The characterisation of magnetic couplings and the development of a thruster module for an ROV

This dissertation focuses on the development of thruster modules and the characterisation of magnetic couplings for a Remotely Operated Underwater Vehicle (ROV). The dissertation begins with an introduction to the Seahog ROV developed at the University of Cape Town's Robotics and Agents Research Laboratory (RARL). The history, relevance and features of commercial ROVs are discussed in chapter two to introduce the reader to this form of underwater robotics. After this the dissertation is divided into two separate sections. The first section, chapters three to eight, detail the mechanical and electrical modifications made to an existing, magnetically coupled, thruster module design. The objective of this section was to improve the thruster module in order to achieve performances that are similar to commercially available thrusters. The modifications included changes to the drivetrain, the design of new electronics and motor drivers and a reduction in weight of the module's housing. A fundamental analysis of the thruster module is presented, no Computational Fluid Dynamics (CFD) is provided as the propeller and kort-nozzle designs remained unchanged. Even though the improvements produced a reliable and efficient thruster module a greater understanding of magnetic couplings was required to produce a design that was as lightweight as commercial modules. Therefore the second section of this dissertation, chapters nine to twelve, implement and validate an analytical model to calculate the torque and slip characteristics of magnetic couplings. The dissertation is concluded in chapter thirteen with recommendations that incorporate the knowledge gained in magnetic coupling design with the modifications made to the thruster module to produce a thruster design that is both efficient and light