FeGa/PZT圆柱体复合材料非线性瞬态磁电响应研究

磁致伸缩/压电复合材料在磁场探测领域极具应用前景,然而,瞬态磁场激励下复合材料的非线性磁电效应尚未明确。研究了FeGa/PZT圆柱体复合材料在瞬态磁场激励下的磁电响应特性。实验发现,在瞬态磁场激励下,复合材料输出电压存在阻尼振荡现象,且振荡周期为其固有周期;当瞬态磁场宽度为固有周期倍数时,阻尼振荡现象几乎消失。另外,研究了FeGa/PZT材料对瞬态磁场宽度和幅值的传感特性。结果表明,材料输出电压脉宽与瞬态磁场脉宽呈线性变化;复合材料对10μs、25μs宽度瞬态磁场幅值测量灵敏度分别为17.329 mV/Oe和24.405 mV/Oe。由此可知,FeGa/PZT材料在瞬态磁场测量领域有极大的应用前景。     

GMM 、PZT和超声变幅杆复合结构磁电换能器研究

将超磁致伸缩材料(GMM)、压电材料(PZT-5H)与超声变幅杆复合,构造了一种新型的磁电换能器.超声变幅杆具有聚能和放大应变的功能,可以数十到数百倍增强换能过程中对压电材料的激励,提高机电换能输出和增强磁电耦合效应.实验表明,在800 Oe偏置磁场和峰峰值为1 Oe交变磁场激励下,谐振点处的磁电耦合电压峰峰值达到498 mV,在负载电阻为2.55 kΩ时,输出功率达到4.08 μW.     

一种磁电换能器及其能量管理电路研究

设计了一种双弹性基底磁电换能器,实现较宽频带内的交变磁场能量到电能的转换.并设计了电源管理电路,实现长时间内对磁电换能器输出电能的收集,瞬间放电,驱动负载工作.实验表明,这种双弹性基底磁电换能器的磁电响应带宽比单弹性基底的磁电换能器的带宽有所提高.而电源管理电路中的储能超级电容经过一定时间的充电,当其两端电压达到0.5V时,能量瞬间释放电路工作,成功驱动最大功耗为75nlw的无线传感器节点正常工作,工作时长为620ms.     

采用同轴反相激励非晶合金/压电复合磁电双单元非线性磁电效应的磁传感器

具有高磁导率的非晶合金在低于10Oe磁场激励下就发生饱和磁化,从而非晶合金/压电复合材料在较高幅度、频率为f₀f₀的交变磁场激励下产生非线性磁电效应,通过解调奇次谐波(f₀,3f₀,…)输出,可实现静态/准静态弱磁场测量,且无需另外施加偏置磁场。利用两个同轴配置的FeNiMoSiB/PZT/FeNiMoSiB复合结构单元,设计180°反相磁场激励,并且采用压电双晶片的电连接方式配置两磁电单元压电层输出,从而实现传感器灵敏度倍增和共模噪声抑制。磁电电压信号经差分放大和锁相解调后,得到传感输出信号。测试结果表明：在±100μT线性区范围内,传感器的灵敏度达到2.77×10⁴μV/μT;对频率为1 Hz磁场的最低探测极限为10 nT。     

Terfenol-D/PZT和弹性基板阵列换能器的磁电效应研究

利用共振原理,将磁致伸缩材料(Terfenol-D)、压电材料(PZT-8)复合于弹性基板上构造了一种新型的换能器.当激励磁场的频率等于或者接近于弹性基板的固有频率时,Terfenol-D将驱动弹性基板振动并发生共振,粘结于弹性基板上的压电材料的输出电压将达到最大.实验研究表明,在800 Oe偏置磁场和1Oe交变磁场激励下,在谐振点392 kHz处,阵列结构换能器的最大磁电耦合电压系数和最大输出功率分别达到了235.5 mWOe和2.403μW,相比MP层合结构换能器,分别提高了13.77%和33.7%.     

