海事天線追蹤低軌道衛星與控制單元開發;Tracking algorithm development of Maritime Antenna Control Unit for low earth orbit satellites

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题名:	海事天線追蹤低軌道衛星與控制單元開發;Tracking algorithm development of Maritime Antenna Control Unit for low earth orbit satellites
作者:	林彥夫;Lin, Yen-Fu
贡献者:	太空科學研究所
关键词:	天線機構;姿態控制;馬達角度運算;ACU
日期:	2021-07-21
上传时间:	2021-12-07 11:20:38 (UTC+8)
出版者:	國立中央大學
摘要:	追蹤低軌衛星之海事天線會面臨許多問題，本研究中主要探討如何克服低軌衛星通過海面接收站的短時間限制、衛星通過造成的指向變化限制，並且有效進行最大訊號追蹤同時克服海面晃動的所要計算的姿態補償。研究主要開發給海事天線的天線控制單元(Antenna Control Unit, ACU)，其利用SGP4衛星軌道推算器去計算衛星在ECI座標下的衛星位置，在利用高精度的ECI到ECEF座標轉換將衛星位置以ECEF座標表示，再將接收站的位置座標透過GPS得到經緯高度並將衛星從ECEF座標轉換到ENU座標。透過三軸座標與球座標的關係，將從接收站到目標衛星的指向換算成天線馬達轉動的指令。本次研究使用三軸天線進行追蹤模擬，並且使用陀螺儀、加速計、磁力計所構成的姿態辨識儀對海面晃動造成的姿態變化進行量測，姿態變化造成的指向差異會透過三軸角度計算回饋至馬達的角度指令。本次研究主要研究於軌道推算、姿態感測以及三軸馬達指令的相關研究，而對於天線機構會建立簡易的三軸機構進行模擬，而海面晃動也會根據海面晃動規格利用氣動桌與提供晃動動力的電動缸和馬達來建立驗證平台。研究實驗主要是將研究設計的整體的天線馬達角度演算器利用簡易機構與驗證平台來驗證其演算法。;Maritime antenna for low orbit satellites will face lots of difficulties. This research mainly discussed how to overcome the time limit of the pass of low orbit satellites by a terminal, and the variation of pointing limit. Evermore, the research committed to maximum signal strength tracking and attitude compensation causing by ocean waves. The research developed Maritime Antenna Control Unit. It uses SGP4 satellite propagator to calculate the position of satellites in ECI coordinate. And get satellite in ECEF coordinate by using high precise ECI to ECEF coordinate transfer. It uses GPS to get the LLA of the terminal and get satellite in ENU coordinate by the LLA. Through the relation of 3-axis coordinate and spherical coordinate, it could transfer the 3-axis pointing direction to the motor rotating commands. The research made use of 3-axis maritime antenna in order to simulation satellite tracking. And it used ASM composed of gyroscopes, magnetometers and accelerometers to measure attitude variation causing by ocean waves. And the difference of pointing direction would be calculated toward 3-axis angle for motor commands. This research mainly committed to studying satellites orbit algorithm, attitude measurement and 3-axis maritime antenna motor commands. For 3-axis maritime antenna model, the group of research built a simple model with 3-axis motor structure instead of real one. Moreover, we build the verification platform which is composed of air bearing and motors for dynamics to simulate ocean waves. The experiment main purpose is to verify the satellite tracking algorithm by using the simple antenna model and verification platform.
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