Weather-Optimal Positioning Control for Underactuated USVs

Abstract

This thesis considers the design and development of a weather optimal positioning control system which is implemented on a developed 6 degrees of freedom vessel model of a Viknes 830 augmented with actuator and environmental models. The intuitive pendulum principle provides a geometrical approach which gives a fuelefficient weather optimal dynamic positioning controller. The convergence to the weather optimal heading is found to be related to the virtual pendulum length. Based on this a virtual anchoring function, and a positioning function was developed. Positioning control is achieved through moving the suspension point of the pendulum. Both functions subject to environmental disturbances were functionality tested using computer simulations and full scale experiments.The Viknes 830, initially developed for combined pleasure and light fishing purposes wasused in the tests. This vessel had lots of lacks, and was far from what can be characterized as an ideal design, both regarding heading stability and propulsion configuration. Despite this, the full scale test system implementation has proven that weather optimal and course independent positioning has the necessary versatility to sufficiently fit a wide range of crafts and purposes.