基于压电悬臂梁振动能量收集器的摩擦自激振动能量收集

针对机械装备滑动摩擦副广泛存在的高强度摩擦自激振动,设计了结构简单的压电悬臂梁振动能量收集器并安装在滑动摩擦副上,以实现将摩擦自激振动能量转换为电能。通过在CETR摩擦磨损试验机上开展摩擦自激振动能量收集试验以及进行相应的有限元和数值仿真分析,验证设计的压电悬臂梁振动能量收集器的效果并分析其机理。结果表明,压电悬臂梁振动能量收集器输出电压的时域演变规律和频域特性与相应的摩擦自激振动信号一致,故设计的压电悬臂梁振动能量收集器可有效地将摩擦自激振动能量转换为电能,实现了摩擦自激振动能量的收集;法向载荷的增大使得输入摩擦系统的能量显著增强,导致摩擦副界面摩擦自激振动强度增大,从而增加了压电悬臂梁振动能量收集器的激励源强度,使其输出电压显著增大;在较大的法向载荷作用下压电悬臂梁振动能量收集器的输出电压最大值达到近4 V且频率较高,可为低功率传感器提供电能供应。     

压电薄膜微传感器的动态特性分析

论述了压电薄膜微传感器的结构和工作原理,应用有限元方法对压电膜微传感器进行了动力学分析。利用有限元软件ANSYS7．0对压电薄膜微传感器结构的振动模态进行了仿真,并拟合了感应电压和动态外力幅度、频率以及结构几何参数之间的关系,这些分析为此类微传感器的设计提供了理论依据。     

滚动轴承测振系统的研究

本文对目前我国使用的轴承振动加速度测试系统进行了理论分析和实验研究,得出下列几点结论性意见：1.从理论计算、实测传感系统的谐振频率和实测轴承振动的频谱,都说明目前所用的弹簧连接的压电晶体加速度计测试系统谐振频率在3～4kHz之间。2.从理论和实验都证明弹簧连接的压电晶体加速度计轴承振动测试系统,在触针和轴承外圈之间加油能降低系统的谐振幅值,而不能提高系统的谐振频率到10kHz以上,谐振频率仍在3～4kHz之间。3.本文对目前使用的动圈式轴承振动速度传感测试系统的谐振频率进行了实测,说明速度传感系统谐振频率在12kHz附近。众所周知,轴承振动频率一般在50Hz～10kHz之间,动圈式速度传感系统谐振频率在12kHz左右,和动圈式速度传感系统测试轴承振动,能真实地反映出轴承的振动情况;而触针式压电晶体加速度计测试系统谐振频率在3～4kHz之间系统的固有频率会影响测值的真实性,因此它不能反映同承的真实振动情况,所以对于轴承这种特殊零件的振动测量,速度传感器比加速度传感器适用。因此本文最后建议用动圈式速度传器对轴承振动进行速度测量。     

高效压电陶瓷加工原理探讨

针对波导管等特殊管状物体内壁的加工,提出了内腔压电超声换能推挤原理,采用了具有频率自动跟踪系统的超声波发生器,自行设计了用于管内腔超声推挤的压电陶瓷换能器,并设计给出了变幅杆--推刀振动子系统的谐振频率、位移节点、放大倍数等计算公式,测出了声学系统的电导--电纳特性,并进行了工艺试验,探讨了超声推挤过程.     

基于模糊控制压电抑振的2R柔性机械臂跟踪实验研究

基于压电陶瓷的模糊控制抑振,利用电阻应变传感器检测机械臂振动信息,经动态应变仪采集到计算机系统,根据控制规律进行模糊运算,得到控制电压,再以该电压驱动压电陶瓷片,产生与振动方向相反控制力矩,抑制机械臂柔性变形,进而改善驱动效果,提高柔性机械臂跟踪精度.实验结果显示,压电抑振效果显著,机械臂跟踪精度也大幅度提高.     

电流变液与压电陶瓷复合的自适应阻尼器设计和...

