Vibration Reduction for Offshore Platforms via Delayed Sliding Mode H∞ Control

Abstract

This paper deals with delayed sliding mode H∞ control for an offshore steel jacket platform subject to nonlinear self-excited wave force and external disturbance. By using both current and delayed states, a delayed sliding mode H∞ controller is designed to attenuate vibration of the offshore platform. It is observed through simulation results that the delayed sliding mode H∞ controller is capable of reducing the oscillation amplitudes of the offshore platform significantly. Moreover, compared with the delay-free sliding mode H∞ controller, the oscillation amplitudes of the offshore platform under the controllers are almost the same, while the control force required by the delayed sliding mode H∞ controller is less than that by the delay-free sliding mode H∞ controller.