多线圈磁电感应的逆压电式FBG磁场传感器

将光纤Bragg光栅(FBG)的传感检测技术、直流发电机内部结构的磁电感应原理及压电陶瓷的逆压电效应相结合,研制了一种多线圈磁电感应的逆压电式FBG磁场传感器.设计中采用多线圈磁电感应,输出电流的变化变小,测量均匀磁场的多线圈磁电感应的逆压电式FBG传感器的灵敏度和准确率都能显著提高.对设计的磁场传感器进行了正反行程的重复性测试,并进行对比分析.测试结果表明:该磁场传感器的灵敏度为0.1128 pm/Gs,迟滞为6.61％FS,重复性误差为6.29 ％FS.     

磁致/压电/磁致层合材料磁电响应分析

对沿长度方向振动(LT模式)的磁致/压电/磁致(MPM)层合材料的磁电响应进行了理论分析,其中磁致层沿长度方向磁化,压电层沿厚度方向极化.从压电效应和压磁效应本构方程出发,结合材料的机械运动学方程和电路状态方程,重新推导了LT模式下MPM结构的等效电路,完善了文献中的方法,得到了复合材料的磁电电压系数、开路电流、材料内阻、可供电功率与压电、磁致材料各物理参数以及体积参数之间的关系式.以Terfenol-D/PZT/Terfenol-D层合材料为例,对材料磁电响应进行了数值计算,将计算结果与相关实验结果进行了比较.利用磁电响应仿真结果,对磁电层合材料用于磁敏传感器以及自供电换能器进行了讨论.     

磁致伸缩材料与石英音叉复合低阻尼谐振磁电效应

采用磁致伸缩材料与石英音叉谐振器复合设计了一种低阻尼的谐振式磁电敏感单元。石英音叉工作在弯曲振动模式,音叉叉指结合区域(底部)产生的应力/应变方向相反、弯矩相互抵消,实际为解耦区域。将底部与磁致伸缩材料粘接复合设计谐振式磁电敏感单元的Q值主要取决于音叉谐振器自身的高Q值,磁致伸缩材料的高磁机阻尼被隔离。动态磁场作用下,磁-机-电转换过程可看作一个受迫振动过程,当激励磁场频率接近于音叉谐振频率时,输出电信号最大。实验结果表明:磁电敏感单元Q值高达5 034;谐振磁电电流系数达到799.2 nA/Oe;在接近谐振频率32.774 kHz信号激励下,磁电电流系数相对偏置磁场变化的灵敏度达到5 (nA/Oe)/Oe。     

基于自偏置磁-机-电耦合效应的电流传感器研究

基于自偏置磁-机-电耦合效应,提出了一种新型电流传感器,其由磁电层合材料Sr Fe12O19/Fe Cu Nb Si B/PZT、质量块、基座组成。磁电层合材料Sr Fe12O19/Fe Cu Nb Si B/PZT具有自偏置磁-机-电耦合效应。通过该磁电层合材料与载流电线周围的涡流磁场耦合,该新型电流传感器具有较大的输出电压和电流灵敏度,无需额外的直流偏置磁场等优点。实验结果表明,所提出的传感器在载流电线的电流频率为50 Hz时具有198.91 m V/A的较高灵敏度,并且电流传感器的输出电压与施加的50 Hz电流大小之间呈现出良好的线性关系。另外,提出的传感器还可以区分小至0.01 A的微小电流。这种基于自偏置磁-机-电耦合效应的电流传感原型器件在电流监测领域具有极大的应用前景。     

瞬态电流激励下复合材料Terfenol-D/PZT/Terfenol-D磁电响应研究

磁电复合材料在电流传感领域具有极大的应用前景。以Terfenol-D/PZT/Terfenol-D层合材料为对象,研究了其在方波电流、8/20μs标准雷电流激励下的磁电响应。实验表明材料在方波电流激励的上升、下降沿结束后均以本征频率进行阻尼振荡,同时材料输出电压可以有效跟随电流的上升、下降变化。研究了材料对8/20μs标准雷电流的峰值传感特性,在50 A-3 kA范围内,材料输出电压峰值对感应雷电峰值呈近似线性(R²=0.995 6),灵敏度为6.8 mV/A;同时,随着复合材料与载流导线距离增加,层合材料输出电压逐渐呈指数下降。因此,在实际应用中,为了提高检测精度,Terfenol-D/PZT/Terfenol-D层合材料与载流导线距离应固定。结果表明：磁电复合材料可用于瞬态电流、雷电流测量领域。     