设计制作了两种电流变液与压电陶瓷复合的自适应阻尼器,其特点是：压电陶瓷响应振动产生高电压,用这个高电压直接去激励固化阻尼器内的电流变液实现了阻尼的自动调节。随着振动频率,振幅的变化,电流变液的响应改变,形成对振动的自适应控制。     

基于啁啾光纤光栅的电压传感性能研究

电压的实时测量是电力系统稳定、安全的关键。提出了一种基于啁啾光纤光栅的电压传感器,利用压电陶瓷的逆压电效应带动黏贴在其上面的传感啁啾光栅发生形变,使传感啁啾光栅的波长发生漂移,通过检测传感啁啾光栅和参考啁啾光栅反射光包络的强度变化,获取被测电压的幅值和频率信息。理论分析了电压与光功率变化的关系,搭建了带温度补偿的双啁啾光栅传感系统,实验研究了传感器的静态和实时动态特性。实验结果表明,该传感器的相关系数R2为0.999 8,电压灵敏度达到0.048mW/V,既能直接检测直流电压,也能较好地检测交流电压及其频谱信息,为在复杂环境评估电能质量提供了参考。     

复合型悬臂梁压电振子振动模型及发电试验研究

单悬臂梁压电振子俘获环境中振动能时,对环境振动频率敏感且频带有限,在谐振频率与环境振动频率不匹配的情况下,会导致压电振子俘能效率低下。基于此,设计复合型悬臂梁压电振子并建立其振动模型,采用激光测振仪对复合型悬臂梁压电振子进行扫频测试。研究结果表明,复合型悬臂梁压电振子谐振频率范围为56～72Hz,与理论分析结果基本吻合,试验验证了理论模型的正确性。相比于单悬臂梁压电振子,复合型悬臂梁压电振子有效地拓宽了其谐振频带,易于实现与环境振动源振动频率匹配以提高压电发电效率。在此基础上,进行复合型悬臂梁压电发电装置的发电能力测试,在负载为820?,工作频率为60Hz时最大输出功率达到4.9mW,产生的能量能够满足网络传感器等低耗能微电子产品的供能需求。     

基于摩擦自激振动升频效应的超低频振动能量收集

低频振动在环境中广泛存在,针对目前低频振动能量收集效率低的问题,提出将外界低频振动转化成摩擦系统的自激振动,实现低频振动到高频振动的升频转换,以达到提高低频能量收集效率的目的 .为此,首先建立了集总参数模型,从理论上阐明低频振动能量收集方法的可行性,并分析模拟了该模型压电电压与功率的输出特性;其次分别设计了往复摩擦自激振动能量收集试验和压电悬臂梁碰撞能量收集试验,对比分析将低频振动转化为摩擦振动能否提高压电输出功率.试验与仿真结果表明,利用摩擦自激振动能够显著提升振动频率.摩擦自激振动电压幅值随着激励频率的增大而增大,与碰撞电压相比,其电压幅值较低,但是频率得到了大幅提升.由于频率的提升,压电振子的能量输出大幅提升,使得超低频振动能量收集性能明显提高.     

压电晶体化学传感器测量用频率计的研制

采用简单的计数方式设计了定时器和计数器,用单片机系统进行控制,实现了压电晶体化学感器频率大小的测量和频率差的计算,并且将差频通过Ｄ／Ａ转换器变换成电压信号,用以区动记录仪。该仪器性能稳定、操作简便、价格低廉,已成功地用于二氧化硫和有机物蒸汽测定的压电石晶体传感器的研制。     

压电智能悬臂梁结构振动主动控制仿真

为了提高LQR最优控制方法对压电类智能结构的振动控制效果,推导了表面离散分布压电元件的柔性悬臂梁结构的驱动和传感方程以及梁的弯曲振动方程,用模态分析方法对方程进行解耦和模型降阶,建立控制系统的状态空间方程。利用有限元分析方法来衡量压电元件对梁固有特性的影响,对状态空间方程的自振频率和振型函数进行修正,得到更为精确的数学模型。通过一悬臂梁的LQR最优控制仿真实例表明,经过模型修正后的最优振动控制效果更好。     

