【作者】 邓勇；

【导师】 李以贵；

【作者基本信息】 上海交通大学 ， 微电子学与固体电子学， 2011， 硕士

【摘要】 随着电子技术、网络技术、通信技术的迅速发展,对集成化电子产品的应用已然成为人们生活中不可或缺的环节,并且在这些电子产品的基本功能以外,人们还非常注重应用时的体验,这种趋势必然会加速产品便携化与智能化发展脚步。对于广泛应用于各类网络或系统中的微型传感器而言,这类器件往往具有体积小、数量大、定位散、维护难等特点,因此对其供能部件提出了很高的要求。利用能量采集技术可以将电子器件工作环境中的各类能量转换为电能,从而实现器件的自供能,使电子器件摆脱体积大、重量大、供能时间有限、回收处理成本高的传统电池的束缚,对电子器件便携化、智能化的发展趋势有着深远影响。目前,能量采集已然成为一个重要的研究方向,吸引了国内外众多科研团体的关注。在各类能量采集器中,尤其以压电式振动能量采集器的前景最为广阔,其一因为机械振动是一种普遍存在且输出功率密度较大的能量来源,其二因为器件具备结构简单、与MEMS工艺的兼容性较好、输出能量密度大、无需启动电源、便于与电子器件集成等优点。目前较为流行的是单层直线型悬臂梁振动式压电能量采集器,已有一些成熟的产品问世,而对双层悬臂梁器件的研究还停留在模型阶段。除继承了单层器件的优点以外,双层悬臂梁压电器件相比于单层器件,还具备系统刚度大、压电层数量多、节省空间等优势,因此对双层器件的研究工作具有重要的现实意义。本文旨在研究系统参数对于双层悬臂梁压电能量采集器输出性能的影响,设计、制造了器件模型与夹具,搭建了测试系统对其进行测试,设计了基于ANSYS图形用户界面的器件仿真步骤、编写了APDL程序,通过仿真数据与实测数据的对比形成结论,为将来利用MEMS技术制造微型器件提供了指导性建议。所制造的器件模型由上下悬臂梁、两个间隔块以及一个质量块组成,上下悬臂梁由支撑层、PZT层、电极与导线组成,整体尺寸为50mm×8mm×0.6mm;用到的间隔块有四种尺寸,分别为18mm×8mm×10mm,12mm×6mm×10mm,9mm×8mm×10mm,7.2mm×10mm×10mm,质量统一为1.4g;用到的三个不同质量块的质量分别为10.5g、6.7g、4.2g。所制造的夹具由中轴、固定上颚、固定下颚、活动螺母、活动螺丝五个部分组成,它的具体作用是对不同厚度的双层悬臂梁振动能量采集器进行上下咬合。器件与夹具的可靠性经过了验证。在上下悬臂梁间距为4mm、振动加速度为5m/s2的条件下,分别对质量块质量为10.5g、6.7g、4.2g的器件模型进行了测试,结果发现悬臂梁自由端载重越大,器件的谐振频率越低,器件的谐振点电压输出越高;在质量块质量为4.2g、振动加速度为5m/s2的条件下,分别对上下悬臂梁间距为4mm、6mm、8mm、10mm的器件模型进行了测试,结果发现上下悬臂梁间距越大,器件的谐振频率越高,器件的谐振点电压输出越低,上下悬臂梁间距对器件的谐振频率的影响不大,但对器件的谐振点电压输出有较为显著的影响。在整个测试过程中,质量块质量为10.5g、上下悬臂梁间距为4mm的器件模型性能最为优越,其谐振频率为43Hz,在5m/s2的振动加速度条件下电压输出达到11.5V。使用ANSYS对器件模型进行有限元仿真,通过对仿真结果与实测结果的综合分析,得出了四点结论:量块的质量越大,器件的输出性能越好;上下悬臂梁的间距越小,器件的输出性能越好;压电悬臂梁的长度越大,器件的输出性能越好;器件宽度的变化对器件的输出性能几乎没有影响。这些结论反映出未来器件在MEMS制造过程中的两点关键,即在有限的空间里增加悬臂梁自由端的等效载重,以及减小器件上下悬臂梁之间的间距。本文不仅展示了能够应用于低频环境的双层悬臂梁压电能量采集器,并且提出了一种针对器件性能研究的系统方法,即物理建模与有限元仿真相结合的方法,该方法具备三大优势:通过该方法,能够在微器件制造之前,对不同系统参数造成的影响以及器件的总体性能做出初步判断,从而减少制造过程中由于选材、选型不当导致的失败;通过该方法,能够有效避免因单方面疏漏而形成错误的结论,从而保证研究的准确性,使研究者少走弯路;通过该方法,能够发现决定器件性能的关键性要素,从而推动微器件制造技术的发展。更多还原

