基于硅悬臂高阶谐振的动态原子力显微镜的快速扫描

利用原子力显微镜(AFM)硅悬臂器件具有多阶谐振模态的特性,提出了基于硅悬臂高阶谐振特性构建动态AFM来实现快速扫描的方法,并研制了可工作于一阶模态和高阶模态的AFM。介绍了高阶谐振AFM系统的基本结构和工作原理,从理论上证明了利用硅悬臂梁高阶谐振特性实现快速扫描的可行性。以自制的AFM为研究对象,分析了影响动态AFM扫描速度的主要因素,对系统各模块的响应时间进行了分析、测试,并通过实验证明了AFM在二阶谐振模态下的稳定时间明显小于一阶谐振模态下的稳定时间。最后,分别用一阶、二阶谐振模态对光栅试样在同一区域的表面形貌进行了扫描测试,测试数据表明:在相同条件下,AFM的扫描速度在二阶谐振模态下约是一阶模态下的3.3倍。理论分析和实验结果证明了利用高阶谐振探针提高AFM扫描速度的可行性和有效性。     

基于多通道锁相放大器的硅微半球谐振陀螺性能测试方法

针对硅微半球谐振陀螺的性能评测问题,研究了一种利用多通道锁相放大器(HF2LI)的快捷、有效测试方法。该方法首先利用多通道锁相放大器对硅微半球陀螺进行扫频,得到硅微半球陀螺的谐振频率和两模态的频差。再记录硅微半球陀螺谐振信号的衰减过程,通过MATLAB指数拟合,从而求得硅微半球陀螺的品质因数。再对调谐电极和模态电极同时施加直流偏压可实现两模态匹配,进而利用该锁相放大器的解调、PLL、PID等模块构建驱动闭环和敏感开环检测系统,测得硅微半球陀螺的标度因数和零偏不稳定性等参数。测试结果表明,该方法具有简单、快捷和有效等特点,可广泛应用于MEMS谐振器件的性能参数测试。     

参数化方法在微机械谐振器设计中的应用

从理论上分析了微机械音叉谐振器的机械力学特性,给出了活动梳齿的工作模态频率解析解,提供谐振器结构设计的依据.利用基于MAST语言实现的MEMS宏模块建立微谐振器系统级通用参数化仿真模型,为验证外围电路提供了基础.事例仿真结果与理论模态分析相一致,验证了模型的有效性.通过减少梁固接端弹性系数、合理安排激励电极能抑制一阶模态扰动.工作模态谐振频率对结构参数的敏感性分析为优化谐振器性能提供基础,使工作模态远离其它高阶模态.敏感性仿真表明在横向振动微谐振器中,工作模态谐振频率随梁长的增加而减小;随梁宽的增加而增大;结构层厚度对横向振动频率没有影响;梳齿部分所有参数的变化造成频率的相反变化.     

四模态匹配三轴硅微陀螺仪

为了实现单片集成六自由度微惯性测量单元,提出了一种改进的由4个大质量块和4个小质量块组合而成的四方全对称结构的三轴陀螺仪.介绍了该惯性测量元件的结构及工作原理,根据结构参数计算出了详细的性能指标,并进行了面内驱动模态和面内外的敏感模态仿真.为提高各敏感模态的机械灵敏度,提出采用双重静电频率调谐方案,即先对公共质量块施加调谐电压,使驱动模态和航向模态的频差最小;再对小质量块上方的多晶硅电极施加另外的调谐电压,最终使四模态频率偏差小于30 Hz,从而说明该频率调谐方法是有效的.然后,通过分析热弹性阻尼能量耗散机理,对驱动及敏感谐振模态的品质因数进行仿真.结果表明:真空环境不考虑空气阻尼情况下,两种模态的品质因数分别为23 816和19 507.最后,基于表面加工和体加工工艺,设计了高深宽比的加工流程.对该四方对称解耦结构的设计和仿真表明其模态匹配和品质因数性能满足三轴陀螺的设计要求.     

