Residual load sway reduction for double-pendulum overhead cranes using simple motion trajectory

When the hook mass is larger than the load mass or the load has distributed mass property, the load sway of the crane system presents as double-pendulum effect. In this situation, crane system has two different natural frequencies so that the sway characteristic becomes more complex and greatly increases the difficulty of the dynamic performance analysis and controller design. In order to solve the aforementioned problems, the linear dynamics of a 2-D overhead crane with double-pendulum effect is derived based on a disturbance observer, and is decoupled for controller design by modal analysis. Next, an S-shaped curve which is widely used in industrial applications is generated on the basis of the decoupled linear crane model for suppressing residual double-pendulum load sway. Parameters of the trajectory can be easily obtained by calculating algebraic equations. Finally, simulation results validate the effectiveness of the proposed method.