基于仿生学的压电风能采集系统研究

According to the characteristics of wind in natural environments, inspired by the sways of plants under multi-directional, low and medium speed wind, a new structure of small-scale piezoelectric trees for wind energy harvesting was proposed based on the research on wind energy harvesting bionics. Furthermore, by considering the characteristics of micromachining processes, a new structure of MEMS piezoelectric trees was proposed. By studying the mechanism and condition of the enhancement effect of coupling between vortex-induced vibration and galloping/flutter, an efficient piezoelectric wind energy harvesting element will be designed. The matching methods of stiffness and mass for trunk, branches, leaves and fruits will be studied. Two types of piezoelectric trees in form of small-scale configuration and MEMS based architecture will be designed, respectively. By optimizing such key processes as preparing the piezoelectric thin film at low temperature on flexible substrates and the releasing of three-dimensional MEMS flexible structures, a process flow of flexible piezoelectric composite membranes and a process flow of MEMS piezoelectric trees will be developed. The small-scale piezoelectric tree and the MEMS based type will be fabricated. The performance evaluation methods and the power management circuits of the wind energy harvesting piezoelectric trees with many mechanical-electrical conversion elements will be studied and the trees will be tested and evaluated. The piezoelectric trees proposed here have a better adaptability to environments and can be used to scavenge multi-directional, low and medium speed wind. They are promising power sources of wireless sensor nodes as the substitution of common chemical batteries.

针对自然环境中风的特点，受植物在不同方向的中低速风作用下的摆动现象启发，在对植物的高效风能采集仿生学进行研究的基础上，提出一种风能采集微型压电树新结构；结合MEMS加工工艺特点，提出一种可采用MEMS工艺加工的风能采集MEMS压电树新结构。研究涡振与驰振/颤振耦合增强的机理与条件，完成基于耦合增强效应的高效率压电风能采集单元的设计；研究压电树的树干、树枝、树叶和果实的刚度、质量匹配方法，完成风能采集压电树的设计；研究在柔性薄膜上低温制备高性能压电薄膜和三维MEMS柔性结构释放等关键工艺，开发出基于MEMS工艺的柔性压电复合膜制备工艺和三维MEMS柔性压电树加工工艺，研制出微型压电树和MEMS压电树；研究由众多采集单元构成的压电树的性能评价方法和电源管理电路，完成性能的测试与评价。拟研制的新型压电树可以高效采集环境中不同方向的中低速风，环境适应性强，在无线传感等领域具有广阔应用前景。

自然环境中的风速通常相对较低，风向往往也随时间而变化，目前报道的大部分基于风致振动机理的风能采集器对低速风能的采集效率不高，输出功率对风向很敏感，难以在实际环境中得到应用。针对应用环境风速低的问题，本项目利用涡振与驰振的耦合增强效应有效地提高了低速风能的采集效率，先后建立了涡振与驰振耦合增强压电风能采集器的几何线性模型和几何非线性模型，实验表明，两种模型均可以准确地预测涡振与弛振的耦合，在风速较高时，非线性模型具有更高的精度；研究了基于流体动力学仿真提取钝体气动系数的方法，建立了一套完整的涡振与驰振耦合增强压电风能采集器的设计方法，该方法无需采用风洞实验提取钝体的气动力系数，易于实施，方便快速，为涡振与弛振耦合增强压电风能采集器的优化设计形成了一定的理论支撑。针对风向随时间变化的问题，从树木的外形得到启示，提出多种平面内全向风能采集器结构，如平面内全向涡振压电风能采集器、平面内全向颤振压电风能采集器和包含多个平面内全向颤振压电风能采集器的压电树等；首次建立了平面内全向压电风能采集器的完整理论模型，该模型可用于计算涡振压电风能采集器受到平面内任意方向风的作用时的机电响应，为开展多参数对风能采集器方向性的影响研究提供了一个理论模型，建模过程为全向风能采集器的建模提供了一个可参考的实例；研制出了平面内全向压电风能采集器样机，其中平面内全向颤振压电风能采集器样机的临界风速为3.5 m/s，当风速为7.5m/s，风向在平面内任意变化时，样机的最小与最大输出功率分别为1.15 mW和1.52 mW，从半功率的意义上讲，实现了平面内全向风能的采集，样机同时具有结构紧凑、体积小、功率密度大、临界风速低和可阵列化等优点。本项目在低速、多方向风能采集的解析模型、设计方法、器件结构等方面取得的研究成果，对促进风能采集器在无线传感等领域的应用具有重要参考价值。