A thrust sensitivity analysis based on a synthesized positioning capability criterion in DPCap/DynCap analysis for marine vessels

Dynamic positioning capability/dynamic station-keeping capability (DPCap/DynCap) analysis determines the maximum environmental forces that the dynamic positioning (DP) thrust system can counteract for a vessel on any given heading. These forces and moment are statically/dynamically balanced by the thrust forces and moment provided by the thrust system comprising several types and configurations of thrusters. The thrust provided by each thruster is vital for the positioning capability of the vessel; however, to date no method has been reported in the literature to quantitatively identify the influence that each individual thruster exerts on the combined positioning capability of a vessel. This study proposes a novel thrust sensitivity analysis method based on a newly defined synthesized positioning capability criterion for DPCap/DynCap analysis, which allows the sensitivity of the thrusters to be determined. Once the most sensitive thruster is determined, it should then be given the most attention since, if it fails, the remaining thrusters cannot supply sufficient forces and moment to hold the vessel on course or in position. It is demonstrated that the analysis is helpful for determining the most sensitive thruster and may provide reliable guidance in the design of the thrust system.