Wave force attenuation control for offshore steel jacket platforms via optimal guaranteed cost sliding mode schemes

This paper is concerned with optimal guaranteed cost sliding mode control for an offshore steel jacket platform subject to nonlinear self-excited wave force. A nonlinear quadratic performance index which directly associates with the wave force is introduced first. Then, by combining the guaranteed cost control scheme and the integral sliding mode control scheme, an optimal guaranteed cost sliding mode controller is proposed to attenuate the wave force and improve the performance of the offshore platform. It is shown through simulation results that the oscillation amplitudes of the offshore platform under the optimal guaranteed cost sliding mode controller are small than those under the integral sliding mode controller and the delayed dynamic output feedback controller. Moreover, the required control force by the optimal guaranteed cost sliding mode controller is less than the ones by the integral sliding mode controller and the delayed dynamic output feedback controller.