静电梳状硅微单侧直脚谐振器的力学性能

建立单侧支撑直脚型静电梳状硅微谐振器的三次超静定简化力学模型,给出该模型中谐振频率、弹性系数和横向最大位移的计算公式.与五次超静定系统的双侧支撑直脚型静电梳状硅微谐振器的各力学性能参数的计算公式对比发现它们有显著差别.分析表明,与双侧支撑直脚型静电梳状硅微谐振器显著不同,单侧支撑直脚型静电梳状硅微谐振器的谐振频率、弹性系数、横向最大位移会随两根支撑梁的间距变化而改变,并当此间距超过某一值后,上述三变量的变化均很小且趋向于一定值.同样,后者的谐振频率会随支撑梁厚度的变化而单调改变,这也是前者所没有的现象.为此从两者因为超静定次数不同而约束冗余度不同的角度,对此现象进行了物理意义上的解释.经与试验结果对比,单侧支撑直脚型静电梳状硅微谐振器横向谐振频率的理论值与实测值吻合较好,最大误差为12.07%.     

不同型式支撑的静电硅微谐振器的性能比较

针对直脚型、蟹脚型、之字型和弓型四种支撑梁结构型式的静电梳状谐振器,介绍了符合问题实质的五次超静定力学模型,给出了横向谐振频率、弹性系数和位移随谐振器结构参数和材料参数变化的函数关系。经与试验结果对比,各类谐振器横向谐振频率的理论值与实测值吻合较好,最大误差为11.62%。比较分析表明:在特征尺寸相同的情况下,直脚型、蟹脚型、之字型和弓型静电梳状谐振器的横向谐振频率依次减小,且都与谐振器的厚度无关;在特征尺寸和驱动电压相同的情况下,直脚型、蟹脚型、之字型和弓型静电梳状谐振器的横向位移输出能力依次增加;直脚型、蟹脚型、之字型和弓型静电梳状谐振器的横向弹性系数,均只与材料的杨氏模量和支撑梁的几何参数有关,而与横向位移无关。     

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.     

静电硅微多折叠梁谐振器设计和试验研究

建立了静电硅微多折叠梁谐振器的横向振动模型,得到了多折叠梁的变形方程和该类谐振器谐振频率的解析表达式。用标准体硅微工艺设计加工出两类共4种该类谐振器,通过试验测定其谐振频率,并用ANSYS软件进行了模态分析。结果表明,该类谐振器谐振频率的理论计算值和ANSYS模拟值与实测值间的相对误差均小于2％,验证了该理论模型的正确性。采用多折叠梁谐振器可以实现低频下大振幅的电能-微机械能的转换。     

基于氧化锌纳米线的硅谐振式加速度计

设计制作了一种基于氧化锌纳米线的谐振式硅加速度计,该加速度计的敏感单元为由氧化锌纳米线横跨金属微电极组成的谐振器。采用介电电泳的方法组装了氧化锌纳米线,并利用FIB沉积Pt将氧化锌纳米线固定在微结构上以确保结构的可靠性。在加速度的作用下,质量块引起的惯性力通过支撑梁对纳米线施加应力,因此,在谐振条件下,纳米线谐振频率的变化反映了加速度的大小。谐振式加速度计的准数字输出能解决多数MEMS器件输出微弱信号检测难的问题。实验结果表明,加速度计的灵敏度随着纳米线的厚度的减小而急剧增加,选择500 nm厚度的纳米线作为理论分析,加速度计的灵敏度可达2.5 kHz/g以上。     

硅微谐振压力传感器自动增益控制与相位补偿研究

硅微谐振压力传感器检测信号的幅值稳定性与频率跟踪性对其性能至关重要,但目前幅值控制与频率跟踪方法的非线性特征会造成谐振器振动频率的非线性变化,限制了传感器综合精度的进一步提升。为降低谐振器振动频率非线性变化的影响,基于自动增益控制(Automatic gain control,AGC)的线性化分析理论,建立高Q值硅微谐振压力传感器自动增益控制和相位补偿模型,分析AGC幅值控制和频率跟踪线性化的控制特性,以及相位补偿对闭环控制性能的影响。基于自动增益控制(AGC)的自激驱动被证实可使谐振器稳定工作于谐振频率,且保持幅值稳定,通过Simulink/PSpice建模仿真,验证非线性系统线性化分析的准确性。同时基于自动增益控制与相位补偿模型设计与制作的硅谐振压力传感器控制电路,经测试可使整表频率稳定性优于±0.05 Hz@采样周期5 ms,综合精度优于±0.02%FS,实现自动增益控制在谐振压力传感器的工程化应用,解决了谐振器频率跟踪非线性引起的传感器性能下降问题,可广泛应用于高Q值谐振器闭环控制。     