【Abstract】 With the development of electronic technique, network technique and communication technique in recent years, it becomes a must to apply various electronic products in our life, and except for the basic function of those equipments, people pay great attention to experience when applying, this will make electronic devices to be more and more intelligentized. For microtransducers widely used in networks and systems, they always have small size and large number, and their scattered location as well as difficult maintenance put power components on high-level requirements. Using energy harvesting technique for converting various kinds of power in environment to electric energy can make electronic devices break the tether bring by traditional power source, it now becomes an important research field and attract a lot of attention.Among different types of energy harvester, piezoelectric device has the most broad prospects. Mechanical vibration exists everywhere and output large power density, it creates favorable conditions for piezoelectric energy harvester’s development. Some one-layer cantilever piezoelectric products have appeared, but two-layer devices’research only stays at modeling stage. Because two-layer piezoelectric energy harvester has some peculiar advantages, it is meaningful to do research work about devices’characteristics.The thesis is aimed at figuring out how system parameters affect two-layer cantilever piezoelectric energy harvester output performance. Here, device model and its fixture were designed and fabricated, testing system was established, simulation steps and code were completed, experimental data and simulation data were compared, and some conclusions and suggests were obtained. The specific work is as following:The energy harvester model consisted of upper and under cantilever, two space blocks and one mass block. Upper and under cantilever consisted of support layer, PZT layer, electrode layer and wire, the size of cantilever was 50mm×8mm×0.6mm; Different space blocks were used to make device models with different parameters, the four sizes were 18mm×8mm×10mm,12mm×6mm×10mm,9mm×8mm×10mm and 7.2mm×10mm×10mm, and the uniform mass was 1.4g; The weights of three different mass blocks used were 10.5g, 6.7g, and 4.2g. The fixture consisted of middle axle, fixed upper jaw, fixed under jaw, movable nut and movable screw, it’s specifically used to clamp energy harvesters with various thickness. In addition, the reliability of device model and fixture was checked.In conditions of 4mm distance between upper cantilever and under cantilever and 5m/s2 acceleration of vibration, devices with three different mass blocks which separately weighed 10.5g, 6.7g and 4.2g were tested, the results showed that the larger mass loaded, the lower resonance frequency and the higher resonant voltage with devices; In conditions of 4.2g weight of mass block and 5m/s2 acceleration of vibration, devices with four different distances which separately were 4mm, 6mm, 8mm and 10mm between upper cantilever and under cantilever were tested, the results showed that the larger the distance, the higher resonance frequency and the lower resonant voltage with devices, furthermore, the distance impacted device’s resonance frequency weakly but device’s resonant voltage obviously. During the experiment, the device with mass block of 10.5g and distance of 4mm between two cantilevers showed the best performance, it had a resonance frequency of 43Hz and a resonant voltage of 11.5V under 5m/s2 acceleration.After finite element simulation on the energy harvester model was done by ANSYS software, simulation results and experimental results were compared, the conclusion was found that the device’s performance could get better by increasing the weight of mass block, decreasing the distance between two cantilevers or increasing the length of cantilever, however, the width of cantilever made almost no impact on device’s performance. Consequently, there are two key points in device’s MEMS fabrication: increasing equivalent load mass on free end of cantilever in limited space and decreasing the distance between two layers of cantilever of energy harvester.The thesis not only showed a two-layer cantilever piezoelectric energy harvester appropriate for low-frequency environment, but also offered a systematic method which combined physical modeling and finite element simulation to research device’s performance, there are three advantages with this method: It can reduce failures caused by unreasonably choosing system parameters in fabrication; It can avoid incorrect conclusion caused by carelessness in ex-parte work; It can find import factors which impact device’s performance so as to promote the development of micro manufacturing technology.更多还原