Cooperative Surface/Underwater Navigation for AUV Path following missions

:The paper presents acoustic navigation aiding and path following results from demonstration experiments in Lisbon, Portugal. The demonstration was carried out as part of the second year CADDY Review Meeting. The paper presents the concept of the underwater leader, which entails an underwater vehicle, performing a desired task, and a surface vehicle maintaining relative position to improve navigation aiding through acoustics.The surface controller, utilizing the artificial potential field method, is proposed as an alternative to classical tracking and positioning controllers. Even in presence of multiple agents, the controller offers a more "relaxed" tracking and positioning algorithm for autonomous vehicles. The acoustic data-exchange scheme, required to achieve situation awareness of all agents, is described to specify cycle times and delays that have to be taken into account during state estimation. Finally, results from public demonstrations are presented and analyzed both from the surface and underwater perspectives.