悬臂梁压电振子宽带低频振动能量俘获的随机共振机理研究

研究了利用系统非线性来提高悬臂梁压电振子宽带低频振动能量俘获效率的随机共振机理,通过增加一对矩形永磁铁对传统线性悬臂梁压电振子结构进行了改进,结果揭示:在外部非线性磁力作用以及合适的磁铁间距条件下,这种外加磁力悬臂梁压电振子会构成一个双稳系统,在外部宽带低频随机振动源激励下发生随机共振现象,且发生随机共振时的输出电压明显增大,从而可以扩展悬臂梁压电振子的共振频率范围、提高低频振动能量的转化输出. 关键词： 压电悬臂粱 振动能量俘获 宽带低频 随机共振     

非线性磁式压电振动能量采集系统建模与分析

为便于评价、优化磁式压电振动能量采集系统的性能,系统研究了该类系统的建模与分析方法,建立了非线性的分布参数模型用于描述系统的非线性动力学行为,并采用谐波平衡法给出了谐波响应的解析解.随后利用仿真模型分析了磁铁间距、加速度幅值、负载阻抗对输出功率的影响,比较了不同激励频率和加速度幅值下的最优阻抗.结果表明:双稳态特性适用于低强度的振动环境,且愈接近临界区域,输出功率愈高,而单稳态渐硬特性适用于高强度振动环境,其最优间距并不靠近临界区域;阱间大幅运动和阱内小幅运动均存在高低能量态共存的现象,愈接近临界区域,现象愈明显;激振频率是影响最优负载阻抗的决定性因素.     

具有频率涨落的简谐力激励下线性谐振子的随机共振

针对线性谐振子受到具有频率涨落的简谐力激励的情况, 计算出系统响应的一阶矩解析表达式.研究发现系统的输出响应以固有频率振动, 响应振幅随简谐激励力频率的变化出现"真实"随机共振,随固有频率的变化出现抑制和 共振两种现象.     

弹性支撑双稳压电悬臂梁振动响应及能量采集研究

在分析了常规刚性支撑非线性能量采集系统的研究基础上,提出外部磁铁弹性支撑的结构设想,保证系统在低强度激励条件下也能处于双稳态振荡,提高机电能量转换效率.研究表明,对于强度变化的随机激励历程,弹性支撑非线性能量采集系统不需要实时调整磁铁间距,能够更好地迎合强度时刻变化的随机激励源,实现高效的机电能量转换.     

基于磁化电流法的双稳压电悬臂梁磁力精确分析

双稳压电悬臂梁结构常常用于振动能量采集系统,其中的非线性磁力与系统势函数和动力学方程的建立紧密相关,非线性磁力的正确分析和精确计算对系统振动响应和能量采集效果的准确预测至关重要.本文采用形状函数分析方法,通过悬臂梁弯曲斜率的整体积分计算,得到了悬臂梁末端的运动轨迹及其末端磁铁精确的位置与姿态,并由此根据磁化电流理论建立了双稳压电悬臂梁能量采集系统的磁力计算模型,给出了末端磁铁受到的水平轴向磁力和竖直纵向磁力及其合磁力的变化规律.数值模拟发现,随着末端磁铁竖直纵向位移逐渐增大,磁铁受到的水平轴向磁力和竖直纵向磁力都会依次由排斥力转变为吸引力,从而导致磁力合力的方向会随磁铁位移发生跨越两个象限的大幅度变化.实验验证表明,磁力计算结果与实验测量结果符合良好,其精确度优于现有文献方法的精度,因此本文的方法可以准确预测双稳压电悬臂梁振动过程的磁力变化规律.     

双稳随机共振参数特性的研究

以双稳系统为研究对象，探讨了影响和产生双稳随机共振的参数选择特性.双稳系统参数和二次采样频率参数有着内在的物理联系，它们的改变都会引起势垒、势阱间距和粒子跃迁速率的改变，并使噪声能量相对重新分配，进而影响随机共振效果.根据随机共振的参数选择规律，可通过适当的参数选择来得到最佳的随机共振状态，为后续数据处理奠定基础.     

