An icevaning control for dynamic positioning in managed ice condition

Abstract

The presence of sea ice is the primary challenge for marine operations in the Arctic region. It is widely accepted that offshore structures running in the Arctic condition need station-keeping methods as well as ice management actions by icebreakers. Dynamic positioning (DP) is one of the station-keeping methods that can provide mobility and flexibility in marine operations. The presence of sea ice adds complex external forces and moments on the vessel which must be managed by the DP system. This paper presents an icevaning control algorithm of the Arctic DP system. To make the icevaning action of the Arctic offshore vessels without any measurements and estimation of the ice condition including ice drifting, a task space and a null space are defined in the vessel model, and the control law is formulated in the task space. A backstepping technique is utilized to handle the nonlinearity of the Arctic offshore vessel's dynamic model, and the Lyapunov stability theory is applied to guarantee the stability of the proposed icevaning control algorithm. A set of experimental tests are conducted in the ice tank of the Korea Research Institute of Ships and Ocean Engineering to examine the practical feasibility of the proposed icevaning control algorithm.