微谐振传感器同频干扰的建模与消除

主要研究了静电激励/电容拾振谐振式硅微加速度传感器的同频干扰问题,分析了几种干扰源,建立了同频干扰的电路等效模型,提出一种基于双端激励/双端检测的结构,采用二次差分的方式消除同频干扰.     

硅谐振梁式微传感器同频干扰的研究

主要研究了静电激励/电容拾振的谐振梁式微传感器的同频干扰问题及解决的方法,提出了采用梁的二阶振动模态解决同频干扰的方法.     

扩散硅谐振式压力传感器同频干扰的建模与消除

为简化谐振式微机械压力传感器的制备工艺,提出了一种采用扩散硅作为谐振梁的压力传感器,并采用电磁激励实现传感器的闭环控制.实验中发现:由于采用扩散硅材料,传感器受到较为严重的同频干扰影响,因此,消除传感器的同频干扰成为需要解决的一个主要问题.通过对采用扩散硅作为谐振梁的压力传感器微结构进行分析,建立了传感器主要噪声来源同频干扰的等效电路模型,据此提出一种新的不对称双端激励解决方法.实验结果表明,该方法可有效地降低传感器的同频干扰,传感器的信噪比由1.53提高至35,为传感器闭环激励和检测提供了有效的手段.     

基于三梁结构的电热驱动谐振式微加速度传感器研究

为了提高电热激励/压阻拾振谐振式微加速度传感器的品质因数和消除交叉灵敏度,提出一种基于三梁结构的新设计.依据有限元模拟得到的固有振型来选择三梁结构参数,以减少能量耗散,提高品质因数.分析本设计消除交叉灵敏度的机制和独特的三梁结构的激振方式并对其进行有限元模拟.模拟结果证实这种谐振式微加速度传感器的灵敏度高于1000 Hz/g.     

谐振传感器技术中光学激振拾振原理研究

全光纤－谐振传器技术是８０年代中期出现的一种新型传感器技术，由于它兼有光纤、谐振传感技术和硅微结构的优点，因而被认为在航空、医学等领域尤其具有重要的应用价值。硅微细加工工艺、光学激振和拾振是这一技术研制中的三个着急问题。本将就方形硅膜片光学激振和拾振的原理进行了探讨和分析。     

单线圈光电式振弦传感器测频系统的设计

在对振弦传感器的特性和工程应用进行研究的基础上,创新的设计了一种单线圈光电式振弦传感器,同时给出了相应的激振、拾振和测频系统的设计。振弦传感器采用单线圈电磁激振方式,应用光电管结合MCU进行振动信号反馈,不但简化了硬件电路,而且解除了激振和拾振中电磁干扰问题,提高了测量的精度和稳定性。激振中采用的扫频技术也使振弦的起振更加稳定可靠。     

电磁激励的硅谐振梁设计和有限元分析

介绍了电磁激励硅谐振梁的激励和检测原理,给出了双端固支的硅谐振梁谐振频率公式,并利用该公式分析了双端固支梁的谐振频率和梁尺寸的关系.本文利用有限元软件模态分析计算了三种不同的谐振频率情况,并逐一加以比较分析.本文还利用有限元软件对受力弯曲的工字梁做了静态分析,从而得出了在一定磁场力作用下的应力分布图,从而对压敏电阻的设计提供了一定的依据.     

谐振敏感元件特性模拟器的研究

为了实现谐振式硅微传感器测试仪器的直接校验,以及进行谐振式传感器反馈控制电路的优化研究,设计了能够模拟压阻拾振式谐振敏感元件特性的电路.其中压阻变换是该电路实现的关键.文章采用模拟电路实现对谐振敏感元件的电阻拾振特性的模拟,得到受电压线性控制的交变电阻.对该电路进行了高频特性分析,提出一种可拓宽其频带的反馈补偿技术,从...     

