| Summary: | 碩士 === 國立臺灣大學 === 機械工程學研究所 === 107 === Piezoelectric energy harvesters using wind as a vibration source have received a lot of research in recent years, but mainly use cantilever beams as the structure, so the energy can only be captured at single wind speed direction. In this thesis, a frame-shaped beam is combined with a cylinder to designed a Bi-directional energy harvester, which can capture energy in two orthogonal wind speed directions that using a phenomenon called vortex-induced vibration as the vibration source. As for the theoretical model of this thesis, the governing equations of the coupling system are derived from conventional beam theory and piezoelectric constitutive equation and lift oscillator model. The dynamic response of the coupling system is solved by numerical method, adjusting the fitting parameters of the lift oscillator model to let the simulation results closer to experimental result. In addition, this study will perform parametric analysis, such as adjust the aspect ratio of the structure and use different cylinder diameters and then try to reproduce the dynamic response with theoretical model. Overall, the harvester designed in this study can harvest wind energy in both directional, and the wind speed range and acquisition voltage will both increase as the diameter of the cylinder increase, but at the same time it will easier to suffered from unexpected deformation. By adjusting the appropriate aspect ratio of the structure and the diameter of the cylinder, better acquisition results can be achieved without unexpected deformation of the harvester structure.
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