傾斜式追日機構誤差及控制

Abstract

雙軸追日系統以仰角-方位角形式為主流，這類的追日機構於太陽仰角九十度時會有奇異點的產生，因而造成系統控制的問題。本研究所使用的追日機構將仰角方位角轉換為成對X軸與Y軸的旋轉角，並且基準面與地球自轉軸平行，因此和地平面夾當地的緯度，在此基準面上建立雙軸追日與太陽軌跡的對應關係，一軸由伺服馬達配合減速機輸出每天追日所需角度，另一軸則以電動推桿推動太陽能板因應季節改變造成的角度變化。目前利用太陽演算法追日精度可達到0.0003°，控制方法的優點為不受天候影響，即使在多雲或陰天的日子裡，追日系統也可以按照預先設定的軌跡穩定運轉，但是易受到系統結構與安裝誤差以及疲勞應變、應力應變、熱應變等形變效應所影響。

Most of biaxial solar tracking systems are based on elevation-azimuth serial mechanism. This mechanism is difficult to control because it produces a singular point at noon. In this thesis, we convert the azimuth-elevation into x and y axes of rotation angle. The reference plane is parallel to the earth’s rotation axis. Therefore, the angle between the ground plane and the reference plane is equal to local latitude. This thesis establishes correspondence between biaxial solar tracking system and sun locus in this reference plane. One axis of the mechanism is driven by servo motor which can track the sun in a day. The other axis of the mechanism is driven by the linear actuator which can adjust the angle because of seasonal variation. At the present, the accuracy of the system can reach 0.0003 degrees by means of the solar-tracking algorithm. The control method is independent of weather which worked fine in cloudy days. The tracking system can also be operated stable in accordance with the preset trajectory. But the system is sensitive to the structure and installation error and the effect of fatigue, strain deformation, stress strain, thermal strain.