Open Access Dissertation
Date of Award
The dynamic behavior of marine surface vessels is highly nonlinear. Moreover, it is significantly influenced by environmental disturbances induced by winds, random sea waves and currents. To yield a desired response of the ship, the guidance and control system of the ship should be robust to both modeling imprecision and significant environmental disturbances.
The focus of the current work is threefold. First, a six degree-of-freedom nonlinear model for a marine surface vessel is developed. It accounts for the coriolis and centripetal acceleration terms, added mass and wave damping terms, wave excitation forces, so-called "memory" effect terms, nonlinear restoring forces, wind and current effects, and control forces and moments. In addition, the formulation accounts for the physical limitations of the rudder and the powertrain system of the ship. In the current work, the detailed model of the vessel is used as a test bed to assess the performances of the proposed guidance system, controllers, and observers under various environmental conditions.
A robust sliding mode controller and a self-tuning fuzzy sliding mode controller have been designed in the current work and proven to yield the desired response of the ship through digital simulations. Furthermore, a new guidance system has also been designed based on the line-of-sight and the acceptance radius concepts. The integration of the guidance system with the controllers has led to the design of a fully-autonomous surface vessel that is capable of accurately tracking a specified trajectory without any interference from the person at the helm.
Moreover, nonlinear robust observers are designed, based on the sliding mode methodology and the self-tuning fuzzy sliding mode, to yield accurate estimates of the state variables that are needed for the computation of the control actions. The observers play a central role in the integrated guidance and control system proposed for the ship.
Khaled, Nassim, "Robust Observers And Controllers For Marine Surface Vessels Undergoing Maneuvering And Course-Keeping Tasks" (2010). Wayne State University Dissertations. Paper 16.