A Piezoelectric Friction-Inertial Linear Motor Based on Piezoelectric Single-Crystal Cymbal Displacement Amplification Mechanism

Piezoelectric friction-inertial motor is known for its promise for a long-range and high-resolution motion.The movement of the slider/rotor of the motor is achieved by stick-slip effect.We report a relaxor-based-ferroelectric-single-crystal cymbal actuator and a miniature piezoelectric friction-inertial linear motor(abbreviated as PFILM)fabricated with the cymbal actuator.The cymbal actuator is fabricated with a 10 mm diameter disk of 0.70Pb(Mg_(1/3)Nb_(2/3))O_3-0.30PbTiO_3 single crystal.The displacement of the cymbal actuator increases almost proportionally from 0to 23μm with driving voltage up to 500 V,and the minimal hysteresis is observed.The cymbalPFILM with 20 mm motion range works under driving voltage frequency of ca.100 Hz to ca.5kHz,the fastest speed is obtained with 3.5kHz and the no-load speed is 14mm/s and the maximum thrust force is 98 mN.Compared with a PFILM based on multilayer piezoelectric ceramic,the proposed motor has a larger stroke under DC/quasistatic input voltage in fine motion mode,but a smaller driving force in long-travel mode due to lower resonance frequency.

Revealing the contribution of basilar membrane's biological activity to the mechanism of the cochlear phonosensitive amplification

Explaining the mechanism of the cochlear active phonosensitive amplification has been a major problem in medicine.The basilar membrane(BM)is the key infrastructure.In 1960,Nobel Laureate von B′ek′esy first discovered BM's traveling wave motion.Since that time,BM's models only have considered the traveling wave but not the biological activity.Therefore,a new model considering changes of BM's stiffness in space and time is established based on the immersed boundary method to describe its biological activity.It not only reproduces the results of traveling wave motion but also explains the mechanization on the generation of traveling wave.An important discovery is that changes of BM's stiffness in space and time will cause the unstable global resonance,which will induce amplification of sounds in cochlea.An important inference is that biological activity shall be included in the application of mechanical principles to the analysis of life,which is the essential difference between biomechanics and general mechanics.

Amplification mechanism of perturbation energy in controlled backward-facing step flow

A body force resembling the streamwise Lorentz force which decays exponentially in the wall-normalwise direction is applied in the primary and secondary separation bubbles to modify the base flow and thereby adjust the amplification rate of the perturbation energy.The amplification mechanisms are investigated numerically via analyzing the characteristics of the terms in the Reynolds-Orr equation which describes the growth rate of the perturbation energy.The results demonstrate that the main convective term always promotes the increase in the growth rate while the viscous terms usually play the reverse role.The contours of the product of the wall-normalwise and streamwise perturbation velocities distribute on both sides of the isoline,which represents the zero wall-normalwise gradient of the streamwise velocity in the base flow,due to the Kelvin-Helmholtz(KH)instability.For the case without control,the isoline downstream the reattachment point of the primary separation bubble is closer to the lower wall,and thus the viscous term near the lower wall might suppress the amplification rate.For the case in which the body force only acts on the secondary separation bubble,the secondary separation bubble is removed,and the magnitude of the negative wall-normalwise gradient of the base flow streamwise velocity decreases along the streamwise direction,and thus the growth rate of the perturbation energy is smaller than that for the case without control.For the case where the body force acts on both the separation bubbles,the secondary separation bubble is removed,the isoline stays in the central part of the channel,and thereby the viscous term has less effects on the amplification rate of which the peak value could be the maximum one for some control number.

Research and Application of"Soft"Devices for Realizing Servo Amplification

This article analyzes and discusses the working principle and problems encountered by various servo amplification devices used in the on-site continuous adjustment system,analyzes and discusses the application of the servo mechanism,and analyzes the mechanism of the servo device's implementation of the"positioning"func-tion on the control device.Intended to guide the continuous adjustment process in controlling the function/accuracy of actuator equipment and application debugging,ensuring the safe and stable operation of production equipment and facilities.

