Simultaneous navigation state and sea current estimation through augmented state Unscented Kalman Filter

An Unscented Kalman Filter (UKF) to simultaneously estimate the navigation state of an Autonomous Underwater Vehicle (AUV) and the sea current, a priori unknown, is proposed. The filter is the result of a modification of an UKF developed in the past by the authors for the sole purpose of navigation state estimation. The new algorithm has been obtained by integrating the vehicle model with a contribution due to a constant sea current and by augmenting the state vector dimension including the North and the East components of the current itself. The resulting algorithm has been validated offline exploiting the signals of the Typhoon AUV on-board sensors collected during a sea experimental campaign.