Application of Nonlinear Digital Filters to Modeling LowFrequency, Nonlinear Drift Oscillations of Moored Vessels in Random Seas

The problem of modelling and forecasting the sway motion response of a moored vessel to random sea waves is discussed. When the sea wave fluctuation is measured and recorded digitally with a proper sampling rate, the future response of the vessel can be actually predicted with relatively high accuracy by utilizing an (adaptive) quadratic filtering technique, which is summarized in this paper. Some experimental results based on a scaled model wave basin test are also presented to demonstrate the utility of the above technique.