Nonlinear control of decarbonization path following underactuated ships

Decarbonizing shipping is one of the most critical challenges in controlling global carbon emissions. Therefore, from the point of view of general shipping control, it is essential to control carbon dioxide emissions from underactuated ships, the primary mode of transport in the shipping industry. In this paper, we proposed an extended state observer to deal with the uncertainty of the ship model and the estimation of external disturbances. Then, we developed an improved " dynamic virtual ship" guidance algorithm and an energy-saving ship path following controller by combining nonlinear feedback and adaptive backstepping. Finally, it is found that the proposed nonlinear control algorithms result in improved path following control where the average ship output rudder angle is reduced by 17%, the average steering power is reduced by 10%, the Energy Efficiency Design Index (EEDI) of the ship is reduced by 2%, the average ship speed is increased by 0.3 knots, and the carbon dioxide emissions during general shipping are reduced by 32.45%. We anticipate that the proposed algorithm will play an essential role in the process of decarbonization in shipping.