A marine crane is a special type of crane that performs transportation operations in a marine environment. It is mainly used for important tasks such as transportation and transportation of goods between ships, sea replenishment, and placement and recovery of underwater operation equipment. The special application environment at sea brings great challenges to the control of marine cranes. On the one hand, similar to various under-actuated crane equipment on land, it is necessary to control the swing generated during the load transportation to ensure its positioning accuracy and transportation efficiency; on the other hand, because the crane is fixed on a sports platform such as a ship, the platform itself The motion has a strong influence on the load motion, and in many cases, the motion at the load lifting and landing points is inconsistent with the motion of the crane itself. Specifically, during the work, the crane ship and the receiving ship will sway, roll and heave with the waves. These movements will cause the load to oscillate; especially during the lifting process, such movement of the ship is likely to cause the hoisting The load once again collided with the deck, or the load that had been lowered but not yet removed from the hook was again suspended, which would threaten the safety of the work. This coupling movement can have very serious consequences, especially when inter-ship ammunition replenishment is carried out.
In recent years, the control of marine cranes has received widespread attention from military and civil marine engineering in various countries. The study of such nonlinear and strongly coupled underactuated systems under special disturbances also has important theoretical and universal significance.
The control of marine cranes is mainly divided into two aspects: vertical control to reduce the influence of hull movement and lateral anti-swing to suppress load swing. For vertical control, the common method is to connect the receiving ship through the mechanical structure on the crane ship and sense its relative motion, so that the change of the length of the sling is synchronized with the heave motion of the receiving ship, thereby compensating the relative motion of the two ships. On this basis, the loading and unloading of the load is completed. This method has special requirements on the mechanical structure of the crane and also has a large limitation on the lifting quality. Kuchler et al. carried out dynamic modeling of the underwater equipment lifting process. They considered the sling elastic and hydrodynamic factors, and designed the trajectory tracking and disturbance suppression controller based on the feedback linearization method. Johansen et al. used a feedforward-based wave synchronization technique to compensate for the effects of heave motion and ultimately achieve precise control of the water entering process of the load. In recent years, horizontal anti-swing control has also received a lot of attention. In order to strengthen the swing control of the sling and load, the Maryland Rigging System is installed on some cranes, that is, the rope is added to the middle of the sling to reduce the swing of the load. In view of such a marine crane with a special mechanism, various modeling and control methods have been successively proposed in recent years. However, such organizations have a large limitation on the working space of the crane system, which reduces the flexibility of the original system. For this reason, many studies use various sensors to obtain motion information of the hull, crane, and load without changing the mechanical structure of the crane, and then suppress the load swing during transportation by designing a reasonable arm motion controller. Among them, Parker et al. used the command shaping technology to control the pitch rotation of the crane arm and verified it on a small-scale experimental platform. McKenna et al. modeled the pitch and hull movement of the arm and combined the feedforward compensation link with the feedback control strategy to suppress load swing in one direction. Masoud et al. used a time-lag position feedback control method to reduce the two-dimensional swing angle of the load by manipulating the pitch and rotation of the arm. Sandia National Laboratory designed a multi-sensor information fusion control scheme that compensates for hull motion by controlling the motion of the crane, which better suppresses the swing of the load. This method was tested on the US Navy TACS system and achieved good control results. Subsequently, Schaub et al. made further improvements to this control scheme.
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