非线性振动能量俘获技术的若干进展

随着工程中低功耗电子设备和自供能无线传感网络的迅速发展, 使得振动能量俘获在航空航天工程、机械工程、生物医学工程和可持续能源工程等领域得到了广泛地应用. 振动能量俘获不仅可以将振动能转化为可用的电能为微电子设备供电, 还能减少有害振动保护仪器设备. 根据振动能量不同转换机制, 可以将振动能量俘获系统分为静电式、电磁式、压电式、磁致伸缩式、摩擦起电式以及它们的混合式. 其中压电和电磁振动能量转化机制由于结构简单、容易组装、能量转换性能高等优点, 已被广泛应用于各种工程领域中. 受极端环境干扰, 工程中容易出现宽带、低频等振动, 迫使振动能量俘获技术向非线性方向迅猛发展, 进一步吸引了诸多学者对振动能量俘获系统的结构和电路进行优化设计研究. 本文首先综述了非线性振动能量俘获技术近十年来的研究进展, 主要包括设计技术基础、非线性结构设计、动力学分析等方面的研究现状. 其次, 重点阐述了振动能量俘获与振动抑制一体化的主要研究成果, 包括非线性准零刚度和非线性能量汇在振动能量俘获领域的应用. 最后, 总结了振动能量俘获外接电路和主动控制策略的优化设计, 分析了进一步提升非线性振动能量俘获效能的有效方法.      

柱体流激振动能量俘获理论与技术研究若干进展

潮流能分布广泛,且储量巨大,具备巨大的规模化开发利用价值.流激振动是一种常见的流固耦合现象,通过柱体流激振动能够在流速较低时实现有效的能量转换,基于柱体流激振动的能量俘获技术在未来具备广阔的工程应用前景.近年来,针对柱体结构流激振动特性和能量俘获性能,出现了大量的实验和数值仿真研究工作.文章全面阐述了多种截面形式的单个柱体、柱群结构流激振动能量俘获理论与技术方面的研究进展:对于单个圆柱流激振动能量俘获,目前已基本揭示了被动湍流控制器参数、系统阻尼、雷诺数和边界条件等因素对能量俘获性能的影响规律,基本完成了理论和技术积累;对于非圆截面柱体流激振动能量俘获,已初步明确特定来流攻角、系统质量比、系统阻尼、系统刚度和雷诺数条件下三角形、四边形、多边形与异形等多种截面形式柱体的流激振动作用机理和能量俘获能力;对于柱群的流激振动能量俘获,各柱体振子之间存在流场干涉,需要合理设计柱体排布形式、柱体间距和系统阻尼等参数,实现流体能量俘获最大化.通过综述国内外流激振动能量俘获理论和技术方面的研究进展,对今后该问题的研究进行了力所能及的展望,期望促进流激振动能量俘获理论的发展和流激振动能量转换装置的工程应...     

质量比对D形截面柱体流致振动的影响

利用涡激振动进行海流能收集的VIVACE装置是新能源领域的研究热点.应用FLUENT软件采用k-ωSST湍流模型和Newmark-β法,通过数值模拟探究了四个质量比(2, 5, 7和10)在迎流角90°下D形截面柱体的流致振动响应,系统分析了D形截面柱体在横流向上的振动幅值、频率、平衡位置偏移量、尾涡脱落模式以及能量转化效率.所模拟的雷诺数范围为288～2880,对应的约化速度为2～20.结果表明,质量比对D形截面柱体流致振动的影响明显,质量比会改变D形截面柱体流致振动的响应分支.质量比越大, D形截面柱体进入驰振对应的约化速度越低;质量比增大, D形截面柱体平衡位置偏移量相对减小.随着约化速度的增大, D形截面柱体出现了涡激振动、涡激振动-驰振及完全驰振等响应分支.在所模拟的范围内, D形截面柱体高能量转化效率出现在涡激振动分支,而不是在驰振分支;在质量比为10且约化速度为4.5时,一级能量转化效率达到最大值44%.相关研究可为VIVACE装置的振子选型提供参考.     

