人造衛星天線反射面之展開機構設計與表面形狀控制

Abstract

本文主要包含了對於人造衛星天線反射面的研究展開機構之設計與表面形狀控制二大部份。展開機構是由八組平行四邊形的連桿所組成。藉著力的施加，可將結構由閉合狀態逐漸張開成全展開狀態。人造衛星承受日照和日蔭，使得天線的形狀會發生熱變形，因而影響電波的傳遞。所以為了補償形狀的變形，本論文同時利用不同厚度的壓電高分子薄膜PVDF(Polyvinylidene Fluoride) 材料當作感測器與致動器。反射面為一圓形高分子薄膜，由實驗得知，致動器和感測器的相對位置以上下貼的方式最為理想。致動器為雙層壓電致動器(Bimorph)。當反射面受熱而產生形變時，感測器會產生電壓，送入PI或PID控制器，控制器輸出的電壓放大後，輸出給PVDF致動器，進行表面形狀補償的動作。在烤箱內執行即時控制的實驗結果發現，PI和PID所得到的控制結果相差不多。由於烤箱的溫度緩慢的變化，所造成的形變量也是緩慢的增加，因此不會有過大的波動產生，所以 值的大小對結果影響不大。

For satellite antenna reflectors, this thesis deals with deployment mechanism design and surface shape control. The proposed deployment mechanism is composed of eight identical parallelograms. When a force is applied to the mechanism, the structure can be gradually extended from a folded form to a fully deployment form. Subject to sunlight and sunshade, the reflector surface generates thermal distortion, which will change the original shape of the antenna reflector and thus degrade microwave transmission. Concerning shape control, this study uses PVDF (Polyvinylidene Fluoride) materials of two thicknesses as sensors and actuators. From experiments, it was found that the ideal positions of sensors and actuators are distributed over the upper and lower surfaces on the reflector. The proposed antenna reflector is made of a circular shape polymer film. As actuators, bimorph beams are used. During thermal distortion, the induced strain will make the sensor generate electrical voltage that enters a proportional-integral(PI) or proportional-integral-derivative(PID) controller. Amplified voltage drives the actuators. The actuators generate counteracting moment to control the shape of the reflector. The result shows that had little effect on the control processes. PI and PID control had almost the same effect on the surface compensation. This is because the oven temperature gradually changes and so does the surface deformation.