MEMS悬臂梁的静态力学模型研究

研究分析了MEMS悬臂梁的静态力学特性。对比分析了集总式静力学模型和枢纽式静力学模型。对于集总式静力学模型,将MEMS悬臂梁的下拉位移假设为处处相等的普通电容极板,得到悬臂梁下拉位移和下拉电压。对于枢纽式静力学模型,将MEMS悬臂梁假设为下拉位移处处不等的转轴,通过寻找悬臂梁在下拉过程中的等效受力点,得到下拉位移和下拉电压。比较了两种模型的静电力学下拉位移与下拉电压的相对误差。结果表明,集总式静力学模型的误差为20.5%,枢纽式静力学模型的误差仅有5.3%。这表明,枢纽式静力学模型的特性优于集总式静力学模型。     

轴向压缩悬臂梁压电双晶片动静态特性研究

研究施加轴向压缩力于悬臂梁压电双晶片端部以增大端部输出位移和力的问题,对其进行了有限元分析,并推导了弹性力学解析解及模态方程,得到了符合程度较好的结果。研究结果表明,在120V电压及5.5N轴向力作用下,端部阻塞力达0.25N,输出位移较原来增大3倍以上(达5mm),而一阶特征频率随轴向力增大而加速减小。当轴向力达到一阶临界屈曲时,一阶特征频率趋于0,但当轴向力取一阶屈曲力的70%时,其1阶固有频率仍有45Hz,相较于普通伺服舵机有较大的优势,可有效提高微小型飞行器的操稳性。     

交流电动机矢量控制变压变频调速系统（二） 第二讲 异步电动机在静止坐标系上的数学模型

本文首先介绍了异步电动机空间矢量的概念，对异步电动机的各种坐标系进行了定义，在此基础上，根据电磁感应定律得到了异步电动机在静止坐标系上的数学模型，最后分析了异步电动机数学模型的性质。     

脸部动画中的肌肉和皮肤动态模型

本文提出了以脸部组织学、解剖学和生物力学特点为基础的脸部肌肉和皮肤运动的动态模型, 该模型以分层设计的规则逻辑网格构造脸部轮廓,以脸部动作编码系统的运动单元为依据建立分层仿真的组织模型,采用肌肉的动力和弹力性能及皮肤层的体保持力和位恢复力性能控制脸部组织运动, 从而产生相应的脸部表情的动画.     

关于线性电容之静态电容和动态电容作用的研究

在对由两个初始电压不为零的电容及一个电阻串联构成的一阶电路分析时,发现研究动态电路的过渡过程时要区分静态电容和动态电容,否则有可能会导致分析计算的错误。计算线性电容储存能量公式中的电容是电容元件的静态电容,初始电荷不等的两个电容元件串联时,其等效静态电容无法确定。一阶RC电路的时间常数中的电容是电容元件的动态电容或电容元件串联、并联的等效动态电容。在分析一阶电路的动态过程时要特别注意这些问题,希望引起从事电路教学工作的同行注意。     

Constrained Model Predictive Control of the Drive System With Mechanical Elasticity

In this paper, the application of model predictive control (MPC) for high-performance speed control and torsional vibration suppression in the drive system with flexible coupling is demonstrated. The control methodology presented in this paper relies on incorporating the drive's safety and physical limitations directly into the control problem formulation so that future constraint violations are anticipated and prevented. In order to reduce the computational complexity, the standard MPC controller is replaced by its explicit form. The resulting explicit controller achieves the same level of performance as the conventional MPC, but requires only a fraction of the real-time computational machinery, thus leading to fast and reliable implementation. The simulation results are confirmed by laboratory experiments.      

乙醇在静磁场作用下的傅里叶红外光谱研究

采用衰减全反射-傅里叶红外光谱法研究了静磁场作用对乙醇和乙醇-水溶液的红外光谱的影响.发现磁场作用下乙醇的红外光谱发生了明显的改变,在400～4000cm-1范围内,吸收强度随磁场作用时间的增长而增加;在1031,1054,2052,2075,2842和2865cm-1处,由于磁场的作用出现了新的吸收峰,而且磁场作用时间越长,新的吸收峰越明显.乙醇-水溶液的光谱在磁场作用后也发生了改变.这些结果说明磁场作用不仅增强了乙醇溶液分子间氢键,同时还影响了O-H,-CH2和-CH3的振动.     

利用单电极不对称双向脉冲刺激实现哺乳动物有髓神经纤维选择性兴奋的仿真研究

本研究的目的是要从理论上探讨利用单电极双向脉冲刺激实现哺乳动物神经纤维选择性刺激,(即当刺激一束神经时,不兴奋粗神经而兴奋细神经)的可能性.双向脉冲刺激可以降低刺激脉冲对神经纤维产生的电化学损伤.为研究哺乳动物有髓神经纤维的电特性,建立了一个基于简单的无穷大、各向同性的容积导体模型的仿真系统.利用该仿真系统,采用"不对称但电荷平衡"的双向脉冲刺激,计算了神经纤维的兴奋和阻断阈值与纤维直径、纤维-电极间距离的关系.结果表明:在距电极一定距离内采用该双向脉冲刺激模式确实可以实现哺乳动物有髓神经纤维的选择性兴奋.     

