静电微梁器件的降阶模型及其动态Pull-in不稳定性研究

微器件的设计需要利用计算机技术快速准确仿真其动态特性。以器件中结构件的模态振型函数作为基函数,结合Galerkin映射建立静电-结构耦合微梁器件的自由度缩减模型,该降阶模型能考虑初始轴向载荷、大变形几何非线性效应对器件基频及动态特性的影响。在Simulink~中建立单模态模型,并对器件的Pull-in过程进行动态仿真,分析了有阻尼和无阻尼情况下,静电器件动态Pull-in的分叉现象。     

自卸汽车铝合金车箱结构模态分析

有限元模态分析和试验模态分析方法是辨识车辆结构动态性能的一种有效手段。为分析自卸汽车铝合金车箱的动态特性,建立了以板壳单元为基本单元的车箱有限元分析模型,应用HyperMesh有限元分析软件计算了该车箱在自由状态下的模态参数。建立了车箱模态试验系统,进行车箱模态试验,提取了模态参数。计算结果与试验结果对比分析表明,所建立的有限元模型和采用的分析方法是可行的。     

自卸汽车铝合金车箱结构模态分析

有限元模态分析和试验模态分析方法是辨识车辆结构动态性能的一种有效手段.为分析自卸汽车铝合金车箱的动态特性,建立了以板壳单元为基本单元的车箱有限元分析模型,应用HyperMesh有限元分析软件计算了该车箱在自由状态下的模态参数.建立了车箱模态试验系统,进行车箱模态试验,提取了模态参数.计算结果与试验结果对比分析表明,所建立的有限元模型和采用的分析方法是可行的.     

焊点密度对焊接板件模态影响的仿真分析

板件焊接中,焊点的密度决定了焊接后结构的静态和动态性能,而有限元模态分析是了解系统动态特性的方法之一。基于有限元方法,详细阐述了焊接板件有限元模型的建立方法以及模态分析方法。模态分析结果表明焊点密度对焊接板件模态频率、振型有一定影响,对板件焊接实际应用有一定的指导意义。     

基于遗传算法和神经网络的塔机结构动态优化设计

利用遗传算法和BP神经网络建立复杂结构系统动态优化的计算模型,该模型可代替系统原来的有限元模型,用于振动系统的快速重分析。首先对塔式起重机结构系统进行模态分析及谐响应动力学分析,找出对结构动态特性影响最大的模态频率,再利用灵敏度分析,确定对动态特性较敏感的设计变量作为神经网络的输入变量,并利用正交试验法确定神经网络训练样本,用有限元模型计算出样本点数据,建立反映结构振动特性的人工神经网络模型,最后利用遗传算法对所建立的神经网络模型寻优,得到使结构动态性能最优的设计参数。     

基于异构宏模型的MEMS系统级建模方法

针对含复杂结构的MEMS器件,提出基于异构宏模型的系统级建模方法,即将基于解析法和基于数值计算的宏建模方法结合起来提取复杂器件的参数化宏模型,在此基础上实现MEMS系统级仿真。以z轴加速度计为例,在Saber中进行其系统级的时域、频域仿真,将仿真结果与有限元分析进行了比较,其仿真时间小于3min,相对误差小于3%,表明该方法能够快速有效地实现复杂结构MEMS器件的系统级仿真。     

非线性转子系统动态特性分析的模态-摄动方法

将模态迭加法和矩阵摄动法相结合，应用于非线性转子系统的动态特性分析。在初始步长时，用子空间迭代法求解固有频率和模态，此后的非线性模态谱用矩阵摄动法计算。对于有模态截断的情况，可以采用部分模态迭加法。在没有外载荷非线性的情况下，该方法避免了在数值分析中局部模态的重新计算。非线性转子系统的数值仿真表明：该方法是研究非线性系统动态特性的快速而有效的方法。     

一种基于复杂永磁体阵列的悬浮式振动能量采集器的精确模型及验证

为提高振动能量采集器的输出性能和工作频带，基于永磁体阵列和多自由度器件受到广泛关注。然而这类器件存在磁场分布复杂，动态特性难以模拟等问题。以一种基于复杂永磁体阵列的可调频磁悬浮振动能量采集器为研究对象，建立器件解析模型和有限元模型的联合分析模型，理论模型显示系统具有非线性振动特性，其动力学模型可简化为Duffing方程形式，并通过有限元模型简化了对非线性系统的分析。利用COMSOL有限元仿真研究器件磁场分布、非线性磁力特性，分析磁力和线圈位置对器件输出特性的影响。搭建测试平台对研制的可调频磁悬浮振动能量采集器进行试验表征，以验证联合分析模型。试验结果表明，在20～35 mm的固定磁铁间距离变化范围内，器件谐振频率变化范围为8.6～13.1 Hz，0.35g加速度下输出电压峰峰值为352.9～658.2 mV，联合分析模型与试验之间具有一致性。     

