基于单端口多模态微悬臂梁的谐振式大量程智能气体传感器(英文)

基于悬臂梁的谐振气体传感器可以通过测量悬臂梁谐振频率的偏移而检测相应气体分子.本文介绍了一种使用自激励自检测(SAD)电路驱动单端口多模态微悬臂梁的智能谐振式气体传感器.这种激励模式简化了悬臂梁结构和微加工过程.另外,还可以通过便捷地改变悬臂梁谐振模态实现大量程的气体浓度检测.通过仿真分析了不同模态下悬臂梁的模型和敏感度.通过测量这种基于单端口多模态悬臂梁的气体传感器对于气体的响应情况,展示了这种多模态SAD系统以及其改变模态增加测量量程的功能.     

Design and fabrication of a PZT cantilever for low frequency vibration energy harvesting

In this study, a PZT cantilever with a Si proof mass is designed and fabricated for a low frequency energy harvesting application. A mathematical model of a multi-layer composite beam was derived and applied in a parametric analysis of the piezoelectric cantilever. Finally, the dimensions of the cantilever were determined for the resonant frequency of the cantilever. Our cantilever design was based on MATLAB and ANSYS simulations. For this simulation, the proof mass volumes were varied from 0 to 0.5 mm3 and resonant frequencies were calculated from 833.5 Hz to 125.5 Hz, respectively. Based on simulation, we fabricated a device with beam dimensions of about 4.10 mm x 0.48 mm x 0.012 mm, and an integrated Si proof mass with dimensions of about 0.481 mm x 0.48 mm x 0.45 mm. The resonant frequency, maximum peak voltage, and highest average power of the cantilever device were 224.8 Hz, 4.8 mV, and 2.24 nW, respectively.     

Multimode Air-Coupled Excitation of Micromechanical Structures

The development of an acoustic measurement system for multimode air-coupled excitation and detection of micrometer-scale cantilever structures, which are, for example, used in micro-electromechanical systems (MEMSs), is detailed and reported for the first time. The source of noncontact vibrational excitation is a pulsed acoustic field generated by an air-coupled transducer. In the experimental system, the transient response of the cantilever beam is obtained at various points along the beam axis to extract its resonance frequencies and corresponding mode shapes. We demonstrate that measurable amplitudes of vibrations can be obtained at various excitation levels in the megahertz range, and higher harmonics of vibration of a microbeam can be excited by the air-coupled mechanism from a distance on the order of 10 mm. In the specific utilizations of the reported system, resonance frequencies and mode shapes can be related to the mechanical properties and geometric attributes (dimensions and defects), as well as the residual stress state in a microstructural element using various established computational and experimental inverse techniques. Another potential application area of the reported system is in the sensors for detecting the bending stiffness of deposited films on cantilever oscillators (in addition to its film mass loading) to increase the detection sensitivity and selectivity in a single sensing element.     

Study of Silicon Cantilevers by the Photoacoustic Elastic Bending Method

Rectangular silicon cantilevers are studied by the photoacoustic (PA) elastic bending method. Experimental signals versus modulation frequency of the excitation optical beam are measured and analyzed in a frequency range from 20 Hz to 50 000 Hz. The procedure for experimental signal correction to eliminate the frequency characteristics of the measuring system is given. The corrected experimental signal shows a good correlation with theoretically calculated PA signal at frequencies below 32 000 Hz. The corrected experimental PA elastic bending signals for cantilevers with different thicknesses are analyzed. The experimental results allow identifying the resonant frequency (the first resonant mode) of the cantilever vibrations. These values are in good agreement with the theoretically computed values. A theoretical model of the optically excited Si cantilever is derived, taking into account plasmaelastic, thermoelastic, and thermodiffusion mechanisms. Dynamic relations for the amplitude and phase of electronic and thermal elastic vibrations in optically excited cantilevers are derived. The theoretical model is compared to the experimental results.     

