Cooperative ASV/AUV system exploiting active acoustic localization

The lack of GPS signal in the underwater environment poses limitations in terms of localization and navigation of mobile robots. Strategies based on acoustic localization systems are employed to improve underwater navigation. In this paper we describe a first step towards the development of a marine system of systems involving autonomous mobile nodes. The approach relies on communication networking between an Autonomous Surface Vehicle (ASV), equipped with an Ultra Short BaseLine (USBL) device, and an Autonomous Underwater Vehicle (AUV). An active acoustic communication protocol prioritizes the AUV positioning rate, whereas a model-based navigation filter handles the delayed measurements caused by the acoustic communication latency. The system has been tested in a real marine environment to analyze its behavior and the quality of the navigation estimation. The experimental results show that the navigation algorithm on-board the AUV provides an estimate of its position with an error of a few meters with respect to the GPS ground-truth, over a total path of approximately 210m, exploiting acoustic positioning data provided by the ASV in order to limit drift problems.