H∞ control for offshore structures with persistent disturbances

This paper investigates the problem of H∞ control for offshore structures with persistent disturbances. The time delay is introduced into the controller as a positive factor to counteract the persistent disturbances, such as wind and waveloads. Using Lyapunov stability theory and an integral matrix inequality, a new bounded real lemma is derived and, based on this, an H∞ controller with input delay for the system is designed. Finally, a numerical example is given to demonstrate effectiveness of the proposed methods.