Observer-based adaptive fuzzy control of underactuated offshore cranes for cargo stabilization with respect to ship decks

Offshore crane systems are widely employed to transport cargoes on vessels due to their outstanding flexibility. However, they always suffer from various disturbances in the special working environment, which will appear in not only the actuated part (jib and cable) but also the unactuated part (cargo). In particular, some platform parameters cannot be measured precisely. Additionally, the task scenarios of offshore cranes are divided into stabilizing cargoes with respect to the ground and the ship deck, respectively, i.e., in the earth-fixed (inertia) and ship-fixed (non-inertia) coordinate frame. However, existing methods focus on the former. To address the above problems, a nonlinear observer-based adaptive fuzzy controller is suggested to stabilize the cargo with respect to the ship deck, and the swing can be simultaneously suppressed. The closed-loop stability is theoretically guaranteed by Lyapunov methods. To our best knowledge, this is the first control scheme that can stabilize the cargo with respect to the ship deck for underactuated offshore cranes with uncertainties, input dead zones, and external disturbances. Finally, we employ some experiments to validate the effectiveness of the proposed control approach.

Automated summary

A nonlinear observer-based adaptive fuzzy controller is proposed to stabilize the cargo on offshore cranes and suppress the swing simultaneously. This is the first control scheme that addresses the disturbance issues in the special working environment of offshore cranes.