微型双稳态板压电俘能器的理论和实验研究

With the development of micro / nano fabrication technology, the size of wireless sensor is smaller. Meanwhile, there has been a huge demand of long-life batteries for micro or nano scale wireless sensors. With the ability of absorb energy from the ambient environment, micro energy harvester continues to receive both industrial and academic interests. In this project, a micro energy harvester based on bi-stable piezoelectric plate is investigated. The strain gradient theory with small scale effect is applied to obtain the constitutive equation which contains the feature dimension. Strength-heat-electric multi-field coupling nonlinear dynamic model is established considering the effects of piezoelectric, temperature and geometric nonlinearity. Complex nonlinear dynamic responses such as bifurcation and chaos are investigated via both theoretical analysis and numerical simulation. Also, nonlinear phenomena e.g. sub-harmonic resonance and chaos as well as snap-through between two different stable states are used to achieve large amplitude and wide band frequency spectrum cycle which makes the energy harvester more effective. Experiments are done to investigate the relationship between piezoelectric constant of the piezoelectric material, electromechanical coupling coefficient, parameters of the material, geometry of the structure as well as the small scale effect and the energy conversion efficiency. This project will provide theoretical and experimental basis for application and optimization of micro energy harvesters.

随着微/纳加工技术的发展，无线传感器尺寸越来越小，对长寿命电源的需求越来越强烈。所以，能够吸收环境振动，为其提供电能的微型压电俘能器成为研究热点。本项目针对微型的双稳态板结构，利用应变梯度理论，考虑尺度效应，构建包含特征长度的本构方程；综合考虑压电效应、温度和几何非线性的影响，建立力-热-电多场耦合的非线性动力学模型。通过理论分析和数值模拟研究系统的分岔特性和混沌运动等复杂非线性动力学响应。并且利用压谐共振和混沌等非线性现象，以及两个稳态之间的跳变（snap-through)，在非共振频率的环境下实现大幅宽频振动，从而使压电俘能器达到更好的发电效率。通过和实验相结合的方法研究压电材料的压电常数，机电耦合系数，基体材料参数，结构几何尺寸和微尺度效应对能量转换效率的影响规律。本项目的研究为微型压电俘能器的实际应用和优化设计提供了理论依据和实验参考。

在传统能源如石油、天然气、煤炭等不可再生能源的过量使用对人们赖以生存的环境造成了不可恢复的破坏，新能源的开发和新型材料的利用得到了世界各国的重视的背景下。本项目针对微型的双稳态板结构，建立力-热-电多场耦合的非线性动力学模型。通过理论分析和数值模拟研究系统的分岔特性和混沌运动等复杂非线性动力学响应。并且利用超谐共振和混沌等非线性现象，以及两个稳态之间的跳变，在非共振频率的环境下实现大幅宽频振动，从而使压电俘能器达到更好的发电效率。通过和实验相结合的方法研究能量转换效率的影响规律。通过本项目的研究发现：（1）当结构尺寸达到微米量级时，需要考虑尺寸效应。（2）本项目采用的应变梯度理论，可以描述和解释微尺度带来的本构关系的改变。（3）微型双稳态俘能器在俘能的过程中，存在着跳变导致的大幅振动现象，并且发生了1/3的超谐共振现象，提高了俘获电压和效率。（4）当结构尺寸达到纳米量级时，挠曲电效应需要考虑，并且与压电效应相互耦合，提高了双稳态压电俘能器的能量转换效率。（5）基于Abques软件，针对微型双稳态压电俘能器，本项目开发了一种新的热-电-力耦合微型单元，运用进行有限元分析。（6）为了拓宽俘能器的工作频宽，提高自适应能力，本项目设计了一种新型的自调谐双稳态压电俘能器。通过附加箱子和滚动球，利用球位置的改变，自动调节结构的固有频率，增加俘能器的工作频率范围。