Author: Zhou, Junjie
Title: Analysis and design of an X-shaped structure based vibration energy harvesting system
Degree: M.Sc.
Year: 2017
Subject: Hong Kong Polytechnic University -- Dissertations
Energy harvesting
Interface circuits
Piezoelectric transducers
Department: Faculty of Engineering
Pages: 85 pages : color illustrations
Language: English
Abstract: The research presented in this thesis is to develop a complete vibration energy harvesting system which would include mechanical structure, piezoelectric transducer and electrical circuit. Due to the flexibility and vast advantages over other piezoelectric material, the MFC is employed as transducer to bond with structure for converting vibration energy into electrical energy and to be stored. MFCs are characterized by their flexibility on large deformation, which enables them to harvest energy from ambient vibration without risk of brittle. Inspired by the nonlinear characteristics of X-shaped structure, a two-layer X-shaped energy harvesting structure is designed, manufactured and experimentally studied for vibration energy harvesting performance. Two mounting methods of piezoelectric material on X-shaped structure are employed. For the first one, a hinged-hinged beam with MFC bond on its surface is connected to the middle layer of X-shaped structure. This kind of mounting is named as bender type. The other one is lever type, a MFC cantilever beam mounted on lever system. Then the lever system is combined with X-shaped structure. By experimentally study on performance of these two mounting types, the ultra-low frequency and high voltage peak energy harvesting performance can be observed. Especially lever type has shown two peaks which can demonstrate the nonlinear coupling effect between lever system and X-shaped structure and wider bandwidth can be achieved. These are all new characteristics compared with traditional energy harvesters like cantilever beam. The related comparative study also been carried out.
The energy harvesting performance is determined by some easy-to-tune parameters. By experimentally tuning the parameters of structure, apparent variation tendency can be seen, like resonant frequencies or peak value. It can be proved that the structure is parameter adjustable according to the practical need. A complete energy harvesting circuit has been proposed and designed. The SSHI circuit is employed as rectification circuit. The market available energy harvesting module EH301A is employed as power conditioning and energy storage device. Through simulation and experiment study, SSHI circuit has been proven to be a more efficient AC-DC circuit than traditional SEH circuit. the increased efficiency of SSHI circuit is largely depended on the external excitation level. A complete circuit demonstration of energy harvesting is carried out. About 55mJ is stored on the bank of EH301A during a cycle. And then the LED bulb is lighten for nearly three minutes by EH301A without other power supply. The X-shaped structure based energy harvesting system has been shown great advantage and demonstrated bright application prospect. For example, this system can be put in marine wave or railway track environments to harvest energy and power up sensors or some other electronic devices.
Rights: All rights reserved
Access: restricted access

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