Torsional Vibrations Reduction in More Electric Ships Propellers Using Model Predictive Control

In recent years, more electric ships are gaining importance for their capability of reducing CO$_{2}$ emissions. In these vessels, the use of electric propulsion, in which the electrical energy is provided through an electric grid, allows 35$\%$ of fuel savings. However, to reduce the weight of the propulsion system, the shaft connections in the overall system are often very flexible, allowing vibrations to be excited. Torsional vibrations can be excited by sea perturbations such as ventilation, damaging the propeller or reducing its life. This paper studies the excitation of torsional vibrations and proposes a Model Predictive Control (MPC) strategy to reduce them. For this, a simplified model of marine vessel propellers is considered and the MPC strategy is applied and analysed for different sources of vibrations. The proposed strategy is also analysed under different operation points and its robustness to parameter uncertainty is assessed. The technique is validated through simulations and hardware-in-the-loop experimental tests. The obtained results show that the proposed MPC reduces the torsional vibrations while maintaining the same speed control characteristics.