en
×

分享给微信好友或者朋友圈

使用微信“扫一扫”功能。
通讯作者:

靳艳飞,E-mail:jinyf@bit.edu.cn

中图分类号:O324

文献标识码:A

文章编号:1672-6553-2023-21(3)-053-010

DOI:10.6052/1672-6553-2022-011

参考文献 1
ERTURK A,HOFFMANN J,INMAN D J.A piezo-magnetoelastic structure for broadband vibration energy harvesting [J].Applied Physics Letters,2009,94(25):254102-254104.
参考文献 2
GLYNE-JONES P,WHITE N M.Self-powered systems:a review of energy sources [J].Sensors Review,2001,21(2):91-97.
参考文献 3
ROUNDY S,WRIGHT P K.A piezoelectric vibration based generator for wireless electronics [J].Smart Materials and Structures,2004,13(5):1131-1144.
参考文献 4
杨斌强,徐文潭,王广庆.带弹性放大器的双稳态压电振动能量采集器 [J].传感技术学报,2017,30(5):684-691.YANG B Q,XU W T,WANG G Q.A bistable piezoelectric vibration energy harvester with an elastic magnifier [J].Chinese Journal of Sensors and Actuators,2017,30(5):684-691.(in Chinese)
参考文献 5
GUAN M J,LIAO W H.On the efficiencies of piezoelectric energy harvesting circuits towards storage device voltages [J].Smart Materials and Structures,2007,16(2):498-505.
参考文献 6
YAO M H,MA L,ZHANG W.Study on power generations and dynamic responses of the bistable straight beam and the bistable L-shaped beam [J].Science China-Technological Sciences,2018,61(9):1404-1416.
参考文献 7
ARRIETA A F,HAGEDORN P,ERTURK A,et al.A piezoelectric bistable plate for nonlinear broadband energy harvesting [J].Applied Physics Letters,2010,97(10):174103.
参考文献 8
STANTON S C,OWENS B,MANN B P.Harmonic balance analysis of the bistable piezoelectric inertial generator [J].Journal of Sound and Vibration,2012,331(15):3617-3627.
参考文献 9
HARNE R L,WANG K W.A review of the recent research on vibration energy harvesting via bi-stable systems [J].Smart Materials and Structures,2013,22(2):023001.
参考文献 10
吴子英,叶文腾,刘蕊.一种新型双稳态电磁式振动能量捕获器动力学特性研究 [J].应用力学学报,2017,34(5):848-854.WU Z Y,YE W T,LIU R.Dynamics of a novel bi-stable electromagnetic vibration energy harvester [J].Chinese Journal of Applied Mechanics,2017,34(5):848-854.(in Chinese)
参考文献 11
ZHU P,REN X M,QIN W Y,et al.Improving energy harvesting in a tri-stable piezomagnetoelastic beam with two attractive external magnets subjected to random excitation [J].Archive of Applied Mechanics,2016,87(1):1-13.
参考文献 12
ZHU P,REN X M,QIN W Y,et al.Theoretical and experimental studies on the characteristics of a tri-stable piezoelectric harvester [J].Archive of Applied Mechanics,2017,87(9):1541-1554.
参考文献 13
ZHOU S X,CAO J Y,INMAN D J,et al.Broadband tristable energy harvester:modeling and experiment verification [J].Applied Energy,2014,133(1):33-39.
参考文献 14
ZHOU Z Y,QIN W Y,ZHU P.Energy harvesting in a quad-stable harvester subjected to random excitation [J].Aip Advances,2016,6(2):785-791.
参考文献 15
KIM P,SEOK J.Dynamic and energetic characteristics of a tri-stable magnetopiezoelastic energy harvester [J].Mechanism & Machine Theory,2015,94:41-63.
参考文献 16
LENG Y G,TAN D,LIU J J,et al.Magnetic force analysis and performance of a tri-stable piezoelectric energy harvester under random excitation [J].Journal of Sound and Vibration,2017,406:146-160.
参考文献 17
BEEBY S P,WANG L,ZHU D,et al.A comparison of power output from linear and nonlinear kinetic energy harvesters using real vibration data [J].Smart Materials and Structures,2013,22(7):075022.
参考文献 18
ZHU W Q,LU M Q,WU Q T.Jump and bifurcation of duffing oscillator under narrowband excitation [J].Acta Mechanica Sinica,1994,10(1):73-81.
参考文献 19
戎海武,王向东,徐伟.窄带随机噪声作用下Duffing振子的双峰稳态概率密度 [J].物理学报,2005,54(6):2557-2560.RONG H W,WANG X D,XU W.On double-peak probability density functions of a Duffing oscillator under narrow-band random excitation [J].Acta Physica Sinica,2005,54(6):2557-2560.(in Chinese)
参考文献 20
吴娟娟.窄带随机激励下双稳压电悬臂梁响应特性与能量采集研究 [D].天津:天津大学,2018.WU J J.Response characteristic of a nonlinear bi-stable piezoelectric cantilever beam under narrow-band random excitations and its energy harvesting [D].Tianjin:Tianjin University,2018.(in Chinese)
参考文献 21
JIN Y F,ZHANG Y X.Dynamics of a delayed Duffing-type energy harvester under narrow-band random excitation.Acta Mechanica,2021,232:1045-1060.
参考文献 22
满大伟.非线性多稳态压电俘能器的动力特性分析 [D].合肥:合肥工业大学,2019.MAN D W.Analysis of dynamic characteristics of nonlinear multi-stable piezoelectric energy harvester [D].Hefei:Hefei University of Technology,2019.(in Chinese)
参考文献 23
唐炜,王小璞,曹景军.非线性磁式压电振动能量采集系统建模与分析 [J].物理学报,2014,63(24):72-85.TANG W,WANG X P,CAO J J.Modeling and analysis of piezoelectric vibration energy harvesting system using permanent magnetics [J].Acta Physica Sinica,2014,63(24):72-85.(in Chinese)
参考文献 24
满大伟,王建国.梁端磁铁尺寸对三稳态压电俘能器性能影响分析.应用力学学报,2020,37(4):1-7.MAN D W,WANG J G.Size effect of tip magnet on the performance of tri-stable piezoelectric energy harvesters [J].Chinese Journal of Applied Mechanics,2020,37(4):1-7.(in Chinese)
参考文献 25
DAVIES H G,LIU Q.The response envelope probability density function of a Duffing oscillator with random narrow-band excitation [J].Journal of Sound and Vibration,1990,139(1):1-8.
目录contents

