Full-Dimensional Nonlinear Dynamic Analysis for Lift Operation of a DP Crane Vessel

Heavy lift vessels are widely used in the installation and decommissioning of offshore structures. During offshore construction, heavy lift vessels under dynamic positioning must deal with complicated nonlinear dynamics due to the influence of large external disturbances. Existing studies on the nonlinear dynamics of heavy lift vessels mainly focus on moored vessels in surge, heave, and pitch directions, while neglecting other degrees of freedom. This article introduces a comprehensive nonlinear dynamic analysis of heavy lift vessels under dynamic positioning control. The full-dimensional nonlinear mathematical model is presented and analyzed using chaos theory. The vessel's behavior is visualized through Poincaré maps, showing stability around the fixed point under control. The dynamics of the vessel are affected by factors, such as the load mass, proportion–integration–differentiation controller parameters, and environmental forces. Simulations are conducted to validate the mathematical analysis.