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...     

谐振式微机械加速度计设计的关键技术

谐振式微机械加速度计直接输出频率信号,具有稳定性好、精度高的特点.分析了谐振式微机械加速度计的工作机理,建立了第一级敏感结构、杠杆机构和第二级敏感结构的数学模型,指出了实现高灵敏度加速度测量的关键技术在于支撑梁、质量块、谐振器和杠杆机构的设计.提出了一种谐振式微机械加速度计结构,进行了结构的优化设计和仿真计算,得出的性能指标:谐振频率98 858 Hz,Q值673.9,灵敏度24.52 Hz/gn.     

一种新颖的微杆杠结构的理论建模及其在谐振式微加速度传感器中的应用

为了提高谐振式微加速度传感器的灵敏度,提出一种新颖的微杠杆结构.分析该结构的工作原理,推导该结构的理论模型,得到这种微杆杠放大倍数的解析表达式.在这个理论模型的基础上,为了进一步提高微杆杠的放大倍数,对其参数进行优化,分析微杆杠结构中各参数对于放大倍数的影响,优化后该结构的放大倍数高达200.基于这种微杠杆结构设计两种分别为静电驱动/电容检测和电热驱动/压阻拾振的谐振式微加速度传感器,分别介绍这两种传感器的工作原理及其特点,并对这两种结构进行有限元模拟.模拟结果证实这两种微加速度传感器的灵敏度均高于1 000 Hz/gn,进而验证这种新提出的微杠杆结构的有效性.     

一种电容式微机械加速度计的设计

介绍了一种新型基于滑膜阻尼的电容式微机械加速度计.该加速度计根据差分电容极板间正对面积的改变来检测加速度大小,保证了输出电压与加速度之间的线性度.对加速度计进行了结构设计和分析.给出了加速度计的制作工艺流程,研究了解决深反应离子刻蚀过程中的过刻蚀现象的方法.初步测试结果表明,该加速度计的灵敏度比较理想,谐振频率与理论计算相吻合.     

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。     

双电容接口式微机械陀螺的信号检测方法

在研究双电容接口式微机械陀螺结构与分析传统差分电容检测方法对其驱动力的影响的基础上,提出了一种适合于该陀螺的新型信号检测方法,此方法具有两个显著特点:第一,能够使公共电容极板偏置到零电压,消除其对驱动力的影响,进而提高微机械陀螺的系统灵敏度;第二,能够消除直流电压的不匹配以及失调电压对输出信号的影响.最后,通过HSPICE软件仿真验证了该方法的可行性.     

预载电压对力平衡式微硅加速度计性能的影响

在实验中发现,力平衡式加速度计的施力电压变化范围和传统计算中的并不相同。为研究预载电压对加速度计性能指标的影响,重新推导了力发生器的传递函数和静电负刚度等参数的表达式。对参数的分析显示:预载电压直接影响了加速度计的灵敏度、量程和分辨力,但不影响非线性。在综合各种影响的基础上,提出了根据不同应用的要求选取预载电压的方法,并进行了实验验证。     

基于三梁结构的电热驱动谐振式微加速度传感器研究

为了提高电热激励/压阻拾振谐振式微加速度传感器的品质因数和消除交叉灵敏度,提出一种基于三梁结构的新设计.依据有限元模拟得到的固有振型来选择三梁结构参数,以减少能量耗散,提高品质因数.分析本设计消除交叉灵敏度的机制和独特的三梁结构的激振方式并对其进行有限元模拟.模拟结果证实这种谐振式微加速度传感器的灵敏度高于1000 Hz/g.     

谐振微悬臂梁传感器的工作原理及其在生化检测中的研究进展

谐振微悬臂梁是一种可以将质量变化转换为频率信号的微质量型传感器，因其分辨率高、灵敏度高、成本低、易于集成和小型化等优点而备受关注。谐振微悬臂梁现已被广泛应用于流量控制、生物医学痕量检测、气态和液态分子分析等领域。近年来，随着微机电系统（Micro-Electro-Mechanical System,MEMS）技术的快速发展，针对谐振式微悬臂梁传感器的研究与应用越来越多，对近年来谐振式微悬臂梁传感器在环境检测、生物医学等领域的具体应用进行了综述，并对未来的发展方向做出了展望。     

基于MEMS电容式加速度计的闭环读出电路设计

设计了面向圆片级封装的一种闭环加速度计读出电路.在基于电容式微加速度计结构的读出电路设计中考虑了寄生电容对整个系统的影响.用MATLAB SIMULINK对所设计的读出电路进行了建模仿真.在仿真过程中分析了噪声、圆片级封装与普通封装的寄生参数及实际工艺中流水结构的不对称性的影响并进行了比较.结果表明,所设计传感器及读出电路的非线性误差在量程±20 gn范围内小于0.5％;圆片级封装的稳定时间在2 ms,小于普通封装的稳定时间;基于圆片级封装的对称性梳齿结构的输出电压灵敏度为328 mV/gn.     

