Modeling and Control for the Reduction of Wave Induced Motion of Ramp- Connected Ships

The focus of the research in this thesis is the control of a unique vehicle in development called the T-Craft. The T-Craft is a surface effect ship (SES) capable of functioning like a catamaran or an air cushion vehicle (ACV). The goal is to ultimately stabilize a ramp connecting a large medium speed roll on/roll off (LMSR) vehicle, such as an aircraft carrier, to the T-Craft. The combination of the T-Craft connected to the LMSR is called the sea base.;The system was first modeled by treating each vessel as semi-cylinder monohulls and simulated using SimMechanics, a rigid body mechanical toolbox available in Matlab. The ships were connected in a bow-to-stern orientation. In this setup, extremum seeking (ES) was used to tune the ramp length and wave heading to minimize the oscillations. Significant reduction of ramp oscillation was observed.;Following tests on the SimMechanics model, a more accurate system model was produced that utilized a wave seakeeping program called AEGIR. This program produces hydrodynamic forces based upon the hull geometry and wave information inputs. In this setup, the T-Craft was modeled as a dual hull catamaran with air cushion effects added separately and the LMSR was modeled as a large mono-hull. Passive control was tested on this new system in the form of a spring damper connection between the ramp and each vessel. Additionally, backstepping was used to control the air cushion pressure in order to reduce the heave of the T-Craft in a side by side connected system. In both cases, ramp angle oscillation reduction is observed.