Sliding Mode Observation and Control for Overhead Cranes with Varying Rope Length

This paper proposes a state observer and controller based on the second-order sliding mode scheme for under-actuated overhead cranes with load hoisting and lowering. The designed state observer can effectively estimate the uncertainty and unmodeled dynamics of crane systems, and provide appropriate driving force compensations for the sliding mode controller designed by coupling the load swing angle. This guarantees an accurate load positioning and residual swing elimination. Based on the Lyapunov stability criterion, the asymptotic stability of the control system is proved. Several simulations are implemented to verify the effectiveness and robustness of the proposed controller for anti-sway and positioning controls.