窄带随机激励下三稳态压电俘能器的动力学特性与实验研究

本文研究了窄带随机激励下三稳态压电俘能器的动力学输出特性.首先,建立了非线性三稳态压电俘能器的分布参数型机电耦合运动方程,并基于多尺度法推导得到系统运动方程响应的解析解以及一阶、二阶稳态矩的表达式.其次,分析了磁铁间距、噪声强度和激励幅值等参数对系统稳态响应的影响.研究结果表明,在一定参数范围内,随着噪声强度的增加,压电振动俘能器会经历阱内振动、阱间振动甚至大轨道周期运动,以表现出单稳态、双稳态和三稳态特性;改变磁铁水平间距和竖直间距构造三稳态压电俘能器,其振动幅值和采集电压相较于双稳态明显提高.最后,通过实验比较了压电俘能器在不同位形时的采集性能,结果表明了三稳态压电俘能器的优越性,为窄带随机激励下的非线性振动俘能器的设计提供一定的理论依据.     

Design and experimental study of broadband hybrid energy harvester with frequency-up conversion and nonlinear magnetic force

In this paper, a novel broadband hybrid piezoelectric and electromagnetic energy harvester using in the low frequency vibration environment is proposed, which combines nonlinear magnet force and frequency-up conversion mechanism simultaneously. Performances are studied by theoretical analysis and experimental test. Electromechanical governed equations of harvester are established, and analytical solutions of vibration response, output voltage and power are derived. Then, effects of nonlinear force, spacing between low frequency vibration beam and piezoelectric beam, load resistance and input excitation on harvester performances are investigated by experimental test. It can be concluded that the harvester can be used to work at the low-frequency environment efficiently, and the resonant frequency and harvesting bandwidth can be tuned by the nonlinear force between the magnets and the spacing between beams. Moreover, the larger the nonlinear magnetic force and the smaller the distance between two beams, the lower working frequency and the larger bandwidth. Compared with the corresponding linear apartment, output power and bandwidth of proposed harvester are improved 90% and 125% respectively.

     

A magnetoelectric energy harvester and management circuit for wireless sensor network

This paper presents an electromagnetic energy harvesting scheme by using a composite magnetoelectric (ME) transducer and a power management circuit. In the transducer, the vibrating wave induced from the magnetostrictive Terfenol-D plate in dynamic magnetic field is converged by using an ultrasonic horn. Consequently more vibrating energy can be converted into electricity by the piezoelectric element. A switching capacitor network for storing electricity is developed. The output of the transducer charges the storage capacitors in parallel until the voltage across the capacitors arrives at the threshold, and then the capacitors are automatically switched to being in series. More capacitors can be employed in the capacitor network to further raise the output voltage in discharging. For the weak magnetic field environment, an active magnetic generator and a magnetic coil antenna under ground are used for producing an ac magnetic field of 0.2–1 Oe at a distance of 25–50 m. In combination with the supply management circuit, the electromagnetic energy harvester with a rather weak power output (about 20 μW) under an ac magnetic field of 1 Oe can supply power for wireless sensor nodes with power consumption of 75 mW at a duration of 620 ms.     

