Robust Antiswing Control for Offshore Boom Cranes Subject to Disturbances on Both Actuated and Unactuated States

Underactuated offshore boom cranes are specialized machines widely utilized for marine cargo transportation. Heavily influenced by the ship motions excited by sea waves, the antiswing control problem for such systems is challenging. Worse still, many other external disturbances, such as nonvanishing wind perturbations, mechanical noises, and shocks, act on the unactuated states frequently, which aggravates the payload swing. This article studies the robust antiswing control problem for the electrohydraulic/winch-cable-driven offshore boom cranes. A novel control law is proposed without considering any linearization for the dynamic model, which successfully deals with the unknown disturbances acting on both actuated and unactuated states. Specifically, a sliding mode signal is first constructed to enhance the coupling between the actuated and unactuated states, whose convergence can make the swing angle uniformly ultimately bounded even when nonvanishing disturbances act on the payload directly. Furthermore, the robust integral of the sign of the error signal is utilized to design a continuous sliding mode controller. The stability of the designed control system is proven by Lyapunov techniques. Finally, simulation tests and hardware experiments are implemented, whose results clearly verify the performance of the designed control method.