The application of floating wind turbines is limited by the high cost that increases with the water depth. Offshore installation and maintenance continue to consume a high percentage of the project budget. To improve the installation efficiency of the floating offshore wind turbine, a novel concept is proposed by the SFI MOVE project. Several wind turbine superstructure components are preassembled onshore and carried to the installation site by a catamaran construction vessel. Each assembly can then be installed using only one lift, and the concept is less sensitive to weather conditions. In this paper, a control algorithm of the proposed hydraulic active heave compensator system is developed using singular perturbation theory to cancel the relative motion between the spar top and gripped preassembly bottom. Closed-loop stability is proven, and the simulation results show that the installation efficiency is improved with an increase in the acceptable weather conditions.

Being one of the most commonly used offshore operations, offshore lifting operations become increasingly challenging due to the gradually growing size and weight of payloads. The research on automatic control in lifting operations, e.g., anti-swing control and heave compensation, only considers simple-shaped payloads, such as lumped-mass rigid points. However, the sizes and orientations of many structures cannot be neglected. To lift heavy and large-scale payloads, larger and higher cranes are required. Alternatively, it is possible to share the total loads by enhancing the number of lift wires that may limit the tension on each lift wire. However, the complicated configuration introduces significant complexity into the design of the automatic anti-swing algorithm, especially to the control allocation module. This paper performs a preliminary study on the anti-swing control of a complex-shaped suspended payload lift using a floating crane vessel and a large number of lift wires. Inspired by the knowledge of inverse dynamics and range-based localization, a general model-free anti-swing control scheme is proposed. The controller has a simple form without considering state–space equations, but it can reduce the pendular payload motion regardless of the detailed system configuration. An offshore wind turbine tower–nacelle–rotor preassembly installation using floating crane vessel is adopted as a case study to verify the performance of the proposed control strategy.