Nonlinear control for underactuated multi-rope cranes: Modeling, theoretical design and hardware experiments

Abstract

Researches on overhead cranes are mainly aimed at single-rope ones. However, to guarantee safety and increase the transportation efficiency, many overhead cranes tend to use more ropes to suspend the payload during the actual operation, which results in severe gap between theory and practice. The study on multi-rope cranes has achieved little progress in the past years, and no precise model has been proposed for such systems. So far, existing results for multi-rope cranes are usually based on linearizations or approximations, whose performance can be hardly guaranteed in many cases. Motivated to solve this problem, a dynamic model for multi-rope cranes is first set up in this paper by utilizing Lagrangian modeling method. Based on that, a nonlinear controller is further proposed, which incorporates more swing-related information into the control law, so as to enhance the robustness and swing suppression performance of the closed-loop system. The asymptotic stability of the desired equilibrium point is rigorously guaranteed by Lyapunov techniques and LaSalle’s invariance theorem. Finally, to demonstrate the feasibility and efficiency of the designed controller, hardware experimental results are provided as a convincing validation.