A comparison of methods of identifying operating condition for ship roll stabilization control

Ship roll stabilisation may be improved by utilizing a bank of parallel controllers in which individual controllers are activated in pairs for roll control via actuation of rudder and tins. To achieve this, it is necessary to identify the ship's operating condition, thus facilitating the activation of the appropriate controller pair. Operating conditions depend mainly on ship speed and wave encounter angle and, whereas only the ship speed is known to the system, the other conditions need to be identified. An approach has been designed to detect the actual seagoing condition via roll frequency detection. Two different methods are illustrated and discussed in this work.