The dismantling of offshore structures, known as decommissioning, is a complex task in the oil and gas industry, driven by strict environmental standards. As the environments in which decommissioning is necessary become more challenging, autonomy presents itself as a solution to conduct this work as cost-effectively and safely as possible, namely by taking Remotely Operated Vehicles (ROVs) and divers out of the equation. In this thesis, three avenues are researched in support of Autonomous Underwater Vehicles (AUVs) for decommissioning: navigation, attachment, and manipulation. First, the Iterative Closest Point method (ICP) is investigated as a means to correct position drift of an inertial navigation system, by using a previously obtained coarse map. Using real sonar data from a current decommissioning site in the Gulf of Mexico, the algorithm is able to reconcile the internally dead-reckoned pose of the vehicle with that calculated via ICP, to an accuracy of 7cm from a 100k-point sonar scan. Second, to attach lifting points to subsea scrap without bracing onto it, a single mechanism was designed to both drill and affix anchors in a single penetration, from a vehicle in free flight. A prototype was fabricated and its functionality verified. Third, to promote robust and stable robotic interactions using an industry standard non-backdrivable manipulator, a control law was developed to have the vehicle-manipulator system passively interact with its environment, by mimicking an arrangement of masses, springs, and dashpots. This control law was tested and analyzed in a simple experiment that achieved a 90% reduction in settling time. Daniel for the constant reminder that everything will be alright, and Ray for always making that possible in more ways than imaginable. Finally, the author would like to thank Prof. Franz Hover for having gone above and beyond his role as an advisor from the start, and without whom none of this would have been possible. 5 6

Nitinol, a nickel-titanium shape memory alloy, was analyzed for its feasibility as a linear actuator to be used in a thermal buoyancy engine of an autonomous underwater ocean glider fueled by the temperature gradient of the ocean's thermocline. A nitinol mass suspension apparatus was fabricated to measure the displacement of an array of masses ranging from 0:5kg to 8kg as the wire was transitioned into its heated austenite phase, and then cooled back to its martensite phase, thus representing the expansion and contraction of a buoyancy engine piston under hydrostatic pressure. In validation of nitinol manufacturer Dynalloy; Inc: specifications, the maximum stroke observed in this dead weight bias configuration was 4:25±0:24%, only a 6% difference from the documented 4% stroke.