Disturbance observer-based nonlinear control for underactuated bridge cranes: high-order fully actuated system approach

In this paper, a disturbance observer-based nonlinear control method is proposed for a class of underactuated bridge crane systems. Specifically, the underactuated bridge crane system is transformed into a high-order fully actuated (HOFA) system through a diffeomorphism transformation. The proposed approach utilizes a predetermined-time disturbance observer based on the HOFA system, eliminating the need for any prior knowledge of disturbance upper bounds and ensuring independence from controller design. This designed scheme effectively achieves both anti-swing and positioning control objectives in underactuated bridge crane systems. Rigorous demonstrations are provided to ensure the stability of positioning error and load swing angle. Simulation experiments conclusively demonstrate the effectiveness and robustness of the designed control scheme. This paper represents the first application of HOFA system theory to underactuated bridge crane systems, thereby expanding the scope of its applicability.