Xin-Yuan Zhang

During offshore wind turbine maintenance operations, maintenance vessels typically rely on transfer gangways to achieve safe transfer of personnel from the vessel to the wind turbine. With the development of offshore wind farms toward far sea areas, working sea state conditions have become increasingly complex. In recent years, the application of large-scale active wave compensation (AWC) transfer gangways has mitigated the adverse effects of ship motions on transfer operations to a certain extent, but the problem of limited motion ranges of each gangway joint has also emerged as a prominent issue. Under complex sea state conditions, if the station-keeping position of the maintenance vessel is improperly selected, joint limit violations may occur during the gangway compensation process, thereby posing safety risks. To address the above problems, this paper develops a novel geometric-envelope-based analytical method for operational sea states and ranges that explicitly accounts for gangway joint constraints and wave-induced vessel motions to meet the safety requirements of large-scale gangways. Subject to the motion constraints of gangway joints, to ensure that the initially selected station-keeping position of the vessel satisfies the requirements for safe gangway transfer, the feasible domain and motion range of the gangway base point under different sea states are obtained. By solving for the solutions where the motion range of the base point lies entirely within the feasible domain, feasible schemes for vessel station-keeping operations under different sea states are derived. The results show that the gangway can operate safely under sea states 3 and 4 but fails under sea state 5. The allowable height difference between the transfer point and the gangway base is [−2.7 m, 8.7 m] for sea state 3 and [1.8 m, 3.5 m] for sea state 4. The operational area on the horizontal plane presents a partial ring shape, and the ring width first increases and then decreases with increasing height difference. Finally, random numerical examples are designed to demonstrate the applicability and internal consistency of the proposed analytical method.

With the rapid expansion of offshore wind farms into deeper waters, large-scale wave-compensated transfer gangways have become critical equipment for ensuring safe personnel transfer between maintenance vessels and wind turbines. However, the increased mass and inertia of large gangways introduce significant control delays in hydraulic actuation, data acquisition, and compensation calculation processes, which severely degrade compensation accuracy and threaten operational safety. This paper proposes a predictive active wave compensation control scheme based on Back Propagation (BP) neural network to address this challenge. First, a ship vertical-plane kinematic model was established to derive the mapping relationship between ship motions (roll, pitch, heave) and gangway end-point positions. The impact of 3–5 s control delays on gangway stability was systematically analyzed, revealing that uncompensated delays can cause end-point deviations exceeding 4 m. Then, an optimized BP neural network model was constructed for short-term ship six-degree-of-freedom (6-DOF) motion prediction, with key parameters (input duration, hidden layer nodes, random seed) tuned to achieve high prediction accuracy. Finally, the proposed predictive control scheme was validated through numerical simulations. The results demonstrate that the scheme can reduce the maximum end-point deviations by more than 80% for delays up to 5 s, effectively mitigating the adverse effects of control delays. This research provides a technical solution for improving the safety and reliability of large offshore transfer gangways.