    摘要

    本文研究了窄带随机激励下三稳态压电俘能器的动力学输出特性.首先,建立了非线性三稳态压电俘能器的分布参数型机电耦合运动方程,并基于多尺度法推导得到系统运动方程响应的解析解以及一阶、二阶稳态矩的表达式.其次,分析了磁铁间距、噪声强度和激励幅值等参数对系统稳态响应的影响.研究结果表明,在一定参数范围内,随着噪声强度的增加,压电振动俘能器会经历阱内振动、阱间振动甚至大轨道周期运动,以表现出单稳态、双稳态和三稳态特性;改变磁铁水平间距和竖直间距构造三稳态压电俘能器,其振动幅值和采集电压相较于双稳态明显提高.最后,通过实验比较了压电俘能器在不同位形时的采集性能,结果表明了三稳态压电俘能器的优越性,为窄带随机激励下的非线性振动俘能器的设计提供一定的理论依据.

    Abstract

    In this paper, the dynamical behaviors of a tri-stable piezoelectric energy harvester under the narrow-band random excitation is studied. Firstly, the dynamical equation of a tri-stable nonlinear cantilever piezoelectric energy harvesting system is established. The analytical expressions of the dynamical response of the system together with the first and second steady moments are obtained by using the multiple scales method. Secondly, the effects of the distance between the tip magnet and the external magnets, the noise intensity and the excitation amplitude on the system response and harvesting performance are discussed. The obtained results show that as the noise intensity increases, the piezoelectric vibration energy harvester will experience mono-stable, bi-stable and tri-stable motion. Changing the horizontal and vertical spacing of the magnets makes the piezoelectric energy harvester perform tri-stable motion, and the displacement and acquisition voltage are significantly improved compared to the bi-stable case. Finally, the collection performance of the piezoelectric energy harvester in different configurations is compared through experiments.The results show the superiority of the tri-stable piezoelectric energy harvester, which provide the theoretical support for the design of the vibration energy harvester under the narrow-band random excitation.

  • 引言

  • 随着能源短缺问题加剧,以及微电子技术和无线传感网络技术的高速发展,能源采集技术得到广泛重视[12].压电振动俘能器是利用压电效应将环境中的振动能量转换为电能的装置,具有结构简单、转换效率高、抗干扰能力强等优点[34],在国防军事、环境监测、医疗系统等领域应用广泛[5].由于线性结构的压电俘能器具有狭窄的固有频率特征,利用非线性结构实现宽频响应的能量采集方式得到了广泛关注.姚明辉等[6]提出了双稳态L型悬臂梁结构,理论分析得到系统的势能函数具有两个对称的稳定势阱,当考虑重力势能时,势能函数出现不对称的双势阱.Arrieta等[7]设计了一种非线性双稳态压电悬臂梁来实现宽带振动能量俘获,实验结果表明,该装置能够从定宽带振动源中收集较多的电能.Stanton等[8]提出了一种双稳态压电俘能器模型,利用谐波平衡法求出了系统运动方程的解析解.

  • 双稳态压电俘能器在弱激励条件下无法进入大幅阱间运动[910],而多稳态压电俘能器被证明具有更浅、更宽的势能阱,这一特点使其在较弱的振动环境中也有较高的输出性能[1112].周生喜等[13]通过数值仿真和实验方法验证了弱激励条件下三稳态压电俘能器的俘能效果优于双稳态压电俘能器.Zhou等[14]通过最小误差遗传算法证明三稳态压电俘能器具有更宽的工作频带和更高的采集效率.Kim和Seok[15]提出一种三稳态压电俘能器,研究了影响势能阱深度的各种因素.Leng等[16]利用等效磁化电流法建立了磁铁间的非线性磁力模型,研究了随机激励下三稳态压电俘能器的系统响应.

  • 这些基于低频宽带随机激励或单频周期激励下的研究成果对优化多稳态压电俘能器结构、提高输出性能有参考价值.同时随着研究的深入,人们发现日常生活和工作环境中的振动激励形式往往是能量集中在一定频率范围内的窄带随机激励,例如悬索桥上的振动能量集中在22Hz到46Hz范围内[17],人行走的振动频率在1Hz左右.已有不少学者使用不同方法对窄带随机激励下非线性悬臂梁系统的系统响应和能量转换效率进行研究.例如,Zhu等[18]利用数值分析方法研究了Duffing振子在窄带随机噪声激励下系统响应的双峰稳态概率密度问题,以及分叉和跳跃现象.戎海武等[19]利用多尺度法和线性化方法,研究了窄带随机激励下Duffing振子输出响应的双峰稳态概率密度问题.首先用多尺度法分离系统的快变项,再用线性化方法求解双峰稳态概率密度的表达式.吴娟娟[20]讨论了窄带随机激励的中心频率、强度和带宽对双稳态悬臂梁能采集系统输出电压的影响规律,论证了系统在分界点间距处始终存在响应峰值的特征规律.Jin等[21]研究了窄带随机激励下时滞Duffing型压电俘能器的输出响应和稳定性.然而,大多数研究集中于窄带随机激励下单稳或双稳态振动俘能器,对窄带随机激励下三稳态振动俘能器动力学的研究较少.