流致振动能量收集的钝头体几何设计研究

流致振动蕴含着可观的能量, 通过能量收集技术可将其转化为电能. 为提高低速流场中能量转化效率, 本文实验研究了不同截面下钝头体以及它们的宽厚比(W/T)对流致振动能量收集特性的影响, 并通过计算流体动力学(computational fluid dynamic, CFD)仿真分析了尾流特性. 流致振动能量收集装置由压电悬臂梁和不同截面的钝头体构成. 首先搭建了流致振动能量收集风洞实验平台, 钝头体的截面分别设置为矩形、三角形和D形, 宽厚比分别设定为1, 1.3, 1.8和2.5. 然后利用实验方法分析不同形状钝头体的宽厚比(W/T)对位移响应和电压响应的影响规律. 最后通过计算流体动力学模拟揭示实验结果的内在力学机理. 实验结果表明, 当钝头体截面为矩形时, 增大宽厚比可以显著提高电压输出峰值; 当钝头体为三角形和D形时, 增加宽厚比将使系统呈现“驰振”→“驰振 + 涡激振动”→“涡激振动”响应特性变化趋势, 提高了低风速时的能量收集效果. CFD结果解释了实验现象, 即随着宽厚比增加, 钝头体尾流会产生更加强劲的涡街, 显著提高流致振动能量收集效果. 相关结果可优化流致振动能量收集装置结构, 为提高低速流场的能量收集效果提供理论和实验依据.      

三稳态尾流驰振能量捕获系统发电性能研究

利用流体动能能量发电为微电子器件供电已逐渐成为非线性振动领域的研究热点。利用永磁铁产生非线性回复力，将非线性回复力引入到悬臂梁压电能量捕获装置中，提出了一种三稳态尾流驰振能量压电发电装置，获得力学模型及系统控制方程，获得了三稳态系统的稳定和不稳定平衡点表达式，给出了发电系统存在三稳态运动时的结构参数的取值范围。重点研究了等平衡点不同势阱深度、等势阱深度不同平衡点位置对系统的动力学响应及发电性能的影响。结果表明，等平衡点条件下浅阱系统的起振折合流速更低、发电性能更好。     

振动能量俘获专题序

振动能量俘获技术需要进行多学科交叉融合, 只有能量俘获结构与外接电路协同工作并形成自供能系统, 才能将环境或宿主结构的振动能量最终高效地转化为无线传感网络长久稳定的电能. 通过解决一些非常棘手的力学难题, 振动能量俘获系统的效率可以得到有效的提升, 这其中包括能量俘获结构设计、动力学建模、理论分析、力电耦合机理的研究等. 这是振动能量俘获技术在各个学科应用中所面临的挑战, 同时也是一个共同发展、相互促进的机遇. 通过突破振动能量俘获技术的瓶颈, 将能量俘获推向更广的商业应用平台. 为了提高振动能量俘获系统的效率及其实用性, 需要解决一些基本问题, 包括: (1)如何设计与环境或宿主结构振动特征相匹配的能量俘获结构？(2)如何建立振动能量俘获器的精确动力学模型？(3)如何揭示其中的力电耦合机理？(4)如何高效存储振动能量俘获器产生的能量？围绕上述问题, 《力学学报》组织了《振动能量俘获》这一专题. 由于篇幅限制, 该专题包含了3篇综述论文和11篇研究论文, 从侧面反映了国内科研人员在该方向上的一部分最新研究进展, 供读者参考.      