半球谐振子关键性能及制造工艺研究新进展

半球谐振陀螺具有结构简单、精度高、可靠性高、工作寿命长等特性,在国防军事、通信卫星、载人航天、天文观测、海洋工程等领域具有重大应用场景。半球谐振子作为半球谐振陀螺仪的核心器件,其加工质量直接影响半球谐振子的频率裂解和品质因数,进而影响半球谐振陀螺仪的工作精度和使用寿命,因此非常有必要对半球谐振子的性能及制造工艺进行研究。主要从半球谐振陀螺仪工作原理和研究历程、半球谐振子的频率裂解和品质因数、半球谐振子的制造工艺三个方面进行综述,重点分析了半球谐振子的频率裂解与品质因数的研究方法和最新进展以及半球谐振子的超精密磨削工艺和抛光工艺,并探讨分析了其在发展过程中面临的挑战和仍需要解决的问题,希望为后续精确计算、测量半球谐振子的频率裂解和品质因数,改进半球谐振子的制造工艺,提高半球谐振陀螺仪的导航精度提供参考。     

一种静电驱动微机械谐振传感器的接口电路及应用

针对静电驱动微机械谐振传感器接口动态电容的测量,文中介绍了一种读取接口电路,采用了高频方波对振动信号进行调制,模拟开关进行解调。以静电驱动的某真空封装微机械振动双框架陀螺为例,接口电路实验测试得到的波形与设计预期一致,并利用接口电路和频率扫描方法成功测得微机械振动陀螺驱动模态谐振频率为13.552 k Hz,品质因数为1863。     

滚筒式干燥机筒体应力特性分析

滚筒式干燥机的筒体结构特性对于燥过程会产生很大的影响,利用有限元对筒体进行静态应力和模态分析以及筒体的作用载荷研究,得出了正常工作状态和启动状态时筒体、螺栓孔和人孔的应力分布及干燥机筒体的各阶振型,为提高滚筒式干燥机的效率和筒体结构的设计、制造提供了理论依据.     

基于模态分析法的谐波谐振分析

谐波谐振包括并联谐振和串联谐振,会引起过电压和过电流,影响系统正常运行,所以研究一种谐波谐振问题的分析方法很重要。文章主要介绍模态分析法在分析谐波谐振问题上的可行性。针对典型的三母线测试系统,分别利用频谱分析法和模态分析法对并联谐振和串联谐振进行了分析,并对两种方法的结果进行了比较;除此之外在串联谐振分析中,还介绍了根据谐波源位置不同的模态分析法与回路阻抗法、虚拟支路法相结合的分析方法。仿真比较结果显示,模态分析法和频谱分析法可得到一致的谐振频率点,同时模态分析法还可准确定位谐振位置和影响程度:证明了模态分析法在谐波谐振分析中的可行性和优越性。     

导纳圆图在压电式超声波换能器中的研究

分析压电式超声波换能器的等效电路，并由等效电路输入阻抗的导纳圆图确定了换能器的元器件参数以及谐振频率、机械品质因数和工作带宽等特征参量。     

基于有限元法计算机直接制版设备辊筒模态分析

针对计算机直接制版设备辊筒进行有限元法动力学理论推导和临界转速的确定,利用Ansys workbench对辊筒进行模态分析,得出前六阶振型和极限转速。在满足辊筒20μm振动条件下,对辊筒进行静态分析,得出辊筒的最大转速、强度和挠度满足实际工况需求,并验证辊筒在最大工作转速下不会产生共振现象,实现了辊筒静动态特性的分析。     

Characteristics of a dynamic atomic force microscopy based on a higher-order resonant silicon cantilever and experiments