Design and dynamic analysis of integrated architecture for vibration energy harvesting including piezoelectric frame and mechanical amplifier

Vibration energy harvesters(VEHs) can transform ambient vibration energy to electricity and have been widely investigated as promising self-powered devices for wireless sensor networks, wearable sensors, and applications of a micro-electro-mechanical system(MEMS). However, the ambient vibration is always too weak to hinder the high energy conversion efficiency. In this paper, the integrated frame composed of piezoelectric beams and mechanical amplifiers is proposed to improve the energy conversion efficiency of a VEH. First, the initial structures of a piezoelectric frame(PF) and an amplification frame(AF) are designed. The dynamic model is then established to analyze the influence of key structural parameters on the mechanical amplification factor. Finite element simulation is conducted to study the energy harvesting performance, where the stiffness characteristics and power output in the cases of series and parallel load resistance are discussed in detail. Furthermore, piezoelectric beams with variable cross-sections are introduced to optimize and improve the energy harvesting efficiency. Advantages of the PF with the AF are illustrated by comparison with conventional piezoelectric cantilever beams. The results show that the proposed integrated VEH has a good mechanical amplification capability and is more suitable for low-frequency vibration conditions.

The response law of far-field seismic ground motion of the Wenchuan earthquake and its damaging mechanism in the Loess Plateau

A series of housing collapses and other serious damage was caused by the 2008 Wenchuan M_(S)8.0 earthquake in the seismic intensity Ⅵ areas of the Loess Plateau, which is hundreds of kilometers away from the epicenter, and which showed a remarkable seismic intensity anomaly. The seismic disasters are closely related to the seismic response characteristics of the site, therefore, the systematic study of the far-field seismic response law of the Wenchuan earthquake in the Loess Plateau is of great significance to prevent the far-field disaster of great earthquake. In this paper, the seismic acceleration records of several bedrock stations and loess stations from the seismogenic fault of the Wenchuan earthquake to the Loess Plateau were collected, and the attenuation law of ground motion along the propagation path and the characteristics of seismic response on the loess site are studied,and the mechanism of amplification effect of ground motion is analyzed based on the dynamic feature parameters of the loess site obtained through the HVSR method. Taking a typical loess site of thick deposit as the prototype, a series of shaking table tests of dynamic response of loess site models with different thicknesses were carried out.Amplification effect, spectral characteristics of acceleration in model sites were analyzed under the action of a farfield seismic wave of the Wenchuan earthquake. The results show that seismic attenuation on the propagation path along the NE strike of the seismogenic fault to the Loess Plateau is slower than that in other directions, and the predominant period range of ground motion on bedrock site of the Loess Plateau presents broadband characteristics. Because the natural periods of loess sites with thick deposits are within the predominant period range of bedrock input wave, loess sites appear significant amplification effect of ground motion, the horizontal acceleration of ground motion exceeds 0.1 g, the seismic intensity reaches 7°. The thicker the loess deposit is, the more significant the change of spectral characteristics of ground motion on loess sites, and the narrower the predominant period range of ground motion becomes, and the closer it is to the natural period of loess sites.Therefore, for some old houses on thick loess sites, the poor seismic performance and strong seismic response eventually led to their collapses and damages because their natural periods are very close to the predominant period of ground motion of the Wenchuan earthquake on thick loess sites;For these damaged high-rise buildings,the resonance effect might be the main reason for their damages because their natural periods are included in the predominant period range of ground motion of the Wenchuan earthquake on thick loess sites.These research results would provide a basis for seismic disasters prediction and evaluation and seismic design of construction engineering in the Loess Plateau.

