• Autonomous Robots
• Bearing-only measurements
• Consensus
• Particle Filter
• Underwater Surveillance

Distributed systems and cooperative control are the main themes of the thesis work. The objective was the development of an algorithm capable of detecting and locating in a distributed way an underwater target by a team of Autonomous Underwater Vehicles (AUV). We are talking about passive detection and localization, so the sensors with which the vehicles are equipped, detect the target only when it emits a noise above a certain threshold (detection threshold), and they do not emit any acoustic signal. In fact, an additional objective was to detect the target without it being aware of the presence of the team. The innovation lies precisely in the use of a team of cooperating vehicles, which tow linear arrays in order to inspect a portion of an underwater area. The first arrays were in fact connected by winches and towed by individual boats and were hundreds of meters long, also had diameters of several centimeters and therefore the current autonomous underwater vehicles could not be able to withstand this load. During these inspections the first hydrophones that made up the array were mounted several meters from the stern of the ship, in order to avoid that the noise emitted by the engine compromised the measurements in acquisition. The advance of technology led to the development of linear arrays, whose diameter was less than 30 millimetres, drastically reducing the weight. It was therefore possible to think of dividing the overall length of the array and using a fleet of vehicles instead of a single vessel, thus introducing the problem of controlling a distributed system. Moreover, since the old arrays were several hundred meters long, in order to equalize the inspections carried out by large vessels, it is necessary that the team of vehicles maintain a certain distance and therefore a certain formation, so as to cover a wide geographical area. A first step in this area was taken during the European WiMUST (Widely scalable Mobile Underwater Sonar Technology) project. This project involved the use of a small fleet of autonomous underwater vehicles to carry out geophysical inspections. The arrays consisted of hydrophones streamers of small aperture in order to collect environmental data. One of the advantages revealed in WiMUST is that by controlling the geometry of the team it was possible to change the shape of the arrays according to the required goal. The innovation of the WiMUST project is therefore represented by the use of a team of cooperating underwater vehicles working as a distributed system, acquiring data locally on board each vehicle. However, the amount of data to be exchanged, in the order of Gigabytes, was too high, which is why the data processing was carried out off-line. As in WiMUST, in my thesis work, the data acquisition takes place locally on board of the vehicles, while regarding the communication between the vehicles, this takes place in real time through an appropriate communication strategy, thanks to which the agents of the network can share the information acquired with the other members of the team.