Integrated robust ship roll stabilisation

The pernicious consequences of roll motions have a profound effect on the operational effectiveness of all types of ships. In warships the motions may be serious enough to curtail helicopter excursions from the deck, and degrade performance of the weapons systems and radars. Thus rendering the warship impotent to perform its designated role. For ships in general, roll motions may reduce personnel to simply hanging on to a fixed object to maintain balance, cargo may be disturbed, interruptions to machinery may occur and these motions may greatly agitate passengers. All these factors act in conglomeration to produce an inherent degradation in ship operability. The H infinity optimisation offers a technique to design a controller which not only encompasses these variations but also accounts for robust stability and guaranteed levels of performance, analogous to disturbance rejection. In this paper H infinity synthesis is utilised to design a fin/rudder controller given appropriate weightings. The system is decomposed into its fractional representation in order to assess whether robust stability and performance criteria are attained.