Adaptive optimal control of multi-modular floating platforms in random seas

This paper presents an adaptive optimal control method to suppress the oscillation of a floating platforms system in random seas. The system consists of multiple modules which are connected by flexible connectors with strong geometrical nonlinearity. To cope with the uncertain waves, a disturbance estimator is introduced to assess the actual wave excitation. This adaptive scheme of the estimator is integrated with an optimal control method subject to a limitation on the control outputs of actuators, where the optimal control process is carried out by the sequential quadratic program method. In numerical experiments, a floating platform with five semi-submersible modules is considered. Control process deals with 20 control variables to stabilize the surge, sway and yaw motions of a 30-DOF floating system, subject to unknown irregular waves and limitation of control output. Numerical results have verified the efficiency of the control strategy and show that the proposed control method performs very well.