The paper deals with the operation assessment of an autonomous underwater vehicle equipped with a three-degrees-of-freedom vectored thruster. The vehicle, which should be considered as a "concept submersible", follows the actual criteria on autonomous systems being portable, cheap and characterised by excellent manoeuvrability and mission range. Thanks to the hybrid propulsion and guidance system the vehicle's streamlined hull is free of hydrodynamic appendages, such as rudders or fins, and no auxiliary motors are needed to increase the control capabilities. The guidance system, moreover, represents an innovative solution for submersibles that enhance the low speed manoeuvring and path following potential.
The study deals with the design process of a new-concept powering and steering system for Autonomous Underwater Vehicle, developed to exceed the limitations inherent existing settings. Presently, a big effort is made to realise everyday use AUVs enhancing the robustness of the control systems and autonomy, studying ease of use interfaces and reducing the size of the vehicle (Amat et al., 1999). The need for better manoeuvrability and agility pushed to investigate and to conceive sophisticated real time control systems (Filaretov and Kihney, 2000). As a matter of fact, a large number of papers has been written dealing with the problem of underwater vehicles control, aiming at new solutions and strategies. However, contemporary AUVs need several degrees of freedom (DOF), in order to ensure good manoeuvrability. Therefore, underwater vehicles, as a rule, have 4–6 thrusters. Such layout increases considerably the vehicle's size and weight and deteriorate its dynamical properties emphasizing the disturbing effects of fluid environment (viscous friction, added mass and added moment of inertia). The design of a compact and nimble vehicle requires the ideation of a new propulsion system that changes its orientation and grants of the AUV's motion along arbitrary space trajectories with steady attitude.