多方向压电振动能量收集装置及其优化设计

摘要：为实现对不同方向环境振动能量的收集,提出了一种新颖的多方向振动能量收集装置的设计结构,装置的换能部分采用了一种Rainbow型压电结构。为提高多方向振动能量收集装置收集能量的效果,以多方向振动能量收集装置输出的总电能为目标函数,综合考虑金属弹性基片的强度、装置振动的固有频率及装置的尺寸空间要求等多种因素,采用序列二次规划法对能量收集装置的结构参数进行了优化。该多方向振动能量收集装置经过优化后,在Y向激励时,其输出的总电能为37.146μJ,比优化前提高了30.82%,当沿装置体对角线方向激励时,结构装置输出的总电能为58.715μJ,比优化前提高了29.24%,装置的能量收集效果得到了明显提高。分析结果为多方向振动能量收集装置的设计、制造及应用提供了技术依据。     

二维声学黑洞应用于压电振动能量收集

声学黑洞(acoustic black hole, ABH)效应可以产生强烈的能量集中,能够将高频率低振幅的低品质振动能量转化为高振幅的高品质振动能量,从而便于利用。提出并研究了一种环形二维声学黑洞压电能量收集装置。有限元分析结果表明,环形二维ABH结构能在宽频域内显著提高能量收集效率。搭建了环形二维声学黑洞压电能量收集器试验测试平台,通过试验验证了仿真结果的正确性。与经典二维ABH结构相比,环形二维ABH结构具有更好的能量收集效率和结构强度。分析了压电片几何尺寸等因素对装置能量收集效率的影响,得到了能获得较高输出功率的几何尺寸范围,并进行了正交试验设计,研究了截断厚度、压电片尺寸、中央平台直径、幂指数等多因素的综合影响。     

谐振式压电叠堆的高效换能结构研究

压电叠堆具有纵向机电耦合系数高、耐疲劳性强的特点,但在低频振动条件下,压电叠堆的机电转换效率低,从而限制了其在结构振动能量收集方面的应用。通过将谐振频率接近结构振动频率的谐振器附加在压电叠堆表面形成谐振式压电换能系统,可以有效提高谐振频率附近的机电能量转换效率。本文对谐振式压电换能结构进行参数建模,以压电叠堆所受纵向力与结构激励力的比值衡量谐振式压电叠堆的换能效率,确定系统有效换能频带的宽度与系统的结构设计参数的关系,从而给出谐振式压电换能系统参数优化设计方法。谐振式压电换能结构的实验表明谐振器能有效增加较低振动频率下的机电能量转换效率,提高输出的开路电压     

共振频率可调式非线性压电振动能量收集器

振动能量回收技术能够将环境中的机械振动能转换成电能,进而为微功耗装置供电,具有良好的应用前景。设计了一种利用压电材料的新型振动能量收集器,该机电耦合结构由一对非对称压电悬臂梁组成,悬臂梁末端固定有永磁体,利用永磁体产生的非线性力,实现了悬臂梁共振频率与外界激振频率的匹配调节。提出了该结构的理论模型,借助Matlab/Simulink数值分析软件对理论模型进行了仿真分析,并通过实验进行了验证。实验结果表明外界激励加速度幅值为3 m/s~2的时,结构即能实现较大频带范围内的频率匹配调节,频带范围不低于6.5Hz,最大回收功率不低于2 mW。     

基于压电效应的时均流能量收集研究进展

基于压电技术的时均流能量收集是一种新型的环境能量收集形式,具有结构简单、成本低廉、无污染、无电磁干扰和使用寿命长的特点。按照不同的时均流能量收集原理分类介绍了最新研究进展,对各种装置之间的性能做了比较,其中采用时均流激声发动机驱动压电换能器的方法能够实现更高的能量转化效率。     

多方向振动能量收集装置输出特性分析

针对一种压电振动能量收集装置输出特性展开研究,以实现多方向、宽频振动能量收集。首先,建立压电悬臂梁单自由度振动系统的微分方程,分析外激励下悬臂梁的输出响应。在此基础上,采用COMSOL建立多悬臂梁式振动能量回收装置有限元模型,并进行模态、输出电压及输出功率等分析,仿真结果表明振动能量回收装置在不同方向激励时均具有较高的电压、功率输出。此外,进一步讨论了装置的在不同方向激励下宽频输出特性,结果显示其在200～400 Hz频带范围内具有多个幅值相当的峰值。     