硅微谐振式加速度计的实现及性能测试

为了提高硅微谐振式加速度计性能,从一种基于DDSOG(Deep Dry Silicon on Glass)工艺的硅微谐振式加速度计样机入手,介绍了加速度计的结构、加工方法和接口电路。该谐振式加速度计结构包括敏感质量块、谐振器和微杠杆3部分,采用差动结构来减小共模误差的影响。接口电路中采用了自动增益控制电路来稳定谐振器的振幅,成功实现了谐振器的闭环自激振荡和频率检测。分析了谐振式加速度计频率输出与加速度输入的关系,测试了硅微谐振式加速度计样机性能,结果为量程±50g,标度因数143 Hz/g,零偏稳定性1.2 mg,零偏重复性0.88 mg,阈值170μg。文章最后提出,DDSOG工艺中采用的玻璃材料和硅材料温度系数不同,影响了加速度计的温度特性,因此需要进步一改进加工工艺。     

一种用于微谐振器频率调节的静电梳齿结构设计

针对微梳齿谐振器频率偏移的问题,提出了一种用于微谐振器频率调节的曲线形状静电梳齿结构。通过对梳齿简单模型的静电力分析,得出其静电力-位移特性,其斜率就是静电弹性系数;然后从谐振频率出发,分析了影响谐振频率的因素。研究结果表明,对于梳齿式微谐振器,当调谐电压从0 V变化到80 V左右时,器件的有效弹性系数从2.64 N/m减小到1.23 N/m左右,且谐振频率从自然谐振频率18.9 kHz减小到13 kHz,降幅分别为53%和31%。实验结果表明,这种曲线梳齿"软化"了静电微谐振器或者微驱动器的系统弹性,能够有效地调节谐振频率。     

一种基于MEMS技术的新型谐振式微流量传感器

提出了一种新颖的微机械谐振式微流量传感器.该传感器采用电磁激励方式.传感器主要由1个3 μm 厚H型谐振器、1个40 μm厚的悬臂梁平板(2 000 μm×5 000 μm)以及连接平板和框架的2根40 μm厚的支撑梁组成.谐振器采用低应力富硅氮化硅SiN制作,可以方便地使用湿法腐蚀释放谐振器,从而简化工艺流程,提高成品率.文中分析了理论模型、有限元仿真(FEA)、工艺制造和测试结果.测试结果显示,传感器在1 SLM(标准L/min)流量下,频率漂移为500 Hz,分辨率达到5/1 000.但在输出(谐振器频率漂移)和输入(气体流量)间存在二次曲线关系.     

硅微机械音叉式谐振器

应用体硅微机械加工技术,制作了一种双端固定音叉式谐振器。它在音叉的两个臂上连接了梳齿电容结构,用来驱动音叉臂在硅片平面内侧向、反相振动,同时检测音叉的振动频率。当驱动力的频率等于音叉的固有频率时,音叉产生谐振。此时,检测梳齿电容输出的电流最大。用有限元方法对谐振器进行了模态分析和结构优化。音叉臂长800μm,宽5μm,梳齿电容齿长25μm,结构层厚度为80μm,在30V交流电压激励下,测得其谐振频率为25kHz。当音叉受到轴向力的作用时,音叉的固有频率会发生变化,根据这一原理,设计了谐振式加速度计。用有限元分析软件对加速度计工作情况仿真,估算其灵敏度约为2Hz/g。这种音叉式谐振器结构和工艺简单,性能可靠,成本较低,对于进一步研究微机电系统谐振器件具有重要意义。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

Limits of topographic measurement by the scanning tunnelling and atomic force microscopes

Parameters describing the topographic character of a surface (height, surface wavelength, slope and curvature) can be derived from equivalent sinusoidal profiles. The response of a surface-measuring instrument may be modelled in terms of instrument parameters such as stylus radius, and scanning range and resolution. The performance of the instrument may then be mapped as a zone in amplitude-wavelength (AW) space to show the sinusoidal profiles it is capable of measuring. In a first-order analysis the STM and AFM are considered as equivalent to contact-stylus instruments with a notional stylus radius equal to the tip radius plus the gap. Comparisons between different instruments and types of instrument are readily made by mapping in AW space. The error arising from convolution of the sinusoidal profile with that of the finite tip may be quantified and plotted as contours in AW space.