Experimental study of adaptive course controllers with nonlinear modulators for surface ships in shallow water

The present paper proposes a new adaptive controller with nonlinear modulators to improve the controller adaptability and rudder efficiency so that a satisfactory course tracking performance of ships can be achieved. First, a new adaptive control law on basis of Internal Model Control (IMC) is designed to address the speed dependency of the controller. Three types of nonlinear modulators are then added to the developed adaptive controller to increase the rudder efficiency. Subsequently, the control system’s stability is analysed. Both course keeping and changing performance of the proposed controller are investigated via towing tank tests using a ship model of a Liquefied Natural Gas carrier. Finally, the applicability of controllers in shallow water is discussed. During experiments the developed algorithms show satisfactory course tracking ability in shallow and deep water. The advantages of better adaptability and higher rudder efficiency are verified by comparative results. Moreover, the impact of water depth on the controller cannot be ignored. •A new adaptive controller with nonlinear modulators is proposed to improve adaptability and rudder efficiency.•Around 5,000 model tests have been executed to study the performance of the designed controllers instead of more common simulations.•This research focuses on investigating the course tracking ability of controllers in shallow water for large vessels.