  • 本文考虑三稳态压电俘能器的非线性特性,建立了集中参数型机电耦合运动方程,以带通滤波器输出一定带宽的窄带随机激励模拟环境振动,基于多尺度法得到系统运动响应的解析解,分析了窄带随机激励下磁铁间距、噪声强度和激励幅值等参数对系统动力学特性和采集性能的影响,并通过实验对比了俘能器做双稳态运动和三稳态运动时的输出特性.

  • 1 三稳态压电俘能器的数学模型

  • 图1为本文所研究的三稳态压电俘能器结构示意图.其中,悬臂梁长度为l,由弹性基体和黏结在其上、下表面的一对极化方向相反的压电片组成,压电片串联连接外部负载电阻R.悬臂梁一端固定在基座左侧面上,另一端与末端磁铁A连接.外部磁铁B和C沿悬臂梁水平轴线延长线对称分布在基座右侧面上,其与末端磁铁的水平间距为dx,外部磁铁B、C之间的竖直间距为2dy,磁铁的偏心距为a/2,末端磁铁A受到外部磁铁B和C的非线性磁力排斥作用.

  • 图1 三稳态压电俘能器结构示意图

  • Fig.1 The model of a tri-stable piezoelectric energy harvester

  • 假设磁场在磁铁ABC中分布均匀,把每个磁铁等效成点磁荷.采用磁偶极子模型[22],可得磁铁之间的势能为:

  • Um=μ04πmBrBA23+mCrCA23-mArBA3rBArBA25-mCrCA3rCArCA25mA
    (1)
  • 式中,μ0=4π×10-7H/m为真空磁导率.磁偶极矩和方向向量分别为:

  • mA=MAcosαi+MAsinαj, mB=-VBMBi, mC=-VBMCi, rBA=-dxi+w (l, t) -dyj, rCA=-dxi+w (l, t) +dyj

  • 其中,ij分别为x向和z向的单位矢量,VxMxx=ABC)分别为磁铁x的体积和磁化强度. wlt)为悬臂梁末端相对固定端的振动位移,α是末端磁铁A的偏转角,满足tanα=wlt),水平间距Δx=a(1-cosα)/2.

  • 仅考虑第1阶模态,将Um进行泰勒级数展开,系统的势函数可以表示为[23]:

  • U(X-)=12k1X-2+14k2X-4+16k3X-6
    (2)
  • 式中,k1k2k3分别表示线性、三次和五次方刚度系数,与磁铁间距dxdy的关系表达式参考文献[24].根据方程(2)可知,当k1>0,k2<0,k3>0且满足k22-41-k1k3>0时,势能曲线有三个稳定平衡点: X-si=-k2-k22-k1k3/2k3X-si=0i=1,23以及两个不稳定平衡点X-ui=-k2+k22-k1k3/2k3i=1,2.系统具有三稳态势的结构,如图2所示.

  • 图2 势函数曲线(k1=1.3,k2=-3.2,k3=1.1)

  • Fig.2 The plot of potential function by choosing stiffness coefficients as k1=1.3, k2=-3.2, k3=1.1

  • 当压电悬臂梁工作在一阶弯曲振动模态时,根据牛顿第二定律、基尔霍夫定律,系统的运动方程为:

  • M-X-¨(t)+C-X-˙(t)+dU-(X-)dX--χ-V-(t)=-M-X-¨bCPV-˙(t)+V-(t)R+κ-X-˙(t)=0
    (3)
  • 其中,X-为末端磁铁A的位移,X-˙为末端磁铁A的速度,X-¨b为激励加速度. M-C-分别为俘能器的等效质量和等效阻尼. χ-为线性机电耦合系数,κ-为电路中的压电耦合项,CP为采集电路的等效电容,V-t为负载两端电压,R为负载电阻.

  • 引入无量纲参数进行归一化处理,令:

  • x=X-l, xb=X-bl, V=CPV-χ-l, ωn=k1M-, c=C-M-, α^=K2l2M-, β^=K3l4M, χ^=χ-2lM-Cp, λ=1RCp, κ=κ-χ-

  • 式(3)无量纲化后可以表示为:

  • x¨(t)+cx˙(t)+dU(x)/dx-χ˙V(t)=-x¨b
    (4a)
  • V˙(t)+λV(t)+κx˙(t)=0
    (4b)
  • 其中,无量纲线性阻尼系数c=2μ^ωn,无量纲势函数Ux=ωn2/2x2+α^x4/4+β^x6/6μ^表示无量纲阻尼系数,α^β^表示无量纲刚度系数.外界振动激励x¨b满足窄带随机激励ξt=F^cosΩt+γWt,这里,Wt)为标准维纳过程,F^为振幅,Ω为恒定转速,γ为噪声强度.ξt)的功率谱Sω)表达式为[25]:

  • S(ω)=F^2γ2Ω2+ω2+γ442Ω2-ω2+γ242+ω2γ4
    (5)
  • 由式(5)可知,当噪声强度增加时,峰的带宽随之增加.当噪声强度趋近于无穷,式(5)趋近于均匀分布的白噪声功率谱.当噪声强度γ趋近于0时,Sω)在ωΩ处趋于无穷大,此时为典型的窄带随机噪声的功率谱.