基于宽频-多模态的复合俘能器的解析模型与实验研究

为提高单频压电振动俘能器的能量转换效率和工作频带,结合压电和电磁能量转换机制,提出了一种新的混合俘能器系统。该系统由PZT悬臂梁、弹性悬挂磁铁块、粘附于悬臂梁末端磁铁块及谐振器等组成,引入谐振器及磁铁可实现增加系统模态数量和非线性。基于此混合振动俘能器建立了改进型连续体机电耦合解析模型,并由龙格-库塔算法进行了求解。在此基础上,研制了振动俘能器原理样机,并搭建了实验系统,通过实验和解析评估方法完成了单一式和复合式俘能器性能比对和评估;研究表明,所研究的混合型振动俘能器相对常规振动能量俘集原理可实现较宽的频率范围及多模态振动能量俘集,且能量俘集效率明显提高,具有较好的应用前景。     

基于拓扑优化的压电分流阻尼抑振实验研究

将结构拓扑优化引入压电分流振动抑制中,以压电元件的分布面积为设计变量,压电元件产生的电荷最大化为优化目标,对压电元件的拓扑进行了优化以获得最佳抑振效果。针对悬臂梁结构,得到了对不同的结构模态进行抑制时的压电元件最优拓扑构型。建立了带有压电分流阻尼系统的悬臂梁振动控制实验模型,将压电元件拓扑优化后的压电分流阻尼系统应用于悬臂梁多阶弯曲模态的振动响应抑制实验,并对比分析了带最优拓扑和非优拓扑压电元件的悬臂梁压电分流阻尼抑振效果。结果表明,对压电元件进行拓扑优化可以明显提高压电分流阻尼系统的抑振效果。     

基于能量有限元法的功能梯度梁振动分析

功能梯度材料(Functionally Graded Material,FGM)由于其优良的结构性能和重要的应用价值,近些年来得到了广泛的研究和关注。采用能量有限元法对功能梯度梁和耦合梁的弯曲振动特性进行研究,推导了功能梯度材料梁的能量密度控制方程、能量有限元矩阵方程以及耦合梁的能量有限元方程,从而得到梁中的能量密度和能量流。以一简支功能梯度梁为例,分别采用该方法和传统有限元法计算了梁弯曲振动时的能量密度,通过对比验证了能量有限元法求解的准确性。在此基础上进一步对耦合功能梯度梁结构的能量密度和能量流进行了求解,得到其能量分布特征。该研究为基于能量有限元法分析复杂功能梯度材料结构的振动特性提供了理论基础。     

垂向动磁式压电振动能量收集器建模及实验研究

该研究展示了一种垂向动磁式压电振动能量收集器,利用垂向磁铁的非线性力改善了单一悬臂梁的收集性能;为了对该结构进行设计分析与参数优化,建立了集总参数理论模型,利用仿真对多种模式进行了研究。聚焦于低频排斥模式,利用实验开展进一步研究;使用铝合金与压电纤维材料MFC搭建了实验平台,并验证了系统的能量收集性能。实验结果表明,该结构能够有效优化能量收集性能,且在误差允许范围内,数值仿真可有效预测结构性质;基于仿真及实验,对结构中的磁铁间距及磁感应强度参数进行研究并进行了最优化,在最优化参数下带宽可提高40.6%,峰值功率可提高42.7%。     

悬臂梁压电振动能采集器的集总参数模型和实验验证

压电振动能采集器是无线传感节点的一种理想电源,近年来受到广泛关注．考虑质量块和逆压电效应影响,建立了在基础激励作用下的悬臂梁压电振动能采集器的集总参数运动微分方程,得到了采集器固有频率的解析表达式．引入了2个反映压电层连接方式的常数,建立了对单压电层、双压电层并联和双压电层串联的悬臂梁压电振动能采集器均适用的耦合电路方程．求解以上方程,得到了简谐基础激励下的输出电压表达式．实验结果表明,固有频率和输出电压表达式的相对误差分别小于10％和20％．     

Z型梁结构压电式能量采集性能分析

振动能量采集能够将外部环境中的振动能转化为电能,具有绿色可持续、节能环保、设计灵活等优势,在工业、生物、医学、军事等领域具有广阔的应用前景.为使振动型能量采集器适应更为复杂多变的工作环境,提高其采集功率和工作频带,提出一种多梁结构-Z型梁结构压电式能量采集器.理论分析了该采集器的固有振动特性,并通过有限元分析了结构尺寸...     

