Sensitivity analysis and parametric identification for ship manoeuvring in 4 degrees of freedom

The spiral test is simulated by using a ship manoeuvring mathematical model of 4 degrees of freedom. Based on the simulation data, sensitivity analysis using the direct method is implemented for the hydrodynamic coefficients in the mathematical model, and the mathematical model is simplified by omitting the coefficients of smaller sensitivity according to the sensitivity analysis results. 10 degrees/10 degrees, 20 degrees/20 degrees zigzag tests and 35 degrees turning circle manoeuvre are simulated with the original and the simplified mathematical models. The comparison of simulation results obtained by the original and the simplified models shows the effectiveness of the sensitivity analysis and the validity of the simplified model. The hydrodynamic coefficients in the simplified model are then identified by using the least square support vector machines, with the training samples taken from the simulation data of 20 degrees/20 degrees zigzag test. 20 degrees/20 degrees, 10 degrees/10 degrees zigzag tests and 35 degrees turning circle manoeuvre are predicted by using the identified hydrodynamic coefficients, and the predicted results are compared with the simulation results to demonstrate the validity and generalization performance of the identification method.