This study principally adopts the weather forecast data of WAVEWATCH III (WW3) model and Ocean Surface Currents Analysis – Real time (OSCAR) system as inputs of our weather routing system. For the sake of different purposes of routing problems, the proposed 3DMI (3-Dimensional Modified Isochrone) method considers two types of routing strategies, i.e. ETA (Estimated Time of Arrival) routing and FUEL (FUEL-saving) routing, with different constraints, such as land boundaries, significant wave heights, engine revolution speeds and roll responses. Eventually, it is demonstrated that the robustness of the proposed method seems to be a solution to multi-objective problems by adjusting the safety threshold for the trade-off of ship efficiency and economics.

This study develops a heuristic searching technique for obstacle-avoidance of autonomous underwater vehicles (AUVs) in varying ocean environments by using the self-tuning fuzzy controller. The corresponding hydrodynamic coefficients for the AUV are obtained by the test of Planar Motion Mechanism (PMM), which serves as the important data inputs for the control system. Subsequently, the self-tuning fuzzy controller would be adopted to command the propulsion of AUVs. The function of obstacle-avoidance is based on the underwater image detection method with the BK triangle sub-product of fuzzy relations which can evaluate the safety and remoteness of the candidate routes and the successive optimal strategic routing can then be selected. In the present simulations, the current effect is used to investigate the maneuvering performance of obstacle-avoidance. Eventually, the present study indicates that the self-tuning fuzzy controller, combined with the image detection technique based on BK triangle sub-product of fuzzy relations, is verified to be a useful searching technique for obstacle-avoidance of AUVs in depth variation.

In this paper, the authors proposed a ship weather-routing algorithm based on the composite influence of dynamic forces, i.e. wind, wave and current forces, for determining the optimized transoceanic voyages. Our developed routing algorithm, three-dimensional modified isochrones (3DMI) method, utilizes the recursive forward technique and floating grid system for both the east- and west-bound ship routes in the North Pacific Ocean. In order to achieve the goals of minimized fuel-consumption or the maximized-safety routes for the transoceanic voyages, two sailing methods are applied as the prerequisite routes in the earth coordinate systems. The illustrative analysis of ship routes has been presented and discussed based on the realistic constraints, such as the presence of land boundaries, non-navigable sea, external forces, parametric roll responses as well as ship speed loss. As a result, the proposed calculation is verified to be effective for the optimized sailings by adjusting the weighting parameters in the objective functions.

In order to enhance the efficiency and safety of a ship sailing in rough seas, the authors aim to develop a ship dynamic performance system, which can be used to predict ship motion responses, wave loads as well as quasi-mean added resistance. Two-dimensional strip theory discretized by the source distribution method is implemented to calculate Response Amplitude Operators (RAOs) for 6 DOF motion as well as the wave loads for the vertical shear force and bending moment. In addition, the ITTC directional wave spectrum of the short-crested wave adopts the one-hundred years return sea state as the input for testing the sea-keeping performance. Subsequently, we developed a database for a specific ship to realize the relationship between the sea-keeping performance and a combination of wave headings and ship speeds. Since the calculation of hydrodynamic coefficients correspond to the instantaneous hull form below the free surface (draft), the B-spline curve fitting technique based on the fourth order Runge-Kutta method is introduced to describe the relative wave heights together with second order nonlinear forces.

A kinematics model of the ship wake in the presence of surface waves, generated by wind is presented. It is found that the stationary wave structure behind the ship covered a wedge region with the 16.9° half an angle at the top of the wake and only divergent waves are present in a ship wake for co propagating wind waves. Wind waves field directed at some nonzero angle to the ship motion can cause essential asymmetry of the wake and compressing of its windward half. The extension of Whitham-Lighthill kinematics theory of ship wake for the intermediate sea depth is also presented. The ship wake structure essentially depends from the Froude ( Fr ) number based on the value of the sea depth and ship velocity. For Froude number less than unit both longitudinal and cross waves are presented in the wake region and Kelvin wake angle increased with Fr . For Fr>1 wake angle decreased with Froude number and finally only divergent waves directed almost normally to the ship track are presented in the very narrow ship wake.