Hybrid Energy Harvesters: Toward Sustainable Energy Harvesting

Recently, sustainable green energy harvesting systems have been receiving great attention for their potential use in self‐powered smart wireless sensor network (WSN) systems. In particular, though the developed WSN systems are able to advance public good, very high and long‐term budgets will be required in order to use them to supply electrical energy through temporary batteries or connecting power cables. This report summarizes recent significant progress in the development of hybrid nanogenerators for a sustainable energy harvesting system that use natural and artificial energies such as solar, wind, wave, heat, machine vibration, and automobile noise. It starts with a brief introduction of energy harvesting systems, and then summarizes the different hybrid energy harvesting systems: integration of mechanical and photovoltaic energy harvesters, integration of mechanical and thermal energy harvesters, integration of thermal and photovoltaic energy harvesters, and others. In terms of the reported hybrid nanogenerators, a systematic summary of their structures, working mechanisms, and output performances is provided. Specifically, electromagnetic induction, triboelectric, piezoelectric, photovoltaic, thermoelectric, and pyroelectric effects are reviewed on the basis of the individual and hybrid power performances of hybrid nanogenerators and their practical applications with various device designs. Finally, the perspectives on and challenges in developing high performance and sustainable hybrid nanogenerator systems are presented.     

Energy Harvesting Research: The Road from Single Source to Multisource

Energy harvesting technology may be considered an ultimate solution to replace batteries and provide a long‐term power supply for wireless sensor networks. Looking back into its research history, individual energy harvesters for the conversion of single energy sources into electricity are developed first, followed by hybrid counterparts designed for use with multiple energy sources. Very recently, the concept of a truly multisource energy harvester built from only a single piece of material as the energy conversion component is proposed. This review, from the aspect of materials and device configurations, explains in detail a wide scope to give an overview of energy harvesting research. It covers single‐source devices including solar, thermal, kinetic and other types of energy harvesters, hybrid energy harvesting configurations for both single and multiple energy sources and single material, and multisource energy harvesters. It also includes the energy conversion principles of photovoltaic, electromagnetic, piezoelectric, triboelectric, electrostatic, electrostrictive, thermoelectric, pyroelectric, magnetostrictive, and dielectric devices. This is one of the most comprehensive reviews conducted to date, focusing on the entire energy harvesting research scene and providing a guide to seeking deeper and more specific research references and resources from every corner of the scientific community.     

基于并联电感同步开关控制的振动能量回收方法研究

针对振动能量回收使用的并联电感同步开关(SSHI)控制方法研究中未考虑的控制损耗、储能负载和激励环境等问题,设计了一种基于电流监控、比较器、单片机和双向电子开关的低功耗回收控制电路。单片机通过比较器产生的中断信号控制双向开关适时闭合,成功实现了并联SSHI回收控制电路的功能。以储能装置为负载时,分析了整流电压、振子电容、激励幅值和频率对并联SSHI回收电路控制效果的影响,结果表明该方法在整流电压值较高、振子电容较大、激励频率较高、激励力较小时能够更有效地提高回收效率,为并联SSHI控制方法的应用奠定了一定的理论基础。     

Time and frequency domain analysis of piezoelectric energy harvesters by monolithic finite element modeling