In order to improve the sensitivity and scanning speed of the dynamic AFM, a surface scanning method using higher-order resonant cantilever is adopted and investigated based on the higher-order resonance characteristics of the silicon cantilever, and the theoretical analysis and experimental verification on the higher-order resonance characteristics of the corresponding dynamic AFM cantilever are given. In this method, the cantilever is excited to oscillate near to its higher-order resonant frequency which is several times higher than that of the fundamental mode. Then the characteristic changes a lot compared with the first-order resonant cantilever. Because of the changes of the quality factor, amplitude and the mode shape of the cantilever, the higher-order resonant AFM gets higher sensitivity and scanning speed. Based on the home-built tapping-mode AFM experiment system, the resolution and the response time of the first and second order resonance measured by experiment are respectively: 0.83 nm, 0.42 nm; 1265 μs, 573 μs. The higher-order resonance cantilever has higher sensitivity and the dynamic measurement performance of the cantilever is significantly improved from the experimental results. This can be a useful method to develop AFM with high speed and high sensitivity. Besides above, the surface profile of a grating sample and its three-dimensional topography are obtained by the higher-order resonant mode AFM.     

Effects of various baffle designs on acoustic characteristics in combustion chamber of liquid rocket engine

Effects of various baffle designs on acoustic characteristics in combustion chamber are numerically investigated by adopting linear acoustic analysis. A hub-blade configuration with five blades is selected as a candidate baffle and five variants of baffles with various specifications are designed depending on baffle height and hub position. As damping parameters, natural-frequency shift and damping factor are considered and the damping capacity of various baffle designs is evaluated. Increase in baffle height results in more damping capacity and the hub position affects appreciably the damping of the first radial resonant mode. Depending on baffle height, two close resonant modes could be overlapped and thereby the damping factor for one resonant mode is increased exceedingly. The present procedure based on acoustic analysis is expected to be a useful tool to predict acoustic field in combustion chamber and to design the passive control devices such as baffle and acoustic resonator.     

大型起竖设备四级液压缸的动力学建模

大型起竖设备四级液压缸因内部结构复杂,且负载很大,摩擦力特性较为复杂,以往对其动力学建模时常常忽略摩擦力。而快速起竖系统要求对速度进行精确规划控制,以减缓换级冲击,且液压缸结构稳定性分析时也需要准确找到危险工况,其中摩擦力是很关键的一个因素。LuGre摩擦模型能较好描述大部分情况下的摩擦稳态、瞬态特性,据此,考虑滑动油膜动态等性方程,基于LuGre模型对四级缸摩擦力建模,而后对风载荷、起竖力等进行分析,进而对起竖过程动力学建模。该研究所建的全新动力学模型可为起竖速度的精确控制和油缸应力应变及模态分析提供参考。     

基于ADAMS的单缸内燃机动力学分析与研究

引起内燃机振动的一个重要因素是其曲柄连杆机构往复运动产生的惯性力和惯性力矩.基于动力学仿真软件ADAMS和Pm/E,建立了单缸内燃机的虚拟样机参数化实体模型,进行了动力学仿真分析,并将速度、加速度等分析值与理论分析结果比较,结果吻合验证了所建模型的正确性;研究了惯性力对机体产生干扰力和力矩的影响以及惯性力平衡问题.通过参数优化分析,确定了构件的最佳质量特性参数,改善了机构的动力学性能,同时提高了设计效率.     

Analysis of fluid-structure interaction for predicting resonant frequencies and quality factors of a microcantilever on a squeeze-film

The dynamic behavior of a flexible microcantilever vibrating above a substrate such as the cantilever-based structure of a radio frequency microelectromechanical switch is strongly affected by the motion of gas between the microcantilever and the substrate. In this paper, parameter studies to investigate the effects of geometry, material properties of a microcantilever, and ambient pressure on the resonant frequencies and quality factors of the microcantilever are described. A Reynolds-equation-based continuum model is used to derive the gas force reflecting the gas rarefaction effect due to the size effect of MEMS packed at low ambient pressure. The frequency response function of an inertially-excited microcantilever is developed using the mode superposition method. One interaction parameter, including information on geometry, material properties of a microcantilever, and ambient pressure, is defined to investigate the fluidstructure interaction in a microcantilever vibrating on a squeeze-film. The quality factors of the first three bending modes increase with the decreasing interaction parameter. The changing trend of associated resonant frequencies depends on the order of the bending mode.     