直线电动机进给系统滚动导轨结合面动态特性参数识别优化

机床结合面对整机的动静态特性有着重要的影响,结合面动态特性参数的识别对提高整机性能、缩短研发周期有重要意义。提出基于LMS Test.Lab试验模态分析和ANSYS响应面法的动态特性参数识别优化方法。基于结合面等效刚度和阻尼值在ANSYS软件中建立直线电动机进给系统有限元模型,对系统进行仿真模态分析,并通过LMS Test.Lab系统进行模态试验测试,对比仿真模态参数和试验测试模态参数,并通过试验测试结果修正有限元模型。最终使仿真模态参数值与试验测试结果相差在8%以内,验证了该有限元模型的准确性。     

基于遗传算法和神经网络算法的吊车结构优化设计与实现

论文综合利用BP神经网络、遗传算法有限元法以及正交试验法对吊车结构系统进行优化研究。利用遗传算法和BP神经网络建立复杂结构系统动态优化的计算模型,该模型可代替系统原来的有限元模型。首先对吊车起重机结构系统进行模态分析及谐响应动力学分析,找出对结构动态特性影响最大的模态频率,再利用灵敏度分析,确定对动态特性较敏感的设计变量作为神经网络的输入变量,并利用正交试验法确定神经网络训练样本,用有限元模型计算出样本点数据,建立反映结构振动特性的人工神经网络模型,最后利用遗传算法对所建立的神经网络模型寻优,得到使结构动态性能最优的设计参数。     

Static deflection and pull-in instability analysis of an electrostatically actuated mirocantilever gyroscope considering geometric nonlinearities

In this paper, a mathematical modeling of a microcantilever gyroscope is presented considering the nonlinearities of the system due to electrostatic forces, fringing field, geometry and the inertial terms. The microgyroscope is actuated and detected by electrostatic methods and subjected to coupled bending oscillations. First a system of two nonlinear integro-differential equations is derived which describes flexural-flexural motion of electrostatically actuated and detected microbeam gyroscopes. Afterward, static deflection and pull-in instability of the microgyroscopes acted upon by DC voltages in both (driving and sensing) directions are studied for different parameters. The model’s predictions are in good agreement with the experimental data found in the literature and finite element simulation. Results show that the nonlinearities become important when pull-in happens.     

The nonlinear electrostatic behavior for shaped electrode actuators

The nonlinear electrostatic pull-in behavior of shaped actuators in micro-electro-mechanical systems (MEMS) is investigated in this article. The differential quadrature method (DQM) was used to solve the nonlinear interaction between the curved electrostatic field force and the deflection of shaped cantilever actuators. Various electro-statically actuated micro-structures, such as cantilever beam-type and fixed–fixed beam-type shaped actuators are studied. The proposed models include the fringing effects of the electrical field. Both the small beam deflection and the large beam deflection models are implemented in this work to elucidate the possible effect of the deflection model on the accuracy. The results calculated from the proposed model agree closely with the measured data. The numerical results reveal that the profile shapes of the actuators may not only influence the distribution of the electrostatic force but also considerably change the nonlinear pull-in voltage.     

MEMS器件建模与仿真分析方法研究

基于主振型叠加法和拉格朗日动力学方程,建立微机电系统多场耦合分析的宏模型。这一模型是由常微分方程组成的有限自由度系统,自由度较少,系统状态方程简单,显著地减少计算时间,为micro-electro-mechanical systems（MEMS）设计提供一种有效而准确的分析工具。算例表明,文中所提方法用于MEMS器件建模仿真分析是有效的。     

Dynamic identification of electrostatically actuated MEMS in the frequency domain

Micro-electro-mechanical systems (MEMS) are commonly constituted by suspended structures such as beams and spring-supported plates and are applied in a wide range of fields such as sensing, optics, radio frequency communications, fluidics, biology, etc. The components that form the basis of MEMS devices are often actuated using electrostatic capacitive strategy, and performances are improved by the micro-scale dielectric gap between the electrodes. The dynamic dimensioning and characterization are made more complicated by the nonlinearity of the electrostatic actuation and by the electro-mechanical coupling, which involves the capacitive force and the elastic reaction of the structure. The dynamic characterization is affected by specific problems related to electro-mechanical coupling, which need a dedicated approach. Some of the effects that take place during the dynamic tests on electrostatically actuated MEMS are studied in this work and are described using compact analytic models; using the proposed approaches, results of experiments in the presence of electro-mechanical coupled domains can be predicted and interpreted correctly. Structural properties such as residual stress or strain dependent on the fabrication process may influence the measurements in both, the static and dynamic fields. The goal of this study is to describe the most common experimental problems related to the dynamic characterization of electrostatically actuated microsystems; theoretical approaches that are able to describe the effects involved are proposed to predict and interpret experimental results.     

