Optimal H-Infinity Control of Ship Heading

A mathematical model is presented to describe the horizontal behavior of a ship. In order to design a robust controller for maneuvering problem, a number of uncertainties are considered. The transfer function derived from the mathematical model contains coefficients related to body configuration and hydrodynamic behavior. The multiplicative uncertainty bound on the plant transfer function is calculated with variation of hydrodynamic and geometric coefficients. The limitation on the rudder saturation is also considered. The robust control problem is formulated as an optimal H_∞ control problem. The robustness, nominal performance and tracking objectives are fully met in the range of the plant linearity, while the control effort is well below the requirement.