柴油机气缸盖的模态分析

利用有限元法对柴油机气缸盖进行了模态分析,获得了气缸盖的基本振型和相关频率,与试验结果进行比较,两者有较好的一致性,因而可利用所建立的有限元模型完成气缸盖的动态响应分析及设计优化.     

电液步进油缸特性的理论分析及试验研究

针对在高炉和连铸机等重工业恶劣工况下,采用传统液压伺服系统,抗油液污染能力低、可靠性差等问题,依据直接位移反馈闭环控制原理,结合数字化控制方式,开发了步进式电液控制液压缸。阐述了电液步进缸的工作机理,并对其进行数学建模和理论分析,建立了系统传递函数方框图。在试验台上对电液步进缸的内泄漏流量、十脉冲精度、一步精度、重复位置精度和频率响应等静动态性能进行测试,结果表明,电液步进缸在开环状态下也具有较高的控制精度和响应速度,可靠性高、抗油液污染能力强。     

基于ANSYS的柴油机缸体模态分析

针对新设计的某型染油机缸体,用CAD建立缸体的三维有限元模型,采用大型有限元软件ANSYS,对缸体进行了模态分析,得到了缸体的固有频率和振型,为今后进行缸体动力响应计算奠定了基础.     

Study of the tip mass and interaction force effects on the frequency response and mode shapes of the AFM cantilever

The vibrational characteristics of an atomic force microscope (AFM) cantilever beam play a key role in dynamic mode of the atomic force microscope. As the oscillating AFM cantilever tip approaches the sample, the tip–sample interaction force influences the cantilever dynamics. In this paper, we present a detailed theoretical analysis of the frequency response and mode shape behavior of a cantilever beam in the dynamic mode subject to changes in the tip mass and the interaction regime between the AFM cantilever system and the sample. We consider a distributed parameter model for AFM and use Euler–Bernoulli method to derive an expression for AFM characteristics equation contains tip mass and interaction force terms. We study the frequency response of AFM cantilever under variations of interaction force between AFM tip and sample. Also, we investigate the effect of tip mass on the frequency response and also the quality factor and spring constant of each eigenmodes of AFM micro-cantilever. In addition, the mode shape analysis of AFM cantilever under variations of tip mass and interaction force is investigated. This will incorporate the presentation of explicit analytical expressions and numerical analysis. The results show that by considering the tip mass, the resonance frequencies of the cantilever are decreased. Also, the tip mass has a significant effect on the mode shape of the higher eigenmodes of the AFM cantilever. Moreover, tip mass affects the quality factor and spring constant of each modes.     

Measurement uncertainties in resonant characteristics of MEMS resonators

This paper reports measurement of random uncertainties in resonant characteristics (resonance frequency and quality factor) of microelectromechanical system (MEMS) resonators. We employ different methods to extract resonant characteristics of 4 different MEMS resonators which are either clamped-free or clamped-clamped beams. Each beam type operates either in air or in a partial vacuum, and therefore, different vacuum levels can be examined. Three different methods, including frequency sweep, impulse response, and thermal noise, are applied to each resonator type excited with electrostatic or piezo-crystal actuation. We make a thorough analysis and comparison for three different methods. Depending on device type and operating condition, there exists a better and recommended way to extract resonant characteristics of MEMS resonators. For example, the impulse response is best-suited for the quality factor measurement of a clamped-clamped beam operating in a vacuum. Our results show that the quality factor of MEMS resonators may be noticeably different and exhibit appreciable systematic and random uncertainties, and suggests a better way to extract the quality factor for a given situation.