Transverse vibration of rotary tapered microbeam based on modified couple stress theory and generalized differential quadrature element method

The transverse vibration of a rotary tapered microbeam is studied based on a modified couple stress theory and Euler–Bernoulli beam model. The governing differential equation and boundary conditions are derived according to Hamilton's principle. The generalized differential quadrature element method is then used to solve the governing equation for cantilever and propped cantilever boundary conditions. The effect of the small-scale parameter, beam length, rate of cross-section change, hub radius, and nondimensional angular velocity on the vibration behavior of the microbeam is presented.     

Phenomenological representation of mechanical spectroscopy of high damping MnCuNiFe alloy

ABSTRACT

MnCuNiFe damping alloy was prepared to characterise the dynamic mechanical behaviour under varied frequency by employing dynamic mechanical analyzer, optical microscopy and X-ray diffraction. The relationship of characteristic temperatures is disentangled by antiferromagnetic transition (AFT), the strain glass transition and reverse martensitic transformation. It is reported that although only f.c.c. (γ) phase exists in the alloy under solution state, twins are induced by AFT. The aged alloy shows an elevated damping capacity while the maximum internal friction decreases from 0.1 to 10?Hz and then increases to 150?Hz, demonstrating the system resonant frequency of about 10?Hz under the vibration mode of double cantilever beam.     

中低频集中质量悬臂式簧片仪基频分析方法研究

簧片仪是一种中低频冲击响应谱测量装置,设计时可将其简化为端部附带集中质量的悬臂梁。簧片仪的振型方程中存在超越函数,对于等截面簧片仪来说,可使用二分法等数值方法求解,计算量较大,该方法不适用于复杂截面簧片仪基频设计。首先利用悬臂梁自由端受集中力的挠度公式,推导出其等效刚度等效单自由度的弹簧振子系统,利用弹簧振子相关频率公式解决求解集中质量等截面悬臂梁的基频问题,该方法与振型方程求解的基频对比,发现在10 Hz以下的中低频区域,可以很好的保证等截面悬臂梁的基频精度,大于10 Hz的中频段,误差随频率的升高而迅速增大。接下来,通过Mohr积分的方法,推导出等强度集中质量悬臂梁自由端的最大挠度,并给出其基频的设计公式,该方法与试验进行对比,发现误差与等截面悬臂梁有相同趋势,因此利用瑞利能量法修正设计公式中的质量参数,修正后与实验误差在5%左右。经理论与试验验证,所提出的簧片仪设计方法简单可行、计算结果可信。     

A simple wide-band sine wave quadrature oscillator

A simple sine wave oscillator delivering two signals in quadrature has been developed. It covers the frequency range from below 1 Hz to 100 MHz and is voltage-controllable over each frequency decade. The circuit consists of two 90° phase shift stages using active allpass filters and an inverter, all arranged in a feedback loop. Although general application is envisaged, the design is particularly suitable in particle electrorotation studies     

Nanocantilever signal transduction by electron transfer

Microfabricated cantilever beams promise to bring about a revolution in the field of chemical, physical, and biological sensor development. The resonance frequency of a microfabricated cantilever shifts sensitively because of mass loading from molecular adsorption. The minimum detectable adsorbed mass on a cantilever sensor can be increased by orders of magnitude by changing the dimensions of the device; smaller and thicker cantilevers offer higher resonance frequency and therefore better mass detection sensitivity. Here we describe micromachined silicon cantilevers that are 0.5 to 4 microns in length, fabricated with the use of a focused ion beam (FIB). In addition, we demonstrate a technique for detection of the cantilever resonance frequency that is based on electron transfer.     

