壓電材料在眾多能源擷取的研究中，是收集社會大眾在一般生活中耗散能量很好的工具，為了更好的擷取壓電片所產生的電能，有許多相關的研究都持續進行。 本研究是使用一根Timoshenko樑於單邊貼附雙片壓電片做發電量與電能獵取之研究，第一步先求得複合樑壓電系統的運動方程式，第二步以有限元素法探討複合樑壓電系統在受到作用力時的靜態與動態行為，再利用Newmark法來求出複合樑壓電系統受到作用力時的感應電壓，第三步設計一組電能儲存電路，經過整流、濾波、穩壓後，將電能從交流電轉為直流電，擷取並儲存下來，做為電能來源使用，最後經過模擬與實做來驗證，壓電片在樑上不同位置的發電量比較。

Extend Abstract

Circuit Design of Storing Energy through Timoshenko Beam with Unilateral Surface Mounted Two Discrete Piezoelectric Layers

Author: Wu, Jhen-Ning
Advisor: Wang, Rong-Tyai
Department of Engineering Science, National Cheng Kung University

SUMMARY
This study aims to investigate the voltage generated from the piezoelectric materials via the vibration of the Timoshenko Beam through two piezoelectric layers mounted on the Timoshenko beam. The finite element technique and the Newmark’s method were adopted to calculate the displacement and the induced voltage. An energy harvesting circuit is designed to store the electric current generating from the piezoelectric material. The energy harvesting circuit includes the filter circuit, rectifier circuit, voltage regulator, and charge device. In order to store the energy effectively, the PSPISE software was adopted to simulate the circuit and an experiment was taken.

INTRODUCTION
The green energy has become more and more important in the world. Piezoelectric materials and many piezo systems found in the 18th century Due to the piezoelectric effect, and then gradually developed after. This material can be used in our household appliance, such as computer speakers, when the music turns on, the piezoelectric materials will start to vibrate. Piezoelectricity will be the future of the renewable energy.

MATERIAL&METHOD
Fig.(a) Cantilever Beam with Piezoelectric Material
Two piezoelectric material mounted on bilateral surface of the host beam is display in Fig.(a). The displacements and rotations of all components of the entire beam are set. The strains field, stresses field, strain energy, kinetic energy and electrical enthalpy of the entire team are derived. The governing equations of the entire system are derived from performing Hamilton’s principle, and the finite element technique is set by solving the equations of static equilibrium. Finite element is used to calculate the static responses. The Newmark’s method is used to analyze the dynamics of the entire beam.Finally,experimental measurement voltage on the load capacitor.

RESULT&DISCUSSION
The piezoelectric material considered in the thesis is PZT-5H. The respective length, width and thickness of the host beam are 42cm, 0.8cm, and 0.1 cm. Only the effect of location of the piezoelectric layer on the vertical displacement w of the entire host beam will be presented. Results displayed in Fig. (b) indicates that applying a vertical force of magnitude 6.37N at the free end at t=0, the closer piezoelectric layer to the fixed end is, the less w is. Results presented in Fig. (c)indicate that applying a vertical force of magnitude 6.37N at the free end during t=0s to t=0.025s leads to result showing that the closer the piezoelectric layer to the fixed end is, the bigger voltage will be generated.Results presented in Fig.(d) the energy harvesting circuit in this research design.Results presented in Fig. (e)indicates that applying a vertical force of magnitude 6.37N at the free endduring t=0s to t=0.025sleads to the result showing that the closer the piezoelectric layer to the fixed end is, the bigger voltage will be generated on load capacitance.

Conclusion
The results showed that the closer the piezoelectric layer to the fix end is, the larger generated voltage will be.An energy harvesting circuit is designed to store the electric current which is converted from electric charge induced on the piezoelectric surfaces by external force. Comparisons the harvesting voltage show that the present circuit has a better performance than the reference circuits.
 

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