- 學位論文
以全球導航衛星系統實現剛體姿態量測
GNSS-based Attitude Determination for a Rigid Body
摘要
全球導航衛星系統(Global Navigation Satellite System, GNSS)現今在科學和工程應用十分的廣泛且扮演一個重要的角色。本論文著重在利用導航衛星系統的電碼虛擬距離與載波相位觀測量，來獲取姿態資訊。其方法為差分定位技術，將定位方程式重新改寫待求之未定參數，由原先估計天線位置轉而估計剛體姿態。 經由二次差分後的觀測量為基線模型，其方程式推導過程詳列於本論文。為使用高精度載波相位觀測量，求解過程中需處理相位模稜及其參數間高相關之問題。本文使用尺度因子調整和LLL(Lenstra–Lenstra–Lovász)解相關技術，並因剛體共用相同之旋轉矩陣，此額外限制條件縮小搜尋空間，使LLL方法有效率的搜尋出正確相位模稜，進而達成即時且精確的要求。姿態求解方法採用最小二乘平差獲得最佳無偏估計值。 本文包含兩種靜態平台測試。透過模擬及實驗證實較長的基線能提供較佳的姿態精度。衛星組合強烈影響姿態求解是否有系統性偏差。單頻的成果展現證明方法的可行性和強健性，在單頻、單時刻靜態的情況下最佳精度可達0.30°等級。文末會提出方法的改進方向，檢驗方法的限制條件。最終期望方法可實踐在單頻、單時刻動態的情況下的即時運用。
並列摘要
Global Navigation Satellite System(GNSS) now plays an important role in science and engineering applications. This research topic is to develop a GNSS-based attitude determination method for a rigid body by using pseudo-range and carrier phase measurements. The method is based on differential GNSS technique. The differential equation is reconstructed for estimating the attitude parameters instead of baseline parameters. By double differencing the observations, the differential equation is called baseline model, which derivation process is listed in the methodology. In order to use high precision carrier phase observables, phase ambiguities and high correlation between parameters have to considered. The Lenstra–Lenstra–Lovász(LLL) method is used to search ambiguities. Besides, the additional constraint, the rotation is the same in a same rigid body, reduce the searching space, which increases the efficiency. LLL method and the additional constraint result in solutions which are precise and correct. The solutions come from a least-squares adjustment. The static experiments are included in the thesis. Results demonstrate the feasibility and the robustness of the attitude determination method. The improvement and limitation are discussed in the final part in order to fit the method for single frequency and simple epoch situation in real-time.