Author(s): Andreas Orsten; Petter Norgren; Roger Skjetne
Linked Author(s):
Keywords: No Keywords
Abstract: Motivated by the need to develop a reliable and safe way oftowing icebergs, this paper investigates the use of a feedback-based guidance algorithm for steering the iceberg along a pre-defined safe track. A simplified, linear iceberg model is developed in 2 degrees of freedom (DOF) to capture the horizontal motion, including the effect of constant and irrotational ocean currents. Previously, a Line-of-Sight (LOS) algorithm has been implemented for steering a ship along a predefined path. The algorithm has been modified to include the effect of an ocean current, using integral action. In this paper, the current-modified LOS algorithm is augmented in order to apply it to the 2-DOF horizontal iceberg model. The output of the iceberg LOS algorithm is the desired towline angle αLOS. Guidance ofthe model is achieved through a tow force T with direction α that should conform to αLOS. Simulation studies, showing the performance ofthe LOS algorithm, are performed in the presence ofboth a constant, and a slowly-varying ocean current. A towing vessel reference model is proposed in order to obtain as better resemblance between the change ofthe towline angle and the movements of the towing vessel. The simulation studies all show that the iceberg trajectories converge to and move along the desired path, and that the vessel reference model provides feasible trajectories for the towing vessel.
Year: 2014