面向压电振动能量俘获的电能管理电路综述

随着物联网(internet of things, IoT)技术的高速发展, 传统的电池供电方式已经不能满足其供电需求. 利用压电能量俘获技术将机械能转换为电能, 可为IoT提供持久的电能, 具有广阔的应用前景. 本文在讨论压电振动俘能器的电学特性基础上, 全面总结了面向压电振动俘能器的电能管理电路的最新研究成果. 电能管理电路通常由AC-DC变换和DC-DC开关变换器(包括控制算法)两部分组成, 前者用于将压电振动俘能器输出的交流电转变为直流电, 后者用于提高能量俘获效率. 首先, 针对AC-DC变换, 分析了全桥整流器、电压倍增器、同步开关电感电路和同步开关电容电路的工作原理和优缺点. 接着, 重点讨论了用于压电振动俘能器的典型开关变换器电路, 包括电感式、全电容式和变压器式DC-DC开关变换器以及AC-DC开关变换器, 分析了它们的特点和适用场合. 最后, 针对压电振动俘能器的特点, 分析了实现最大能量俘获的几种典型控制算法, 包括最大功率点跟踪、阻抗匹配和同步电荷提取控制算法. 本文通过对面向压电振动俘能器的电能管理电路的全面分析和综述, 揭示了该领域目前存在的瓶颈问题, 并展望了其未来发展方向, 对压电能量俘获自供电系统的研究和开发具有重要的参考价值.      

T形截面振子的流致振动特性试验研究

近年来人们将流致振动(FIV)作为一种新的能源利用手段,针对圆柱型振子开展了较多的研究。随着研究的深入,发现异型截面振子因振动特性不同于圆柱型振子而具有更好的能量汲取特性。本文利用自循环水槽进行T形截面振子流致振动特性试验研究,对比研究T形振子与圆柱振子的流致振动响应差异,分析其能量捕获能力的优劣及适用范围,以期揭示阻尼比对T形振子的振动特性的影响。结果表明:不同于圆形截面振子,T形截面振子的振动表现为"非自限制"特性,出现驰振分支;增大阻尼会抑制T形截面振子的振动与驰振发生的可能性;相对于圆柱型振子而言,T形振子更适用于大流速下的能量汲取。     

基于动态磁耦合的驰振能量收集器动力学分析

为了提高能量收集系统在低风速下的能量收集效率,将动态磁铁非线性引入到驰振能量收集系统中。在悬臂梁的末端和底座上分别安装一对磁极相斥的磁铁,其中安装在底座上的磁铁与弹簧相连,可随着磁斥力的变化而垂直移动。首先,根据能量法建立了磁耦合驰振能量收集系统的多场耦合振动控制方程。其次,通过Runge-Kutta数值计算方法比较分析了低风速下动态磁耦合驰振能量收集系统(DM-GEH)和固定磁耦合驰振能量收集系统(FM-GEH)的电压输出。DM-GEH系统的切入风速提前了81.82%,在1 m/s～5 m/s风速范围内能量收集效率提高了124.22%。最后,针对弹簧支撑刚度进行参数优化,提升了低风速下的能量收集效率。结果表明,通过改变磁铁支撑方式至弹性支撑将改变系统的振动频率并且降低切入风速,相较于弹簧刚度为1 000 N/m时,弹簧刚度为500 N/m时的系统的切入风速降低了54.55%,能量收集效率提高了15.35%。     

压电与摩擦电复合型旋转能量采集动力学协同调控机制研究

低转速激励下能量采集性能差是目前制约旋转能量采集技术应用的瓶颈问题. 本文提出了动力学协同调控机制, 并用于调控系统的动力学行为, 可以使器件在低转速激励下有效工作, 提高了旋转能量采集系统的电学性能. 旋转刚度软化、非线性磁力、几何边界的协同调控既可以增加系统在低速下的振动位移以及压电材料的形变, 也可调控系统的最大位移, 使其振动可控并限制位移过大提高可靠性. 此外, 几何边界可以方便地集成摩擦纳米发电机, 实现压电与摩擦两种机电转换机制在振动和碰撞过程中协同发电, 有效利用空间和提高输出电能. 基于哈密顿原理建立了系统的机电耦合动力学模型并进行了实验验证. 实验结果表明系统能够在0~250 r/min的低转速范围内有效工作, 在转速为250 r/min时, 压电单元和摩擦纳米发电机的最大峰峰值电压分别为132 V和1128 V, 总平均功率为1426 μW. 本文提出的动力学协同调控机制为能量采集系统动力学和电学性能改进提供新的途径, 有益于促进自供能物联网技术的发展与应用.      

