Numerical and experimental study of bistable piezoelectric energy harvester

Piezoelectric energy harvesting from mechanical vibrations is a reliable technology to charge low power electronic equipment. It has been reported in the literature that low frequency broadband vibrations cannot be harvested effectively using linear piezoelectric energy harvester (PEH). In this paper a bistable nonlinear PEH with two distinct energy wells generated using repulsive magnetic interactions between a cantilever magnetic proof mass and an external magnet is considered. It has been modeled using finite element method and validated with experimental results. Experimental results verify that, for our study, distance between magnetic proof mass and external magnet of 1.32 T flux density should be less than or equal to 8.5?mm for maintaining bistability. This distance also affects to the resonance frequency of harvester. Maximum efficiency of the harvester has been noticed at 8.5mm. Further it has been shown experimentally that the bistable nonlinear piezoelectric energy harvester takes almost half of the time taken by its linear counterpart to charge a 20 mAh battery.     

压电式振动能量采集电源管理电路分析

压电式振动能量采集的应用十分广泛,在许多能量采集装置中都采用压电元件实现能量转换。分析了振动能量采集装置中压电元件采集的能量输出管理电路,包括标准能量采集电路、DC-DC变换的优化标准能量采集电路、同步电荷提取电路、电感同步开关采集电路和双同步开关采集电路等五种电源管理电路的原理,比较了它们的能量采集输出效率,指出了各种电源管理电路的特点和适用条件。     

Piezoelectric materials for bistable energy harvester: A comparative study

This paper deals with the potential of various lead-free piezoelectric materials for energy harvesting. The performance of these materials is simulated for unimorph bistable piezoelectric energy harvester. The finite element method considering first-order shear deformation theory is used to model the system. The energy harvesting potential of bistable system (Non-linear) is compared with its linear counterpart. The results depict that the mean power density is almost 100% higher in case of bistable system. K_0.5Na_0.5NbO₃-LiSbO₃ (KNN-LS) family exhibited better performance than the conventional lead-based piezoelectric material lead zirconate titanate (PZT). The mean power density of K_0.5Na_0.5NbO₃-LiSbO₃-CaTiO₃ (2 wt.%) is reported to be 65% higher than PZT.     

复合式动能采集器的多自由度宽频带设计优化

提出了一种多自由度宽频带压电 磁电复合式动能采集器,该动能采集器可以在多方向采集动能,有效地工作于较宽的频带,且可以同时以压电和磁电方式收集动能,大大提高了动能采集效率。介绍了复合式动能采集器的结构;分析和优化了采集器的拾振系统,从理论上验证了采集器的多自由度和宽频带的特性;介绍了磁电换能系统。研究结果表明,采集器在不同的工作频率下出现了两个振动峰值,验证了采集器的宽频带动能采集特性。通过实验测试进一步得出,与压电或磁电换能系统各自的输出性能相比,压电 磁电复合式换能系统的总体输出性能有所提高。     

基于压电材料的变压器振动能量收集装置研究

变压器振动信号在线监测是检测变压器运行状态的重要手段,振动传感器的供能方式制约了振动检测方法的应用。为了实现振动传感器取能,文中设计了一种基于压电材料的变压器振动能量收集装置,利用收集的振动能量为振动传感器供电。首先,根据变压器振动特性,采用多模态取能方式,建立三悬臂式压电取能结构的输出电压与输出功率模型。其次,通过Comsol Multiphysics仿真分析能量收集装置输出功率和外加激励频率的关系。最后,搭建变压器振动能量收集实验平台,测得压电式能量收集装置的实际输出功率为11.547 μW。利用振动能量收集装置为振动传感器供电,可以保障在线监测设备的供电,减少外接电源对设备安全稳定运行的影响。     

Experimental study on a wide-band piezoelectric energy harvester with rotating beams vibrating in perpendicular directions

We present here a new design for a wide-band piezoelectric energy harvester. Our system consists of two mutually perpendicular cantilever beams with attached PZT (lead zirconate titanate) patches. Traditional piezoelectric energy harvesters can only generate a single resonance peak and therefore they are limited by a narrow band and low power output. In this paper, by using two piezoelectric cantilever beams aligned in a mutually perpendicular direction, two resonance peaks are observed. Additionally, by adjusting the rotation angle of these beams, the operational frequency bandwidth has been enlarged by 70%–100%. Therefore, our new piezoelectric energy harvester has the potential to harvest energy in a wider frequency range for practical applications with variable frequency sources.     

