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

Abstract

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 Froude'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.

Parameter identification of ship roll motion based on vibration tests and CFD method

“…Taylan [28] studied the influence of the nonlinear terms of the damping moment and the restoring moment on the roll motion of a ship. Ueno et al [29] applied the improved energy method and the genetic algorithm to calculate the damping moment and restoring moment coefficients of ship rolling. Mahfouz [30] combined a linear regression and a neural network to calculate the linear and nonlinear coefficients of the damping moment and restoring moment in a ship rolling system.…”

“…Due to the complex nonlinearity of a ship-rolling system [9,[28][29][30][31][32], the identification of its parameters is rather challenging, and all the above identification approaches exhibit shortcomings. For example, some studies ignore the nonlinear terms, some only consider the stiffness or damping terms, and some only acquire the parameters by numerical simulation.…”