基于电磁激励的SOI-MEMS谐振式加速度计的闭环检测系统(英文)

介绍了一种基于电磁激励方式,采用基于绝缘体上硅的微电子机械系统(SOI-MEMS)加工方法制作谐振式加速度计及其闭环控制电路系统.传感器芯片制作采用的是SOI材料(10μm+2μm+290μm),利用MEMS加工工艺制作.当外界z轴方向加速度作用于加速度计时,加速度计的两根"H"型谐振梁因受到弯曲应力而产生谐振频率的漂移,通过检测谐振梁频率的变化标定加速度的大小.电磁激励检测方式有利于加速度计的最终闭环控制.闭环电路控制系统主要由增益放大部分、自动增益控制(AGC)电路缓冲系统和移相器组成.测试结果显示,当有1g重力加速度作用于加速度计,闭环电路可稳定输出检测正弦频率信号58.958 kHz,与开环扫频结果一致.加速度计的"H"型谐振梁空气中检测Q值约为400,灵敏度可达584 Hz/g.     

基于Pierce振荡器架构的BAW传感器读出电路

薄膜体声波谐振器(FBAR)不仅能作为手机射频前端的滤波器,还具有充当传感器表头的潜力。为实现对体声波(BAW)传感器输出射频信号的检测,设计一种基于Pierce振荡器的BAW传感器读出电路。读出电路采用双路差分方式,将体声波谐振器构成两路振荡器,一路作为参考电路用于检测外界环境等因素的干扰,另一路作为传感电路用于检测待测物理量。两路振荡器信号通过混频滤波得到由待测物理量引起的谐振频率偏移。然后通过放大与整形将模拟信号转换为数字信号,最后送入FPGA进行频率检测。以一个2 GHz的体声波质量传感器为例,给出电路各模块的设计方法,经各模块仿真以及信号转换电路的实验验证,电路可检测的最大谐振频率偏移量为99 MHz。     

40Cr合金钢切削过程中切削用量对刀具振动的影响

针对40Cr合金钢的切削过程,研究切削用量对刀具振动的影响.结果表明:进给量为0.24 mm/r时表面粗糙度最大,为1.87μm;刀具振动频率在0.48～0.96 MHz时,刀具振幅较小,在此频率下加工表面的完整性较好.     

新型静电驱动双向平动MEMS变形镜(英文)

设计了一种新型静电驱动双向平动的MEMS变形镜,其结构包括3部分:中央下电极,4个静电驱动杠杆结构以及反射镜面(上电极).该变形镜有两种驱动模式:向下驱动模式和向上驱动模式.在向上驱动时,4个杠杆结构实现了位移的放大;向下驱动时,利用了非线性弹性系数法扩展了镜面的平动范围.采用表面硅工艺完成了变形镜的加工.通过白光干涉仪对变形镜的测试表明:在向上驱动模式下,变形镜在驱动电压为31 V时位移达到1.1μm;在向下驱动模式下,变形镜在6 V的驱动电压下位移达到1.1μm.变形镜的总行程为2.2μm,达到了同样工艺下传统变形镜的3倍左右.     

碳纳米管12～18GHz电磁波衰减实验研究

用电磁波穿透方法实验研究了长度为2μm和15μm,直径分别为30,60,100nm 6种碳纳米管12~18GHz电磁波衰减特性.实验结果表明:直径为30nm时长度15μm碳纳米管的衰减能力大于长度2μm的;直径为60nm时长度2μm碳纳米管衰减能力大于长度15μm的;直径为100nm时长度15μm纳米管的电磁波衰减能力大于长度为2μm的.在长度相同的情况下,不同直径碳纳米管的电磁波衰减能力为:60nm>100nm>30nm.电磁波衰减效果最好的是φ 60nm×2μm的碳纳米管;最差的是φ 30nm×2μm的碳纳米管.6种碳纳米管的电磁波衰减能力为:φ 60nm×2μm>φ 60nm×15μm>φ 100nm×15>μmφ 100nm×2μm>φ 30nm×15μm>φ 30nm×2μm.     

