Marine Cybernetics Vessel CS Saucer: - Design, construction and control

Abstract

This thesis presents the design, construction and control systems development of the marine cybernetics vessel CS Saucer. CS Saucer is a fully actuated and highly controllable vessel with a spherically shaped hull, much like a flying saucer. The vessel is fitted with three azimuth thrusters which are driven by three Torpedo 800 motors. The embedded controller myRIO from National Instruments is used to control the vessel. The system is powered by a three cell 11.1V Lithium Polymer battery.

The hull of the vessel is constructed from three millimeter MDF sheeting, milled Divinycell foam and a woven carbon sheet fitted to the exterior of the vessel with epoxy. This results in a rigid and watertight hull with a low draft. The vessel has a detachable lid made of plexi glass that is secured to the top of the vessel with four butterfly screws.

The drag forces acting on the vessel have been analyzed through testing in the Marine Cybernetics Laboratory (MC Lab) at NTNU. The results have been used to derive the parameters for a dynamic model used in Hardware-in- the-loop testing and for future model based control design. The forces produced by each of the thrusters have been mapped and approximated with linear curve fitting. This approximated force mapping has been used in the implemented thrust allocation with fixed thruster angles.

Manual thruster control and manual force control of the vessel can be operated by the application on the host computer or directly from the Dashboard app from National Instruments available on Android and iOS devices. A dynamic positioning system has been implemented on the CS Saucer and tested in the MC Lab. The dynamic positioning system performs as desired when changing the setpoint for the vessel position. A tentative path following controller has also been implemented and tested on the vessel.

The completed CS Saucer is a fully functioning vessel and a stable and expandable platform for use in future demonstrations, projects and research at the MC Lab.