Modeling of Ship Manoeuvring Motion in 4 Degrees of Freedom Based on Support Vector Machines

Ship manoeuvring motion in waves is usually accompanied by nonlinear roll motion of large amplitude. In this paper, by taking account of the influence of the roll motion, a 4 degrees of freedom mathematical model of ship manoeuvring motion is derived. A method based on least squares support vector machines (LS-SVM) is proposed for identifying the hydrodynamic derivatives in the mathematical model by analyzing the data of surge speed, sway speed, yaw rate, roll rate, roll angle and rudder angle. To verify the identification method, 10°/10° zigzag tests are simulated for a container ship by using the hydrodynamic derivatives obtained from the roll planar motion mechanism (RPMM) test; the simulation data are used to identify the hydrodynamic derivatives, and the identification results are compared with those of RPMM test. The 10°/10° zigzag manoeuvring motion is predicted with the identified hydrodynamic derivatives. Besides, the identified model is used to predict the 20°/20° zigzag and 35° turning circle manoeuvres, and the predicted results are compared with those of simulation tests to demonstrate the generalization performance of the identified mathematical model.