局域共振型压电超材料增强宽带低频环境振动能量俘获机理与方法

How to provide long-term and reliable power for wireless sensor network nodes is one of bottle-neck problems in applications of Internet of Things. It is a promising technical solution to transform environmental vibration energy into electrical energy based on piezoelectric effects. While traditional assumptions of localized vibrations at a fixed spatial point are not fit for environmental vibrations, which is one of fundamental reasons of low-efficiency piezoelectric energy harvesting for environmental vibrations. Thus this project aims at the significant need of self-powered low power consumption sensors and actuators. Main focuses are paid on the problem of broadband, low-frequency and propagation of environmental vibration energy in many cases. By introducing the band-gap mechanism of local resonances, broadband and low-frequency environmental vibration energy harvesting enhanced by piezoelectric metamaterial is deeply studied based on a system-level standpoint of 'from environmental vibration energy to DC energy'. Firstly, characteristics of elastic wave propagation in a thin piezoelectric metamaterial plate are investigated. Based on them, the principles of vibration band-gap and energy localization are exposed. Then, a system-level elastoelectromechanical model of vibration energy harvesting systems using piezoelectric metamaterials is built and its solution algorithm is proposed. In the end, basic mechanism of a system-level topology optimization is presented. Thus high efficient energy harvesting and conversion can be achieved for broadband and low-frequency environmental vibrations. In summary, the proposed method in this project will provide theoretic and technical support for making low power consumption wireless sensor network nodes self-powered.

如何为无线传感器网络节点长久可靠供电是物联网未来应用中的瓶颈问题之一，利用压电效应俘获环境振动能量并转化为电能是一种极具潜力的技术途径，而传统研究采用的固定位置、能量集中的振动激励假设并不符合实际环境振动，这是导致目前环境振动压电俘能效率不高的根本原因之一。为此，本项目瞄准低功耗传感器和致动器自供电的重大需求，针对很多环境振动能量具有宽带、低频、波动的特性，通过引入局域共振带隙机理，从“环境振动能到直流电输出”全系统角度深入开展压电超材料增强宽带低频环境振动能量俘获理论研究，剖析局域共振型压电超材料薄板内弹性波传播特性，揭示其振动带隙和能量局域化机理，建立压电超材料振动俘能全系统的弹-机-电耦合模型及其求解方法，阐明系统级的拓扑优化机制，实现高效的宽带低频环境振动能量俘获与转换，为低功耗无线传感器网络节点自供电提供理论和方法支持。

针对工程应用场合结构振动具有不定向传播、能量以弹性波形式存在、宽带低频等特性，引入局域共振带隙机理构建了压电超材料薄板，首先引入哈密尔顿原理，从理论上建立了压电超材料薄板横向振动弹性波传播模型，通过数值仿真分析了其振型、揭示了振动能量局域化机理，针对外接纯电阻负载建立了压电超材料薄板振动发电的机电耦合模型，理论推导了压电超材料薄板的固有频率、横向振动位移和输出电压的表达式；接着，基于Bloch定理仿真分析了局域共振型压电超材料薄板的振动带隙特性，验证了带隙产生的原因为局域共振机理，而不是布拉格散射机理；然后，针对自供电P-SSHI电路的开关时延问题，建立了开关时延的理论模型，分析了开关时延的影响因素，提出了一种低时延的自供电P-SSHI电路，平均能量俘获效率提高约11%，另外还在已有同步电荷提取电路中引入谐振电感，提出了一种谐振式同步电荷提取电路，电压幅值约增加200%，明显提高了AC-DC的转化效率；从理论上建立了局域共振型压电超材料薄板振动俘能全系统的弹-机-电耦合模型，推导了外接同步电荷提取电路的等效阻抗，并采用Bloch定理和波有限元方法提出了上述弹-机-电耦合模型的数值计算算法，在此基础上分别提出了压电超材料薄板材料拓扑优化和结构拓扑优化方法，为系统级材料、结构和电路参数优化提供了理论依据；最后，搭建了实验系统，测试验证了本项目所研方法的有效性。项目研究成果可用于优化设计局域共振型压电超材料薄板振动俘能系统，实现宽带低频结构振动能量的高效俘获，对推动实现嵌入式无线结构健康监控具有重要意义。