Optimization design of two-stage amplification micro-drive system without additional motion based on particle swarm optimization algorithm

With the increasing requirements of precision mechanical systems in electronic packaging,ultra-precision machining,biomedicine and other high-tech fields,it is necessary to study a precision two-stage amplification micro-drive system that can safely provide high precision and a large amplification ratio.In view of the disadvantages of the current two-stage amplification and micro-drive system,such as poor security,low motion accuracy and limited amplification ratio,an optimization design of a precise symmetrical two-stage amplification micro-drive system was completed in this study,and its related performance was studied.Based on the guiding principle of the flexure hinge,a two-stage amplification micro-drive mechanism with no parasitic motion or non-motion direction force was designed.In addition,the structure optimization design of the mechanism was completed using the particle swarm optimization algorithm,which increased the amplification ratio of the mechanism from 5 to 18 times.A precise symmetrical two-stage amplification system was designed using a piezoelectric ceramic actuator and two-stage amplification micro-drive mechanism as the micro-driver and actuator,respectively.The driving,strength,and motion performances of the system were subsequently studied.The results showed that the driving linearity of the system was high,the strength satisfied the design requirements,the motion amplification ratio was high and the motion accuracy was high(relative error was 5.31%).The research in this study can promote the optimization of micro-drive systems.

Advances in understanding the mechanisms of Arctic amplification

The near-surface temperatures in the Arctic are increasing at more than twice the global average rate,a phenomenon known as Arctic amplification(AA).In recent years,numerous studies using ground-based and satellite observations,along with model simulations,have explored the potential mechanisms behind AA,offering a variety of observational evidence and theoretical explanations.Although the understanding of AA drivers has improved,significant uncertainties remain in quantifying the contributions of different influential factors.On the basis of the latest research,this article thoroughly examines the factors driving rapid warming in the Arctic,including local feedbacks,atmospheric circulation,ocean currents,and aerosols,and compares quantitative results across studies.The analysis highlights the complex interplay of multiple factors contributing to AA,with no clear consensus on the relative contributions of each driver.Finally,the article underscores key challenges in current research,emphasizing the need for more reliable observational data,a deeper understanding of AA mechanisms,improved model parameterizations,and the disentanglement of interactions among driving factors,all of which are essential for future investigations.

A New Differential Operator Method to Study the Mechanical Vibration

In this paper, we propose a unified differential operator method to study mechanical vibrations, solving inhomogeneous linear ordinary differential equations with constant coefficients. The main advantage of this new method is that the differential operator D in the numerator of the fraction has no effect on input functions (i.e., the derivative operation is removed) because we take the fraction as a whole part in the partial fraction expansion. The method in various variants is widely implemented in related fields in mechanics and engineering. We also point out that the same mistakes in the differential operator method are found in the related references [1-4].

海上风电场经交流海缆并网谐波谐振放大分析

采用交流海缆接入电网的海上风电场在电缆线路分布电容的作用下,可能出现陆上风电场不常见的谐波谐振与谐波放大现象,严重威胁到海上风电场安全可靠运行。为研究海上风电场谐波谐振机理与谐波放大影响因素,首先,建立了海上风电场输电系统与集电系统两部分的状态空间模型,并给出谐波放大倍数、谐波含量等指标的计算方法;其次,通过特征值和参与因子揭示了谐波谐振机理及关键影响因素;然后,通过根轨迹法研究了电网短路容量、高压电缆参数和风电机组并网台数对谐振模态的影响;最后,在Matlab/Simulink仿真平台搭建江苏某海上风电场.验证理论分析的有效性。

基于柔性铰链结构的大口径压电快摆镜

为了解决压电作动器驱动的快速反射镜因压电作动器伸长量较小,导致快速反射镜偏转角过小的问题,该文提出了一款新型快速反射镜设计方案。采用三级杠杆式柔性铰链放大机构实现压电作动器位移的放大,采用柔性轴承作为快摆镜的运动关节实现快摆镜的大角度定轴偏转。通过理论推导和有限元仿真对快摆镜的最大偏转角度、等效应力、谐振频率以及振型进行分析。实验结果表明,所设计的快摆镜可以实现大于2 mrad的镜面偏转,满足大范围、高精度的光束定位要求。