一种机械式多稳态压电俘能器及其特性研究

该文提出了一种机械式非线性多稳态压电悬臂梁装置。利用集中参数法建立了系统的数学模型,分析系统势能可知,随着系统参数的变化,系统具有多稳态的特性;采用数值仿真法分析了在简谐激励和随机激励下系统的运动状态及俘能性能。结果表明,在简谐激励下,中低频环境中系统为三稳态时具有较好的俘能特性,高频环境中系统为单稳态时具有较好的俘能特性;在随机激励下,系统为三稳态时能在较低噪声强度下越过势垒而做大幅运动,从而输出较大电压;随着噪声强度增加,阱间运动发生的频率增加,输出电压也增加。     

The Dynamic Behavioral Model of RF Power Amplifiers With the Modified ANFIS

The adaptive neuro-fuzzy inference system (ANFIS) has been widely used for modeling different kinds of nonlinear systems including RF power amplifiers (PAs). The modified ANFIS (MANFIS) architecture is simpler than that of ANFIS, but with nearly the same performance for modeling nonlinear systems. In this paper, the MANFIS is applied to model RF PAs with memory effects. The simulation and experimental results both in the time and frequency domains show that this model has good modeling accuracy and the characteristics of faster convergence and lower computational complexity compared with the ANFIS model. The normalized mean squared errors of the MANFIS model are slightly lower than those of some other neural network models such as the real-valued time delay neural network, radial basis-function neural network, etc. Finally, the MANFIS model is successfully used in a digital predistortion system, which can provide over 10- dB adjacent channel leakage ratio improvement for three-carrier wideband code division multiple access signals.     

Simulation of Laser-Induced Thermotherapy Using a Dual-Reciprocity Boundary Element Model With Dynamic Tissue Properties

This paper presents a nonlinear dual-reciprocity boundary element method (DRBEM) for bioheat transfer in laser-induced thermotherapy. The nonlinearity stems from the dynamic changes of tissue thermophysical and optical properties and the blood perfusion rate during laser heating. The proposed DRBEM is coupled with a modified Monte Carlo method and the Arrhenius rate equation to investigate laser light propagation, bioheat transfer, and irreversible thermal damage in tumors. The computer code is justified by comparing the DRBEM results with the finite-difference results. The photothermal processes in interstitial laser thermotherapy with single or double laser fiber scattering applicators are chosen as the demonstrative examples. The dynamic nature, together with the unique advantages of “boundary-only” and excellent adaptability to complex anatomical geometries that the DRBEM method offers, makes the present nonlinear DRBEM a powerful tool for analysis and optimization of the parameters in laser surgical procedure.      

动静态监测光纤光栅传感信号的实验研究

基于可调谐光纤TF Fabry-Pent（FP）滤波扫描传感光纤Bragg光栅（FBG）反射峰的原理．提出一种新颖的探测方法,分别从动静态两方面监测传感FBG反射谱与TF F-P透射谱的合成谱。实验中．通过加载到TF F-P滤波器的驱动信号的不同,在静态监测下,模拟并分析了光信号功率与转化电压的趋势图以及多次实验中探测到最大信号时两者的关系;用双踪示波器动态实时监测并分析了经光电探测（PD）及其放大调理电路转换后的电压变化信号。实验结果表明．PD探测的最大值与传感FBG反射峰对应。经过标定后的系统分辨率可达1pm,测量精度为0．01nm。     

An Apparatus for Generating Controlled Ramp Movements During Studies of Muscle Spindle Afferent Activity and Muscle Tone in Man

With the increasing use of refimed techniques such as micro-neurography for the study of motor control in man, the need for a mechanical device capable of generating accurate and reproducible displacements and of measuring graded levels of contraction has arisen.     

Analyses of Static and Dynamic Random Offset Voltages in Dynamic Comparators

When mismatches are present in a dynamic comparator, due to internal positive feedback and transient response, it is always challenging to analytically predict the input-referred random offset voltages since the operating points of transistors are time varying. In this paper, a novel balanced method is proposed to facilitate the evaluation of operating points of transistors in a dynamic comparator. Thus, it becomes possible to obtain an explicit expression for offset voltage in dynamic comparators. We include two types of mismatches in the model: 1) static offset voltages from the mismatch in $muhbox{C}_{rm ox}$ and threshold voltage ${rm V}_{rm th}$ and 2) dynamic offset voltage due to the mismatch in the parasitic capacitances. From the analytical models, designers can obtain an intuition about the main contributors to offset and also fully explore the tradeoffs in dynamic comparator design, such as offset voltage, area and speed. To validate the balanced method, two topologies of dynamic comparator implemented in 0.25- $mu{hbox {m}}$ and 40-nm CMOS technology are applied as examples. Input-referred offset voltages are first derived analytically based on SPICE Level 1 model, whose values are compared with more accurate Monte Carlo transient simulations using a sophisticated BSIM3 model. A good agreement between those two verifies the effectiveness of the balanced method. To illustrate its potential, the explicit expressions of offset voltage were applied to guide the optimization of “Lewis-Gray” structure. Compared to the original design, the input offset voltage was easily reduced by 41% after the optimization while maintaining the same silicon area.      

