However, for given samples from real manoeuvring tests, such a modification of excitation might be not applicable; in other words, this approach might only work for simulation data.
Based on these ideas, three approaches are presented to diminish the drift of hydrodynamic coefficients, including simplification of the manoeuvring model, difference of the samples, and the method of additional signal.
Sensitivity analysis provides another way to simplify the mathematical model of ship manoeuvring [49-53].
It is noted that such a reconstruction does not require a new manoeuvring to obtain new input-output samples for system identification but modify the obtained samples.
Such a method had been successfully applied to the identification of ship manoeuvring by analyzing simulation data  and captive model test results .
As a result, the manoeuvring characteristics of the original system, which might cause the parameter drift as described in the Section 3.
It is noted that the design of additional signal depends on the characteristic of the data samples or the manoeuvring motion.
Based on the regression model, 25[degrees]/5[degrees] zigzag manoeuvring motion is simulated and the predicted results are compared with the experimental results, as shown in Figure 2.
Some parameters in the manoeuvring model cannot be obtained using SI, while some parameters deviate from true values even if they can be derived.
Guedes Soares, "Recursive neural network model of catamaran manoeuvring," International Journal of Maritime Engineering, vol.