重力平衡法應用於追日機構之設計與分析

Abstract

本研究應用重力平衡(Gravity Balance)理論來設計太陽能追日機構，使追日機構在全行程中慢速驅動負載物件時，可趨近於無重力狀態，減少驅動馬達在轉動中與固定位置時的輸出扭矩與負荷，達成節能的目標。 本研究以四連桿機構之重力平衡架構為主，在設計的過程中，首先確定太陽能追日機構設計需求，分析參考文獻中各種太陽能追日系統，瞭解目前發展方向與特點。接著利用機構合成法設計符合讓太陽能板全程可連續旋轉90度以上的需求之初步連桿機構。接著，利用田口實驗法進行連桿尺寸優化的規劃與分析，選取最佳驅動馬達扭矩輸出的連桿組成架構。最後採用重力平衡理論，以靜力平衡的條件，計算出適合的彈簧常數與彈簧連接位置，再將設計構想藉由CAD系統建構模型及進行動力分析與評估。由模擬結果可得知最佳設計連桿組合的追日機構，與其裝設重力平衡裝置後的驅動馬達扭矩比較，在固定速度為1(rpm)的轉速條件時，後者扭矩大幅減小，僅約為前者的0.13%，本研究成果可作為設計追日機構時達到節能與改善機械效益目標的參考。

In this paper, we apply the gravity balance theory to design the solar tracker. We select springs to add into the solar tracker in order to achieve the conditions of gravity balance. It makes the solar tracker to drive the loading object approaching the agravic situation in the whole process at the slow speed. Then it can reduce the output torque and loading of the driving motor under rotating and fixed position so as to achieve the goal of lowering power depletion. We are here mainly concerned with the four-bar mechanism of the gravity balance structure. First of all, we need to determine the requirements of the solar tracker in the design process, analyze the various solar tracker systems of the references, figure out the directions of current developments, and compare the characteristics of those systems. Also, we try to design the initial linkage mechanism that fits in with the demands which make the solar plate can be continuously rotated at least 90 degrees in the whole process by means of mechanism synthesis. After that, we use the Taguchi method to deal with optimization planning and analysis of linkage dimension in order to select the optimum linkage combinations that have minimum output torque of drive motor. Finally, we adopt the gravity balance theory, under static equilibrium conditions, to calculate the spring coefficients and the spring connecting positions. Then we put the design idea through CAD system to fit model and analyze the dynamics for the purpose of assessing and comparing the efficiency changes of tracking mechanism after applying gravity balance theory. The results of our simulation show that the driving motor torque of the mechanism approaches to zero in the slow rotation. Our research can be used as a foundation of improving mechanical efficiency in designing solar tracker.