网络时代农产品质量安全事件风险放大机制研究——基于价值累加理论的扎根分析

随着互联网的飞速发展,农产品质量安全事件借助网络媒体持续关联与聚合、发酵与扩散,极大地影响着公众的情感和态度,易引发集体非理性恐慌,网络时代信息扩散和迭代呈现全新特征和趋势,故加强农产品质量安全事件风险放大机制研究具有重要意义。基于斯梅尔塞的价值累加理论,结合“土坑酸菜”事件,利用Python技术获取媒体原始资料,对资料进行扎根编码分析,构建农产品质量安全事件风险放大机制模型。根据编码结果识别出农产品质量安全事件风险放大六大主范畴,包括结构性诱因、结构性紧张、一般化信念、(有效的)组织动员、社会控制、风险放大,将主范畴内容纳入价值累加理论六大因素中,分析表明农产品质量安全事件风险放大是以突发事件为分界点,分为前期蓄势、中期造势、紧急处理三个阶段,前期蓄势和中期造势阶段通过多轮循环相互反馈影响,最终放大农产品质量安全事件风险。在整个风险扩散过程中,网络是农产品质量安全事件风险的“社会放大站”,其加速了信息传播,强化了公众风险感知。本研究运用价值累加理论、基于宏观和微观整合层面,细化探究了网络时代农产品质量安全事件风险放大的完整过程机制,进一步完善了风险放大SARF研究框架,为相关研究做了有益补充。

基于放大机构的压电叠堆泵设计分析及试验

为了克服压电叠堆输出位移较小、对泵振子泵送能力弱的缺点,综合杠杆铰链与三角形铰链结构性能优点,提出基于放大机构的压电叠堆泵,分别开展理论放大倍数分析、ANSYS仿真分析、流固耦合分析及泵送性能试验测定研究.结果表明,压电叠堆泵仿真放大倍数约为20.3时,与理论计算值相对误差为11.7%;ANSYS仿真分析表明,泵振子的二阶频率对应的弯振为最佳振型,该振型对应的工作频率为1356.30 Hz,在该工作频率下对压电叠堆泵进行流固耦合分析,得出泵送流量为41.78 mL/min.在上述研究分析的基础上试制压电叠堆泵样机并进行泵送性能试验,发现在驱动电压50 V下,测得泵送流量为32.50 mL/min,仿真流量与试验流量相对误差为28.5%,进而分析了误差产生的原因,最大泵送压差值为13.7 mm.试验结果具有良好的稳定性,验证了仿真数据结果的可靠性,可为压电泵新型放大机构和压电叠堆驱动方式的进一步研究提供可靠参考.

三维桥式放大机构的柔性微定位平台的研究与改进

在微定位平台的设计中,引入能够产生高位移放大倍数的三维桥式放大机构,并在此基础上引入了能够有效减少输出端寄生位移的四杆对称式导向机构,从而使所设计的微定位平台能够充分结合二者优势。根据应变能理论、卡氏第二定理、拉格朗日定理,建立该微定位平台的静动态数学模型,理论分析了平台关键尺寸对平台位移放大倍数的影响;并通过计算获得了最优参数下的放大倍数和固有频率,其值分别为19.90和193.26 Hz。通过有限元方法验证了放大倍数和固有频率,其相对误差分别为4.3%和5.9%,从而证明了所改进的微定位平台的优越性能以及理论分析方法的准确性,为放大机构的柔性微定位平台的数学模型构建提供了一定的理论指导。

