磁流变阻尼力建模及主共振研究

通过实验建模,提出了一种改进的Bingham模型来描述磁流变阻尼力,模型中的各参数具有明确的物理意义,都与磁流变阻尼器的特性有关．另外,还采用此模型研究了单自由度天棚阻尼控制系统的主共振,利用平均法得到了系统的理论解,并对理论解进行了数值验证．最后,研究了各参数对主共振的影响,从而可以更加有效地控制主共振．     

多输入时滞反馈控制下的斜拉梁主共振响应

研究了多输入时滞反馈控制作用下斜拉梁主共振问题.采用多尺度法,推导了位移时滞和速度时滞反馈控制作用下斜拉梁非线性主共振的解析解,分析了主共振响应随参数变化的规律,控制参数时滞和控制增益对系统非线性主共振响应的影响.结果表明:合理地调整时滞值、控制增益可以提高振动控制的效率,拓宽减振频率范围,且在参数的调节中时滞较控制增益对减振更为有效.     

一种新型压阻式加速度传感器的设计与加工

提出了一种新型的基于AlAs/InxGa1-xAs/GaAs共振隧穿纳米薄膜结构的压阻式加速度计结构,运用MATLAB软件对敏感结构参数进行了计算,并利用ANSYS软件对加速度计结构进行了静态和模态分析,首次采用空气桥和控制孔加工工艺对共振隧穿二极管和悬臂梁-质量块结构进行了加工,并对加工出来的加速度计结构进行了频响特性实验。     

基于人听觉机理的宽动态压缩算法的仿真实验

通过人的听觉机理方式获取共振峰的位置,利用宽动态压缩算法方式,分别对共振峰的频率范围和其他频率范围计算并应用相应增益,最后利用自动增益控制将最大的输出进行限制,防止声音音量过大而使听障患者的听力造成二次损伤。实验结果表明,该算法在保护共振峰的基础上,实现了响度补偿技术,提高了语言的辨识度和听觉的舒适度,同时具有一定的抗噪性能。     

基于虚拟仪器的液态调配器控制系统

基于虚拟仪器技术设计了HT-7托卡马克离子回旋共振加热液态调配器控制系统。系统硬件由PC机、液压传感器、数据采集卡,模拟输出卡、接口电路和油泵、电动球阀组成的油路系统等组成。系统界面采用虚拟仪器开发软件LabVIEW设计。系统根据测量得到的液态调配器各支节当前硅油液位高度,和匹配高度相比较,采用自动或手动控制的方法,对各支节中的硅油液位进行控制,从而达到离子回旋共振加热系统阻抗匹配的目的。     

有效提取耳语音共振峰的改进方法

耳语音是噪声源激励,与正常音相比,其共振峰位置发生了偏移,带宽增宽。故采用传统的线性预测法提取耳语音共振峰时存在虚假峰问题。通过分析功率谱,提出了一种改进算法。根据极点功率不变的原则,利用极点交互因子修正共振峰的带宽,从而准确地提取出耳语音的共振峰。对汉语普通话单元音音素仿真实验的结果证明了该算法的有效性。     

抗共振反射集成光学传感器的研究进展

抗共振反射光波导(ARROW)具有与传统光波导所不同的传播特性。利用覆盖层的抗共振反射性质,ARROW传播单模、高阶模被泄漏到基体。基于折射率的变化,抗共振反射传感器对物理量、化学量和生物分子间的相互作用有很高的敏感性。介绍了ARROW的结构、传感器的工作原理以及最新研究进展。由于可采用CMOS工艺制作波导,且能与光探测器在一块集成,抗共振反射传感器将具有广阔的应用前景。     

索受外激励作用下索拱结构非线性动力学分析

研究索拱结构中索受外激励作用下索拱之间非线性动力学问题．利用已建立的索拱结构非线性动力学耦合面内运动微分方程,采用Galerkin方法把索拱结构的面内运动方程进行离散,然后利用多尺度法对离散的运动方程进行摄动得到索主共振情况下的平均方程,研究在索受到外激励作用下索振动对拱的振动产生的影响,同时对索拱结构内共振时的稳定、分叉及混沌情况进行了分析．结果表明：索某阶频率与拱某阶频率接近时可能出现内共振现象,能量在索拱之间相互传递,原本静止的拱也可能出现共振现象,共振频域区间内索拱振动将出现跳跃、分叉及混沌等复杂的非线性动力学行为．     

基于MOCVD生长材料的高电流密度太赫兹共振隧穿二极管

为获得高功率的太赫兹共振隧穿器件,优化设计了AlAs/InGaAs/AlAs共振遂穿二极管材料结构,在国内首次采用MOCVD设备在半绝缘InP单晶片上生长了RTD外延材料。利用接触光刻工艺和空气桥搭接技术,制作了InP基共振遂穿二极管器件。并在室温下测试了器件的电学特性:峰值电流密度>400 kA/cm~2,峰谷电流比(PVCR)>2.4。     

生物分子相互作用分析仪的自动控制系统设计

为达到光学表面等离子共振SPR传感的生物分子相互作用分析仪性能指标和功能要求,必须保证其自动控制系统的可靠性.针对时间相位调制SPR传感的特点,开发了一套自动控制系统.该系统利用CAN总线技术对仪器底层各个模块进行分布式控制,实现了按生物试验流程的自动控制.同时,采用等步距和等时间的离散加速度曲线法,分别控制盘库和波片机构的驱动电机,并采用数字PID控制流体池温度稳定和使CCD可靠制冷.试验结果表明,系统达到了分析仪的各项性能指标和功能要求.     