表面对称电极含金属芯聚偏二氟乙烯纤维的简谐振动传感器

模仿蜘蛛毛发感受器的结构和功能,设计制备了表面对称电极含金属芯聚偏二氟乙烯(PVDF)纤维(SMPF)的简谐振动传感器。用挤压拉伸的方法制备纤维胚体,将纵向表面涂镀形状完全对称的导电胶作为外部电极,经过极化后,制备成SMPF简谐振动传感器。基于压电方程和振动理论,建立了悬臂梁结构的SMPF简谐振动传感器的理论模型,分析了传感信号与简谐振动角度和幅值的关系。将SMPF简谐振动传感器固定在基体上,搭建了实验系统,测试了SMPF简谐振动传感器对简谐振动的响应,验证了理论模型。结果表明,SMPF简谐振动传感器能够准确感知简谐振动的频率,传感信号和简谐振动的幅值呈线性关系,和振动方向成"8"字形关系,共振频率为15.6Hz,灵敏度为0.019pC/mm。该SMPF传感器能够测量简谐振动频率、幅值或方向,具有广泛的工程应用前景。     

Vibration Control of a Composite Beam Using Self-sensing Semi-active Approach

Structural vibration control was an active research area for the past twenty years because of their potential applications in aerospace structures,civil structures,naval structures,etc.Semi-active vibration control methods based on piezoelectric actuators and synchronized switch damping on inductance(SSDI) techniques attract the attention of many researchers recently due to their advantages over passive and active methods.In the SSDI method,a switch shunt circuit is connected to the piezoelectric patch to shift the phase and amplify the magnitude of the voltage on the piezoelectric patch.The most important issue in SSDI method is to control the switching actions synchronously with the maximum vibration displacement or maximum strain.Hence,usually a displacement sensor is used to measure the vibration displacement or a collocated piezoelectric sensor is needed to measure the strain of the structure near the piezoelectric actuator.A self-sensing SSDI approach is proposed and applied to the vibration control of a composite beam,which avoids using a separate sensor.In the self-sensing technique,the same piezoelectric element functions as both a sensor and an actuator so that the total number of required piezoelectric elements can be reduced.One problem in the self-sensing actuator,which is the same as that in the traditional collocated piezoelectric sensors,is the noise generated in the sensor signal by the impact of voltage inversion,which may cause extra switching actions and deteriorate control performance.In order to prevent the shunt circuit from over-frequent on-and-off actions,a simple switch control algorithm is proposed.The results of control experiments show that the self-sensing SSDI approach combined with the improved switch control algorithm can effectively suppress over-frequent switching actions and gives good control performance by reducing the vibration amplitude by 45%,about 50% improvement from the traditional SSDI with a separate piezoelectric element and a classical switch.     

Effect of boundary (support) conditions on piezoelectric damping in the case of SSDI vibration control technique

Piezoelectric transducers in conjunction with appropriate electric networks can be used as a mechanical energy dissipation device. If a piezoelectric element is attached to a structure, it is strained as the structure deforms and converts a portion of the vibration energy into electrical energy that can be dissipated through a shunt network in the form of heating. These vibration control devices experienced a great development in recent years, due to their performances and advantages compared with active techniques. One of them is the synchronized switch damping (SSD) and derived techniques, which were developed in the field of piezoelectric damping, and which lead to a very good trade-off between the simplicity, the required power supply and their performances. This technique consists in a non-linear processing of the piezoelectric voltage, which induces an increase in electromechanical energy conversion. The control law consists in triggering the inverting switch on each extremum of voltage (or displacement). In this study, the proposed method for the switching sequence is based on the statistical evaluation of structural deflection. The purpose of this paper is to present an experimental study of the synchronized switch damping on inductance (SSDI) control technique sensitivity to the system boundary conditions. It is observed that the fundamental natural frequency greatly depends on these conditions. The effect of these constraints is distributed all over the system and significantly affects the results.     

