Payload swing suppression for offshore cranes using a novel triple-tagline system: Theory and experiment

Offshore cranes are widely used for lifting operations at sea. However, due to the ship motions and crane operations, the payload swing is unavoidable, hence putting the operators in danger. Thus, this article proposes a novel triple-tagline system which has three taglines forming a triangle structure in the space and can suppress the payload swing in arbitrary directions. The kinematic and dynamic models are built in a systematic manner, which establish the theoretical basis of position synchronization and tension setting of the taglines. Then, dynamic analysis is carried out to explore the effect of the taglines’ tension on payload swing suppression, but it is unexpected to find that the taglines cannot suppress the dynamic payload swing if they always hold the static equilibrium condition. Furthermore, inspired by the air damping phenomenon, a damp-based tagline tension setting method is proposed to guarantee the resultant force of the taglines would always keep the tendency to damp the payload swing. At last, a tension/position hybrid control strategy is presented to prevent the interference of the taglines to crane operations. The validity of the proposed method and strategy are verified by experimental results.