大區域GPS/INS整合系統與實驗

Abstract

現今全球定位系統（GPS）已成為應用最廣泛且重要的導航輔助系統。然而GPS於使用上常受限於周遭環境條件，當衛星訊號品質不佳，可能導致GPS接收機無法提供即時準確之導航資訊。因此我們藉由慣性感測器（INS）的自主導航特性，發展出GPS/INS整合式導航系統，解決GPS訊號中斷的問題。 由於INS輸出值包含偏置值、比例因子及安裝校準誤差，使得其定位誤差易隨時間放大。因此在本研究中先行對加速規及陀螺儀靜態校正，並於動態使用延伸型卡爾曼濾波器，於GPS訊號良好時估測慣性感測器的偏置值、比例因子及安裝校準誤差，若GPS訊號中斷則使用校正過的INS進行定位，使整合系統可以克服GPS、INS單獨定位的缺點並提供更佳的導航資訊。 本文利用載具在平面上運動的方程式建立二維GPS/INS整合式導航系統，然而此二維GPS/INS整合式導航系統因為當地座標系統定義上的限制，一旦載具位移超過使用者定義切橢球平面，將出現觀測誤差。為增加此二維GPS/INS整合系統使用者於長時間定位下使用範圍，本文藉由適時轉換載具於當地座標系統的定位切平面，以克服目前系統定位範圍上的限制。 為檢驗我們所發展系統之大範圍定位及真實環境下的適用性，本文整合GPS接收機、慣性感測器及電子羅盤，進行單接收機由台北至屏東之大範圍路測實驗及隧道路測實驗，實驗結果證實，即使在短時間無GPS訊號的情況下，我們所發展的整合導航系統確實可達成定位推估之有效性及可靠性的目標，並適用於大範圍定位而不失真。

Nowadays, the Global Positioning System (GPS) has become the most widely used and important navigation-aided systems. However, using GPS in the city is often limited by satellite signal quality. GPS receiver cannot provide precise and real-time positioning information when its signal is blocked. To deal with this problem, another independent navigation system INS (Inertial Navigation System) can be adopted and the GPS/INS integrated system may be developed to provide the positioning information during the GPS signal outage. Although INS is autonomous, the errors of using INS would increase with respect to time due to the sensor errors such as bias, scale factor, and misalignment in the integration procedure. In this thesis, the static methods are used to calibrate the gyro and accelerometer. Then, the unknown parameters of INS may be estimated and corrected by GPS signal by using the extend Kalman filter in dynamic situation. Alternatively, when the GPS signal is outage, the INS can still provide positioning information. The integration system can not only solve the sensor’s problem but also enhance the performance of the navigation system significantly. In this thesis, the 2-D GPS/INS integrated system is developed for vehicles moving on the plane. Usually, the navigation coordinates are determined on local plane, which is a tangent plane to the Earth ellipsoid at a specific point. If the distance between reference position and the current position is large, the corresponding local plane becomes invalid. To deal with this problem, we choose a new tangent plane timely and the errors can be reduced significantly. In order to test the applicability of our design, a wide-range road test (from Taipei to Pingtung) and a tunnel road test were performed by integrating a GPS receiver, inertial sensors and an electronic compass. The performance of the algorithm is verified by the experimental results.