Enhanced galloping energy harvester with cooperative mode of vibration and collision

The low power and narrow speed range remain bottlenecks that constrain the application of small-scale wind energy harvesting. This paper proposes a simple, low-cost, and reliable method to address these critical issues. A galloping energy harvester with the cooperative mode of vibration and collision (GEH-VC) is presented. A pair of curved boundaries attached with functional materials are introduced, which not only improve the performance of the vibration energy harvesting system, but also convert more mechanical energy into electrical energy during collision. The beam deforms and the piezoelectric energy harvester (PEH) generates electricity during the flow-induced vibration. In addition, the beam contacts and separates from the boundaries, and the triboelectric nanogenerator (TENG) generates electricity during the collision. In order to reduce the influence of the boundaries on the aerodynamic performance and the feasibility of increasing the working area of the TENG, a vertical structure is designed. When the wind speed is high, the curved boundaries maintain a stable amplitude of the vibration system and increase the frequency of the vibration system, thereby avoiding damage to the piezoelectric sheet and improving the electromechanical conversion efficiency, and the TENG works with the PEH to generate electricity. Since the boundaries can protect the PEH at high wind speeds, its stiffness can be designed to be low to start working at low wind speeds. The electromechanical coupling dynamic model is established according to the GEH-VC operating principle and is verified experimentally. The results show that the GEH-VC has a wide range of operating wind speeds, and the average power can be increased by 180% compared with the traditional galloping PEH. The GEH-VC prototype is demonstrated to power a commercial temperature sensor. This study provides a novel perspective on the design of hybrid electromechanical conversion mechanisms, that is, to combine and collaborate based on their respective characteristics.

     

Recent advancement of flow-induced piezoelectric vibration energy harvesting techniques: principles,structures, and nonlinear designs

Energy harvesting induced from flowing fluids (e.g., air and water flows) is a well-known process, which can be regarded as a sustainable and renewable energy source. In addition to traditional high-efficiency devices (e.g., turbines and watermills), the micro-power extracting technologies based on the flow-induced vibration (FIV) effect have sparked great concerns by virtue of their prospective applications as a self-power source for the microelectronic devices in recent years. This article aims to conduct a comprehensive review for the FIV working principle and their potential applications for energy harvesting. First, various classifications of the FIV effect for energy harvesting are briefly introduced, such as vortex-induced vibration (VIV), galloping, flutter, and wake-induced vibration (WIV). Next, the development of FIV energy harvesting techniques is reviewed to discuss the research works in the past three years. The application of hybrid FIV energy harvesting techniques that can enhance the harvesting performance is also presented. Furthermore, the nonlinear designs of FIV-based energy harvesters are reported in this study, e.g., multi-stability and limit-cycle oscillation (LCO) phenomena. Moreover, advanced FIV-based energy harvesting studies for fluid engineering applications are briefly mentioned. Finally, conclusions and future outlook are summarized.

     

Investigation on Savonius turbine technology as harvesting instrument of non-fossil energy: Technical development and potential implementation

Environmental risk due to excessive residual emission is rising. Greenhouse effect, ice melting in the Arctic, reduction of air quality are several concerns which need immediate development and change. Energy harvesting equipment is one of the key solutions. Environment potential, e.g. water resource can be collaborated with mechanical equipment to harvest clean energy. Savonius turbine has been proposed and studied for this purpose and can be placed on several energy resources, i.e. water and wind. Still, real-world implementation of this technology is lacking,especially in tropical archipelago countries which have abundant water resources. In this work,assessment of Savonius turbine technology as instrument to harvest clean energy is conducted. A series of development on the turbine performance and technical modification is considered as reference to implement the technology in water and open air environments. It is noted that rotor design, operation depth and nozzle attachment are several key influencing factors.     

