Selection of maximum power transfer region for resonant inductively coupled wireless charging system

In order to uphold the maximum power transfer in a resonant inductively coupled wireless power transfer system, an operating region has been proposed based on the coupling coefficient, frequency and electric load. The effectiveness of the proposed condition has been examined both theoretically and experimentally. The obtained results are in well agreement with each other. It has been seen that the operating frequency region is different for different electric loads corresponding to the coupling coefficient between the transmitter and receiver coils of the resonant inductive link. The operating frequency region shifts to lower frequency side for lower value of electric load at larger value of coupling coefficient even maintaining the optimum power transfer. The obtained knowledge reveals the design modus operandi through which an effective wireless charging system can be intended not only for low power device applications but also for high power EV charging.     

压电式微固体模态陀螺谐振频率自动跟踪电路

压电式微固体模态陀螺振子通过交变电压激振、传感电极感应出电荷。当激励电压频率为某阶振动模态谐振频率时,感应电荷达到最大值。设计了谐振频率自动跟踪电路,使陀螺稳定工作在谐振模态。使用现场可编程门阵列(FPGA)控制直接数字频率合成器(DDS)产生频率精确可调的激励电压,驱动陀螺振子振动。检测谐振点对应的激励电压和感应信号间的相位差,作为反馈信号调节激励电压频率。实验结果表明,当相位差锁定区域处在98.48°~100.27°时,振子感应电极输出信号最大,振子处于谐振状态,实现了振子谐振频率的跟踪锁定。该系统可用于以谐振器为核心器件的振子工作模态锁定与跟踪。     

AlN薄膜异质结构声波激发特性研究

该文分别开发了两种基于AlN压电材料和原子数分数为10%的Sc掺杂AlN压电材料的薄膜叠层异质谐振器。通过有限元仿真和实验对比分析了器件的频率温度性能和Sc掺杂对谐振器声激励的影响。结果表明,Sc掺杂可能会影响压电薄膜叠层谐振器所激励声波的谐振频率、机电耦合系数和对应的频率温度系数(TCF),且对所激励声波的正反谐振点的TCF影响不同。此研究在传感及滤波器件领域极具应用潜力。     

Analytical modeling of piezoelectric vibration-induced micro power generator

In this article, a novel piezoelectric cantilever bimorph micro transducer electro-mechanical energy conversion model is proposed. Based on the curvature basis approach, the relationship between the deduced voltage and the mechanical strain induced piezoelectric polarization is formulated. In addition to the working equation for piezoelectric sensors, the damping effect is included to enable the resonance frequency, the maximum induced voltage at the resonance, the conversion energy density and the dimensions of the piezoelectric micro power generator to be analytically estimated. The analytical model shows that the vibration-induced voltage is proportional to the excitation frequency and the width of the device but is inversely proportional to the length of the cantilever beam and the damping factor. To verify the theoretical analysis, two micro transducer clusters are fabricated. The experimental results demonstrate that the maximum output voltage coincides with the energy conversion analytical model.     

压电单晶扬声器低频性能的优化及实验研究

压电扬声器因其压电谐振式工作原理而成为顺应电子设备小型化趋势的研究热点,但是由于低频性能不突出而限制了其应用。该文为了降低压电扬声器谐振频率,在分析压电扬声器低频振动原理的基础上,提出了基于弯曲振动模态的压电单晶切型计算模型,并通过计算确定了其优化切型;利用有限元分析法验证了切型对扬声器谐振频率的影响;制作了扬声器原型器件,并对其谐振频率进行了测试与分析。结果表明,该文计算得到的优化切型将压电扬声器的弯曲谐振频率降低了约10%,证明该文提出的切型判断方法能够有效降低压电扬声器的低频谐振频率。     

电极激励超声谐振谱压电材料定征技术

超声谐振谱（RUS）是一种压电材料单样品定征技术,避免了多样品造成的结果不自洽问题。现有的谐振谱激励方法常使用超声换能器定点激励 拾取,需要有复杂的测试装置。该文提出了一种电极激励 拾取法来获取压电谐振器的超声谐振谱,该方法测试装置简单,同时还可获得模态振型的对称特性,避免了反演过程中峰丢〖JP2〗失和错峰拟合。基于现场可编程门阵列(FPGA)技术搭建了压电谐振器分组扫频激励电路,通过电荷放大器拾取谐振峰。结果表明,通过Levenberg Marquardt算法可完成测试频谱和计算频谱的匹配,成功获得了优化后压电材料参数。     

