Marine crane is a kind of special crane which is used to carry out the transportation operation in the marine environment. It is mainly used for the transportation and transfer of goods between ships, marine replenishment, underwater operation equipment delivery and recovery and other important tasks. The special application environment at sea brings great challenge to the control of marine crane. On the one hand, similar to all kinds of underactuated cranes on land, it is necessary to control the swing generated in the process of load transportation to ensure its positioning accuracy and transportation efficiency; on the other hand, because this kind of crane is fixed on the ship and other moving platform, the movement of the platform itself will have a strong impact on the load movement, and in many cases, the load lifting is very important The movement at the landing point is inconsistent with that of the crane itself. Specifically, in the working process, the crane ship and the receiving ship will pitch, roll and heave with the waves, which will cause the load to swing; especially in the lifting process, this kind of motion of the ship is easy to cause the lifted load to collide with the deck again, or make the load that has been put down but not yet separated from the hook suspended again, which will threaten the safety of operation. Especially in ammunition replenishment between ships, the coupling motion may cause very serious consequences.
The control of marine crane has been widely concerned by many countries and civil marine engineering. It is also of great theoretical value and universal significance to study the control of this kind of nonlinear and strong coupling underactuated system under special disturbance.
The control of marine crane is mainly divided into two aspects: vertical control to reduce the influence of ship motion and lateral anti swing to restrain load swing. For vertical control, the commonly used method is to connect the receiving ship through the mechanical structure of the crane ship, and sense its relative motion, so that the change of the length of the lifting rope is synchronized with the heave motion of the receiving ship, so as to compensate the relative motion of the two ships, and on this basis, complete the load take-off and landing transportation. This method has special requirements for the mechanical structure of the crane, and also has great restrictions on the lifting quality.