Structural and electrical dynamics of a grating-patterned triboelectric energy harvester with stick–slip oscillation and magnetic bistability

The majority of research work on triboelectric energy harvesting is on material science, manufacturing and electric circuit design. There is a lack of in-depth research into structural dynamics which is crucial for power generation in triboelectric energy harvesting. In this paper, a novel triboelectric energy harvester with a compact structure working in sliding mode is developed, which is in the form of a casing and an oscillator inside. Unlike most sliding-mode harvesters using single-unit films, the proposed harvester utilizes grating-patterned films which are much more efficient. A bistable mechanism consisting of two pairs of magnets is employed for broadening the frequency bandwidth. A theoretical model is established for the harvester, which couples the structural dynamics domain and electrical dynamics domain. This paper presents the first study about the nonlinear structural dynamics of a triboelectric energy harvester with grating-patterned films, which is also the first triboelectric energy harvester integrating grating-patterned films with a bistable magnetic system for power performance enhancement. Theoretical studies are carried out from the perspectives of both structural and electrical dynamics. Surface charge density and segment configuration of the films affect whether the electrostatic force influences the structural dynamics, which can be neglected under a low surface charge density. Differences in structural response and electrical output are found between a velocity-dependent model and Coulomb’s model for modelling the friction in the triboelectric energy harvesting system. The bistable mechanism can effectively improve the output voltage under low-frequency excitations. Additionally, the output voltage can also be obviously enhanced through increasing the number of the hollowed-out units of the grating-patterned films, which also results in a slight decrease in the optimal load resistance of the harvester. These findings enable innovative designs for triboelectric energy harvesters and provide fabrication guidelines in practical applications.

     

基于反激变压器的压电振动能量双向操控技术

压电材料因其具有良好的机电耦合特性, 在振动能量俘获和结构振动控制领域有着良好的应用前景. 基于同步开关和电感的压电元件接口控制电路, 可以通过振荡电路工作原理调节压电元件的电压幅值和相位, 优化压电振动系统的机电能量转化. 优化型同步电荷提取技术即基于上述接口控制电路实现了压电振动能到电能的高效转换. 本文提出了一种衍生于优化型同步电荷提取电路的压电阻尼半主动控制电路, 借鉴反激变压器的原、副边能量转换特性, 实现了压电振动控制系统从电能到机械能的能量操控, 进而达到结构振动抑制的效果. 至此, 结合了压电电荷能提取与压电阻尼半主动控制技术的新电路, 以反激变压器为核心实现了压电振动能量的双向操纵. 论文首先介绍了相应的控制电路及工作原理, 推导了新型同步开关阻尼技术下的结构的振动阻尼比模型, 搭建了压电悬臂梁振动控制实验平台, 最终通过实验验证了理论模型, 并使用更简单的控制方法解决了振动控制系统的稳定性问题.      

面内压电振动能量采集动力学设计与性能研究

压电振动能量采集将环境中普遍存在的机械能转换为电能，可以实现自供能传感、控制与驱动，具备灵活、节能环保、可持续的优势，具有广阔的应用前景。为了促进压电振动能量采集器件的集成与融合，提出面内压电振动能量采集，将压电振动能量采集器进行扁平化设计，使其在二维平面内采集振动能量，在保证较大功率输出下能够显著减小器件所需三维空间。为了提高输出功率与工作频宽，设计了具有双稳态与力放大机制的面内压电振动能量采集器。考虑弯张小变形，通过能量法建立了面内压电振动能量采集器的机电耦合动力学模型。分析了关键设计参数对面内压电振动能量采集器性能的影响。数值仿真了面内压电振动能量采集器在简谐激励下的俘能性能，结果表明，通过合理的设计，面内压电振动能量采集器可以低频、宽频弱激励下有效俘获能量。面内压电振动能量采集设计方法有利于推动便携式、可穿戴式自供能等方面的应用和产业化。