# Simulation of Autonomous Underwater Vehicles (AUVs) Swarm Diffusion
## 1 Introduction  
This paper is part of several preliminary studies by the Underwater Drones Group (UDG) of the Science Department of the Universita degli Studi \"Roma Tre,\" which is developing several advanced autonomous underwater vehicles (AUVs) for the exploration of deep seas. The final aim of the general project is to create modular task platforms for underwater scientific research that can accommodate a wide range of different payloads optimized for the most missions.  
In this work, we have proposed a new type of AUV swarm and simulated its use in the Channel of Piombino out of the coast of Tuscany (Italy). The architecture of the vehicle, designed for shallow and white waters, will first be illustrated. Then, the swarm architecture and its advantages from the point of view of reliability and operational use will be developed: After that, we will show how to spread a series of underwater drones with \"diffused intelligence\" (swarm) and its microscopic diffusion model in a closed section of the sea when they are inserted from a single starting point. At the end, we are going to present the simulation that confirms that our approach to the swarm is capable of spreading homogeneously over a specific closed area.  
State-of-the-Art and New Approach  
Sometimes, science tries to copy nature; in fact, when drones (intended as autonomous vehicles) have enjoyed a technology that makes them small, economical, and intelligent enough, their use in swarms was a natural step.  
From the point of view of the philosophy of use, the first step was to imitate and borrow the behavior of flocks of birds in the sky or schools of fish in the sea. All this has led to a drone development philosophy in which the single individual (vehicle) collaborates with others in the name of a \"common good\" and all the components of the swarm combine to accomplish a mission [1]. This approach brings precise logical and technological constraints: First of all, a close collaboration between the proximal vehicles, which, in turn, entails a considerable flow of information that must be exchanged. Secondly, each vehicle has a particular task: It is certainly replaceable by the others but, at the moment, it covers that role whereby its \"social position\" must be transmitted to the other members, and this imposesanother penalty in the aggravation of the weight of communications. Due to the great flexibility, it is possible to divide, to satisfy small momentary tasks, the swarm into smaller patrols: In this case as well, a heavy price is paid in terms of communication flow and the general arrangement of the various groups [2; 3; 4; 5].  
For some time, however, the philosophy of the approach to the problem has been changing: Now, the group of drones is seen as composed of more autonomous elements, with much looser mutual constraints: The personal initiative of the individual vehicle becomes, from a philosophical-point-of-view implementation, much more important than \"choral work\": Despite this radical change, it is noted that the swarm is able, in any case, to carry out the mission assigned to it and, often, in a faster and more efficient way [6; 7; 8; 9; 10].  
All this is present in the paradigm of our swarm: The individual components can be considered \"selfish\" as they do not take into account their fellowmen unless they get too close: In that case, a repulsion occurs. On the other hand, the single vehicle, if it is unable to carry out a mission, \"commits suicide\" by isolating itself and returning to base. In this paper, the authors propose the study of a similar paradigm of swarm behavior in an underwater environment that, at the moment, has not yet been investigated.