Wave Attenuating delay-dependent H∞ control for offshore platforms with parameter uncertainties

This paper is concerned with delay-dependent robust H_∞ control for an offshore steel jacket platform subject to wave force. By taking into account the variations of the structural natural frequency and damping ratio, and time-varying control delay, an uncertain time-delay dynamic modal of the offshore platform is established first. Then a delay-dependent robust H_∞ control scheme is proposed to attenuate the wave-induced vibration of the platform. A delay-dependent robust H_∞ controller is obtained in terms of the solvability of a nonlinear minimization problem. Simulation results show that though there exist time-varying control delay and parameter uncertainties in the system, the designed controller can effectively attenuate the vibration of the offshore platform and keep the stability of the system.