  • 2 系统的随机响应分析

  • 2.1 多尺度法求解

  • 采用多尺度法求解运动式(4)的解析解,研究系统非线性响应特性并推导稳态响应矩的表达式.引入无量纲化摄动参数小量和新的时间变量T0T1Tr,···,即

  • Tr=εrt,r=0,1,2,
    (6)
  • 定义偏导数算子表示导数算子,即

  • ddt=D0+εD1+Oε2d2dt2=D02+2εD0D1+Oε2
    (7)
  • 设式(4)中的无量纲系数为ε阶,即

  • μ^=εμ, α^=εα, β^=εβ, χ^=εχ, F^=εF

  • 则式(4)可重新表示为如下形式:

  • x¨(t)+2εμωnx˙(t)+ωn2x(t)+εαx3(t)+εβx5(t)-εχv(t)=εFcos(Ωt+γW(t))V˙(t)+λV(t)+κx˙(t)=0
    (8)
  • 设式(8)中位移和电压的一阶近似解为

  • x(t)=x0T0,T1+εx1T0,T1+Oε2v(t)=v0T0,T1+εv1T0,T1+Oε2
    (9)
  • 其中,T0=tT1=εt分别是快变参数和慢变参数.

  • 将式(7)和式(9)代入式(8),省略ε的二阶以上项,并分别令ε0ε1的系数为零,得到

  • Oε0:D02x0T0,T1+ωn2x0T0,T1=0D0V0T0,T1+λV0T0,T1+D0x0T0,T1=0
    (10)
  • Oε1:D02x1T0,T1+ωn2x1T0,T1=-2D0D1x0T0,T1-2μωnD0x0T0,T1-αx03T0,T1-βx05T0,T1+χV0T0,T1+FcosΩT0+γWT1D0V1T0,T1+λV1T0,T1=-D1V0T0,T1-κD0x1-κD0x0
    (11)
  • 式(16)和式(17)的通解可以写成

  • x0=A1T1expiωnT0+ccv0=B1T1expiωnT0+cc
    (12)
  • 其中,A1T1)为复函数,A-1T1A1T1)的复共轭,cc为复共轭项.将式(12)代入式(10),得:

  • B1iωn+λB1+A1iωnκ=0
    (13)
  • 由式(13)得B1T1)为:

  • B1T1=-iωnκiωn+λA1T1
    (14)
  • 将式(12)中第一式代入式(17),消去永年项得:

  • -2iωnA1'-2iωn2μA1-3αA-1A12-10βA-12A13-iωnκχA1iωn+λ+F2expiΩT0-ωnT0+γWT1=0
    (15)
  • 本文主要研究式(8)中的主共振,引入调谐参数σ表示接近度,设

  • Ω=ωn+εσ
    (16)
  • 根据式(16),式(15)改写为:

  • -2iωnD1A-2iωn2μA1-3αA-1A12-10βA-12A13-iωnκχA1iωn+λ+F2expiσT1+γWT1=0
    (17)
  • A1T1)写成极坐标的形式A1T1)=1/2aT1)exp[iφT1)],其中a为稳态响应的幅值,φ为运动的相位.在式(17)中引入ηT1)=σT1+γWT1)-φT1),并分离实部和虚部,得

  • a'=-μ1a+F2ωnsinη,aη'=σ1a-3αa38ωn-5βa516ωn+F2ωncosη+γaW'T1
    (18)
  • 这里,μ1=μωn+χκλ2ωn2+λ2σ1=σ-χκωn2ωn2+λ.

  • 由式(18)可得aη,进一步得到式(8)中无量纲位移响应和输出电压响应的一阶近似表达式:

  • x(t)=a(εt)cos(Ωt-η(εt))+O(ε)
    (19)
  • V(t)=ωnκωn2+λ2a(εt)cos(Ωt-η(εt)+θ)+O(ε)
    (20)
  • 式中,θ=arctan(λ/ωn).

  • 2.2 稳态响应矩

  • 根据式(18),稳态解可以表示为:

  • da=-μ1a+F2ωnsinηdT1dη=σ1-3αa28ωn-5βa416ωn+F2aωncosηdT1+γdWT1
    (21)
  • γ=0时,式(21)为确定性系统.对于稳态解满足a′=0,η′=0,代入式(18)得

  • σ1a0-3αa038ωn-5βa0516ωn2+μ1a02=F24ωn2
    (22)
  • 下面讨论γ≠0时,噪声强度对系统稳态响应的影响.由于γ较小,可用线性化方法求解,令

  • a=a0+a1η=η0+η1
    (23)
  • 其中,a0η0是确定性谐波激励下的系统稳态响应幅值和相位角,a1η1是小扰动项.将式(23)代入式(21),忽略高阶项,得到线性化方程

  • a1'=-μ1a1+F2ωncosη0η1η1'=σ1a0-9αa08ωn-75βa0316ωna1-F2a0ωnsinη0η1+γW'T1
    (24)
  • 根据式(22),式(24)可以表示为

  • a1'=-μ1a1-M1η1η1'=M2a1-μ1η1+γW'T1
    (25)
  • 其中,M1=σ1a0-3αa03/8ωn-5βa05/16ωnM2=σ1/a0-9αa0/8ωn-75βa03/16ωn.

  • 式(24)中的二阶矩满足下列等式:

  • dEa12dT1=-2μ1Ea12-2M1Ea1η1dEa1η1dT1=M2Ea12-M1Eη12-2μEa1η1dEη12dT1=2M2Ea1η1-2μEη12+γ2
    (26)
  • dEa12dT1=dEa1η1dT1=dEη12dT1=0,通过式(26)得到二阶稳态矩:

  • Ea12=M12γ24μ1μ12+M1M2Ea1η1=-M1γ24μ12+M1M2Eη12=2μ12+M1M2γ24μ1μ12+M1M2
    (27)
  • 对式(23)两边取数学期望,得到解的一阶和二阶稳态矩:

  • Ea=a0,Ea2=a02+Ea12Eη=η0,Eη2=η02+Eη12
    (28)
  • 同理,输出电压的一阶和二阶稳态矩表示为:

  • Ev=ωnκωn2+λ2a0Ev2=2ωnκ2ωn2+λ2a0+Ea12
    (29)
  • 平均输出功率为

  • EP=λχEV2
    (30)
  • 由式(28)和式(29)可见,系统响应幅值和输出电压的一阶稳态矩与调谐参数有关,系统响应幅值和输出电压的二阶稳态矩与一阶稳态矩有关,调谐参数影响的结果对设备的小型化和采集性能的提高都至关重要.基于上述理论结果,在后续研究中,除特殊说明外固定参数ωn=1.0,μ=0.1,χ=1,F=2,ε=0.1,探究系统响应幅值和输出电压的一阶稳态矩与调谐参数的函数关系.

