Cooperative localization of a team of AUVs by a tetrahedral configuration

The paper investigates the principles of a Cooperative Localization Algorithm for a team of at least three Autonomous Underwater Vehicles (AUVs) with respect to a surface support ship, without the use of UltraShort Baseline (USBL). It is assumed that each AUV is equipped with a low-cost Inertial Measurement Unit (IMU), a compass and a depth sensor, but only one of them has a high accuracy navigation sensor such as the Doppler Velocity Log (DVL). The surface boat locates itself by means of Global Positioning System (GPS). Range measurements provided by acoustic modems allow to avoid an unbounded error growth in the position estimate of each AUV. A geometric method, based on a tetrahedral configuration to obtain a deterministic fix for position, is proposed. This method allows to extend the advantages of the use of the DVL to the position estimate of other vehicles not equipped with DVL. The paper addresses also some of the problems related to the limitations of acoustic communication. The algorithm has been implemented and tested in simulations for a fleet of three AUVs and a surface support ship.