一种新型双稳态电磁式振动能量捕获器动力学特性研究

将质量-非线性弹簧-阻尼系统与双稳态振动能量捕获系统相结合,提出了附加非线性振子的双稳态电磁式振动能量捕获器,建立系统的力学模型及控制方程;利用谐波平衡法获得了该发电振子处于高能轨道的运动幅值及发电功率密度解析解表达式。数值仿真表明:附加非线性振子的双稳态振动发电系统的响应幅值及功率密度均明显高于单一双稳态振动发电系统。在简谐激励下,随着质量比和调频比的增大,附加非线性振子双稳态振动能量捕获器的大幅运动响应及发电性能均出现了先增大后减小的趋势;且随着激振频率的增加,发生了随激振频率移动的现象。通过综合比较获得了附加非线性振子双稳态振动能量捕获器的发电性能最佳的参数配置范围m∈[0.8,3]和f∈[π/10,π/3]。上述研究结果可为双稳态振动能量捕获系统的相关研究提供理论基础。     

基于梁结构超谐波振动的信号倍频放大研究

信号发生装置的倍频电路容易受到外界环境因素和器件尺寸的影响,导致工作稳定性变差,影响信号发生装置的性能。为此,本文提出一种基于梁结构机电耦合系统超谐波振动的信号倍频发生方法,给出了超谐波振动倍频信号放大条件。该方法利用激励信号激励梁产生超谐波振动,通过滤波电路滤除激励波信号,保留了激励波三倍频信号,实现了信号的倍频放大功能。设计了超谐波振动倍频信号试验发生装置和高低通滤波电路,滤除激励信号;利用数据采集系统采集超谐波振动信号。试验结果表明:本文的信号倍频放大方法能实现信号频率整数倍放大,超谐波振动倍频信号发生装置能产生稳定的倍频信号。     

逆压电效应对双稳态压电俘能器的性能影响研究

为了研究逆压电效应对压电俘能效果的具体影响,本文首先分析了双稳态压电俘能器的分布参数型能量表达式,然后应用广义Hamilton变分原理推导了该俘能系统的动力学方程,最后采用谐波平衡法获得了动力响应解析解。通过对比不同激励频率下的数值仿真结果,讨论了逆压电效应对俘能系统动力响应的影响规律。结果表明,逆压电效应在不同工况下对俘能效果的影响并非单纯起抑制作用,在一定激励强度的高频激励下,逆压电效应对俘能效果的影响起增强作用;弱强度激励下的俘能效果则全程受到抑制作用。     

简谐激励下的双稳态振动能量收集器动力学分析

振动能量收集技术解决了移动电子系统对于电池的依赖。本文设计了一种基于水平摆的双稳态振动能量收集器,建立了其力学模型和动力学方程,借助雅可比矩阵获得了其稳定性条件,使用数值仿真的方法研究了系统响应特性随谐波激励频率与幅值的变化规律。研究发现:双稳态系统在低激励频率下较小的激励幅值也能产生大幅运动;而当频率越高,产生大幅运动所需要的激励幅值也越高;并且当激励频率确定时随着激励幅值的进一步增大,大幅运动的频带变宽。为双稳态振动能量收集器的研究提供理论基础。     

具有弹性放大器的双稳态压电俘能器建模及参数影响分析

利用广义Hamilton变分原理,建立了具有弹性放大器的双稳态压电俘能系统BPH+EM的动力学方程。考虑谐波激励,采用调和平衡法获得了BPH+EM系统的位移、输出电压和功率的解析解。利用求得的解析解,讨论了BPH+EM系统扩大能量俘获的频率范围和提高能量俘获效率的机理,研究了弹性放大器的刚度质量比对BPH+EM系统的动力性能影响规律。当弹性放大器的刚度质量比趋于无限大时,具有弹性放大器的双稳态压电俘能系统退化为双稳态压电俘能系统BPH。弹性放大器的刚度质量比趋于0但不等于0时,BPH+EM的俘能效率低于BPH。结果表明,在合适的刚度质量比范围内,BPH+EM的俘能效率显著优于BPH。研究结果为BPH+EM系统的优化设计提供了理论指导。     