  • 为了更好地理解调谐参数的影响,图3给出了主共振附近响应幅值Ea在不同非线性刚度αβ下随调谐参数σ的变化规律.一方面,曲线呈现硬化特性,随着α的增大,Ea表现为非线性引起的右弯曲共振曲线,响应峰值和带宽大小均随之减小.这是由于非线性曲率在压电悬臂梁处于一阶模态振动时起主导作用,而表现出硬化特性.另一方面,随着β的增大,Ea向右弯曲的趋势更加明显,响应峰值和带宽大小均迅速减小.

  • 图3 振幅一阶稳态矩随调谐参数的变化函数

  • Fig.3 The first-order steady-state moments of the amplitude Ea as a function of detuning frequency σ

  • 图4绘制了输出电压的一阶矩EV随调谐参数σ的变化图像.增大非线性刚度αβEV同样显示了右弯曲共振曲线,并且五次方刚度系数β的影响比三次方刚度系数α的影响更大.因此,可以考虑合理调整非线性刚度αβ来拓宽能量采集器的工作频带宽度.

  • 图4 电压的一阶稳态矩随调谐参数的变化函数

  • Fig.4 The first-order steady-state moments of the voltage EV as a function of detuning frequency σ

  • 2.3 数值模拟

  • 通过使用四阶Runge-Kutta算法得到式(4)的数值解.为便于分析,通常使用式(31)给出的伪随机信号对ξt)进行建模,实现随机动力学相关的数值模拟.

  • ζ(t)=4ωNk=1N cos2k-1Nωt+φk
    (31)
  • 其中,φk在(0,2π]上均匀分布,N是一个较大的正整数.

  • 当马尔可夫扩散过程达到静止状态,稳态概率密度函数通过条件-+ -+ pxx˙dxdx˙=1p/t=0求解.

  • 由于强非线性刚度,中心差分格式可以表示为:

  • pijx=pi+1,j-pi-1,jΔx,pijx˙=pi,j+1-pi,j-1Δx˙,2pijY2=pi,j+1-2pi,j+pi,j-1Δx˙2
    (32)
  • 进一步探讨系统参数对随机响应的影响,在下面的数值模拟中,除2.2节中给出的参数设置外,其他主要系统参数设置为κ=0.4,λ=0.4,α=-3.2,β=1.1,N=1000.在(xx˙)的计算区域[-1.5,1.5]×[1.5,1.5]上选取50×50组初始值,对不同初始值得到的响应轨迹进行平均,得到系统的稳态概率密度函数.

  • 图5和图6分别是激励幅值F=2和F=4时,系统对应的时间历程图和电压变化图.通过比较发现位移和电压的输出响应在不同F下会发生明显波动,具体表现为:当F较小时,系统的采集输出能力较低,磁铁之间的作用力较弱,此时位移和电压响应较小; 当F增大时,系统的输出响应有较大变化,末端磁铁受到两个外部磁铁之间非线性作用力较大,非线性作用特性影响明显,末端振动位移和输出电压均有提高.可见激励幅值对于系统的能量采集效率至关重要,在一定范围内增大加速度幅值有利于拓宽能量采集器作三稳态运动的工作频带,从而提高系统的采集输出能力.

  • 图5 F=2时系统的输出响应特性

  • Fig.5 Response behaviors of the system for F=2

  • 图6 F=4时系统的输出响应特性

  • Fig.6 Response behaviors of the system for F=4

  • 图7和图8分别是改变噪声强度大小时,系统对应的输出特性仿真结果.当噪声强度γ=0.2时,如图7所示,系统陷入了三稳态的某一势阱中,在对应的平衡点附近作小幅值振动,此时压电俘能器的振动位移、振动速度和输出电压均迅速减小.当噪声强度进一步增大至γ=0.35,如图8所示,系统较易克服磁力的束缚作用,在三个势阱之间来回跳跃做大幅值的振动,此时俘能器的输出性能较γ=0.2时提高更多.由此可见,适当的选择噪声强度有利于提高俘能器的输出性能,从而满足实际情况下的需求.

  • 图7 γ=0.2时系统的输出响应特性

  • Fig.7 Response behaviors of the system for γ=0.2

  • 图8 γ=0.35时系统的输出响应特性

  • Fig.8 Response behaviors of the system for γ=0.35

  • 3 实验验证

  • 为了验证第2节给出的理论结果的正确性,图10为搭建的三稳态压电俘能器实验样机和平台.压电悬臂梁左侧固定在基座上,其右端用高强度胶黏结末端磁铁A,两个外部磁铁B和C也通过高强度胶黏结在可滑动板上,磁铁的型号为N50.基板根部的上、下表面黏结两片大小相同、极化方向相同的压电陶瓷片,并通过金属铜电极串联连接电阻R,压电片的型号为PZT-5H.

  • 图9 实验系统测试中仪器连接

  • Fig.9 Experimental test system of piezoelectric energy harvesting system

  • 搭建实验系统测试平台时,各个实验仪器之间的连接示意图如图9所示.基座通过底部中间的螺钉固定在激振器上,在计算机中生成窄带激励数字信号,然后通过USB输入信号发生器.信号发生器输出后通过功率放大器放大,再输入到激振器作用于能量采集器上.激光位移传感器采集悬臂梁末端位移,压电片产生的电压由示波器进行采集和存储.实验涉及的主要参数见表1.

