Dynamic output feedback antiswing control for bridge cranes with input constraints

Abstract

This paper proposes an observer-based dynamic output feedback nonlinear control method for bridge cranes that addresses challenges such as uncertain dynamics, external disturbances, saturated control input constraints, and the absence of precise velocity feedback. To enhance the system’s anti-swing performance, we introduce a composite signal that strengthens the coupling between system states and an additional swing-related coupling term to give the controller more swing feedback. Furthermore, by employing model transformation, both internal and external disturbances are treated as a lumped disturbance, and an observer is designed to estimate and compensate for this disturbance, thereby improving the system’s robustness. Notably, incorporating a bounded function prevents input saturation and exploits the adjustable gain of the composite signal to alleviate the conservatism often associated with bounded control significantly. The proposed observer also accurately recovers the velocity signal required by the controller, enabling the controller to achieve precise payload positioning and swing elimination using only measurable displacement and angle feedback signals. A rigorous mathematical analysis verifies the asymptotic stability of the closed-loop system at the desired equilibrium point. Simulation and experimental results confirm the effectiveness and robustness of the presented controller.