新型的激光多普勒信号检波系统

为解决超低频、微小振动的高精度测量与装调间的矛盾,提出了一种新型的激光多普勒信号检波系统。该系统通过一运动光栅的衍射,得到约40.5%的测量光强,用另一光栅的衍射消除两束差动光间的夹角以及光波长对测量精度的影响;频移﹑混频分开进行,保证系统装调更方便准确;用1/4波片﹑渥拉斯顿棱镜等得到相位差90°的正余弦信号,实现位移方向识别。实验得出,该系统振动频率和振幅测量精度均为1%,可测频率范围可达到0.5-500Hz,可测振幅范围:1μm-5mm。     

用自混合干涉测量振动

激光二极管自混合干涉信号的频率与外腔振动的速率成正比,为了从自混合干涉信号重建振动信号,采用频率电压变换的方法.用整形后的自混合干涉信号驱动模拟开关,来开关电容做电荷转移实现频率电压变换,用振动的激励信号驱动另一个模拟开关让电容的充电电源随振动的相位变化做极性变换,这样从自混合干涉信号中还原出振动信号.还原出来的信号的振幅与振动的振幅成正比,波形与正弦激励信号的波形一致.该方案操作简便、成本低廉,可以用于有确定激振方式的振动特性测量.     

红外可调声光滤光器的设计和特性分析

根据声光互作用原理，以TeO2晶体为互作用介质，选取互作用长度为28mm，设计制成近红外声光可调滤光器（AOTF），其衍射波长与超声频率存在对应关系。测试结果表明，该器件的工作波长范围为0.9-2.6μm，驱动频率为40－120MHz，光谱分辨力为7.268nm，6.957nm（对应波长分别为1.5μm，2.4μm）。     

基于自抗扰控制算法的麦克斯韦快刀伺服控制系统

使用麦克斯韦力驱动的快速伺服刀具加工自由曲面,可以获得表面质量更优的加工效果.在快刀控制系统中引入适当的控制方式能够改善快刀的频响性能.本文针对麦克斯韦快刀,搭建包括软硬件在内的控制系统,硬件控制结构采用FPGA+DSP嵌入式控制架构,并加入自抗扰先进控制算法实现系统良好的抗干扰性能.为验证闭环控制系统性能,在自主搭建的精密位移测试平台进行系统位移分辨力和闭环带宽的测试,测试结果表明系统位移分辨力为5 nm,对频率108 Hz、峰峰值16μm正弦信号的跟踪误差为0.136μm,对频率540 Hz、峰峰值16μm正弦信号的跟踪误差为0.094μm.快刀系统行程50μm,闭环带宽4 kHz.线下仿真加工实验验证了快刀系统对常规面型的加工能力.     

碳纳米管8～12 GHz 电磁波衰减实验研究

用电磁波穿透方法实验研究了长度为2μm 和15μm , 直径分别为30 、60 和100 nm 的6 种碳纳米管8～12 GHz 电磁波衰减特性。结果表明, 直径为30 nm 时, 长度为15μm 的碳纳米管的电磁波衰减能力大于长度2μm的; 直径分别为60 nm 和100 nm 时, 长度为2μm 的碳纳米管的电磁波衰减能力均大于长度为15μm 的。在长度相同的情况下, 不同直径碳纳米管的电磁波衰减能力为: 60 nm > 100 nm > 30 nm。6 种碳纳米管的电磁波衰减能力为: Ф60 nm ×2μm > Ф60 nm ×15μm > Ф100 nm ×2μm > Ф100 nm ×15μm > Ф30 nm ×15μm > Ф30 nm ×2μm。实验还发现长径比较小的碳纳米管的电磁波衰减能力明显好于长径比较大的磁纳米管的电磁波衰减能力;但碳纳米管长径比与电磁波衰减能力之间并不存在简单的线性关系。      

基于干涉条纹移动量的非接触振动测量研究

为了实现大振幅、高带宽振动的非接触精密测量,本文提出了一种全新的光学测量系统.两束相干光的远场干涉条纹位置与两束光之间相位差有关,相位差的变化将引起干涉条纹移动.获取主条纹的位置,可以计算两束光之间的相位差,基于此可以还原物体的振动位移量.对振幅为10μm的单频余弦信号以及频率为44.1 kHz的声音信号仿真还原结果表明,本文所提光学系统和还原算法可以还原出亚微米级的振动信号,并能准确还原出音频信息.     

