Discrete feedforward and feedback optimal tracking control for offshore steel jacket platforms

This paper is concerned with discrete feedforward and feedback optimal tracking control schemes for an offshore steel jacket platform subject to irregular wave force. By discretizing a dynamic model of the offshore steel jacket platform system, a discrete feedforward and feedback optimal tracking controller is developed first to attenuate the wave-induced vibration of the offshore platform. Then, for the case of the offshore platform with control delays, a discrete feedforward and feedback optimal tracking controller with memory is presented. The controllers can be designed by solving an algebraic Riccati equation and a Stein equation, respectively. It is found through simulation results that compared with the classic state feedback optimal tracking control schemes, the proposed control schemes are more efficient in attenuating the vibration of the offshore platform. In addition, compared with the feedforward and feedback optimal control schemes, the proposed control schemes require less control cost.