振弦式传感器激振策略优化

振弦式传感器的激励常用高压拨弦激振和低压扫频激振两种方式。高压拨弦激振对传感器损伤较大,信号衰减快,测量精度差;低压扫频激振扫描时间长,信号不宜拾取。提出一种反馈式低压激振方法,降低拨弦激振电压对传感器进行预激振,将反馈的振动频率信号作为输出,对传感器进行复振,可以在很短时间内使振弦达到共振状态。设计专用检测电路对调优后的激振策略进行验证,证明该方法激振时间短,共振幅度大。振动幅度的提高可增强抗干扰能力、降低信号处理电路成本、增加可用测量时间、提高频率测量精度。     

微型硅谐振式压力传感器的研制

利用微电子机械加工技术成功地研制出电热激励、压阻拾振的高精度硅谐振梁式压力传感器。传感器的谐振器的品质因素Q值在真空中大于 10 0 0 0。采用特殊闭环自激振荡方式测定压力传感器的压力特性 ,压力测试范围 0～ 40 0kPa ,线性相关系数 0 .9999,测试精度优于 0 .1%FS。     

基于微梁的面内高g值加速度计设计

提出了一种基于微梁的面内高g值加速度计的设计方案。根据材料力学中悬臂梁的相关理论,建立了微梁检测结构的等效模型,推导出了微梁应力和中间主梁应力的比值的表达式。通过改变结构的尺寸来调节比值,可以设计出更高量程和更高灵敏度的压阻式传感器。利用ANSYS软件对微梁和中间主梁的最大应力及电阻区应力进行了仿真分析,验证了设计方案的可行性。完成了一种量程可达15万gn的面内双轴高g值传感器的设计。     

开孔变截面微悬臂梁传感器的等效刚度和固有频率

研究新型开孔变截面微悬臂梁传感器的等效法向刚度及其对固有频率的影响.首先,考虑微梁纵截面孔洞结构引起的弯扭耦合效应,利用二次积分法获得在自由端集中载荷作用下悬臂梁的挠度,基于弹性材料的Hooke定律建立了微梁等效法向刚度分析的解析模型.然后,采用Rayleigh法获得了微梁的固有频率.最后,通过比对实验结果和有限元结果对解析模型进行了验证.研究表明:解析模型对于开孔变截面微梁刚度和频率的预测和标定具有较好的精度;微梁的等效刚度和固有频率与跨宽比负相关,却与内外宽度比正相关.有关结论可为新型变截面微纳机械传感器的设计提供理论依据和参考.     

On the tunability of a MEMS based variable capacitor with a novel structure

In this work a novel MEMS based variable capacitor has been presented. To increase the tunability and decrease the applied voltage, the conventional fixed-fixed beam used in CPW lines has been changed to a fixed-simple supported beam. The proposed structure is a simple cantilever micro-beam in the first step of deflection and is changed to a fixed-simple supported micro-beam in the second step of motion. In the capacitive micro-structures increasing the applied voltage decreases the equivalent stiffness of the structure and leads the system to an unstable condition by undergoing to a saddle node bifurcation. In the proposed structure to avoid pull-in instability and increase the capacitance tuning range, mechanical stiffness of the structure is increased by changing boundary conditions by locating a pedestal in the end of the cantilever beam. The governing nonlinear equation for static deflection of the micro-beam, based on Euler–Bernoulli micro-beam theory has been presented. The results show that the proposed structure increases the capacitance tuning range and decreases the applied voltage. The results also show that the position of the pedestal affects the tunability and the threshold voltage of the structure.     

Dynamic performance improvement of an isolated wind turbine induction generator

A dynamic model of a variable speed stand alone wind generation system is developed. The transient performance of the system under variable wind gust and other disturbance conditions has been studied. It has been observed that a stand alone generator is very vulnerable to transient disturbances in the system. A variable susceptance excitation control system, installed at the generator terminal, has been shown to improve the dynamic performance of the system following transient disturbances. Additional pole-placement based PI and PID controllers in the excitation control circuit are shown to control the violently oscillating and even growing transients very effectively. The robustness of the proposed controller has been tested for various disturbances and also for a range of operation.     

基于Tx-Rx探头的异种金属焊缝缺陷检测及定量分析

异种金属焊接结构在使用过程中容易产生损伤,因此需对其进行检测;脉冲涡流一发一收式非同轴(Transmitter Receiver,Tx-Rx)探头可应用于异种金属焊缝缺陷检测;然而,考虑到异种金属焊接构件成分多样、结构复杂的特点,需对Tx-Rx探头的摆放位置进行了优化;首先,建立仿真模型,讨论了激励线圈的摆放位置对试件中涡流及涡流扰动的影响,结果表明,当激励线圈位于带堆焊的合金钢上方时,其表面涡流强度及涡流扰动强度较大;其次,建立实验平台,实验表明,当激励线圈放置在带堆焊的合金钢上方时,其检测信号幅值和差分信号幅值最大;最后利用差分信号的峰值对焊缝缺陷的定量展开分析;脉冲涡流Tx-Rx探头的研究可为其在异种金属焊缝缺陷的应用提供参考.     