基于Halbach阵列的多方向多模态动能采集器设计

为了使振动能量采集器适应外界振动环境的宽频带、方向随机特性,设计了一套基于Halbach永磁阵列的多方向多模态动能采集器。首先,建立了采集器的立方体-球状物理模型并分析了该模型的动力学特性。接着,设计出采集器的基本结构,重点对弹性梁的设计进行了具体分析,再利用有限元软件对设计出的结构进行动力学分析。同时,在结构设计的基础上,提出了基于Halbach永磁阵列的换能结构,将该阵列与一般的顺次永磁阵列进行比较分析。最后,搭建了实验系统平台,测试出采集器在不同输入激励下的输出电压。实验结果表明,采集器在不同激励方向可以达到对应的振动模态,并且均能产生有效的输出电压。因此,该采集器具有多方向多模态采集特性。     

海洋波浪压电发电装置的进展

本文对海洋波浪压电发电装置的发展进行了回顾。总结和阐明了各种类型装置的性能,指出共振是获得高效率的直接方法。针对变化的海洋环境,优化装置能够有效地提高效率,增加响应的带宽,使装置在较宽频率变化范围内都能保持高效运作,能够适用于实海况随机变化的波浪条件。作者阐明了现有装置的局限性,提出了一种新颖的波浪压电发电装置,该装置将吸收的波能以冲击荷载形式作用于压电发电振子上,使其在各种来波条件下都发生共振,并且以预先设定的频率输出电能。采用具有独立功能的分离式浮体组合,提高波能吸收效率,保障发电机工作环境平稳。最后提出了波浪压电发电研究中所要注意的一些问题。     

Power output estimation and experimental validation for piezoelectric energy harvesting systems

Many modern devices especially for ubiquitous computing or wireless sensor networks need a long life energy source. Batteries or accumulators are often an insufficient solution. Low frequency vibrations can be found in the most technical facilities or even in the human movements. Even while these vibrations are neither wanted nor used in the most times, they enable us to generate electrical energy. Piezoelectric flexural transducers are a promising choice for utilizing the vibrations for energy harvesting. There are two major influences on the amount of generated energy. First there is the frequency behavior of the piezoelectric transducers, for optimal power output the transducer should be driven in resonance. Second, the energy output is highly dependent on the electrical load of the connected application. Both circumstances, working frequency and electrical load, typically are boundary conditions for the development of the generator. Therefore, it is necessary to handpick the type of piezoelectric elements. To meet the requirements of development engineers, a model based design method for energy harvesting systems is needed. As a first step towards such a method, this work proposes a model for the estimations of the power output of piezoelectric flexural transducers. For the validation of this model an experiment is described in detail. The results of the model and the experiments are compared.     

Advances in energy harvesting using low profile piezoelectric transducers

The vast reduction in the size and power consumption of sensors and CMOS circuitry has led to a focused research effort on the on-board power sources which can replace the batteries. The concern with batteries has been that they must always be charged before use. Similarly, the sensors and data acquisition components in distributed networks require centralized energy sources for their operation. In some applications such as sensors for structural health monitoring in remote locations, geographically inaccessible temperature or humidity sensors, the battery charging or replacement operations can be tedious and expensive. Logically, the emphasis in such cases has been on developing the on-site generators that can transform any available form of energy at the location into electrical energy. Piezoelectric energy harvesting has emerged as one of the prime methods for transforming mechanical energy into electric energy. This review article provides a comprehensive coverage of the recent developments in the area of piezoelectric energy harvesting using low profile transducers and provides the results for various energy harvesting prototype devices. A brief discussion is also presented on the selection of the piezoelectric materials for on and off resonance applications. Analytical models reported in literature to describe the efficiency and power magnitude of the energy harvesting process are analyzed.

微型振动式压电发电机的设计与特性分析

为了设计出与应用场合相匹配的微型振动式压电发电机,采用模态分析和谐响应分析方法对压电双晶片发电机的振动特性进行了研究,并分析了压电晶片的长度、宽度、厚度、质量块质量等参数对压电发电机固有频率的影响.在此基础上,基于压电发电机的等效电路模型对发电机的发电特性进行了研究,并分析了压电发电机的上述结构参数对输出电压和功率的影...     

Fabrication and characterization of flexible piezoelectric composites with natural rubber matrix

Abstract

This work aims to fabricate and characterize flexible piezoelectric composites with natural rubber (NR) matrix. Different amounts of Pb(Mg_1/3Nb_2/3)_0.65Ti_0.35O₃ (PMNT) powders were added in NR matrices. Porosity, tensile strength and percent elongation at break of composites tended to decrease with increasing PMNT content. The dielectric constant of the NR materials was found to be 3.5. It was raised up to 4.2, 5.0, 4.5, 4.8 and 5.1 when 60, 80, 100, 120 and 150 phr PMNT powders were added. However, dielectric loss of NR materials did not change with PMNT additions. Among this composite system, the NR/100PMNT composite showed the best piezoelectric properties, which its output voltage, piezoelectric coefficient (d₃₃) and piezoelectric voltage coefficient (g₃₃) values were equal to 1.61 V, 2.1?×?10^?4 pC/N and 5.4?×?10^?6 V?m/N, respectively. This composition composite is a promising material suitable for further improvement to be used as piezoelectric generators in energy harvesting applications.     