Thermal diffusivity imaging with the thermal lens microscope

A coaxial thermal lens microscope was used to generate images based on both the absorbance and thermal diffusivity of histological samples. A pump beam was modulated at frequencies ranging from 50 kHz to 5 MHz using an acousto-optic modulator. The pump and a CW probe beam were combined with a dichroic mirror, directed into an inverted microscope, and focused onto the specimen. The change in the transmitted probe beam's center intensity was detected with a photodiode. The photodiode's signal and a reference signal from the modulator were sent to a high-speed lock-in amplifier. The in-phase and quadrature signals were recorded as a sample was translated through the focused beams and used to generate images based on the amplitude and phase of the lock-in amplifier's signal. The amplitude is related to the absorbance and the phase is related to the thermal diffusivity of the sample. Thin sections of stained liver and bone tissues were imaged; the contrast and signal-to-noise ratio of the phase image was highest at frequencies from 0.1-1 MHz and dropped at higher frequencies. The spatial resolution was 2.5 μm for both amplitude and phase images, limited by the pump beam spot size.     

可调频悬臂梁式动力吸振器多频减振研究

手持打磨工具振动大,存在多个振动峰,且不同工况振动峰对应的频率不同。动力吸振器是控制窄带振动峰的有效方法,传统的“弹簧—质量”形式动力吸振器频率不易调节,且不能同时对多个频率进行动力吸振。为适应实际工程应用,以频率可调、可多频减振为目标,首先从结构阻抗角度阐述动力吸振器减振原理,然后设计一种适用于手持打磨工具的频率可调悬臂梁式动力吸振器,推导悬臂梁等效刚度阐述频率调节方法,该结构可方便地布置多重动力吸振器。最后结合仿真分析与实验测试对悬臂梁式动力吸振器的实用性进行验证,证明频率可调并取得良好的多频减振效果。     

High-frequency, silicon-based ultrasonic nozzles using multiple Fourier horns

This paper presents the design, simulation, and characterization of microfabricated 0.5 MHz, silicon-based, ultrasonic nozzles. Each nozzle is made of a piezoelectric drive section and a silicon resonator consisting of multiple Fourier horns, each with half wavelength design and twice amplitude magnification. Results of finite element three-dimensional (3-D) simulation using a commercial program predicted existence of one resonant frequency of pure longitudinal vibration. Both impedance analysis and measurement of longitudinal vibration confirmed the simulation results with one pure longitudinal vibration mode at the resonant frequency in excellent agreement with the design value. Furthermore, at the resonant frequency, the measured longitudinal vibration amplitude at the nozzle tip increases as the number of Fourier horns (n) increases in good agreement with the theoretical values of 2(n). Using this design, very high vibration amplitude gain at the nozzle tip can be achieved with no reduction in the tip cross-sectional area for contact of liquid to be atomized. Therefore, the required electric drive power should be drastically reduced, decreasing the likelihood of transducer failure in ultrasonic atomization.     

Focusing and defocusing dynamics of weak-light beam in a resonant three-level atomic system

Focusing and defocusing dynamics of weak-light ring-shaped beams in a Λ-type atomic system are investigated. It is found that focusing of weak light is possible due to the quantum interference effect. The focusing or defocusing regime with vanishing absorption can be manipulated by adjusting detunings from the resonant transition. When the fields are tuned appropriately larger than resonant frequencies, the beam propagates in the defocusing regime and diffraction of the beam takes place. Conversely, the beam focuses in the medium when the laser frequencies are tuned smaller than the resonant frequencies.     