多向振动俘能器设计及能量收集实验研究

针对线性、单一的振动能量俘能器存在工作频带狭窄、只能采集单向振动等问题,该文提出了一种适应货运列车等多向振动应用场景的新型多向振动俘能装置,以增强对环境中振动能量的俘获。该装置结合压电和电磁俘能器,通过螺旋圆柱弹簧和顶端质量有效捕获多向振动,并通过磁力传递振动能量至压电梁。合理设计了弹簧-质量结构,使其在较低的频率范围内可实现多种振动模态,拓宽了俘能器的谐振频带。为了充分利用压电材料,采用了变宽度压电悬臂梁,使应力均匀分布。压电梁自由端的永磁体随着压电梁的振动而产生变化的磁场,在线圈中产生感应电压。通过有限元分析和实验测试,验证了复合式俘能器可以采集多向振动能量,并测试了在z向振动激励下压电、电磁及复合式俘能器的最大输出功率。在频率9.5 Hz、z向振幅2 mm的正弦波激励下,复合式俘能器输出最大功率为3.276 mW。该系统在理论上可为低功耗传感器提供持续电力,为机械能收集与能量转换领域提供技术支持。     

电磁感应式无线充电发热与电磁辐射仿真研究

目前大多数对于无线充电电磁环境安全的研究都局限在电动汽车磁共振式无线充电,然而电磁感应式无线充电装置更接近人体,使用时间更长,本文针对电磁感应式无线充电导体异物易感应出涡流引起发热以及人体电磁辐射问题进行了仿真研究. 无线充电系统结构参考Qi标准,首先利用参数电路对负载电阻、线圈间距及偏移距离对传输效率和输出功率的影响进行仿真;随后使用确定的参数仿真研究不同材质的导体异物在30 min内的温升. 仿真结果表明:当导体异物正对线圈时温升明显,金银等材料的温度均可达100 °C以上;当导体异物不正对线圈时,温升在可接受范围内. 最后使用CST仿真得到电磁场强度、人体温度以及CEM43 °C热剂量值,以此来体现电磁感应式无线充电对人体电磁辐射的非热效应及热效应,电场最大值0.642 7 V/m,磁场最大值2.694 0 A/m,人体大脑温度最高37.3 °C,CEM43 °C热剂量值0.009 5,结果基本在正常参考值范围内. 本文研究有利于电磁感应式无线充电装置的推广应用.     

Tunable Capacitor Based on Polymer-Dispersed Liquid Crystal for Power Harvesting Microsystems

A tunable capacitor based on polymer-dispersed liquid-crystal (PDLC) technology is presented in this paper. Its application for robust power harvesting microsystems was investigated. The power harvesting device utilized a piezoelectric microcantilever excited by ambient random vibrations to convert mechanical energy into electric power. For improving the power harvesting efficiency, the PDLC tunable capacitor was used to adjust the resonance frequency of the piezoelectric microcantilever beam to match the frequency of the ambient vibrations in real time. The fabrication process and measurement results of the PDLC tunable capacitor are detailed. The measured tuning ratio of the PDLC tunable capacitor was 63% at 300-Hz excitation frequency when a 25-V driving voltage was applied. The dielectric and optical properties of the fabricated PDLC tunable capacitor have been examined thoroughly. Based on the results of the experiment, an equivalent lumped-element model of the PDLC tunable capacitor has been developed. The simulation results showed that the impedance of the developed model agreed well with that of the fabricated tunable capacitor. This model can be incorporated into the equivalent circuit of the integrated power harvesting system for efficiency optimization.     

压电谐振式微质量测量系统

基于压电晶体的正、逆压电效应,对压电谐振器的构成原理及压电晶片谐振频率的质量敏感原理(Sauerbrey方程)进行了分析。基于Sauerbrey测量原理,设计了压电谐振式微质量测量系统,对该系统的设计方案进行了分析。为减小温度等环境因素对压电晶体检测性能的影响,系统采用两个相同的石英晶体振荡电路构成双谐振式的压电晶体振荡器。采用模块化设计思想,对该测量系统各模块进行了设计与实现,并对系统性能进行了测试。结果表明,当测量端加载的质量越大,系统测量出的谐振差频值则越大,实验结果与理论分析结果吻合较好。相对于线性的理论结果,该实验结果的非线性误差为5.5%。该系统实现了压电谐振频率的变化与被测微质量之间的变换,能够实现对微质量进行测量。     

