The Sliding Mode Control Of Suspended Cargo On Crane Ship

With the consumption of land resources, people gradually increase the exploitation of marine resources. In recent years, sea cargos transfer and ocean engineering have been developed rapidly. Crane ship is an important sea transportation to realize the transfer of cargos and equipments. But when the crane ship is working, suspended cargos in an offshore system are caused to swing and heaving due to the vibratory motion of the ship induced by ocean waves, which can lead to collision between cargos and deck. This phenomenon is not only a threat to the safety of people and equipment, but also greatly reduces the efficiency of cargo transfer, which will result in severe economic losses. Therefore, it is crucial for crane ship systems to analysis its dynamic response and use control action to suppress the swing of cargos and realize its heaving compensation.This paper presents the modelling of a rotary crane ship. Then the control equation of the system is established by sliding mode control theory. The self-stability of the underactuated part and the stability of actuated part are both guaranteed in the sense of Lyapunov. The simulation of a 2 × 8000 ton crane ship done by the Matlab program indicate that the proposed controller can significantly reduce the swing of cargos and realize its heaving compensation. Finally, controller’s robustness about the mass of cargos is verified, which means the controller is insensitive to mass change of cargos.