宽频随机激励下非线性压电能量采集器的相干共振

近年来随着微机电系统的发展,非线性能量采集系统受到了研究者的极大关注.本文采用随机线性化方法对一类环境噪声作用下能量采集系统进行了分析.首先根据受压梁的双稳态特性,建立了等效的随机激励作用下压电能量采集系统的数学模型.采用随机线性化方法获得了输出电压近似闭合形式的表示,并且通过数值分析说明了系统相干共振现象.相干共振的相关研究可应用于优化系统参数使能量采集效果最大化.     

基于振动共振的随机共振控制

分析了非线性双稳系统在高、低两种不同频率信号作用下的动力学特性，给出了高频信号参数与双稳系统输出信号的信噪比和功率谱放大率关系的解析表达式，提出了基于振动共振的随机共振控制方法.理论分析和数值仿真结果表明，通过调节高频信号的幅值或频率大小，能有效地控制双稳系统输出信号的信噪比和功率谱放大率.     

非圆化磨耗激励下高速列车转向架区域噪声边频带产生机理及影响

该文通过对车辆噪声和车轮非圆化磨耗开展跟踪测试和分析,发现存在车轮非圆化磨耗的列车在运行过程中,其转向架区域噪声窄带频谱上会出现了以非圆化磨耗激励频率为中心,以过轨枕频率为间隔等间距分布的噪声峰值(即噪声边频带).这使得车轮非圆化磨耗不仅会影响其激励频率处的列车轨道结构的振动和噪声,还会对其他频段的噪声产生重要影响.为...     

双稳系统的频率耦合与随机共振机理

分析了处于双势阱中的粒子在单一频率信号和双频信号作用下的运动形式,给出在双频信号作用下双稳系统的响应幅值与激励幅值的近似解析关系,揭示了非线性系统所特有的不同频率之间的频率耦合现象和激励输入的频率能量向另一频率转移的渗透现象.从动力学机理和频谱分布的角度进行分析,深化了对双稳系统随机共振机理的认识.数值仿真结果证明了理论分析的有效性.     

Prompt efficiency of energy harvesting by magnetic coupling of an improved bi-stable system

In order to improve the transform efficiency of bi-stable energy harvester(BEH),this paper proposes an advanced bi-stable energy harvester(ABEH),which is composed of two bi-stable beams coupling through their magnets.Theoretical analyzes and simulations for the ABEH are carried out.First,the mathematical model is established and its dynamical equations are derived.The formulas of magnetic force in two directions are given.The potential energy barrier of ABEH is reduced and the snap-through is liable to occur between potential wells.To demonstrate the ABEH's advantage in harvesting energy,comparisons between the ABEH and the BEH are carried out for both harmonic and stochastic excitations.Our results reveal that the ABEH's inter-well response can be elicited by a low-frequency excitation and the harvester can attain frequent jumping between potential wells at fairly weak random excitations.Thus,it can generate a higher output power.The present findings prove that the ABEH is preferable in harvesting energy and can be optimally designed such that it attains the best harvesting performance.     

磁悬浮式电磁-摩擦复合生物机械能量采集器

能量采集技术已经成为智能终端领域的一项关键技术,关于人体机械能采集方式也有大量的研究.针对人体机械能采集的应用需求,本文提出一种基于磁悬浮结构的电磁-摩擦复合式能量采集器.该能量采集器以磁悬浮结构作为核心部件,具有结构简单、感应灵敏、输出功率高的优点.在10 MΩ的外接负载时,两组摩擦发电单元输出功率分别为0.12 mW和0.13 mW;在1kΩ外接负载时,两组电磁发电单元的输出功率分别为36 mW和38 mW.复合能量采集器通过电容储能后,电容器可以输出8 V电压,且输出信号为持续的直流信号,可以为计步器提供持续的能量供给,支撑计步器正常工作.设计的复合能量采集器对于可穿戴电子设备自供电工作模式的实现具有重要意义.     

