An Observer-Based Collaborative Control for Underactuated Dual Ship-Mounted Crane System Considering Spatial Constraints

The dual ship-mounted crane (DSMC) systems are equipment that enables collaborative lifting operations at sea. During engineering transport tasks at sea, the DSMC systems exhibit advantages, such as high lifting capacity and a smooth transportation process. However, DSMC systems have additional state variables, strong coupling, and underactuated characteristics, which require consideration of complex spatial geometric relationships and mechanical structure constraints. In addition, simultaneous consideration of the differing impacts of waves on the two ships, coupled with a lack of information exchange between the booms, can lead to additional steady-state errors and significant load swings. To this end, this article proposes a collaborative control method based on disturbance observers, enabling precise and coordinated transport and hoisting even in the presence of unknown wave disturbances. An observer with switching logic is designed to estimate and compensate for unknown signal disturbances such as wave interference and unmodeled dynamics, effectively enhancing the system’s ability to resist unknown disturbances. Furthermore, carefully designed collaborative signals ensure information exchange between the booms, significantly improving system coordination. Theoretical analysis using Lyapunov methods and LaSalle’s invariance principle examines the asymptotic stability of the closed-loop system at equilibrium points. Finally, the effectiveness and robustness of the method are validated through a series of hardware experiments.