Optimisation of Broadband Energy Harvesters Using Bistable Composites

该提案将通过创建优化方法，在大/中尺度上开发最佳宽带能量采集器。这将通过压电材料将机械振动转换为电能的复合材料层压板来实现。能量收集是一个活跃的研究领域，开发从外部环境中捕获能量的方法来为无线传感器网络等低能耗电子设备供电。能量的一个来源是振动，并且压电材料通常用于将机械振动转换成电能。当前最先进的设备被设计为在谐振频率下捕获电能。虽然这在良好控制的频率环境中工作良好，但是采集性能福尔斯显著地落在谐振频率之外，并且随着设备变小或变大，结构的谐振频率可能很快变得不可达到。这限制了可以使用振动能量收集装置的应用领域。Inman（Co-I）最近发现，由于其非线性动力学特性，所提出的复合材料机制在一定频率范围内具有优异的收获性能。双稳态复合材料板具有由非对称铺层的各向异性材料特性引起的固有双稳态。近年来，在压电致动变形结构的背景下，这些压电复合材料得到了广泛的研究，Kim（PI）和Bowen（Co-I）在2011年推出了第一个也是唯一一个压电复合材料的优化方法。该项目将这些专业知识与Clarke（Co-I）的混合信号电子技术相结合，以开发适用于环境振动的宽带能量采集器。国家物理实验室（NPL）和Perpetuum将通过其实验专业知识、设施和工业和客户需求的数据来支持该项目。非线性弹性复合材料的复杂物理学很难理解和设计，并且申请人最近开发的弹性复合材料的优化方法提供了对设计空间的系统探索，以找到尺寸，纤维取向的厚度和堆叠顺序。在此基础上，该项目将开发由实验研究支持的能量收集复合材料的静态和动态模型，并制定优化方法，用于设计和构建基于真实的世界应用的演示器。该项目将解决三个主要挑战：（1）系统行为的非线性，双稳态的多个平衡状态，压电构造和离散复合材料叠层都提出了重大的科学挑战。拟议的研究采用了一种新的优化方法，以考虑物理学的复杂相互作用，并为工程师提供了一种设计宽带能量采集器的方法，以满足任何给定的要求。(2)到目前为止，还没有研究非线性在能量收集中的作用。我们将探讨这一点的能量收集性能的建模，包括动态非线性耦合机电性能的实验表征。(3)用于产生双稳态的一种流行的机制是经由外部电磁场，其对于周围系统和电气部件来说可能是麻烦的和突兀的。非对称复合材料层合板具有固有的双稳态特性，因此所得到的系统可以更加紧凑且易于安装。

This proposal will develop optimum broadband energy harvesters at the large/meso-scale by creating an optimisation methodology. This will be achieved by bistable composite laminates with piezoelectric materials converting mechanical vibration to electrical energy.Energy harvesting is an active research area developing ways of capturing energy from the external environment to power low energy electronics such as wireless sensor networks. One source of energy is vibration and piezoelectric materials are commonly used to convert mechanical vibration to electrical energy. The current state-of-the-art devices are designed to capture electrical energy at resonant frequencies. Whilst this works well in a well-controlled frequency environment, the harvesting performance falls dramatically outside the resonant frequencies and the resonant frequencies of a structure can quickly become unattainable as a device becomes small or large. This limits the application areas where vibratory energy harvesting devices can be used. The proposed bistable composite mechanism has recently been discovered by Inman (Co-I) to have an excellent harvesting performance over a range of frequencies due to its nonlinear dynamics. Bistable composite plates have an inherent bistability arising from anisotropic material properties of an asymmetrical layup. These bistable composites have been extensively studied in the context of piezo-actuated morphing structures in recent years and Kim (PI) and Bowen (Co-I) introduced the first and the only optimisation methodology for bistable composites in 2011. The project combines these expertise together with mixed signal electronics of Clarke (Co-I) to develop broadband energy harvesters suitable for ambient vibration. The National Physical Laboratory (NPL) and Perpetuum will support this project via their experimental expertise, facilities and data on the industrial and customers' needs.The complex physics of nonlinear bistable composites is difficult to understand and design, and the optimisation methodology for bistable composites recently developed by the applicants offers a systematic exploration of the design space to find the optimum combination of size, thickness and stacking sequence of fibre orientations. Building on from this foundation, the project will develop static and dynamic models of bistable enegy harvesting composites supported by experimental investigations and formulate an optimisation methodology which will be used to design and build demonstrators based on real world applications.There are three main challenges which will be addressed in this project:(1) The nonlinearity of the system behaviour, multiple equilibrium states of bistability, piezoelectric configuration and discrete composite lay-ups all present significant scientific challenges. The proposed research takes a novel approach of optimisation to account for the complex interaction of physics and offers engineers a methodology for designing bistable broadband energy harvesters for any given requirements. (2) No research to date has studied the role of nonlinearities in bistable energy harvesting. We will explore this in the modelling of energy harvesting performance including dynamic nonlinearity with experimental characterisation of coupled electromechanical properties.(3) One popular mechanism for generating bistability is via an external electromagnetic field which can be cumbersome and obtrusive to the surrounding system and the electrical components. Bistability is inherent to asymmetrical composite laminates, therefore the resulting system can be more compact and easily installed.