Real-time estimation of the ship manoeuvrable range in wind

Abstract

A real-time identification procedure is applied to the estimation of hydrodynamic derivatives of ship manoeuvring equations. In the procedure, not only the ship motion data but also the wind data are used for making up a CARX (Continuous Auto Regressive eXogenous) model. The main advantage of the procedure is that the coefficients of the model directly correspond to the hydrodynamic derivatives. The identification algorithm consists of the IIR (Infinite Impulse Response) digital filters and RLS (Recursive Least Square) method. To discuss the reliability of the identified coefficients, the procedure is applied to a full-scale ship's data and the results are compared to the hydrodynamic derivatives provided by the shipbuilding company. Moreover, a simple navigation support system is proposed using the identified hydrodynamic derivatives. The system can indicate the ship manoeuvrable range under wind conditions and its usefulness is shown.