基于虚拟仿真技术的车架动态响应特性分析

采用ALGOR有限元分析软件对车架进行模态分析,得出了前10阶振型及固有频率。运用二自由度汽车振动模型,建立了系统的运动微分方程并利用Matlab中的Simulink模块对车架的振动情况做出了仿真。利用路面谱仿真得到的路面激励信号作为输入,对车架进行动力响应模拟,得到了车架在典型路面上的动态响应特性,为车架的结构优化提供了理论依据。     

A STUDY OF THE INFLUENCE OF VIBRATION ON MAN

The effects of vertical and horizontal mechanical vibrations up to 100 cycles per second on the human being were examined by physical and physiological methods. Resonance phenomena are described. A strain scale is given for vertical and horizontal vibration excitation. Special examinations of the movement of the head show elliptic vibrations in spite of linear excitation. Vibration measurements in a rail-motorcar provide an example for typical resonance phenomena of the mechanical system formed by a ‘ man sitting on a seat’.     

Non-linear vibration behavior of thin multilayer diaphragms

The vibration spectrum of piezoelectrically driven (ZnO) thin silicon diaphragms in the driving frequency range up to 200 kHz has been studied. The response of the structure on the driving conditions (a.c. voltage amplitude and frequency) is presented. The limits of the linear plate theory and specific non-linear effects are discussed. Non-linear effects in the vibration behavior occur for vibration amplitudes even smaller than 4% of the diaphragm thickness. Superharmonic, harmonic and subharmonic vibration modes are observed. The vibration amplitudes of the subharmonic modes are of the same order as the diaphragm thickness. The characteristic non-symmetric resonance peaks of the subharmonic vibration modes indicate the existence of a hard-spring effect in the system. In the case of a system with a hard-spring effect, the concept of vibration modes with fixed resonance frequencies fails.     

A quantified index for bearing vibration analysis based on the resonance modes of mechanical system

In this paper, an envelope estimation algorithm based on the resonance modes of the mechanical system is proposed to apply in the signal processing for the bearing vibrations and the exponential decay frequency of the envelope signal could be further estimated to be a quantified index for the bearing vibration analysis. According to the vibration spectrum of the bearing system, the resonance frequencies in the range of the corresponding resonance modes could be initially designated and further estimated. Under the assumption of stepwise functions for the envelope signals in the corresponding resonance modes, the vibration signal could be decomposed into the sinusoidal function bases with fundamental frequencies at the resonance frequencies. The envelope signals could be derived from their corresponding resonance modes. In addition, the vibration signal could be directly reconstructed from the envelope signals to reject the low-frequency mechanical noise. According to the envelope signals, the exponential decay frequency is also estimated to be a quantified index for diagnosing the running condition of roller bearing. In the simulation study, the envelope spectra show good consistency between the proposed method and the high frequency resonance technique. Finally, the experimental study shows that the envelope estimation algorithm could be effectively applied in the signal processing for the bearing vibrations and the exponential decay frequency could successfully be a quantified index for the bearing defect diagnosis.     

Effect of vibration on eye,head and helmet movements while wearing a helmet‐mounted display

Previous research has demonstrated a loss of helmet‐mounted display (HMD) legibility for users exposed to whole body vibration. A pair of human factors studies was conducted to evaluate the effect of whole body vibration on eye, head, and helmet movements for seated users of a HMD while conducting simple fixation and smooth pursuit tracking tasks. These experiments confirmed that vertical eye motion can be demonstrated, that is consistent with the human visual systems' response to the vestibular–ocular reflex (VOR). Helmet slippage was also shown to occur, which could exacerbate loss of display legibility. The largest amplitudes in eye movements were observed during exposure to sinusoidal vibration in the 4–6 Hz range, which is consistent with the frequencies that past research has associated with whole‐body resonance and the largest decrease in display legibility. Further, the measured eye movements appeared to be correlated with both the angular acceleration of the user's head and the angular slippage of the user's helmet. This research demonstrates that the loss of legibility while wearing HMDs likely results from a combination of VOR‐triggered eye movements and movement of the display. Future compensation algorithms should consider adjusting the display in response to both VOR‐triggered eye and HMD motion.     

