Analysis of the group structure of a school of biomimetic AUVS coordinated using nearest neighbour principles

Biomimetic Autonomous Underwater Vehicles are Autonomous Underwater Vehicles (AUVs) that employ similar propulsion and steering mechanisms as real fish which result in improvements in propulsive efficiency at low speed. However, as with all AUVs the range and endurance of these biologically inspired vehicles are severally limited by the on board power supply. Nevertheless, large area scanning can still be achieved by the coordinated movement of multiple vehicles. To allow this to happen co-ordination algorithms would have to be utilised to ensure that a group of AUVs would be self-organising. The particular methodology presented in this paper again takes inspiration from nature and is based upon the behavioural mechanisms exhibited by schools of fish. Therefore, using a validated mathematical model of a robotic fish (called RoboSalmon), this paper outlines the implementation of this algorithm which similarly to the behavioural mechanisms use nearest neighbor principles to determine the movement of each member of the group. As this paper will use a mathematical model of a biomimetic AUV to implement biologically inspired coordination algorithms, the resulting group structure will be analysed with reference to the formation of a group structure and the number of AUVs within a group that are in a position to take advantage of the hydrodynamic benefits known to exist from fish swimming in close formation. The results demonstrate that the number of nearest neighbours taking into consideration greatly affects the formation of a stable school structure whereas the size of the school dictates the number of AUVs within the group benefitting hydrodynamically from the close proximity of neighbouring fish.