  • 表1 压电俘能器的主要材料参数

  • Table1 Main material parameters of piezoelectric energy harvester

  • 图10 三稳态压电能量采集器实验测试平台

  • Fig.10 Testing platform of tri-stable piezoelectric energy harvester

  • 为了分析实验中系统的振动响应情况,当激励中心频率为12Hz时,图11给出激振器的加速度响应及其频谱图,确保实验在接近真实的窄带随机激励下进行.

  • 图11 激振器的激励状态

  • Fig.11 Excitation state of the vibrator

  • 末端磁铁与外部磁铁间的非线性作用力会严重影响系统振动特性,为了验证理论方法的正确性,在该激励条件下调节磁铁的水平间距和竖直间距对系统进行实验验证与分析.图13~图15为系统在不同磁铁间距下的相图、时间历程图和输出电压波形的实验结果,对应的振动状态分别是: 三稳跃迁振动、三稳单势阱内振动、双稳振动.

  • 图12(a)表明当水平间距dx=10mm,竖直间距dy=5mm时,磁铁之间的非线性作用特性影响明显,压电俘能器较易克服磁力的束缚,在3个稳态平衡位置之间来回跳跃振动,此时系统为三稳态压电俘能器.存在3个势能阱且宽度和深度较为均匀一致,有利于在较小的外部激励下表现出大幅值输出特性,有利于输出性能的提高.从图13中可以看出,系统的末端振动位移、振动速度最大分别为4.5mm和280mm/s,且采集输出电压最大可达30V,具有较好的采集性能.

  • 图12 不同dxdy下俘能器的实验结果

  • Fig.12 Experimental results of VEH with different dx and dy

  • 随着磁铁的间距减小到水平间距dx=8mm和竖直间距dy=5mm,如图12(b)所示,由于磁铁之间作用力较大,系统在相同激励水平下,没有足够的能量摆脱磁力的束缚,陷入初始位置附近的势阱中做井内振动.此种情况下,悬臂梁末端只能在由初始位置确定的某一个平衡点附近做小幅值的周期运动,其性能类似于单稳态系统.此时系统的末端振动位移和振动速度都非常小,分别为1.5mm和100mm/s,采集输出电压最大仅为4V.可以看出,末端磁铁和外部磁铁之间的间距过大、过小都不利于提高压电俘能器的输出性能.

  • 水平间距dx=12mm,竖直间距dy=4mm时,如图12(c)所示,系统有两个近似对称的势能阱,其深度和宽度较大,外部激励提供较大的能量使得压电俘能器克服势垒的阻碍作用呈现双稳态采集特性.末端振动位移、振动速度分别为2.5mm和200mm/s,采集输出电压最大可达到15V.通过实验数据对比分析,系统为三稳态能量采集系统时具有更高的采集效率,输出位移和采集电压更高,进一步说明了三稳态压电俘能器的优越性.

  • 实验结果与仿真结果得到的振动位移和采集电压相比存在一些误差,主要的原因有:样机制作过程中尺寸加工误差和材料特性偏差等因素导致误差,例如材料的弹性模量、密度等参数都是一个范围值,计算时为了简便选取了一个中间值,因此理论与实验结果很难完全一致; 由于末端磁铁的重力因素,实验得到的相图不是完全对称的.

  • 能量采集同时关注工作频率带宽的大小,图13给出了不同噪声强度下三稳态压电俘能器的幅频响应曲线的实验对比结果.当噪声强度γ=0时,窄带随机激励退化成简谐激励; 当噪声强度γ=0.2和γ=0.4时,外部激励为更符合实际振动的窄带随机振动.由图13可以看出,适当的选择噪声强度,三稳态压电俘能器在窄带随机激励下具有更好的输出性能和更宽的工作频带.在实际应用中可以合理调整,以实现更好的机电能量转换.

  • 图13 不同噪声强度下俘能器的幅值幅频响应曲线

  • Fig.13 Amplitude frequency response of VEH with different γ

  • 4 结论

  • 针对三稳态压电俘能系统,基于多尺度法得到系统运动方程的解析解,分析了磁铁间距、噪声强度和加速度幅值等参数对系统响应和采集性能的影响.结果表明:对于一定带宽的窄带随机激励,始终存在一组能够产生响应峰值的磁铁间距,这一特性类似于宽频带随机激励下三稳态系统在最优磁铁间距处产生响应峰值的三稳响应特性; 改变磁铁的水平和垂直间距,俘能器会经历单稳态、双稳态和三稳态三种运动状态.末端磁铁与外部磁铁的间距过大、过小都不利于提高能量采集器的输出性能,而俘能器做三稳态运动可以显著提高俘能器的振动位移和采集电压; 在dx=10mm,dy=10mm时,实验得到的振动位移为,采集到的输出电压最大可达到.真实环境中窄带激励存在变化,需要根据实际情况调整俘能器的磁铁间距,从而实现更好的机电能量转换.

  • 参考文献

    • [1] ERTURK A,HOFFMANN J,INMAN D J.A piezo-magnetoelastic structure for broadband vibration energy harvesting [J].Applied Physics Letters,2009,94(25):254102-254104.

    • [2] GLYNE-JONES P,WHITE N M.Self-powered systems:a review of energy sources [J].Sensors Review,2001,21(2):91-97.

    • [3] ROUNDY S,WRIGHT P K.A piezoelectric vibration based generator for wireless electronics [J].Smart Materials and Structures,2004,13(5):1131-1144.

