小型扭轉式發電機之設計與製作

Abstract

近幾年再生能源的議題不斷被人討論，愈來愈多人研究如何將環境中源源不斷的能量轉換成能有效利用的能源。本研究利用壓電材料的性質，設計一個小型發電裝置擷取週遭環境的機械能，轉換成電能。有別於大多數壓電式的小型發電機利用壓電片彎曲的方式來發電，本研究設計以扭轉振動的方式來發電的小型發電機，利用能量法結合變分學中的漢彌頓原理，計算兩端被夾具夾持的壓電薄板的扭轉共振頻率，並利用複合材料力學，計算三層板的壓電片的應力應變關係式。在實驗設計上，將交流伺服馬達連接鋁製搖臂，搖臂底端安裝設計的小型發電機，控制馬達使搖臂來回擺動，模擬人在行走時手臂搖擺的動作，藉由擺動造成設置在小型發電機裡的擺錘來回擺動，使壓電片發生扭轉變形。擺錘以強力磁鐵作為負載，可藉由增減磁鐵個數改變擺錘重量，使壓電片產生不同程度的變形，把機械能轉換成電能，可提供各種攜行產品的電源。

Recently, renewable energy is under intense investigation. More and more people are studying how to transform the endless energy acquired from ambient vibration into useful energy. In this study, we design a novel mechanism to scavenge mechanical energy from ambient vibration into electrical energy by utilizing piezoelectric materials. Unlike most generators using bending piezoelectric elements to generate electricity, this study deals with torsional vibration of piezoelectric elements to convert from mechanical energy to electrical energy. We use an energy method and Hamilton’s principle in the calculus of variations to calculate the torsional resonance frequency of a piezoelectric beam with both ends clamped by fixtures. Then, we use mechanics of composite to calculate the stress-strain relationship of three-layer piezoelectric beams. In experiments, an AC servo motor is used to shake an aluminum rocker arm, and the other end of the arm is attached to a miniature generator. The motor makes the arm swing back and forth to simulate arm swing when people walk. When the rocker arm swings, the piezoelectric beam deforms by the pendulum in the small generators swings back and forth. We use powerful magnets as the loads of the pendulum. The weight of the pendulum can be changed by varying the number of the magnets, so that the piezoelectric beam produces different level deformation and converts mechanical energy to electrical energy for portable power use.