Second-order sliding mode control for offshore container cranes

Open-sea stevedores of containers provide an alternative way to avoid port congestion. This process involves a mobile harbour equipped with a crane which loads/unloads containers from a large cargo ship. However, the presence of ocean waves and gusty winds can produce an excessive sway to the hoisting ropes of the crane system. This paper presents a second-order sliding mode controller for trajectory tracking and sway suppression of an offshore container crane. From the proposed control law, the asymptotic stability of the closed-loop system is guaranteed in the Lyapunov sense. Simulation results indicate that the developed control system can achieve high performance in trajectory tracking and swing angle suppression despite the presence of parameter variations and external disturbances as in the case of offshore cranes.