Wireless tactile sensing element using stress-sensitive resonator

Robots that work with humans require a soft sensor skin to cover the entire body. In this paper, we propose a new method to realize such a skin. By implanting wireless sensing elements in an elastic body, we obtain an elastic and tough sensor skin which is able to be shaped freely. The element is a passive resonator chip whose resonant frequency reflects the stress around the chip. The resonant frequency is read out by a ground coil located at the bottom of the skin. The chip is simply composed of three functional parts: a coil for receiving and transmitting electrical power with wireless coupling, capacitance sensitive to stress, and ceramic resonator to provide high-Q resonance. The high quality factor brought by the ceramic resonator enables one to distinguish a large number of chips, and to sense the stress with high accuracy. The structure, the method of wireless signal detection, and basic experiments of tactile sensing are presented     

A Branched Beam-Based Vibration Energy Harvester

In this paper, a strategy to utilize a branched beam system to improve the frequency response characteristic of vibration energy harvesting is demonstrated. A basic unit of the device consists of several branch beams with proof mass at their ends and one main cantilever beam with a piezoelectric component at its root and proof mass at its end. The device can utilize the resonance of the branch beams and main beam to generate multiple output voltage peaks, providing a better frequency response characteristic than that of the conventional piezoelectric vibration energy harvester. Multiple branch structure and multiple basic units with similar structures can be connected to generate more output voltage peaks in the frequency response characteristic. Only one piezoelectric component is needed in the device, which makes it competitive in the management of harvested electric energy.     

一种新型阶梯盘形压电陶瓷变压器

提出并研究了一种新型阶梯盘形压电陶瓷变压器,与传统的点环形盘形压电陶瓷变压器相比,原来整个压电陶瓷圆盘由不同厚度的压电陶瓷内盘和外环所代替。论文应用压电方程并结合相关弹性理论对厚度极化的压电陶瓷圆盘和圆环的径向振动进行分析,并利用解析法获得了新型变压器径向振动的机电等效电路。在此基础上,得出了新型变压器的输入阻抗、共振频率、反共振频率、电压增益和功率效率的解析解;将计算所得共振频率、反共振频率与ANSYS模拟结果进行比较验证,模拟结果和理论计算值相吻合;且分析探讨了新型压电变压器的几何尺寸对最大电压增益和其对应的频率的影响。     

悬臂梁式压电振动能量收集系统输出功率的优化研究

针对环境振动能量较小、振动源频带较宽导致压电能量收集系统输出功率较低的问题,探究了悬臂梁式结构能量收集系统采用并联或串联电感优化统输出功率的方法和特性,分析了不同并、串联电感值对输出功率的影响.鉴于压电悬臂梁的工作频率较低,匹配电感值较大,采用无损模拟电感进行了实验验证.理论分析与实验结果均表明,在不同的激振频率下对应不同的匹配电感值,在偏离谐振频率附近也可获得与谐振状态几乎相同的最大输出功率,从而拓宽了工作频率,提高了压电振动能量收集系统的能量收集水平.当激振频率分别是谐振频率的0.8和1.2倍时,并联或串联电感获得的最大输出功率分别是无电感纯电阻负载的26.4倍和18.2倍.     

Effects analysis of bias and excitation conditions on power output of an environmental vibration energy harvesting device using Fe-Ga slice

With the advent of low power VLSI designs and the mass manufacture of CMOS, the power consumption of wireless sensor nodes has been significantly reduced from mW to μW. This opens up a new and interesting research field, that is, the possibility of converting environmental vibration energy to electrical energy for supplying power to the sensors. In this paper, using magnetostrictive materials slice, that is Fe-Ga alloy, a device for harvesting environmental vibration energy is designed and tested. Compared with piezoelectric materials and Terfenal-D alloy, Fe-Ga alloy offers excellent properties for surviving in tough ambient vibration conditions, including higher energy conversion efficiency, longer life cycles, excellent toughness, reduced depolarization and higher flexibility, etc. The designing of vibration energy harvesting process is based on the coupling characteristics of magnetostrictive inverse effect and Faraday electromagnetic induction. The device consists of a Fe-Ga alloy cantilever beam with a magnetostrictive direction throughout the length. It has magnetostrictive inverse effect during vibration and the internal magnetization state will change. A cantilever beam is surrounded by a pickup coil and voltage is induced due to the magnetic field according to Faraday's law. The energy conversion principle among mechanical, magnetic and electric energy is described through a dynamic equation of motion and in conjunction with an electromagnetic conversion equation. The influence law of bias and excitation conditions on output voltage, power and other characteristics of device are investigated in comprehensive experiments. By knowing these influence laws, it is possible to choose an appropriate number of pick up coil for a definite load resistance, to set an appropriate working frequency range, pre-tightening force and pre-magnetized magnetic field such that a maximum power can be harvested. The results derived here can be used as a design guideline for future studies in optimal design and the modeling of vibration energy harvester and force sensor.     

