AUV and ASV in twinned navigation for long term multipurpose survey applications

The coordination between a fleet of ocean automatic vehicles is an interesting area of research. The communication between an Autonomous Underwater Vehicle AUV and in-shore stations is a difficult question. Satellite communications are expensive; they provides only a limited bandwidth and the link is not always guaranteed when it is needed. High speed communications are difficult from underwater vehicles since their antennas are affected by the sea surface conditions when they are on the surface, especially when rough sea conditions are present. Using a Surface Autonomous Vehicle (SAV) in the proximity of the AUV as a coordination station between a Command Center (CC) in shore and the AUV fleet will be an advantage for reaching a good guaranteed link between shore and the individual vehicles. The constraint of avoiding costly satellite communications on AUVs leads to the consideration of using commercial inexpensive communication systems based on UMTS and WIFI protocols, together with inexpensive acoustic underwater devices for range and bearing control and basic communications. In order to be useful for the mission the previously mentioned surface vehicle faces the challenge of operating in a wide range of weather conditions. In this paper a solution is proposed by considering a dual system composed by a SAV and a fleet of AUV in tandem navigation strategy. In order to avoid vehicle damage, malfunction or lose of communication between shore and AUVs, robust and fault tolerant dual system propulsion and a multiple communication platform ASV is proposed.