Delayed non-fragile H∞ control for offshore steel jacket platforms

This paper is concerned with non-fragile H∞ control for offshore steel jacket platforms subject to self-excited nonlinear wave force and external disturbances. A delayed non-fragile H∞ controller is designed to attenuate the oscillation amplitudes of the offshore platform. The positive effects of the time-delays on non-fragile H∞ control for the offshore platform are investigated. It is shown through simulation results that (i) the proposed non-fragile H∞ controller is effective to reduce the vibration of the offshore platform; (ii) the control force required by the delayed non-fragile H∞ controller is smaller than the one by the delay-free non-fragile H∞ controller; and (iii) the allowable maximum time-delay under the delayed non-fragile H∞ controller is much larger than the one under the delayed dynamic output feedback controller.