Resin-bonded NdFeB micromagnets for integration into electromagnetic vibration energy harvesters

A micromachining technique is presented for the fabrication of resin-bonded permanent magnets in the microscale. Magnetic paste is prepared from NdFeB powder and an epoxy resin, filled into lithographically defined photoresist molds or metal molds, and formed into resin-bonded magnets after curing at room temperature. A coercivity of 772.4 kA/m, a remanence of 0.27 T, and a maximum energy product of 22.6 kJ/m³ have been achieved in an NdFeB disk micromagnet with dimensions of Φ200 μm×70 μm. Based on the developed micro-patterning of resin-bonded magnets, a fully integrated electromagnetic vibration energy harvester has been designed and fabricated. The dimensions of the energy harvester are only 4.5 mm×4.5 mm×1.0 mm, and those of the micromagnet are 1.5 mm×1.5 mm×0.2 mm. This microfabrication technique can be used for producing permanent magnets tens or hundreds of micrometers in size for use in various magnetic devices.     

Comparative study of conventional and magnetically coupled piezoelectric energy harvester to optimize output voltage and bandwidth

Energy harvesting has experienced significant attention from researchers globally. This is due to the quest to power remote sensors and portable devices with power requirements of tens to hundreds of μW. Hence, ambient vibration energy has the potential to provide such power demands. Thus, cantilever beams with piezoelectric materials have been utilized to transduce mechanical energy in vibrating bodies to electrical energy. However, the challenge is to develop energy harvesters that can harvest sufficient amount of energy needed to power wireless sensor nodes at wide frequency bandwidth. In this article, piezoelectric energy harvester (PEH) beams with coupled magnets are proposed to address this issue. With macro fiber composite as the piezoelectric transducer, mathematical models of different system configurations having magnetic couplings are derived based on the continuum based model. Simulations of the system dynamics are done using numerical integration technique in MATLAB software to study the influence of magnetic interactions in generating power and frequency bandwidth due to base excitations at low frequency range. Experimental results comparing conventional system and the proposed piezoelectric beam configurations with coupled magnets are also presented. Finally, the optimal beam separation distance between the magnetic oscillator and PEH is presented in this work.

     

A magnetoelectric-based broadband vibration energy harvester for powering wireless sensors

Scavenging vibration energy directly from environments is an attractive technique for potentially powering small and/or wireless electronic devices in a smart structure and system.In this paper,a novel broadband vibration energy harvester is designed and analyzed,which consists of three cantilever beams,two magnetoelectric(ME) transducers and a magnetic circuit.A theoretical model is developed to analyze the effects of the structure parameters on the frequency response and the electrical output for achievin...     

非线性压电振动能量采集器的振动特性与实验研究

为了提高线性压电振动能量采集器的输出特性,在线性压电振动能量采集器悬臂梁末端引入Duffing非线性磁力,构造了一种双稳态非线性压电振动能量采集器;综合考虑能量采集器的动态振型与轴向应变分布情况,建立了系统非线性机电耦合集总参数运动控制模型,并利用4阶、5阶Runge-Kutta算法对能量采集器的非线性振动特性进行了数值模拟;利用谐波平衡法计算获得了能量采集器的幅频响应方程,数值分析了激励频率、激励幅值以及磁铁间距等对系统非线性振动特性的影响,发现双稳态运动可以极大地提高能量采集器的频率响应范围和能量采集效率,并且能量采集器在低频、低幅值激励情况下可以产生大幅值周期运动;最后,通过实验对数值计算结果进行了验证.     

Giant room-temperature magnetocapacitance in Terfenol-D/PZT/Terfenol-D trilayer composites

The giant room-temperature magnetocapacitance is reported in the Terfenol-D/PZT/Terfenol-D which is composed of a trilayer structure. A giant magnetocapacitance as large as 1200% is observed at the resonant frequency of 52.17 kHz and a saturated magnetic field of 1.5 kOe. We experimentally demonstrate that such magnetocapacitance effect correlates with the frequency shift of harmonic oscillator, i.e., PZT, which resulted from the applied magnetic field. In addition, theoretical analysis shows that the frequency shift is attributed to the product effects of the magnetic field-tuned Young's modulus of the Terfenol-D and the strain-capacitance of the ferroelectrics PZT. One can apply this characteristic of resonance frequency shift to design magnetocapacitance composites with a frequency-tunable magnetic filter.