Cooperative current estimation based multi-AUVs localization for deep ocean applications

In deep ocean scenario where drift of Autonomous Underwater Vehicle(AUV) localization system can be fast since no bottom tracking data can be obtained by Doppler Velocity Logger(DVL), missions for AUV are either hardly to be carried out or depended on expensive inertial instruments. This paper presents a multi-AUVs cooperative ocean current estimation method by formulating factor graphs and solving nonlinear optimization problems which can be used for typical applications such as formation maneuvering and cooperative target searching. Considering that only intermittent information is broadcasted by acoustic modems, observability of the system in each case is analyzed with designed simple formation switching strategies. With the help of water tracking velocity acquired by Acoustic Doppler Current Profiler(ADCP) and estimation of ocean current, accuracy of AUV localization system can be improved to an acceptable level for formation control and reliable position of the target can be obtained even with accumulated clock error. At last, field data based simulations have been carried out to demonstrate the feasibility of the proposed methodology.