Stationary response of nonlinear magneto-piezoelectric energy harvester systems under stochastic excitation

Recent years have shown increasing interest of researchers in energy harvesting systems designed to generate electrical energy from ambient energy sources, such as mechanical excitations. In a lot of cases excitation patterns of such systems exhibit random rather than deterministic behaviour with broad-band frequency spectra. In this paper, we study the efficiency of vibration energy harvesting systems with stochastic ambient excitations by solving corresponding Fokker-Planck equations. In the system under consideration, mechanical energy is transformed by a piezoelectric transducer in the presence of mechanical potential functions which are governed by magnetic fields applied to the device. Depending on the magnet positions and orientations the vibrating piezo beam system is subject to characteristic potential functions, including single and double well shapes. Considering random excitation, the probability density function (pdf) of the state variables can be calculated by solving the corresponding Fokker-Planck equation. For this purpose, the pdf is expanded into orthogonal polynomials specially adapted to the problem and the residual is minimized by a Galerkin procedure. The power output has been estimated as a function of basic potential function parameters determining the characteristic pdf shape.     

Snap-through piezoelectric energy harvesting

Snap-through mechanism is employed to harvest electricity from random vibration through piezoelectricity. The random excitation is assumed to be Gaussian white noise. The snap-through piezoelectric energy harvester possesses the bistability. For small-amplitude vibration in a potential well, the Ito stochastic differential equation of the electromechanical coupling system is derived from the Taylor approximation at a stable equilibrium point. The method of the moment differential equations is applied to determine the statistical moments of the displacement response and the output voltage. The effects of the system parameters on the output voltage and the output power are examined. The approximate analytical outcomes are qualitatively and quantitatively supported by the numerical simulations. For large-amplitude interwell motion, the effects of the parameters on the output voltage and the output power are numerically investigated. Nonlinearity produced by the snap-through improves energy harvesting so that the snap-through piezoelectric energy harvester can outperform the linear energy harvester in the similar size under Gaussian white noise excitations.     

带碰撞双稳态压电俘能系统的俘能特性研究

双稳态俘能系统的运动常常会陷入单个势能阱中, 导致俘能效率降低. 为了解决这个问题, 本文提出了一类带碰撞的磁斥力双稳态压电振动能量采集系统. 建立了该碰撞双稳态系统的机电耦合方程, 分析了碰撞对双稳态系统动力学特性的影响. 研究了确定性激励和低强度随机激励下碰撞对系统响应特性和俘能效率的影响. 结果表明: 简谐激励下, 碰撞能够使得原双稳态系统的单阱小幅周期运动转变为双阱间的大幅运动, 从而有效地提高输出功率. 得到了低强度随机激励下, 不同碰撞间隙对系统动力响应特性和输出功率的影响规律. 对一个给定的随机激励, 存在一个最优的碰撞间隙, 此时碰撞能够将原双稳态系统单阱内的随机运动转化为频繁的双阱跳跃, 出现大幅值运动, 从而大幅提高了系统的俘能效率.     

Nonlinear dynamics for broadband energy harvesting: Investigation of a bistable piezoelectric inertial generator

Vibration energy harvesting research has largely focused on linear electromechanical devices excited at resonance. Considering that most realistic vibration environments are more accurately described as either stochastic, multi-frequency, time varying, or some combination thereof, narrowband linear systems are fated to be highly inefficient under these conditions. Nonlinear systems, on the other hand, are capable of responding over a broad frequency range; suggesting an intrinsic suitability for efficient performance in realistic vibration environments. Since a number of nonlinear dynamical responses emerge from dissipative systems undergoing a homoclinic saddle-point bifurcation, we validate this concept with a bistable inertial oscillator comprised of permanent magnets and a piezoelectric cantilever beam. The system is analytically modeled, numerically simulated, and experimentally realized to demonstrate enhanced capabilities and new challenges. In addition, a bifurcation parameter within the design is examined as either a fixed or an adaptable tuning mechanism for enhanced sensitivity to ambient excitation.