微机械加速度计挠性梁机械刚度的实验研究

在使用开环频率响应实验求取微机械加速度计挠性梁机械刚度时,不可避免地受到静电负刚度的影响。通过分析预载电压和扫频信号幅值对静电负刚度的影响,提出了从系统刚度中分离出挠性梁机械刚度的计算方法。通过不同实验条件下得到的实验结果,验证了该方法的正确性。     

Dynamic pull-in of parallel-plate and torsional electrostatic MEMS actuators

An analysis of the dynamic characteristics of pull-in for parallel-plate and torsional electrostatic actuators is presented. Traditionally, the analysis for pull-in has been done using quasi-static assumptions. However, it was recently shown experimentally that a step input can cause a decrease in the voltage required for pull-in to occur. We propose an energy-based solution for the step voltage required for pull-in that predicts the experimentally observed decrease in the pull-in voltage. We then use similar energy techniques to explore pull-in due to an actuation signal that is modulated depending on the sign of the velocity of the plate (i.e., modulated at the instantaneous mechanical resonant frequency). For this type of actuation signal, significant reductions in the pull-in voltage can theoretically be achieved without changing the stiffness of the structure. This analysis is significant to both parallel-plate and torsional electrostatic microelectromechanical systems (MEMS) switching structures where a reduced operating voltage without sacrificing stiffness is desired, as well as electrostatic MEMS oscillators where pull-in due to dynamic effects needs to be avoided.     

MEMS Electrostatic Actuation in Conducting Biological Media

We present design and experimental implementation of electrostatic comb-drive actuators in solutions of high conductivity relevant for biological cells. The actuators are operated in the frequency range 1-10 MHz in ionic and biological cell culture media, with ionic strengths up to 150 mmol/L. Typical displacement is 3.5 mum at an applied peak-to-peak signal of 5 V. Two different actuation schemes are presented and tested for performance at high frequency. A differential drive design is demonstrated to overcome the attenuation due to losses in parasitic impedances. The frequency dependence of the electrostatic force has been characterized in media of different ionic strengths. Circuit models for the electric double layer phenomena are used to understand and predict the actuator behavior. The actuator is integrated into a planar force sensing system to measure the stiffness of cells cultured on suspended structures.     

Micro-mirror laser scanner combined with a varifocal mirror

A laser beam scanning system consisting of a scanning micro-mirror and a varifocal micro-mirror is fabricated for laser beam sensing with variable beam diameter. The scanning micro-mirror is operated under the resonant oscillation condition with an electrostatic comb-drive actuator. The varifocal micro-mirror is driven by a bending moment generated at the circumference of mirror with a parallel-palate electrostatic actuator. The scanning micro-mirror and the varifocal mirror are fabricated on a silicon on insulator wafer. The rotational angle of 9° at 766 Hz is obtained at the voltage of 300 V. The spot size of the laser beam is adjusted from 0.5 to 3.5 cm at the distance of 43 m by changing varifocal voltage. The proposed scanning system can be useful for several sensing techniques.     

Dynamic response of a torsional micromirror to electrostatic force and mechanical shock

In this paper dynamic characteristics of a capacitive torsional micromirror under electrostatic forces and mechanical shocks have been investigated. A 2DOF model considering the torsion and bending stiffness of the micromirror structure has been presented. A set of nonlinear equations have been derived and solved by Runge–Kutta method. The Static pull-in voltage has been calculated by frequency analyzing method, and the dynamic pull-in voltage of the micromirror imposed to a step DC voltage has been derived for different damping ratios. It has been shown that by increasing the damping ratio the dynamic pull-in voltage converges to static one. The effects of linear and torsional shock forces on the mechanical behavior of the electrostatically deflected and undeflected micromirror have been studied. The results have shown that the combined effect of a shock load and an electrostatic actuation makes the instability threshold much lower than the threshold predicted, considering the effect of shock force or electrostatic actuation alone. It has been shown that the torsional shock force has negligible influence on dynamic response of the micromirror in comparison with the linear one. The results have been calculated for linear shocks with different durations, amplitudes, and input times.     

Closed-form solutions of the parallel plate problem

Closed-form solutions to the parallel plate problem have been derived for design of electrostatic devices that employ the parallel plate. With dimensionless height and force introduced to simplify the nonlinear parallel plate problem, a simple cubic equation implying behavior of the height of the movable plate corresponding an applied voltage has been derived and theoretically solved to provide closed-form solutions of the movable plate height, effective stiffness, resonant frequency, capacitance and their sensitivities to voltage. The theoretical height agreed well with experimental data obtained from a surface-micromachined parallel plate. When the applied voltage approaches the pull-in voltage, the height of the movable plate reaches 2/3 of the initial height, the effective stiffness and resonant frequency go to zero and the capacitance becomes 3/2 times the initial capacitance. These closed-form solutions can be used to analyze and design micro- and nano-devices employing electrostatic parallel plates.     

Electrostatic correction of structural imperfections present in a microring gyroscope

This paper describes a procedure for identifying mass and stiffness imperfections present in a microring gyroscope. In general mass and stiffness imperfections will be present as a result of fabrication variances and will contribute to mistuning of the gyroscope. Both mass and stiffness imperfections are treated as perturbations of the ideal isotropic mass and stiffness. The mass and stiffness perturbations are combined to form a structural imperfection, which is shown to be determinable from Nyquist plots of the frequency response functions. An analysis of electrostatic "tuning" is presented and demonstrates that the nonlinear negative spring component produced from a particular arrangement of capacitive electrodes is capable of removing such structural imperfections. If uncorrected the structural imperfections would otherwise result in anisoinertia and anisoelasticity. A comparison between the theoretically predicted tuning voltage and the experimentally derived value is made and shown to be in agreement. The major advantage of electrostatic tuning is that it may be implemented on-chip during operation thus providing active tuning. This is in contrast to the trimming techniques employing laser ablation or focussed ion beam, which may only be done prepackaging.