Concertina effect-based underwater structure inspection by autonomous vehicles in three dimensions

Autonomous underwater vehicles (AUVs) are becoming increasingly widespread in today's industrialised world, with research shifting towards cooperative control between multiple vehicles. Cooperative control between AUVs poses a number of challenges such as collision-avoidance, path-planning and group formation. This paper presents a novel 3D technique for the purposes of inspecting underwater structures using autonomous vehicles. Vehicles are navigated using a combination of traditional artificial potential fields (APFs) and rotational potential fields (RPFs) which are employed using 2D sub-planes in a concertina effect to provide full boundary coverage and inspection of submerged architectures. Vehicles are freed from the usual angular constraints associated with group strategies whilst moving in a fluid formation, reducing computational load. Simulation results show the effectiveness of the technique on two different-sized structures, providing varying customised levels of inspection and successful collision-free journeys throughout with minimal path length.