Application of Rotating Periodic Magnetic Force to Piezoelectric Energy Harvesting

• Main Authors: Wei-Cheng Wang, 王偉丞
• Other Authors: Yi-Chung Shu
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/76bvyv

碩士 === 國立臺灣大學 === 應用力學研究所 === 105 === The thesis aims to develop a theoretical framework together with experimental validation to investigate the piezoelectric energy harvesting under rotational environment. Much work has been done on the study of vibrational energy harvesting under translational excitation along certain directions. However, little work has been done for rotational energy harvesting. Instead, the present thesis studies the energy harvesting from a cantilever piezoelectric bimorph attached to a magnet on its tip which is excited by a rotational movement of another magnet. As a result, such an excitation is similar to the case of periodic impulsive force. In addition, The Fourier expansion of such an impulsive force indicates that the cantilever bimorph is able to be resonantly excited at its first flexural mode as long as the rotational frequency is equal to the integer fraction of the natural frequency of the oscillator. In addition, an experimental setup with LabView interface is developed for validating the proposed model. Both AC and DC harvested power are recorded and found in good agreement with theoretical predictions. The result shows that the driving force increases as the distance between two magnets decreases. However, under this circumstance, the frequency response shows nonlinearity for strongly coupled oscillators while the response remains linear for weakly coupled oscillators. Second, the there is a range of rotational speeds such that power remains accumulated within this period. It is attributed to the non-vanishing Fourier coefficients of the magnetic impulsive force up to tens of terms in its Fourier expansion. But the subsequent coefficients drop to zero when the rotation speed is small. Third, there are a number of peaks of harvested power located at the integer fraction of the natural frequency of the oscillator in the power-frequency plot. But the interactions between two adjacent power curves remain sufficiently high in a wide range of rotational speeds for the case of weakly coupled oscillators. Finally, the experiment shows that the average harvested DC power can be up to 1mW with the rotational frequency range between 5-14Hz.