Guidance and control of iceberg towing operation in open water, with experimental testing
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- Institutt for marin teknikk 
Icebergs pose serious threats to existing and planned offshore structures, vessels, and operations in Arctic waters such as the East Coast of Canada, East and West Greenland, the Barents Sea, and the Kara Sea. A collision between an offshore installation and an iceberg could cause serious damage to the installation, and in a worst case scenario take life. Therefore, if an iceberg is evaluated as a threat, physical iceberg management must be mobilized to mitigate the threat. For open water, this is typically done by single vessel towing of the iceberg using steel hawser and synthetic floating tow lines.This work describes a model for open water iceberg towing using a single towing vessel. This includes a mathematical model of the towing vessel, the iceberg and the towline between them. It also looks into certain towline configuration choices, estimation of damping and mass, and other things that can affect the towing model. The mathematical model was based on the work of [marchenko2008] and then generalized to the Fossen-style of notation [fossen2011].A maneuvering controller was designed for use in the towing operation. The controller was designed using maneuvering theory as described by [skjetne2005]. The controller is responsible for guiding the ship along a path, with the iceberg trailing behind it. Another controller has been designed for controlling the tension in the towline. In addition to the controllers, several observers had to be designed. These observers are responsible for estimating position, velocity, bias, and tension in the system.Finally, an experiment with the CS Enterprise I model vessel, and an emulated iceberg, was conducted in a towing tank. The experiment gave important qualitative data regarding the iceberg towing system, and confirmed that the controller worked in a real-life scenario.