非铁磁性介质中的磁谐振无线传能系统仿真

理论上磁谐振无线能量传输可以做到很高的效率,然而在实际情况下由于各种各样介质的影响,实测效率与理论值难以保持良好的一致性。为了解决实测效率与理论效率偏差较大的问题,提出了基于等效电路模型的非铁磁性介质中的磁谐振无线能量传输系统。从计算与仿真角度分析了不同介质的对线圈阻抗与谐振频率的影响,且计算与仿真结果吻合良好。提出了介质中高效率系统的设计步骤,优化后仿真结果表明可以提高30%以上的效率。     

风车型低频压电振动能量采集器的研究与设计

基于微机电系统（MEMS）设计了风车型结构的压电振动能量采集器,通过压电效应将低频振动能量转化为电能,用以解决环境中低频能量采集的问题。风车型结构的压电振动能量采集器以硅为基底,以PZT 5A为压电材料,包含上、下电极;4条悬臂梁旋转连接中心质量块与四周固定端,类似于风车结构。数学建模与有限元仿真分析表明,在结构尺寸与材料相同的情况下,圆弧风车型结构的谐振频率较直接连接、直角连接结构的谐振频率更低;4条悬臂梁距离中心质量块越远,谐振频率越低;在0.1g(g=9.8 m/s2)加速度谐振状态下,输出电压约为6.2 V,最大位移接近1.2 mm。基于MEMS工艺,通过IntelliSuite软件研究和定义了风车型振动能量采集器的工艺流程。     

Josephson Plasmon Resonance in Tl2Ba2CaCu2O8 High-Temperature Superconductor Tunable Terahertz Metamaterials

The Josephson plasmon resonance (JPR) offers a valuable probe to investigate the superconductivity in layered cuprate superconductors. However, the coupling between free space radiation and JPR in high-temperature superconductor (HTS) film remains challenging because the excitation of JPR demands the c-axis oriented electric field. The subwavelength resonators in metamaterials can enhance the localized electric field, which can be utilized to resolve this difficulty. Here, a tunable terahertz (THz) metamaterial made from Tl₂Ba₂CaCu₂O₈ (Tl-2212) HTS film is developed. The spectral response of Tl-2212 metamaterial has a tunable property at temperatures up to 90 K. The resonant excitation of Josephson plasmon in the metamaterial is observed. Simulation results indicate that the scattering of subwavelength resonators can provide the component of the z-axis electric field for the resonant excitation. The coupling between JPR and resonance modes of metamaterials is observed and explained using coupled mode theory. The temperature dependence of JPR frequency shows accordance with the experimental results of the pure film. This work provides an avenue to excite the JPR and probe superconducting condensate in the layered superconductor. The development of Josephson plasmonic metamaterials may contribute to tunable and nonlinear THz devices.     

基于有限元方法的超声波仿真研究

针对超声波传播的瞬态问题,提出了一种基于多物理场耦合仿真方法。分别对超声波在流体、各向同性材料、各向异性材料中传播的问题以及压电材料作为声源的问题进行了仿真,并与理论结果进行了对比,结果表明该方法能够较好的仿真超声波传播的问题;在各向异性材料中,不同传播方向的波速不同,某一传播方向纵波速度高,则该方向横波传播速度低,反之亦然;压电材料作为声源时,激励电信号频率与压电材料谐振频率相同或接近时,产生的超声波杂波较少,因此激励电信号频率的选择应该以压电材料的谐振频率为参考。     

Wearable,Human‐Interactive,Health‐Monitoring,Wireless Devices Fabricated by Macroscale Printing Techniques

Wearable human‐interactive devices are advanced technologies that will improve the comfort, convenience, and security of humans, and have a wide range of applications from robotics to clinical health monitoring. In this study, a fully printed wearable human‐interactive device called a “smart bandage” is proposed as the first proof of concept. The device incorporates touch and temperature sensors to monitor health, a drug‐delivery system to improve health, and a wireless coil to detect touch. The sensors, microelectromechanical systems (MEMS) structure, and wireless coil are monolithically integrated onto flexible substrates. A smart bandage is demonstrated on a human arm. These types of wearable human‐interactive devices represent a promising platform not only for interactive devices, but also for flexible MEMS technology.