轴向电磁轴承多自由度承载力理论与实验研究

为了实现磁悬浮轴承系统的微型化,对轴向电磁轴承的多自由度承载力进行理论与实验研究。基于轴向磁轴承气隙磁通空间分布,利用分割磁场法建立磁路模型,由虚位移法得到轴向和径向承载力的数学表达式。借助有限元仿真软件,得到轴向磁轴承气隙磁感应强度与磁场空间分布。在搭建的磁轴承三维力学测量平台上,实验测量了轴向磁轴承的轴向与径向承载力,分析总结了多自由度承载力随电流、轴向位移和径向位移的变化规律,结合理论与仿真结果,分析了结构参数变化导致气隙磁场分布变化,进而改变轴向与径向承载力的物理机理,为轴向磁轴承实现多自由度悬浮研究提供了参考依据。     

压电式四维力传感器的有限元分析

选用石英作为敏感元,研究一种压电式四维力传感器,根据不同切型石英的特点按特定方式排列组合,构成一个"晶组"式的传感器,实现无耦合测量空间多方向的力和力矩。通过有限元分析,对所提出的压电式四维力传感器进行仿真,得到影响该传感器原型开发的输出电压与输入力之间关系曲线、电压灵敏度、维间干扰等重要性能指标,并证明了该传感器能够有效地实现空间四维力的测量,为研制新型传感器原型奠定了重要基础。     

无源高温超导磁浮轴承磁悬浮力的计算

本文应用有限元方法和超导临界态理论，推导了高温超导体电流分布和电流密度计算方程。由高温超导体电流计算了高温超导磁浮轴承悬浮力。利用实验测量结果验证了此方法的有效性。     

永磁体磁力与永磁隔振系统固有频率分析

永磁体间的磁力是设计永磁磁悬浮隔振系统的基础.分别用理论计算方法、有限元分析方法以及实验测试方法研究了单对柱形永磁体间的排斥力与磁体间距之间的关系,并分析了所构成的非线性振动系统的固有频率特点,同时也实验测试了多对柱形永磁体间的排斥力与磁体间距之间的关系.结果表明,用理论计算方法和有限元分析方法来计算柱形永磁体的磁力是...     

Energy harvesting using piezoelectric materials: Case of random vibrations

A dramatic consumption reduction of integrated circuits related to the development of mobile electronic devices has been reached over the past years, enabling the use of ambient energy instead of batteries. The focus is here on the transformation of ambient mechanical vibrations into electrical energy. This paper compares the performances of a vibration-powered electrical generator using PZT piezoelectric ceramics associated to two different power conditioning circuits. A new approach of the piezoelectric power conversion based on a nonlinear voltage processing is presented and implemented using a particular circuit. Theoretical predictions and experimental results show that the new technique may increase the power harvested by a factor up to 4 compared to the Standard technique. The power optimization problem is in particular examined in the case of broadband, random vibrations.     

Sustainable micro-power circuit for piezoelectric energy harvesting tile

Piezoelectric energy harvesting tiles are used for converting the power of pedestrian footsteps in to electricity and can be used at the micro- and milli-watt level for storage and powering electronics devices. This paper effectively combines the systems and techniques for developing a sustainable circuit with the self-starting and self-power functions to efficiently store energy and drive low power consumption electronic devices from the piezoelectric energy harvester tile. The main part of the system is 80% efficient impedance matching converter with the self-starting and battery-less operation. The presented circuit has an overall efficiency of 63% and can power a wireless sensor node to transmit the information wirelessly.     

基于涡激振动的PVDF压电风能采集实验研究

为提高PVDF压电薄膜的发电能力,研究了一种基于涡激振动机理的PVDF压电能量采集结构,将风能转换为电能以供微功耗电子产品使用。设计了信号调理电路将压电薄膜的电荷输出转换为电压输出,通过微型风洞实验分别研究了在不同风速下,单片、双片、三片PVDF压电薄膜串联、并联的发电性能。实验结果表明：所选取的PVDF压电薄膜的谐振频率稳定在 50 Hz左右;所设计的信号调理电路输出电压随着风速的增加而增加,可有效滤除高频噪声干扰;PVDF压电薄膜并联并在电路末端接匹配负载可有效提高负载功率,三片压电薄膜并联并在信号调理电路末端接1.25 Ω负载时,负载功率最高可达36 mW。     

能量回馈型超声波电机定子振动特性有限元分析与特性测试

提出一种集精密驱动和振动能量采集于一体的新型多功能压电振动电机——能量回馈型超声波电机,设计了电机夹心式内锥面压电定子,建立了电机压电定子的有限元模型,仿真分析定子振动特性和能量采集输出特性;研制电机原理样机,并对电机进行阻抗和能量采集特性测试与分析。研究结果为工作在极端封闭环境中的微型机器人系统提供一种集驱动与供电一体化的机电器件。