Abstract
To reduce greenhouse gas emissions from ships as required by international environmental regulations, we propose herein an energy-saving method for ships sailing on wavy seas. The effect of applying this method is investigated by a numerical study of a bulk carrier self-propelled in regular head and following waves. The method requires that the ship be equipped with a controllable-pitch propeller (CPP) and an electric propulsion motor, which are controlled in an optimal manner to anticipate impending waves, thereby minimizing energy consumption. Optimal control is implemented using a nonlinear model predictive control method that uses information within a receding horizon to calculate the adjustments, which in turn control actuators that vary the propeller-pitch angle and the drive frequency of the motor. To implement this real-time application, we use a fast algorithm for solving the model predictive control problem. As a result, for a wave steepness of 0.01 and a unity ratio of wavelength to ship length, the energy required to propel a bulk carrier without optimal control is reduced by about 10% with the optimal-control system proposed herein.
Published Version
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