Design of ship-motion regulators for foil catamarans in irregular sea waves

A design technique of ship-motion regulators for foil catamarans is introduced. The main idea of the design technique is how to obtain the robustness of the control system with respect to the ship-motion dynamics in irregular sea waves which is not easily described in a manageable time-domain plant model. The robust controller is designed using the frequency-domain analysis based on the assumption for ship-motion regulation. This offers easy and effective methodology to determine the robustness of the ship-motion regulator in irregular sea waves. For the validation, the design technique is applied to ship-motion regulator design for a foil catamaran and the performance of the control system is verified by theoretical calculations and model tests in regular and irregular waves. Experimental results show the enhanced seakeeping performance by virtue of the motion regulator and close adherence to the theoretical calculations.