基于轴承式杠杆机构的光纤光栅高频地震检波器设计

针对目前高频段信号波的研究相对薄弱的问题,设计了一种基于轴承式杠杆机构的光纤光栅高频地震检波器。该检波器以杠杆机构和其中的轴承支点为创新点,使用仿真软件对检波器模型进行了静态结构分析、模态分析和谐波响应分析。仿真结果表明:该地震检波器的仿真灵敏度为64.588 pm/g,仿真固有频率为1638.5 Hz;调整杠杆放大机构动力臂与阻力臂长度比例和摆线铰链的切割半径,得到检波器的仿真固有频率为1204.4 Hz,仿真灵敏度为75.56 pm/g。

地震作用下岩质边坡的动力破坏过程及破坏机制分析

文中利用FLAC3D的动力分析模块,以ELCentro地震波水平动力荷载作为动力源,考虑了拉破坏对岩质边坡破坏的影响,研究在地震作用下岩质边坡的动力破坏过程、坡面处加速度放大系数及地震峰值水平加速度与破坏深度之间的关系。结果表明,在地震作用下,岩质边坡的破坏不是单纯的剪破坏,而是由坡顶的拉破坏和坡脚的剪破坏逐渐形成贯通面而导致的,且坡面顶部加速度放大系数大于坡面中部加速度放大系数,并大于坡面下部加速度放大系数,表现出明显的“鞭鞘效应”,同时随着地震峰值水平加速度的增加,边坡破坏面逐渐加深。

全柔性微位移放大机构的设计技术研究

全柔性机构是一种新型机构,通过采用免装配、无间隙和无摩擦的设计方式可实现微米级甚至纳米级的高精度。其重要的应用之一是可作为精密驱动系统中的运放机构。为此,对此类机构进行了较为系统的研究,包括典型的结构类型、结构设计中的诸多考虑以及新型运放机构的开发等。所有这些都为精密作业领域中驱动系统的构筑提供了丰富的参考素材。

压电驱动型电液伺服阀前置级驱动器实验研究

针对电液伺服阀电磁式前置级驱动器频响低的问题,提出了一种压电驱动型电液伺服阀前置级驱动器,该驱动器以压电叠堆(积层式压电微位移器)为驱动元件,通过基于三角形放大原理的柔性铰链放大机构,放大压电叠堆的输出位移.同时,设计、研制了实验装置,并在试制样机上对其静、动态特性进行了实验.研究表明,该驱动器具有线性良好、高分辨率、高频响等特点,由有限元分析得到的固有频率达到了1 201kHz,实际测量的固有频率为1kHz.

应用于压电叠堆泵的微位移放大机构

提出了一种应用于压电叠堆泵的微位移放大机构,该机构以压电叠堆(积层式压电微位移器)为驱动元件,通过基于三角形放大原理的柔性铰链放大机构,放大压电叠堆的输出位移。同时,设计、研制了实验装置,并在试制样机上对其静、动态特性进行了实验。实验测试结果表明:该机构对压电叠堆输出位移的放大倍数达到5倍,并且该机构具有线性良好、高分辨率、高频响应等特点。由有限元分析得到的固有频率达到了1.8 kHz,实际测量的固有频率为1.5 kHz。

压电位移放大机构的力学解析模型及有限元分析

研究了压电位移放大机构的运动学和动力学建模问题。基于能量守恒原理和弹性梁弯曲理论推导了桥式位移放大机构的位移放大比等静力学解析模型;在此基础上,通过拉格朗日方程建立了桥式位移放大机构的固有频率解析模型。通过有限元计算验证和分析了提出的解析模型的可行性和优越性,并与国内外典型的位移放大比数学模型进行了比较。结果表明:由于本文提出的模型考虑了位移放大机构的拉伸和弯曲变形,并且摒弃了国内外普遍采用近似几何关系进行数学推导的思路,因此所建立的位移放大比解析模型精度更高;固有频率解析计算结果与有限元模态分析结果的相对误差约为5%。得到的结果显示:本文给出的建模方法以及位移放大比、固有频率等解析模型可为柔性机构的优化设计和研制提供依据和参考。