Response of the seated human body to whole-body vertical vibration: biodynamic responses to sinusoidal and random vibration

The dependence of biodynamic responses of the seated human body on the frequency, magnitude and waveform of vertical vibration has been studied in 20 males and 20 females. With sinusoidal vibration (13 frequencies from 1 to 16 Hz) at five magnitudes (0.1–1.6 ms^? 2 r.m.s.) and with random vibration (1–16 Hz) at the same magnitudes, the apparent mass of the body was similar with random and sinusoidal vibration of the same overall magnitude. With increasing magnitude of vibration, the stiffness and damping of a model fitted to the apparent mass reduced and the resonance frequency decreased (from 6.5 to 4.5 Hz). Male and female subjects had similar apparent mass (after adjusting for subject weight) and a similar principal resonance frequency with both random and sinusoidal vibration. The change in biodynamic response with increasing vibration magnitude depends on the frequency of the vibration excitation, but is similar with sinusoidal and random excitation.     

Effects of stretch reflex on back muscle response during sinusoidal whole body vibration in sitting posture: A model study

This study seeks to examine human vibration response using a musculoskeletal model that appropriately considers stretch reflex. The stretch reflex is modeled with a feedback control approach, and integrated into a generic musculoskeletal model to study the active muscle forces during seated whole body vibration. The model is used to investigate the effects of stretch reflex gain, vibration frequency and vibration magnitude on transmissibility from the seat to upper body and lower body and on muscle activations.The overall model is validated by comparison with thoracic and lumbar muscle activities measured in human participants during whole body vibration. The simulation results were consistent with the experimental results that the peak transmissibility occurred at resonance frequency of 5–6 Hz, and were in line with other experimental studies that found a primary resonance of 4–6 Hz. Furthermore, the peak normalized Electromyography (EMG) level accorded with the activation level for both thoracic and lumbar regions. What's more, an increase of primary resonance frequency was observed with increasing gains of stretch reflex. In contrary, the peak seat transmissibility of the upper body and lower body had a significant reduction.The major contribution of this model is that the proposed stretch reflex model provides a useful method to consider muscle active response in whole body vibration simulation. This may be used in future studies to better understand how stretch reflex affects spinal loading in a variety of conditions.     

An examination of the vibration transmissibility of the hand-arm system in three orthogonal directions

The objective of this study is to enhance the understanding of the vibration transmission in the hand-arm system in three orthogonal directions (X, Y, and Z). For the first time, the transmitted vibrations distributed on the entire hand-arm system exposed in the three orthogonal directions via a 3-D vibration test system were measured using a 3-D laser vibrometer. Seven adult male subjects participated in the experiment. This study confirms that the vibration transmissibility generally decreased with the increase in distance from the hand and it varied with the vibration direction. Specifically, to the upper arm and shoulder, only moderate vibration transmission was measured in the test frequency range (16 to 500 Hz), and virtually no transmission was measured in the frequency range higher than 50 Hz. The resonance vibration on the forearm was primarily in the range of 16–30 Hz with the peak amplitude of approximately 1.5 times of the input vibration amplitude. The major resonance on the dorsal surfaces of the hand and wrist occurred at around 30–40 Hz and, in the Y direction, with peak amplitude of more than 2.5 times of the input amplitude. At higher than 50 Hz, vibration transmission was effectively limited to the hand and fingers. A major finger resonance was observed at around 100 Hz in the X and Y directions and around 200 Hz in the Z direction. In the fingers, the resonance magnitude in the Z direction was generally the lowest, and the resonance magnitude in the Y direction was generally the highest with the resonance amplitude of 3 times the input vibration, which was similar to the transmissibility at the wrist and hand dorsum. The implications of the results are discussed.Relevance to industryProlonged, intensive exposure to hand-transmitted vibration could result in hand-arm vibration syndrome. While the syndrome's precise mechanisms remain unclear, the characterization of the vibration transmissibility of the system in the three orthogonal dimensions performed in this study can help understand the syndrome and help develop improved frequency weightings for assessing the risk of the exposure for developing various components of the syndrome.     

分段阻尼隔振系统的动力学特性分析

针对传统线性隔振器在降低共振峰值的同时会牺牲隔振性能的矛盾,设计了一种含分段阻尼的隔振器.首先,采用移动凸轮变阻尼装置,通过凸轮廓线的设计使系统的垂向阻尼系数的受振动位移大小控制并呈现分段线性特征,分析了该装置的阻尼特性.然后将分段阻尼装置应用于隔振器中,建立了含分段阻尼的积极隔振系统模型及其动力学方程,通过能量等效原理求出了分段阻尼系统的等效线性阻尼系数,求解了简谐力激励下系统响应的理论解,并用四阶龙格-库塔法数值仿真验证了理论解的正确性.最后研究了分段阻尼隔振系统的动态特性,分析了主要参数对幅频响应特性与力传递率特性的影响.结果表明,通过合理的参数选择,分段阻尼隔振器可兼顾无阻尼隔振器与线性阻尼隔振器的优点,既能有效降低系统的共振峰值,又能保证高频区域的优秀隔振性能,为新型非线性隔振器的设计提供了理论依据.