Research On AUV Robust Navigation Technique And The System Implementation Based On A Small Platform

Autonomous Underwater Vehicle (AUV) plays a more and more important role in the field of oceanic engineering. AUVs equipped with various sensor devices can be used in underwater environment monitoring, offshore oil engineering operations, underwater search and mapping etc. The high precision navigation and positioning is technical support for AUVs working securely and reliably under water. Based on a developing small AUV, this dissertation investigates the robust navigation technique, cooperative navigation technique, the system implementation, navigation sensor calibration and the analysis of experimental data, the major research work is as follows:To overcome the problems of filtering precision decline caused by the unknown statistical characteristics of noise and the measurement outliers, this paper combines the Sage-Husa adaptive filtering algorithm and the innovation-based outlier-tolerant algorithm with the Square-root Cubature Kalman Filter (SCKF). Simulation results show that the proposed algorithm can improve the navigation precision. This paper introduces the state-augmented Kalman filter for delayed measurement fusion and the simulation under the USBL-aided AUV navigation scene is done to verify the feasibility of the algorithm.The cooperative navigation algorithm based on Extended Kalman Filter (EKF) is proposed and the simulation is carried out and proves that the validity of algorithm of cooperative navigation. Based on the observability theory of nonlinear system, observability analysis of cooperative navigation is done and the observability condition is obtained. The optimal formation of cooperative navigation is studied by minimizing the position uncertainty based on the a priori error covariance matrix of EKF.The paper also implements the navigation software and hardware system based on a small AUV platform and an open source software platform which is named as MOOS (Mission Orientated Operating Suite). The performance of the navigation system is validated by lake trials. To overcome the existing navigation error, the installation error of Doppler Velocity Log and the deviation of the electronic compass are analyzed and calibrated. The navigation precision can be improved after calibration.