Sliding Mode Control for Tower Crane with Double Spherical Pendulum and Variable Cable Length

The complex dynamics of the double spherical pendulum with variable cable length present a significant challenge in controlling the swing of underactuated tower cranes. In this article, we present a sliding mode anti-sing controller for the underactuated seven degrees of freedom (7-DOF) tower crane with the double spherical pendulum and cable length variations. The underactuated 7-DOF tower crane model provides a comprehensive representation of the dynamics involved in jib slewing, trolley movement, cable length variations, hook swing, and payload swing. Utilizing the elimination method, a fully actuated system model is obtained from the underactuated 7-DOF tower crane model. Based on the fully actuated system model, we designed a sliding mode controller to effectively suppress both hook swing and payload swing. The theoretical analysis and experimental results demonstrate the accuracy of the 7-DOF tower crane dynamic model and the effectiveness of the sliding mode controller.