简谐激励下黏弹性非线性能量阱的研究

黏弹性材料作为一种良好的减振材料,广泛应用于机械、航空和土木等领域.本文用黏弹性Maxwell器件代替传统非线性能量阱中的阻尼元件,提出一种新型的黏弹性非线性能量阱,并对该模型在简谐激励下的减振性能进行分析.首先,根据牛顿第二定律建立系统的动力学方程,采用谐波平衡法求解系统的幅频响应曲线,并利用MATLAB中的Runge-Kutta数值方法验证解析解的正确性,结果吻合良好.然后,分析黏弹性非线性能量阱的减振性能和参数的影响.最后,分析了不同质量比下非线性刚度比和阻尼比同时变化时减振效果的变化趋势,并讨论了黏弹性非线性能量阱的最佳取值范围.研究结果表明:主系统的最大振幅随着非线性刚度的增加先减小后增大;当参数选取恰当时,黏弹性非线性能量阱比传统非线性能量阱的减振效果更优;另外,随着质量比的增加,主系统最大振幅的最小值出现先减小后趋于不变的现象,且非线性刚度比和阻尼比的最佳取值范围有所增大.以上结论对黏弹性非线性能量阱的实际应用提供了一定的理论依据.     

基于非线性谐振电路的双稳态俘能器的俘能与动力学特性研究

双稳态俘能器可实现宽频和高效的俘能效果.目前的研究主要在双稳态结构中接入单一电阻电路进行俘能.本文将非线性RLC (电阻-电感-电容)谐振电路引入到三弹簧式双稳态结构中,构建两自由度非线性系统,以实现俘能特性的提升.设计永磁体与线圈的构型,获得了非线性机电耦合系数.推导并得到了两自由度非线性俘能器的控制方程.利用谐波平衡法推导得到了系统的电流与位移的频率响应关系.基于雅可比矩阵对解的稳定性进行了判别.将解析解与数值解进行了对比验证.结果表明,在双稳态俘能器中引入非线性二阶谐振电路不仅有利于低频俘能,还可进一步提升俘能响应,拓宽俘能带宽.相同的电路参数下,与线性电路相比非线性电路可通过电流的倍频现象实现结构更低频率的能量俘获.减小谐振电路与双稳态结构共振频率之比,增加基础激励幅值,减小静平衡点之间的距离均可提升俘能器的俘能效果.通过调控谐振电路与双稳态共振频率之比和基础激励幅值等参数,可实现系统单倍周期响应、多倍周期响应及混沌响应之间的切换.     

谐波平衡法与复平均法计算强非线性系统稳态响应的区别

近些年,很多学者致力于利用非线性增强振动响应减少的效果或者能量采集器的效率。因而非线性系统的响应值需要从理论计算方面更准确地预测。另外,根据学者已取得的研究成就,非线性能量汇(NES)中存在的立方刚度非线性可以将结构中宽频域的振动能量传递至非线性振子部分。文章将一种由NES和压电能量采集器组成的NES-piezo装置与两自由度主结构耦合连接,系统受谐和激励作用。文章采用谐波平衡法和复平均法分别推导了系统稳态响应,参照数值结果,对比两种近似解析方法在求解强非线性系统稳态响应时的异同。计算结果表明,系统体现较弱非线性时,二者计算结果差异很小;当系统体现强非线性时,复平均法不能准确地呈现系统高阶响应,提高阶数的谐波平衡法能更准确地表示系统响应值。基于谐波平衡法和数值算法,讨论NES-piezo装置对于系统宽频域减振的影响。与仅加入非线性能量汇情况对比,结果表明NES-piezo装置不会恶化宽频域减振效果,并且在第一阶共振频率附近,可以稍微提高结构减振效率。另外,计算结果也表明,采用恰当的NES-piezo装置可实现宽频域范围的结构减振和压电能量采集一体化。此项研究工作为研究不同情形强非线性系统的响应提供了理论方法的指导。另外,研究结果也为宽频域范围的结构减振和压电能量采集一体化提供了理论依据。     