穿孔机械阻抗板的吸声特性研究

为提高低频吸声性能,在机械阻抗板(MIP)上穿少量微孔形成穿孔机械阻抗板(MIPMP)吸声结构。对MIPMP结构吸声性能进行初步研究,建立计算模型,用驻波管测量吸声系数。结果表明,MIPMP结构的吸声为机械阻抗和微穿孔的共同作用。吸声曲线出现两个吸声峰:一个在200~300 Hz,由机械阻抗引起,吸声系数可达0.95;一个出现在300~600Hz,由微穿孔引起。计算模型与实验结果所示趋势一致:随穿孔率的增大,机械阻抗单元吸声峰值先增大后减小,向高频移动,微穿孔单元吸声峰值逐渐减小,带宽增大,向高频移动;随背腔的增厚,机械阻抗单元吸声峰值变大,频率基本不变,微穿孔单元吸声峰值略减小,向低频移动。MIPMP与微穿孔板(MPP)构成的复合吸声结构在200~1 600Hz有好的吸声性能。     

Static and Dynamic Equalization of the L5 Repeatered Line

The residual transmission deviation of the L5 repeatered line can be divided into two categories, static or time invariant and dynamic or time variant. The static deviation, which is due to design limitations and manufacturing deviations of the basic and regulating repeaters, is compensated for by manually adjustable equalizers designatedE1andE2. These equalizers are composed of 28 Bode bump networks whose gains are adjusted to minimize the total mean-squared error of the transmission channel. The residual dynamic transmission deviation, caused by temperature variations of the basic and regulating repeaters, is corrected continuously by an automatic equalizerE3. The time-varying transmission deviations are detected by four pilot tones spaced across the L5 frequency spectrum. Four electronically controlled networks in the equalizer respond to the pilots to correct the dynamic transmission deviations.     

Control of an AC Dynamometer for Dynamic Emulation of Mechanical Loads With Stiff and Flexible Shafts

This paper addresses the emulation of linear and nonlinear loads using a vector-controller dynamometer for the position control of mechanical loads. The emulation strategy allows an electrical machine (dynamometer) to be controlled, so as to emulate both the static and dynamic characteristics of a load with a certain bandwidth. The approach can be used for the experimental validation and testing of the electrical drives and motion-control techniques. The dynamic structure of the emulated load is always preserved. High-order systems such as loads with flexible shafts and nonlinear effects can be emulated accurately. This paper presents the dynamometer-control design, its practical implementation, and experimental results for the position control of the linear and nonlinear emulated loads. Systems with stiff and flexible shafts are considered. Finally, the experimental results are compared with the corresponding simulated loads to validate the emulation strategy.     

分布柔度桥式位移放大机构静动力学性能研究

该文对分布柔度桥式位移放大机构的放大比、刚度特性及固有频率等静动力学性能进行了研究。首先,根据柔性梁单元的刚度矩阵建立了该放大机构的位移放大比及其输入刚度解析模型。随后根据柔性梁的变形曲线方程,通过求解变形曲线对时间的导数,得到梁上任一点速度以获得柔性梁在机构振动过程中动能表达,在此基础上,利用拉格朗日法建立了具有3个广义坐标的桥式放大机构的振动方程,并得到其工作方向的固有频率。最后利用有限元与实验方法对其动力学性能进行了测试。实验结果表明,解析计算结果与有限元分析及实验结果较吻合,证明了所建立的解析模型的准确性。     

Experimental and Theoretical Evaluation of Distortion Effects on SCM Optical Transmissions Due to the Joint Action of Static Chirping,Dynamic Chirping and Dispersive Channel

In optical CATV systems based on subcarrier-multiplexing technique, the joint action of semiconductor laser chirp and fiber chromatic dispersion gives rise to intermodulation distortion phenomena affecting the transmission performance. This problem has been explained analytically, leading to a model valid for every kind of modulating signal and explored in the case of a Gaussian process. In this paper, the model is developed for the important specific case of an analogue SCM modulating signal. The results are assessed experimentally.     

压电双晶片的静动态特性分析与测量

在忽略剪切振动、弯曲振动、扭转振动和横效应振动的近似条件下,分析了压电双晶片的纵效应振动。从压电方程和波动方程出发,推导出了厚度伸缩振动模式的阻抗频响和导纳频响,并在此基础上得到了纵效应振动的一般导纳公式。推导出纵效应振动的等效电路,绘制出阻抗频率响应曲线。另外,采用有限元软件对压电双晶片进行了静态变形、动态特性分析,同时进行了静态和动态测试。将理论计算、有限元分析和实验测试结果进行比对分析,三者结果吻合。