Multipoint laser Doppler vibrometry with single detector: principles, implementations, and signal analyses

A 20-point laser Doppler vibrometer with single photodetector is presented for noncontact dynamic measurement. A 5×4 beam array with various frequency shifts is generated by a 1.55 μm distributed feedback laser and four acousto-optic devices, and illuminating different points on vibrating objects. The reflected beams are coupled into a single-mode fiber by a pigtailed collimator and interfere with a reference beam. The signal output from a high-speed photodetector is amplified and then digitized by a high-speed analog-to-digital converter with a sampling rate of 1 gigasample per second (1 GS/s). Several methods are introduced to avoid the cross talk among different frequencies and extract the vibration information of 20 points from a one-dimensional signal. Two signal processing algorithms based on Fourier transform and windowed Fourier transform are illustrated to extract the vibration signals at different points. The experimental results are compared with that from a commercial single-point laser vibrometer. The results show simultaneous vibration measurement can be realized on multiple points using a single laser source and a single photodetector.     

Amplitude modulation drive to rectangular-plate linear ultrasonic motors with vibrators dimensions 8 mm x 2.16 mm X 1 mm

In this paper, to exploit the contribution from not only the stators but also from other parts of miniature ultrasonic motors, an amplitude modulation drive is proposed to drive a miniature linear ultrasonic motor consisting of two rectangular piezoelectric ceramic plates. Using finite-element software, the first longitudinal and second lateral-bending frequencies of the vibrator are shown to be very close when its dimensions are 8 mm x 2.16 mm x 1 mm. So one single frequency power should be able to drive the motor. However, in practice the motor is found to be hard to move with a single frequency power because of its small vibration amplitudes and big frequency difference between its longitudinal and bending resonance, which is induced by the boundary condition variation. To drive the motor effectively, an amplitude modulation drive is used by superimposing two signals with nearly the same frequencies, around the resonant frequency of the vibrators of the linear motor. When the amplitude modulation frequency is close to the resonant frequency of the vibrator's surroundings, experimental results show that the linear motor can move back and forward with a maximum thrust force (over 0.016 N) and a maximum velocity (over 50 mm/s).     

加热弹性梁在热过屈曲构形附近的自由振动

基于轴向可伸长梁的几何非线性理论建立了弹性直梁在热过屈曲静态大变形附近自由振动的几何非线性模型。在小振幅振动假设下,简化得到热过屈曲梁线性振动的控制方程。采用打靶法分别获得了两端不可移简支(pinned-pinned)和两端固定(fixed-fixed)梁的前四阶固有频率与升温之间的特征关系曲线。数值结果表明,梁在未屈曲时,各阶频率都随升温而单调下降。在过屈曲后,两端不可移简支梁的前两阶频率随升温单调上升,三、四阶频率随升温而单调下降。但是,两端固定梁在过屈曲后的各阶频率都随升温而单调增加。因此,可以通过温度调控来实现对结构固有频率的调整。     

Electromagnetic theory of an open resonator.

Particular higher-order sources give rise to electromagnetic Gaussian beams, which are linearly polarized and have their maximum in the propagation direction. For this dipolar beam the cross-sectional shape changes in the propagation direction. Nodal surfaces exist on which the tangential component of the electric field vanishes in the standing wave that is formed by the two oppositely directed dipolar, electromagnetic Gaussian beams. These surfaces are identified as the mirror shapes for an open resonator that supports this standing wave. For standing waves that have a particular cross-sectional shape at the waist the cross section of the beam near the mirror surfaces is circular. The resonant frequencies for the fundamental transverse mode of such a resonator have been determined as a function of the geometry and the axial mode number. By a perturbation technique the resonant frequency of an open resonator with spherical mirrors has been obtained. This result is valid in only the paraxial approximation. Illustrative numerical results are included.