基于ILC的压电微位移驱动器电源线性化研究

压电微位移驱动器是一种利用压电材料逆压电效应制作的微位移器 ,具有体积小 ,分辨率高 ,重复性好 ,不产生热等优点 ,然而压电驱动器也具有滞回、蠕变、严重的非线性等不良特性 ,给驱动器精确定位带来误差 ,使驱动器电压位移转换信号失真。为使压电驱动器输入输出具有线性度 ,常用的方法是对驱动电源进行电压补偿来实现线性化。这里提出一种实用新颖的电源线性化方法—基于迭代自学习控制 (IL C)策略的线性化方法 ,该法具有在线、快速的优点 ,且可实现动态线性化补偿     

Real-time digital compensation to reduce acceleration's sensitivity in quartz resonator

The paper presents a digital compensator imposing real-time voltage to compensate the frequency offset of quartz resonator under acceleration. To begin with, a triple-axis MEMS acceleration sensor, whose package is less than 3 mm × 3 mm × 0.9 mm, is mounted at the bottom of quartz resonator. Then acceleration sensitivity vector, based on sensor's coordinator, can be calculated by imposing sinusoidal vibration on singular axis and measuring the amplitude of sideband. So, the frequency offset can be calculated and the compensate value can also be inferred. A digital circuit is designed to generate compensate voltage real time to counteract the frequency offset. A FPGA is employed, which can realize computation in one clock period. Experiments show that the digital compensator presented here has a good effect at low frequency vibration just at which mechanical cushion is ineffective. At steady state, it can almost eliminate the frequency offset. Because of the integration and miniaturization of digital elements, the whole compensator is flexible, low cost, and easy to be applied.     

压电阵列径向分布的二维振动能量采集器

为了有效采集多个方向的振动能量,本文提出了一种圆柱形的压电阵列径向分布的二维(2D)振动能量采集器。通过将柔性弧形压电阵列径向分布在圆柱体上,该采集器可以收集到二维(2D)平面内任意方向的振动能量。同时,引入了角度带宽来描述采集器获取二维振动能量的能力。实验结果表明:这种新型结构采集器的角度带宽接近180°;而且,通过把对称位置的聚偏二氟乙烯(PVDF)压电元件进行反向串联,采集器的最大输出电压可以达到11.6V;当把对称位置的聚偏二氟乙烯(PVDF)压电元件反向并联时,最大输出功率达到13.5μW。与传统的悬臂式压电振动能量采集器相比,该二维(2D)采集器具有更好的多方向振动能量采集性能。     

基于机械振动信号的锂离子电池组连接故障诊断

为满足高电压大容量的实际应用场景和需求,锂离子电池组往往由成百上千的电池单体通过螺栓、焊接等方式串并联组成。电池组单体间的连接故障会导致接触电阻升高和连接处异常发热,严重影响电池组的性能和安全。提出一种基于机械振动信号的锂离子电池组连接故障诊断方法。利用压电陶瓷传感器实现电压信号和振动信号的相互转换,在每种故障模式下采集振动信号;基于稀疏测度指标和熵测度方法在频域和时域提取故障特征以描述锂离子电池组在不同连接故障模式下的故障特性;利用最大相关最小冗余算法降低高维特征空间的冗余度,选择出最重要的特征;在此基础上,建立基于差分进化算法优化的支持向量机诊断模型。结果表明,该方法诊断准确度为0.963,可以准确检测到锂离子电池组的连接故障并明确故障发生的位置。     

基于PVDF压电传感器的高压输电塔健康监测研究

针对高压输电塔的健康监测问题,该文设计了一种聚偏氟乙烯薄膜(PVDF)压电传感器,可检测高压输电塔的固有频率,将测得的固有频率与健康时的固有频率对比,分辨出高压输电塔是否受到了损伤。测试结果显示,该PVDF压电传感器表现优良,可以用于实际的信息采集。     

Note: Piezoelectric strain voltage sensing at ultra-low frequencies

Piezoelectric sensors have emerged as a versatile tool for measurement of various quantities such as pressure, acceleration, strain, or force across many industrial applications. When mechanically strained, electric charges are produced inside a piezoelectric transducer. These charges result in an electric field that may be measured as a voltage difference between two electrodes, from which the strain can be inferred. To measure this voltage the sensor must be interfaced with an external device that would typically have a finite input impedance. This, together with the capacitive nature of the piezoelectric sensor, results in an inability to measure strain at low frequencies. We propose a method, based on using a varactor diode in an oscillator circuit, which can result in accurate measurements of the piezoelectric voltage at ultra-low frequencies. We demonstrate successful measurements at 1 mHz.