Kiyoshi Amagai

Estimation of coefficients of the equation of nonlinear roll motion for fishing boats by improved energy method and genetic algorithm

The present paper proposes two estimation methods for estimating not only the coefficients of roll damping moment but also the coefficients of roll restoring moment without calculation of hydrostatics. The first method is an energy method which involves expanding Proude’s method [5] to the case for which the restoring moment is nonlinear. The second method can identify the coefficients of arbitrary form of nonlinear damping and restoring moments by genetic algorithm. The advantage of these methods is that identification of a highly precise coefficient is very easy compared to other conventional methods. This advantage is most important in applications to practical problems. These methods are first applied to numerical simulation data and then to real free-decay data obtained from scale models.