    • [4] 杨斌强,徐文潭,王广庆.带弹性放大器的双稳态压电振动能量采集器 [J].传感技术学报,2017,30(5):684-691.YANG B Q,XU W T,WANG G Q.A bistable piezoelectric vibration energy harvester with an elastic magnifier [J].Chinese Journal of Sensors and Actuators,2017,30(5):684-691.(in Chinese)

    • [5] GUAN M J,LIAO W H.On the efficiencies of piezoelectric energy harvesting circuits towards storage device voltages [J].Smart Materials and Structures,2007,16(2):498-505.

    • [6] YAO M H,MA L,ZHANG W.Study on power generations and dynamic responses of the bistable straight beam and the bistable L-shaped beam [J].Science China-Technological Sciences,2018,61(9):1404-1416.

    • [7] ARRIETA A F,HAGEDORN P,ERTURK A,et al.A piezoelectric bistable plate for nonlinear broadband energy harvesting [J].Applied Physics Letters,2010,97(10):174103.

    • [8] STANTON S C,OWENS B,MANN B P.Harmonic balance analysis of the bistable piezoelectric inertial generator [J].Journal of Sound and Vibration,2012,331(15):3617-3627.

    • [9] HARNE R L,WANG K W.A review of the recent research on vibration energy harvesting via bi-stable systems [J].Smart Materials and Structures,2013,22(2):023001.

    • [10] 吴子英,叶文腾,刘蕊.一种新型双稳态电磁式振动能量捕获器动力学特性研究 [J].应用力学学报,2017,34(5):848-854.WU Z Y,YE W T,LIU R.Dynamics of a novel bi-stable electromagnetic vibration energy harvester [J].Chinese Journal of Applied Mechanics,2017,34(5):848-854.(in Chinese)

    • [11] ZHU P,REN X M,QIN W Y,et al.Improving energy harvesting in a tri-stable piezomagnetoelastic beam with two attractive external magnets subjected to random excitation [J].Archive of Applied Mechanics,2016,87(1):1-13.

    • [12] ZHU P,REN X M,QIN W Y,et al.Theoretical and experimental studies on the characteristics of a tri-stable piezoelectric harvester [J].Archive of Applied Mechanics,2017,87(9):1541-1554.

    • [13] ZHOU S X,CAO J Y,INMAN D J,et al.Broadband tristable energy harvester:modeling and experiment verification [J].Applied Energy,2014,133(1):33-39.

    • [14] ZHOU Z Y,QIN W Y,ZHU P.Energy harvesting in a quad-stable harvester subjected to random excitation [J].Aip Advances,2016,6(2):785-791.

    • [15] KIM P,SEOK J.Dynamic and energetic characteristics of a tri-stable magnetopiezoelastic energy harvester [J].Mechanism & Machine Theory,2015,94:41-63.

    • [16] LENG Y G,TAN D,LIU J J,et al.Magnetic force analysis and performance of a tri-stable piezoelectric energy harvester under random excitation [J].Journal of Sound and Vibration,2017,406:146-160.

    • [17] BEEBY S P,WANG L,ZHU D,et al.A comparison of power output from linear and nonlinear kinetic energy harvesters using real vibration data [J].Smart Materials and Structures,2013,22(7):075022.

    • [18] ZHU W Q,LU M Q,WU Q T.Jump and bifurcation of duffing oscillator under narrowband excitation [J].Acta Mechanica Sinica,1994,10(1):73-81.

    • [19] 戎海武,王向东,徐伟.窄带随机噪声作用下Duffing振子的双峰稳态概率密度 [J].物理学报,2005,54(6):2557-2560.RONG H W,WANG X D,XU W.On double-peak probability density functions of a Duffing oscillator under narrow-band random excitation [J].Acta Physica Sinica,2005,54(6):2557-2560.(in Chinese)

    • [20] 吴娟娟.窄带随机激励下双稳压电悬臂梁响应特性与能量采集研究 [D].天津:天津大学,2018.WU J J.Response characteristic of a nonlinear bi-stable piezoelectric cantilever beam under narrow-band random excitations and its energy harvesting [D].Tianjin:Tianjin University,2018.(in Chinese)

    • [21] JIN Y F,ZHANG Y X.Dynamics of a delayed Duffing-type energy harvester under narrow-band random excitation.Acta Mechanica,2021,232:1045-1060.

    • [22] 满大伟.非线性多稳态压电俘能器的动力特性分析 [D].合肥:合肥工业大学,2019.MAN D W.Analysis of dynamic characteristics of nonlinear multi-stable piezoelectric energy harvester [D].Hefei:Hefei University of Technology,2019.(in Chinese)

    • [23] 唐炜,王小璞,曹景军.非线性磁式压电振动能量采集系统建模与分析 [J].物理学报,2014,63(24):72-85.TANG W,WANG X P,CAO J J.Modeling and analysis of piezoelectric vibration energy harvesting system using permanent magnetics [J].Acta Physica Sinica,2014,63(24):72-85.(in Chinese)

    • [24] 满大伟,王建国.梁端磁铁尺寸对三稳态压电俘能器性能影响分析.应用力学学报,2020,37(4):1-7.MAN D W,WANG J G.Size effect of tip magnet on the performance of tri-stable piezoelectric energy harvesters [J].Chinese Journal of Applied Mechanics,2020,37(4):1-7.(in Chinese)

    • [25] DAVIES H G,LIU Q.The response envelope probability density function of a Duffing oscillator with random narrow-band excitation [J].Journal of Sound and Vibration,1990,139(1):1-8.

  • 参考文献

    • [1] ERTURK A,HOFFMANN J,INMAN D J.A piezo-magnetoelastic structure for broadband vibration energy harvesting [J].Applied Physics Letters,2009,94(25):254102-254104.

    • [2] GLYNE-JONES P,WHITE N M.Self-powered systems:a review of energy sources [J].Sensors Review,2001,21(2):91-97.

