,利用模拟量单元AD003和DA003及外部执行器分别构成煤粉量调节回路和水量调节回路,由2条PID指令自动控制,实现了水煤粉制备系统的随动控制。     

多相流搅拌器流场数值模拟软件

为对搅拌器多相流体间的最终乳化结果进行模拟,结合FLUENT与ANSYS软件,以VB为前台程序开发搅拌器流场数值模拟软件.用VB开发用户交互界面,通过后台调用ANSYS的APDL完成前处理模块,实现搅拌器叶片、筒体的建模,网格划分和组元创建;通过后台调用FLUENT运行日志文件实现流体流场仿真运算与结果后处理,并以图形...     

An artificial intelligence model to estimate the fat addition ratio for the mixing process in the animal feed industry

In animal feed pellets, the fat content is obtained either from the feed ingredients or is directly added during processing. Additional fat is required when the fat level in the feed ingredients is less than the desired level. This fat can be added either during the mixing process or after the pelleting process. However, adding fat at different time leads to different results. The addition of an increasing amount of fat during the mixing process decreases the pellet durability but enhances the pellet production rate. To avoid a reduction in the pellet durability, limiting the inclusion of fats in the mixer is suggested. The use of suitable fat addition ratios during mixing and after pelleting can improve the pellet quality and the production capability. Many factors significantly affect the decision of how much fat to add, such as the fiber inclusion content in the feed formulation, pellet die size, required feed durability, total required fat, and required additional fat. Due to frequent changes in the feed mix, anticipating the suitable amount of fat addition during the mixing process becomes a cumbersome task for a mill. In this paper, a model for estimating the amount of fat required in the mixer for each feed formulation is proposed. The model is based on the local linear map (LLM) and the back-propagation neural network (BPNN) methods. The LLM is used to identify which feed formulations require the addition of fat both during mixing and after pelleting, whereas the BPNN is employed for estimating the proper total fat required in the mixer, and the ratio of fat to add during the mixing process is subsequently estimated by subtracting the fat in the raw material from the total fat required in the mixer. The model is developed using data from one the largest feed mills in Thailand. The proposed model provides an accurate prediction and is practical for implementation in the mill that was studied.