Nonlinear Sliding Mode Tracking Control of Underactuated Tower Cranes

As representative underactuated systems, tower cranes exhibit high nonlinearity and strong state coupling, which makes their controller design (analysis) challenging and of great research values. In addition, since tower cranes are widely applied in outdoor environment with inevitable external disturbances, (the state variables tend to go far away from the equilibrium point), how to ensure the control performance in this case is particularly important; moreover, most existing control methods can only ensure closed loop stability, but cannot theoretically ensure the system states convergence time. Considering the above factors, this paper proposes a nonlinear sliding mode tracking controller, which can realize satisfactory tracking performance and effective swing suppression. To our knowledge, for tower cranes, this is the first tracking method designed based upon the nonlinear dynamics without any linearization, which can eliminate the tracking errors rapidly in finite time by introducing the elaborately constructed sliding mode surface and simultaneously suppress the swing. Furthermore, through rigorous analysis, the system closed loop stability is proven theoretically. Finally, hardware experiments imply that the proposed controller is effective and exhibits satisfactory robustness.

Automated summary

This paper proposes a nonlinear sliding mode tracking controller for tower cranes, which can achieve satisfactory tracking performance and effective swing suppression. The system closed loop stability is theoretically proven through rigorous analysis. The controller is effective and exhibits satisfactory robustness in hardware experiments.