In the field of Maritime Autonomous Surface Ships (MASS), the accurate modeling of ship maneuvering motion for harbor maneuvers is a crucial technology. Non-parametric system identification (SI) methods, which do not require prior knowledge of the target ship, have the potential to produce accurate maneuvering models using observed data. However, the modeling accuracy significantly depends on the distribution of the available data. To address these issues, we propose a probabilistic prediction method of maneuvering motion that incorporates ensemble learning into a non-parametric SI using feedforward neural networks. This approach captures the epistemic uncertainty caused by insufficient or unevenly distributed data. In this paper, we show the prediction accuracy and uncertainty prediction results for various unknown scenarios, including port navigation, zigzag, turning, and random control maneuvers, assuming that only port navigation data is available. Furthermore, this paper demonstrates the utility of the proposed method as a maneuvering simulator for assessing heading-keeping PD control. As a result, it was confirmed that the proposed method can achieve high accuracy if training data with similar state distributions is provided, and that it can also predict high uncertainty for states that deviate from the training data distribution. In the performance evaluation of PD control, it was confirmed that considering worst-case scenarios reduces the possibility of overestimating performance compared to the true system. Finally, we show the results of applying the proposed method to full-scale ship data, demonstrating its applicability to full-scale ships.

A hybrid physics-machine learning modeling framework is proposed for the surface vehicles' maneuvering motions to address the modeling capability and stability in the presence of environmental disturbances. From a deep learning perspective, the framework is based on a variant version of residual networks with additional feature extraction. Initially, an imperfect physical model is derived and identified to capture the fundamental hydrodynamic characteristics of marine vehicles. This model is then integrated with a feedforward network through a residual block. Additionally, feature extraction from trigonometric transformations is employed in the machine learning component to account for the periodic influence of currents and waves. The proposed method is evaluated using real navigational data from the 'JH7500' unmanned surface vehicle. The results demonstrate the robust generalizability and accurate long-term prediction capabilities of the nonlinear dynamic model in specific environmental conditions. This approach has the potential to be extended and applied to develop a comprehensive high-fidelity simulator.

In this paper, a fine-tuning method of the parameters in the MMG model for the real-scale ship is proposed. In the proposed method, all of the arbitrarily indicated target parameters of the MMG model are tuned simultaneously in the framework of SI using time series data of real-sale ship maneuvering motion data to steadily improve the accuracy of the MMG model. Parameter tuning is formulated as a minimization problem of the deviation of the maneuvering motion simulated with given parameters and the real-scale ship trials, and the global solution is explored using CMA-ES. By constraining the exploration ranges to the neighborhood of the previously determined parameter values, the proposed method limits the output in a realistic range. The proposed method is applied to the tuning of 12 parameters for a container ship with five different widths of the exploration range. The results show that, in all cases, the accuracy of the maneuvering simulation is improved by applying the tuned parameters to the MMG model, and the validity of the proposed parameter fine-tuning method is confirmed.