动力吸振器复合非线性能量阱对线性镗杆系统的振动控制

研究了线性动力吸振器复合非线性能量阱对线性镗杆在外部简谐激励下的振动控制. 忽略镗杆系统中的非线性因素, 建立了附加线性动力吸振器和非线性能量阱的镗杆系统的三自由度运动方程, 研究了附加复合式动力吸振器的镗杆系统的受迫振动. 通过平均法得到了附加复合式动力吸振器的镗杆系统的近似解析解, 并利用数值解验证了近似解析解的准确性, 两者具有很好的一致性. 利用近似解析解详细分析了线性动力吸振器和非线性能量阱的参数对镗杆振动抑制性能的影响. 对给定质量的复合式动力吸振器进行了参数优化, 其中线性动力吸振器参数采用H_∞优化方法的近似解析解进行了优化, 非线性能量阱的阻尼利用系统的近似解析解进行了优化. 分析结果表明, 线性动力吸振器与非线性能量阱组合可以有效抑制线性镗杆系统的振动, 而且采用参数优化后的复合式动力吸振器可以获得更好的减振效果. 通过附加非线性能量阱, 不但可以提高线性动力吸振器的振动抑制效果, 而且还可以提高振动控制系统的鲁棒性.      

四角点简支双稳态层合板振动特性研究

双稳态层合板作为一种柔性可变体结构,为实现振动状态下的构型调控,将对其开展固有振动特性的研究.本文以四角点简支约束的矩形非对称铺设双稳态板作为研究对象,运用最小势能原理、一阶剪切变形理论、以及冯卡门几何非线性位移应变关系,得到双稳态板的两种稳态构型.首次给出了适合于四点简支的6参数构型函数与17参数构型函数,研究对比发现对于稳态构型采用17参数的构型函数结果相对更精确;对于应用线性位移应变关系的基于任一稳态构型下振动固有特性而言,这两种构型函数得到的结果基频相差2%,其它阶次频率相差也不大.随后采用6参数构型函数得到的稳态构型研究了几何尺寸、铺层数分别对两种稳态构型固有振动特性的影响.本研究对于进一步研究该类结构动态跳变机理具有重要意义.     

等效刚度对非线性压电俘能系统性能影响研究

基于Hamilton原理,考虑几何非线性和梁的不可伸长条件,建立了五层压电双晶片叠合梁俘能器在直接和参数激励作用下的运动微分方程。利用Galerkin法和谐波平衡法获得了俘能器的位移、输出电压和输出功率的解析解。引入随时间变化的扰动,提出了非线性方程解的稳定性条件。为了对压电俘能器的结构-性能关系进行综合分析,研究了被动层的配置形式、被动层与主动层的厚度比和弹性模量对压电俘能系统性能的影响。结果表明,在叠合梁厚度不变的情况下,采用五层的压电双晶片叠合结构,选择合理的被动层与主动层厚度比、被动层弹性模量、被动层厚度比和负载电阻,可以有效提高能量俘获的效率。     

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.

     

Nonlinear vibration analysis of pipeline considering the effects of soft nonlinear clamp

Applied Mathematics and Mechanics - Soft nonlinear support is a major engineering project, but there are few relevant studies. In this paper, a dynamic pipeline model with soft nonlinear supports...     

