In the robotics field, cooperative approaches involving robot swarms represent a challenging task, in order to guarantee robots safety and accomplish mission goals. This problem becomes more severe when missions involve under-water vehicles, due to electromagnetic waves attenuation in underwater environment which results in several limitations on communication and navigation. In this paper, we describe a stepping stone to an acoustic-based cooperative navigation strategy between an Autonomous Surface Vehicle (ASV) and an Autonomous Underwater Vehicle (AUV). The goal is to provide the ASV with tracking capabilities in order to assist the AUV during the mission and enhance acoustic communication. The proposed tracking approach exploits within an Extended Kalman Filter (EKF) the measurements from the Ultra Short BaseLine (USBL) device installed on-board the ASV. The estimated AUV position is then used by the ASV to implement a pursuit strategy of the underwater vehicle, which consists of moving forward while pointing towards the underwater vehicle. The developed system has been tested in a real marine scenario to assess its behavior and the quality of tracking and pursuit performance. The experimental results show that the tracking algorithm allows the ASV to correctly track the AUV trajectories, while the strategy adopted to follow the AUV effectively allows to decrease distance between the two vehicles.
Keywords: {AUV, autonomous underwater vehicle, ASV, autonomous surface vehicle, underwater acoustic localisation, USBL, cooperative localisation, underwater navigation}