    • [3] ROUNDY S,WRIGHT P K.A piezoelectric vibration based generator for wireless electronics [J].Smart Materials and Structures,2004,13(5):1131-1144.

    • [4] 杨斌强,徐文潭,王广庆.带弹性放大器的双稳态压电振动能量采集器 [J].传感技术学报,2017,30(5):684-691.YANG B Q,XU W T,WANG G Q.A bistable piezoelectric vibration energy harvester with an elastic magnifier [J].Chinese Journal of Sensors and Actuators,2017,30(5):684-691.(in Chinese)

    • [5] GUAN M J,LIAO W H.On the efficiencies of piezoelectric energy harvesting circuits towards storage device voltages [J].Smart Materials and Structures,2007,16(2):498-505.

    • [6] YAO M H,MA L,ZHANG W.Study on power generations and dynamic responses of the bistable straight beam and the bistable L-shaped beam [J].Science China-Technological Sciences,2018,61(9):1404-1416.

    • [7] ARRIETA A F,HAGEDORN P,ERTURK A,et al.A piezoelectric bistable plate for nonlinear broadband energy harvesting [J].Applied Physics Letters,2010,97(10):174103.

    • [8] STANTON S C,OWENS B,MANN B P.Harmonic balance analysis of the bistable piezoelectric inertial generator [J].Journal of Sound and Vibration,2012,331(15):3617-3627.

    • [9] HARNE R L,WANG K W.A review of the recent research on vibration energy harvesting via bi-stable systems [J].Smart Materials and Structures,2013,22(2):023001.

    • [10] 吴子英,叶文腾,刘蕊.一种新型双稳态电磁式振动能量捕获器动力学特性研究 [J].应用力学学报,2017,34(5):848-854.WU Z Y,YE W T,LIU R.Dynamics of a novel bi-stable electromagnetic vibration energy harvester [J].Chinese Journal of Applied Mechanics,2017,34(5):848-854.(in Chinese)

    • [11] ZHU P,REN X M,QIN W Y,et al.Improving energy harvesting in a tri-stable piezomagnetoelastic beam with two attractive external magnets subjected to random excitation [J].Archive of Applied Mechanics,2016,87(1):1-13.

    • [12] ZHU P,REN X M,QIN W Y,et al.Theoretical and experimental studies on the characteristics of a tri-stable piezoelectric harvester [J].Archive of Applied Mechanics,2017,87(9):1541-1554.

    • [13] ZHOU S X,CAO J Y,INMAN D J,et al.Broadband tristable energy harvester:modeling and experiment verification [J].Applied Energy,2014,133(1):33-39.

    • [14] ZHOU Z Y,QIN W Y,ZHU P.Energy harvesting in a quad-stable harvester subjected to random excitation [J].Aip Advances,2016,6(2):785-791.

    • [15] KIM P,SEOK J.Dynamic and energetic characteristics of a tri-stable magnetopiezoelastic energy harvester [J].Mechanism & Machine Theory,2015,94:41-63.

    • [16] LENG Y G,TAN D,LIU J J,et al.Magnetic force analysis and performance of a tri-stable piezoelectric energy harvester under random excitation [J].Journal of Sound and Vibration,2017,406:146-160.

    • [17] BEEBY S P,WANG L,ZHU D,et al.A comparison of power output from linear and nonlinear kinetic energy harvesters using real vibration data [J].Smart Materials and Structures,2013,22(7):075022.

    • [18] ZHU W Q,LU M Q,WU Q T.Jump and bifurcation of duffing oscillator under narrowband excitation [J].Acta Mechanica Sinica,1994,10(1):73-81.

    • [19] 戎海武,王向东,徐伟.窄带随机噪声作用下Duffing振子的双峰稳态概率密度 [J].物理学报,2005,54(6):2557-2560.RONG H W,WANG X D,XU W.On double-peak probability density functions of a Duffing oscillator under narrow-band random excitation [J].Acta Physica Sinica,2005,54(6):2557-2560.(in Chinese)

    • [20] 吴娟娟.窄带随机激励下双稳压电悬臂梁响应特性与能量采集研究 [D].天津:天津大学,2018.WU J J.Response characteristic of a nonlinear bi-stable piezoelectric cantilever beam under narrow-band random excitations and its energy harvesting [D].Tianjin:Tianjin University,2018.(in Chinese)

    • [21] JIN Y F,ZHANG Y X.Dynamics of a delayed Duffing-type energy harvester under narrow-band random excitation.Acta Mechanica,2021,232:1045-1060.

    • [22] 满大伟.非线性多稳态压电俘能器的动力特性分析 [D].合肥:合肥工业大学,2019.MAN D W.Analysis of dynamic characteristics of nonlinear multi-stable piezoelectric energy harvester [D].Hefei:Hefei University of Technology,2019.(in Chinese)

    • [23] 唐炜,王小璞,曹景军.非线性磁式压电振动能量采集系统建模与分析 [J].物理学报,2014,63(24):72-85.TANG W,WANG X P,CAO J J.Modeling and analysis of piezoelectric vibration energy harvesting system using permanent magnetics [J].Acta Physica Sinica,2014,63(24):72-85.(in Chinese)

    • [24] 满大伟,王建国.梁端磁铁尺寸对三稳态压电俘能器性能影响分析.应用力学学报,2020,37(4):1-7.MAN D W,WANG J G.Size effect of tip magnet on the performance of tri-stable piezoelectric energy harvesters [J].Chinese Journal of Applied Mechanics,2020,37(4):1-7.(in Chinese)

    • [25] DAVIES H G,LIU Q.The response envelope probability density function of a Duffing oscillator with random narrow-band excitation [J].Journal of Sound and Vibration,1990,139(1):1-8.

  • 微信公众号二维码

    手机版网站二维码