Modeling and analysis of magnetic spring enhanced lever-type electromagnetic energy harvesters

This study presents a novel enhanced monostable lever-type electromagnetic energy harvester (L-EEH). According to the positions of the coil and the lever pivot, four configurations are discussed to realize a better harvesting performance of the L-EEHs. On the basis of establishing the theoretical model of the L-EEH, the corresponding analytical solutions can be obtained by applying the harmonic balance method. The effects of the nonlinear coe-cient, the lever ratio, the mass ratio, and the circuit parameters on the energy harvesting performance of L-EEHs are analyzed and discussed. The numerical and experimental efforts are carried out to verify the theoretical model and the energy harvesting performance. The results demonstrate that the maximum output voltage can be achieved with an appropriate lever ratio. Furthermore, the L-EEH possesses a considerable energy harvesting performance under a smaller lever ratio compared with the other three configurations. The output power can also be improved by adjusting the tip mass of the lever. The proposed L-EEH has a considerable operating bandwidth and an output power, which can reach 146.6 mW under the excitation amplitude of 0.3g.     

A state-of-the-art review on low-frequency nonlinear vibration isolation with electromagnetic mechanisms

Vibration isolation is one of the most efficient approaches to protecting host structures from harmful vibrations, especially in aerospace, mechanical, and architectural engineering, etc. Traditional linear vibration isolation is hard to meet the requirements of the loading capacity and isolation band simultaneously, which limits further engineering application, especially in the low-frequency range. In recent twenty years, the nonlinear vibration isolation technology has been widely investigated to broaden the vibration isolation band by exploiting beneficial nonlinearities. One of the most widely studied objects is the “three-spring” configured quasi-zero-stiffness (QZS) vibration isolator, which can realize the negative stiffness and high-static-low-dynamic stiffness (HSLDS) characteristics. The nonlinear vibration isolation with QZS can overcome the drawbacks of the linear one to achieve a better broadband vibration isolation performance. Due to the characteristics of fast response, strong stroke, nonlinearities, easy control, and low-cost, the nonlinear vibration with electromagnetic mechanisms has attracted attention. In this review, we focus on the basic theory, design methodology, nonlinear damping mechanism, and active control of electromagnetic QZS vibration isolators. Furthermore, we provide perspectives for further studies with electromagnetic devices to realize high-efficiency vibration isolation.

     

Nonlinear dynamics and performance analysis of modified snap-through vibration energy harvester with time-varying potential function

Vibration energy harvesting has emerged as a promising method to harvest energy for small-scale applications. Enhancing the performance of a vibration energy harvester(VEH) incorporating nonlinear techniques, for example, the snap-through VEH with geometric non-linearity, has gained attention in recent years. A conventional snap-through VEH is a bi-stable system with a time-invariant potential function, which was investigated extensively in the past. In this work, a modified snap-through VEH wit...     

参数和直接激励下非线性压电俘能器性能分析的多尺度法

考虑几何非线性、阻尼非线性和梁的轴向不可伸长条件,利用Hamilton变分原理,建立了参数激励和直接激励下压电俘能器的非线性力电耦合的运动微分方程;利用Galerkin法,将所建立的动力学偏微分方程降阶为力电耦合的Mathieu-Duffing型方程;采用多尺度法获得了梁的位移和输出电压的解析表达式,给出了解的稳定性条件;利用解析表达式研究了单独参数激励以及参数激励和直接激励共同作用下阻尼系数对压电俘能器性能的影响。结果表明,在参数激励情况下,线性阻尼会显著影响超临界分岔点的位置,非线性二次阻尼不会影响超临界分岔点的位置。参数激励和直接激励的结合可以作为提升压电能量俘获器性能的解决方案。     

Effects of springs on a pendulum electromechanical energy harvester

This paper studies a model of energy harvester that consists of an electromechanical pendulum system subjected to nonlinear springs. The output power is analyzed in terms of the intrinsic parameters of the device leading to optimal parameters for energy harvesting. It is found that in an appropriate range of the springs constant, the power attains higher values as compared to the case without springs. The dynamical behavior of the device shows transition to chaos.