The offshore container crane (OCC), as a novel maritime container transfer system, can handle container from a large container-ship anchored in open sea to address the congestion and limited water-depth of port. However, for the wave- and wind-induced movements of the ship, the crane's control system should be redesigned to ensure the load transfer on the sea. In this paper, we derive the nonlinear dynamic equations of OCC system subjected to the ship motions based on dynamic analysis. Then a double-layer sliding manifold is constructed to realize the position tracking and sway control simultaneously, irrespective of ship motions and parameters perturbation. The Lyapunov method is utilized to prove the stability of the proposed control law. Next, virtual prototype of the OCC is established, including the multi-body dynamics model of OCC with flexible rope and the proposed control scheme. Sufficient simulations are provided to illustrate its improved performance versus conventional controller. Experiments are also implemented to evaluate its practical control performance of trajectory following and sway angle suppression.

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