Composite disturbance-observer-based control and terminal sliding mode control for uncertain structural systems

A new type of composite control scheme of disturbance-observer-based control and terminal sliding mode control (TSMC) is proposed for uncertain structural systems. The disturbance are supposed to include two parts. One is generated by an exogenous system, which can represent the harmonic signals with modelling perturbations in structural system. The other part is external excitation in H ₂-norm context. The disturbance observers based on regional pole placement and D-stability theory are presented, which can be designed separately from the controller design. By integrating the disturbance observer with TSMC law, the disturbance with the exogenous system can be estimated and compensated, and external excitation can be attenuated in finite time. Finally, simulations for a four-degree-of-freedom building model excited by 1940 El Centro earthquake excitation are given to demonstrate the effectiveness of the approach and compare the proposed results with the previous schemes with accuracy.     

Numerical study on the effects of linear protrusion on flow-induced carriage excitation force in hard disk drives

The positioning accuracy of magnetic heads needs to be improved to increase the recording capacity of hard disk drives. In our previous study, experimental results confirmed that the head-positioning error could be decreased by attaching linear protrusions on the leading edge of the carriage arms. However, the mechanism underlying the phenomenon has not been elucidated. In the present research, we evaluated the effect of leading-edge protrusions on the flow-induced carriage excitation force using computational fluid dynamics (CFD) analysis and the Hilbert–Huang transform (HHT). We prepared two carriage-arm models, with and without linear protrusions, on the leading edges of the arm, and performed the CFD analyses. Subsequently, we conducted a frequency analysis by applying HHT to the simulated disturbance torque time-series of each carriage-arm model and compared the results. Our results show that the leading-edge protrusions decrease the disturbance torque due to the flow fluctuation between the arm and disk and in the wake flow, although the low-frequency disturbance torque due to the pulsatile flow can be deteriorated.

     

同态解卷处理在基音检测中的应用

语音处理中基音检测是极为重要的环节之一,然而浊音中的基音往往会受到声道特性和噪声的影响而导致检测结果的误差。利用同态解卷处理,将浊音中的激励信号和声道特性进行分离,然后再在激励信号中利用自相关检测基音,可以减小声道特性和噪声对基音检测的影响,从而提高基音检测的精度。通过理论模型验证了该方法的可行性,而且实际语音信号处理结果表明,该方法在基音检测时可以基本不受声道特性和噪声的影响。     

A passive mechanism for thermal stress regulation in micro-machined beam-type structures

In this article, a passive mechanism for thermal stress regulation in micro-bridge structures is proposed. The mechanism is essentially a set of precisely designed parallel chevron beams that replace one of the fixed ends of the micro-bridge. The axial stress/force of the beam is determined by utilizing a sensing mechanism that makes use of two side-electrodes and the electromechanical buckling of the micro-bridge toward one of them. A combination of analytical and finite element methods has been employed for the modeling of the proposed mechanism. It has been demonstrated that the regulator mechanism has negligible dynamic effect on the sensing micro-beam. The model takes into account the effect of electric field fringes between the electrically charged bodies. It has been shown that there is a time delay between the moment that the pull-in occurs and the instant that the sensing beam rests on a side-electrode. The results of the modeling are verified by experiment on two devices fabricated using MetalMUMPs^? fabrication technology. The thermal stress sensitivities of the devices are positive and their residual stresses are in excellent agreement.     

单元机组的非线性自适应反演综合控制

针对同时考虑参数不确定性和外界干扰的单元机组整体模型(锅炉–汽轮机–发电机模型),提出了一种基于自适应反演法和协调无源性理论的非线性综合控制策略.首先,针对预处理后的被控对象各子系统,采用反演法得到汽门控制输入,然后以高压侧电压为控制目标对励磁部分进行优化设计,最后逐步递推设计燃料控制器.在控制律设计过程中,为克服模型参数的不确定性,避免可能出现的参数漂移,通过引入充分光滑投影算子设计了参数自适应律.同时,借助在控制律中添加阻尼项,以有效抑制外界干扰对控制品质的影响.仿真分析和变负荷实验的结果表明,本文所设计的综合控制策略同时优化了单元机组的有功和无功响应特性,使其具有良好的负荷跟踪性能、抗干扰能力和对模型不确定参数的鲁棒性.