Browsing by Author "Li, W."

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A miniature generator using piezoelectric bender with elastic base
(2011-10-01)
Li, W.
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Liu, T. S.
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Hsiao, C. C.
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機械工程學系
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Department of Mechanical Engineering
Nowadays green energy devices such as vibration generators attempt to harvest energy from environment. A lot of studies dealing with vibration generators put emphasis on mechanism designs or power generation methods, but few on lowering the resonant frequency of power generation systems. This study proposes that elastic bases attached to vibration generators can lower natural frequencies, so as to make natural frequencies closer to ambient vibration frequency. Therefore, this study investigates miniature electric generators consisting of piezoelectric benders and elastic bases. To install the elastic base, this work uses a spring with prescribed stiffness and a board with given mass between the piezoelectric bender and a vibration source to make the resonant frequency of piezoelectric benders close to the frequency of ambient vibration. Analytical derivation is carried out to obtain optimal mass and stiffness. Accordingly, more electric power can be generated from piezoelectric generators using an elastic base with appropriate mass and stiffness. According to experimental results, using an elastic base increases 376 times generated power compared with no elastic base. In the presence of the elastic base, the power increases 132% when a point mass is added. (C) 2011 Elsevier Ltd. All rights reserved.
Biodegradable amphiphilic gelatin/calcium phosphate co-delivery systems with simultaneously encapsulating hydrophilic and hydrophobic drugs for enhanced tumor therapy
(2014-07-01)
Chen, S.
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Li, W.
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Su, C.
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Chen, Y.
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材料科學與工程學系
Design and Experiment of Vibration-Based Miniature Generator
(2008)
Li, W.
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Liu, T. S.
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Chu, Y. C.
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Lin, Heng I.
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機械工程學系
To transform endless energy from ambient vibration into useful power. We scavenge mechanical energy and transfer into electrical energy by utilizing piezoelectric materials. We compare generators performance at different situations and then let electric energy be charged to a Ni-MH battery or a capacitor through a full wave rectifier. We also obtain resonance of piezoelectric benders by system identification which can be an important reference when designing the generator. This study proposes a novel mechanism comprising a mass-spring system and magnet repulsive force. According to finite element software and experimental result, below 5 Hz the generator absorbs vibration energy more easily. We have investigated the influence of the mass magnitude and obtained the optimum result of 2.7V and 0.379 mu w when the swinging amplitude of the motor is +/- 1.8 deg at swinging frequency of 3.96 Hz.