The successful design of piezoelectric energy harvesting devices relies upon the identification of optimal geometrical and material configurations to maximize the power output for a specific band of excitation frequencies. Extendable predictive models and associated approximate solution methods are essential for analysis of a wide variety of future advanced energy harvesting devices involving more complex geometries and material distributions. Based on a holistic continuum mechanics modeling approach to the multi‐physics energy harvesting problem, this article proposes a monolithic numerical solution scheme using a mixed‐hybrid 3‐dimensional finite element formulation of the coupled governing equations for analysis in time and frequency domain. The weak form of the electromechanical/circuit system uses velocities and potential rate within the piezoelectric structure, free boundary charge on the electrodes, and potential at the level of the generic electric circuit as global degrees of freedom. The approximation of stress and dielectric displacement follows the work by Pian, Sze, and Pan. Results obtained with the proposed model are compared with analytical results for the reduced‐order model of a cantilevered bimorph harvester with tip mass reported in the literature. The flexibility of the method is demonstrated by studying the influence of partial electrode coverage on the generated power output.     

Optimal design of laminated piezocomposite energy harvesting devices considering stress constraints

Energy harvesting devices are smart structures capable of converting the mechanical energy (generally, in the form of vibrations) that would be wasted otherwise in the environment into usable electrical energy. Laminated piezoelectric plate and shell structures have been largely used in the design of these devices because of their large generation areas. The design of energy harvesting devices is complex, and they can be efficiently designed by using topology optimization methods (TOM). In this work, the design of laminated piezocomposite energy harvesting devices has been studied using TOM. The energy harvesting performance is improved by maximizing the effective electric power generated by the piezoelectric material, measured at a coupled electric resistor, when subjected to a harmonic excitation. However, harmonic vibrations generate mechanical stress distribution that, depending on the frequency and the amplitude of vibration, may lead to piezoceramic failure. This study advocates using a global stress constraint, which accounts for different failure criteria for different types of materials (isotropic, piezoelectric, and orthotropic). Thus, the electric power is maximized by optimally distributing piezoelectric material, by choosing its polarization sign, and by properly choosing the fiber angles of composite materials to satisfy the global stress constraint. In the TOM formulation, the Piezoelectric Material with Penalization and Polarization material model is applied to distribute piezoelectric material and to choose its polarization sign, and the Discrete Material Optimization method is applied to optimize the composite fiber orientation. The finite element method is adopted to model the structure with a piezoelectric multilayered shell element. Numerical examples are presented to illustrate the proposed methodology. Copyright © 2015 John Wiley & Sons, Ltd.     

Piezoelectric Energy Harvesting Design Principles for Materials and Structures: Material Figure-of-Merit and Self-Resonance Tuning

Piezoelectric energy harvesters (PEHs) aim to generate sufficient power to operate targeting device from the limited ambient energy. PEH includes mechanical-to-mechanical, mechanical-to-electrical, and electrical-to-electrical energy conversions, which are related to PEH structures, materials, and circuits, respectively; these should be efficient for increasing the total power. This critical review focuses on PEH structures and materials associated with the two major energy conversions to improve PEH performance. First, the resonance tuning mechanisms for PEH structures maintaining continuous resonance, regardless of a change in the vibration frequency, are presented. Based on the manual tuning technique, the electrically- and mechanically-driven self-resonance tuning (SRT) techniques are introduced in detail. The representative SRT harvesters are summarized in terms of tunability, power consumption, and net power. Second, the figure-of-merits of the piezoelectric materials for output power are summarized based on the operating conditions, and optimal piezoelectric materials are suggested. Piezoelectric materials with large k_ij, d_ij, and g_ij values are suitable for most PEHs, whereas those with large k_ij and Q_m values should be used for on-resonance conditions, wherein the mechanical energy is directly supplied to the piezoelectric material. This comprehensive review provides insights for designing efficient structures and selection of proper piezoelectric materials for PEHs.     

Energy harvesting for self-powered nanosystems

In this article, an introduction is presented about the energy harvesting technologies that have potential for powering nanosystems. Our discussion mainly focuses on the approaches other than the well-known solar cell and thermoelectrics. We mainly introduce the piezoelectric nanogenerators developed using aligned ZnO nanowire arrays. This is a potential technology for converting mechanical movement energy (such as body movement, muscle stretching, blood pressure), vibration energy (such as acoustic/ultrasonic wave), and hydraulic energy (such as fl ow of body fl uid, blood fl ow, contraction of blood vessel, dynamic fl uid in nature) into electric energy for self-powered nanosystems.