DEVELOPMENT OF CN MODELS AND THEIR APPLICATION IN SHIP MANOEUVRABILITY STUDIES

To describe ship motion in a horizontal plane, different mathematical models are used. The majority of them are obtained by extension of the hydrodynamic loads in Taylor's series of kinematic characteristics and control device forces. The application of such a formal approach often leads to badly conditioned matrix of normal equation and instability in the estimation of the parameters, the so-called multicollinearity. To eliminate this disadvantage, essential physical models are intensively elaborated, reflecting the hydrodynamic nature of the phenomena in ship manoeuvring. At present greatest application is attributed to the mathematical models based on the cross-flow concept. The paper considers some approaches for eliminating the above mentioned disadvantage of Cn models. Their applicability is evaluated by means of comparing the calculated results from PMM tests with the data from the free running model tests.