不同频率激励下LY12铝合金悬臂梁的疲劳特性

为了研究激励频率对悬臂梁结构疲劳特性的影响,本文针对LY12铝合金悬臂梁在不同频率(139Hz、141Hz、143Hz)激励下进行了同一应力水平的振动疲劳试验。结果表明:该结构的疲劳特性在不同频率激励下存在差异。在激励频率高于固有频率振动时,结构疲劳寿命最长;激励频率低于固有频率振动时,结构疲劳寿命较短;在固有频率振动时,结构疲劳寿命最短。     

On the stability of a microbeam conveying fluid considering modified couple stress theory

In this paper, the size-dependent vibrational behavior of a microbeam conveying fluid was investigated using the Modified Couple Stress Theory. For cantilever and clamped-clamped microbeams, the small amplitude vibration equation of the micro-beams was solved using a Galerkin based reduced order model and the effects of material length-scale parameter on its natural frequencies were evaluated. It was found that for the both cantilever and clamped-clamped conditions, the critical fluid velocities predicted by the modified couple stress theory are higher than those predicted by the classical beam theory. In addition, the differences between the eigen-frequencies and the critical fluid velocities predicted by the modified couple stress theory and classical beam theory depends on the ratio of the material length-scale parameter to the beam height. In addition an unexpected result in the difference between the first eigen-frequency of the cantilever micro-beam obtained by the classical and the modified couple stress theory has been achieved.     

基于微型杠杆结构谐振式差分微加速度传感器的理论建模

为了提高灵敏度和消除交叉轴串扰，提出了一种包括有效的微型杠杆结构的谐振式差分微加速度传感器，分析了该结构差分检测和消除交叉轴干扰的原理．推导了该设计的理论模型，包括结构建模和轴向力作用下谐振微梁的固有频率偏移的推导，得到了待测加速度与输出固有频率偏移的关系．使用有限元模拟来证实理论模型．模拟结果说明，该设计的灵敏度每重力加速度g高于4kHz．探讨了具体结构参数的选取与输出频差的关系，说明通过调整微型杠杆的尺寸可以进一步提高本设计的灵敏度．     

悬臂梁压电发电装置的实验研究

为了进行压电陶瓷材料发电性能测试与研究,研制了一套悬臂梁压电振子发电系统.设计了悬臂梁压电振子,并对压电振子进行了有限元分析和电导测试.在此基础上,设计了能量存储电路,并在低频下对悬臂梁压电振子发电性能进行了实验研究.研究结果表明,当悬臂梁压电振子处于谐振频率状态下振动时,输出电压和功率达到最大.输出电压随着负载的增大而增大,输出功率并不随着负载的增大而增大;压电振子存在-个最佳阻抗,当负载与最佳阻抗匹配时,此时压电振子的能量转化效率最高且输出功率最大.利用本实验系统进行压电发电实验测试,当负载为50 kΩ时,压电振子输出电压为7 V;当负载电阻为15 kΩ时,此时的输出功率最大可达到1.4 mW,产生的功率可以满足无线传感器等低耗能产品的供能需求.     

基于锁相环的高稳定高频正弦信号发生器

介绍一种基于锁相环的高稳定高频正弦信号发生器,该发生器用差分对管LC谐振电路产生正弦波,利用单片机控制的PLL锁相环电路合成频率,实验结果表明,所设计的信号发生器的频率稳定度达到10^-6,调节频率范围5MHz～70MHz．     

An accurate wide-band phase shifter for sinusoidal signals using anarrow pulse duty cycle network

A technique for producing a constant phase shift of sinusoidal signals independent of frequency by using a narrow pulse switching network is proposed. A phase-locked loop circuit multiplies the frequency of the input signal by an integer factor N and, with a monostable vibrator, provides narrow pulses which excite the MOSFET switches of the network. The working frequency range of the circuit extends to more than five decades and gives a maximum error that cannot exceed 360/N°     

Remote sensing of mechanical properties of materials using a novel ultrasound transducer and signal processing

An ultrasound-based remote sensing method to evaluate the mechanical properties of materials is presented. This method consists of a disk-shaped, piezoelectric transducer, operating at its resonance frequency, and a phase-shifted, feedback circuit. Mechanical parameters are derived by analyzing the signal contained in the phase-shifted values of the reflected signal. It is concluded that, using this novel transducer system and signal processing, remote mechanical measurements can be made. Such measurements obviate the need to apply the force-deformation approach and may be used to enable stiffness imaging.     

