  Accurate maneuvering estimation is essential to establish autonomous berthing
control. The system-based mathematical model is widely used to estimate the
ship's maneuver. Commonly, the system parameters of the mathematical model are
obtained by the captive model test (CMT), which is time-consuming to construct
an accurate model suitable for complex berthing maneuvers. System
identification (SI) is an alternative to constructing the mathematical model.
However, SI on the mathematical model of ship's maneuver has been only
conducted on much simpler maneuver: turning and zig-zag. Therefore, this study
investigates the SI on a mathematical model capable of berthing maneuver. The
main contributions of this study are as follows: (i) construct the system-based
mathematical model on berthing by optimizing system parameters with a reduced
amount of model tests than the CMT-based scheme; (ii) Find the favorable choice
of objective function and type of training data for optimization. Global
optimization scheme CMA-ES explored the system parameters of the MMG model from
the free-running model's trajectories. The berthing simulation with the
parameters obtained by the proposed method showed better agreement with the
free-running model test than parameters obtained by the CMT. Furthermore, the
proposed method required fewer data amounts than a CMT-based scheme.
