Dynamic properties of a container vessel with low metacentric height

Abstract

Inaccuracy in prediction of manoeuvring and lack of robustness of closed-loop autopilot control have been a surprising experience for several ships with low metacentric height. Until now, effective investigations of these phenomena have been hindered by lack of knowledge on the precise interaction between roll and lateral motions. This was changed with the construction of a unique four-degrees-of-freedom roll planar motion mechanism (RPMM) at the Danish Maritime Institute.

The paper presents complete nonlinear models for a container ship obtained with this facility. Model scale predictions are compared with full scale results and shown to give a good replication of the dynamic properties after tuning of a few parameters to account for model to full scale differences. Dynamic control properties are discussed, and the importance of roll couplings is investigated. Finally, response operators for waves are provided for a relevant range of metacentric heights, and wind data are included to make the characterisation of the vessel complete.

Keywords

Ship movement manoeuvring metacentric height autopilot roll motion dynamic control

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