Measurement and theoretical modelling of the damping properties of a uni-directional glass/epoxy composite

The material damping of a uni-directional composite is determined experimentally by the flexural resonance method using cantilever beam specimens with different composite fibre orientations (0 °, 30 °, 45 °, 60 °, 90 °), and for each fibre orientation at three fibre volume fractions (0.35, 0.45, 0.6). The tests were carried out over a frequency range of 100–1000 Hz. A finite element model is also used to predict the damping properties. The results show that the loss factor is higher at low fibre volume fractions with the highest loss factor at a fibre orientation of 30 °. The loss modulus decreases with increasing fibre orientation, and increases with fibre volume fraction. The storage modulus decreases with increasing fibre orientation at each fibre volume fraction. All the results show little or no variation with frequency. Good agreement has been achieved between the theoretical model and the experimental results.     

上海世博文化中心TMD减轻人致振动分析与实测研究

上海世博文化中心是2010上海世博会永久性场馆之一,其主体结构由沿环向的36榀悬臂长度不一的钢桁架和矩形钢管混凝土内框架组成。结构六层为悬挑钢结构楼盖,易引起人致振动问题。对采用调谐质量阻尼器(TMD)进行人致振动控制的上海世博文化中心进行了大量的计算分析和现场实测。结果表明结构各榀桁架的竖向共振频率处于2.5-3.0Hz之间;当人以2.0Hz的频率正常行走时,结构竖向振动较小,TMD基本无影响;而当人以结构竖向共振频率快速走动或奔跑时,TMD能有效减小结构的竖向振动响应,减振效率约为15%。这对长悬臂空间结构的舒适度问题和采用TMD进行人致振动控制问题的研究具有参考借鉴意义     

System modelling of a lateral force microscope

To quantitatively analyse lateral force microscope measurements one needs to develop a model able to relate the photodiode signal to the force acting on the tip apex. In this paper we focus on the modelling of the interaction between the cantilever and the optical chain. The laser beam is discretized by a set of rays which propagates in the system. The analytical equation of a single ray's position on the optical sensor is presented as a function of the reflection's state on top of the cantilever. We use a finite element analysis on the cantilever to connect the optical model with the force acting on the tip apex. A first-order approximation of the constitutive equations are derived along with a definition of the system's crosstalk. Finally, the model is used to analytically simulate the 'wedge method' in the presence of crosstalk in 2D. The analysis shows how the torsion loop and torsion offset signals are affected by the crosstalk.     

Liquid-phase chemical and biochemical detection using fully integrated magnetically actuated complementary metal oxide semiconductor resonant cantilever sensor systems

A novel resonant cantilever sensor system for liquid-phase applications is presented. The monolithic system consists of an array of four electromagnetically actuated cantilevers with transistor-based readout, an analog feedback circuit, and a digital interface. The biochemical sensor chip with a size of 3 mm x 4.5 mm is fabricated in an industrial complementary metal oxide semiconductor (CMOS) process with subsequent CMOS-compatible micromachining. A package, which protects the electrical components and the associated circuitry against liquid exposure, allows for a stable operation of the resonant cantilevers in liquid environments. The device is operated at the fundamental cantilever resonance frequency of approximately 200 kHz in water with a frequency stability better than 3 Hz. The use of the integrated CMOS resonant cantilever system as a chemical sensor for the detection of volatile organic compounds in liquid environments is demonstrated. Low concentrations of toluene, xylenes, and ethylbenzene in deionized water have been detected by coating the cantilevers with chemically sensitive polymers. The liquid-phase detection of analyte concentrations in the single-ppm range has been achieved. Furthermore, the application of this sensor system to the label-free detection of biomarkers, such as tumor markers, is shown. By functionalizing the cantilevers with anti-prostate-specific antigen antibody (anti-PSA), the corresponding antigen (PSA) has been detected at concentration levels as low as 10 ng/mL in a sample fluid.