Dynamic Analysis of Rectangular Micro-plates Under Mechanical Shock in Presence of Electrostatic Actuation

Besides one dimensional beam-type MEMS, two dimensional electrically actuated rectangular micro-plates have lots of applications in micro-engineering. However, there exist only a few works devoted to the analysis of such structures in the open literature to date. Therefore, the present work focuses on the dynamic behavior of electrically actuated rectangular micro-plates under mechanical shock. The micro-plate is modeled using the non-linear Kirchhoff plate theory and the shock is assumed to be induced according to the base excitation scheme. The micro-plate motion is simulated through a novel and computationally very efficient reduced order model which accounts for the inherent non-linearity of distributed electrostatic pressure and the geometric non-linearity of von Kármán mid-plane stretching as well as the influences of both in-plane and out-of-plane displacements. The present findings are compared and successfully validated by those obtained through three-dimensional finite element analysis carried out in COMSOL Multiphysics commercial software as well as the available static results in the literature. It is found that the present procedure can remove the long run-time limitation of the finite element method and produce robust results over the whole operation range of the device up to its instability threshold especially for systems subjected to enormous shock accelerations.     

平板式可变电容器宏建模及其在MEMS设计中的应用实例

平板式可变电容器是MEMS重要的机电耦合部件,建立其宏模型是MEMS系统级快速仿真的迫切需求。本文采用解析法在三维空间内建立了可描述活动极板六自由度运动的宏模型,并以MAST为模型编码语言实现了其多端口参数化组件模型。在SABER仿真平台上构建了电容检测式微加速度计系统级模型,时域仿真结果表明使用该系统级模型能够快速进行有限元分析软件难以实现的复杂机电耦合系统时域行为分析。     

仿生微扑翼机构的设计与机电耦合特性研究

根据昆虫扑翼飞行的原理，设计了一种基于昆虫胸腔式结构的静电驱动微扑翼机构。根据驱动机构的物理模型建立了机电耦合系统的非线性动力学模型，应用数值方法研究了系统在常值电压激励下的动态响应；在相空间中分析了系统的非线性动态特性，研究了阻尼和初值对系统动态特性的影响；讨论了系统在正弦激励电压信号下的响应。研究结论对微扑翼驱动机构的设计、制作和应用提供了一定的理论依据，对于其他静电驱动的微机电系统亦有一定的参考价值。     

静电场耦合微机电系统的动态模型

研究静电场耦合微机电系统（Ｍｉｃｒｏ ｅｌｅｃｔｒｏｍｅｃｈａｎｉｃａｌ ｓｙｓｔｅｍｓ,简记为 ＭＥＭＳ）的动态模型问题。首先,给出了耦合静电场的输入／输出两端点对模型,讨论了微机电系统的独立变量对的选择与分析方法。其次,叙述了所研制的典型微结构,包括ＳＥＭ照片、有限元分析的振动模态,以及简化模型。第三,分析了ＭＥＭＳ传感器系统的静电场与静电力表达式、动力学方程,以及开环和闭环传递函数。第四,给出了ＭＥＭＳ传感器系统的实测频率特性和等效模型参数,并且根据以上分析和试验结果,提出了几点有重要意义的结论。     

强冲击条件下MEMS封装可靠性有限元分析

在强冲击载荷(104g或更高,g为重力加速度)作用下,弹载微电子机械系统(Micro electro-mechanical system,MEMS)(如陀螺仪或加速度计)及电子器件的封装和互连结构失效是影响整弹可靠性及其任务成功性的重要因素.利用有限元建模和动态响应仿真分析方法对强冲击条件下板级微电子机械系统封装结构的可靠性问题及其影响因素进行研究.有限元动态响应分析方法针对MEMS陀螺仪的典型封装结构——无引脚芯片载体进行.分析过程中焊点材料选取更接近工程实际的双线性随动硬化材料模型,详细分析相关敏感因素对焊点互连结构可靠性的影响,并给出提高封装结构可靠性的工程设计建议.