Noninear Vibration Of A Novel Piezoelectric Energy Harvester

Mechanical vibration energy is the most common source of energy in theengineering or natural environment. In the past decades, research on energyharvesting technologies based on environmental vibration has become a closelyconcerned topic in new energy, and piezoelectric vibration energy harvester basedupon direct piezoelectric effect turns into the focus in this field because of itsadvantages of high energy density, fast response, longevity, no pollution, simplestructure and easy assembly. For the moment, there are various structures ofpiezoelectric vibration energy harvester, and how to make a further optimizationaimed at layout designs of the oscillator has the instructive significance to broadresponse bandwidth and high efficiency of energy collection. In this article, a newclass of piezoelectric vibration energy harvester was introduced, and we discussed thevibration characteristics and power generation of the structure by means of nonlineardynamic analysis.The content of this paper can be summarized as follows:(1) A new class ofpiezoelectric vibration energy harvester was designed, which is composed of abuckling unimorph PZT beam, a mass and a nonlinear spring. The buckling beam ismade of two kinds of materials, the upper piezoelectric layer and the lower metal baselayer. When connected to the host structure rigidly, the harvester can gather energycontinuously because the former oscillation will be changed into the vibration of thebuckling unimorph PZT beam.(2) Based on the piezoelectric constitutive relationshipand Euler-Bernoulli beam theory, the nonlinear partial differential equation isconstructed for the free vibration energy harvester using Hamilton’s principle. Thenfirst-order ordinary differential equation is got by using Galerkin method. Upon theabove work, we study the effects on the first order natural frequency of the beam’sphysical dimension, the thickness ratio of the piezoelectric layer, the applied externalvoltage and the initial static deflection.(3) The dynamic model of energy harvesterstructure under exoteric sinusoidal excitation is established, and then we obtainordinary differential equations of single and two degree of freedom through Galerkinmethod. We gain the amplitude-frequency response equation under sub harmonicresonance circumstances by using the perturbation method of multiple scales, andafterwards we work on the relationship between the excitation, the coefficient ofviscous damping and frequency response curves. The response of the nonlinearvibration system is analyzed at the same time.(4)We associate the motion equation ofsingle degree of freedom with the voltage equation in order to find out the property ofpower generation of the piezoelectric vibration harvester. The first order approximate solution of the output voltage is given by means of perturbation analysis, and then weobtain the amplitude-frequency response curves of the output voltage. According tothe curves, we study the influences of external excitation, the length and width of thePZT beam, the mass, the viscous damping and the initial static deflection, attemptingto figure our how to increase the amplitude of the output voltage and how to extendthe response bandwidth.