The successful deployment of offshore wind turbines hinges on the installation process, particularly the temporary suspension of the turbine components during assembly. External factors or imbalances in control forces can induce vibrations, emphasizing the need for precise control, especially in the torsional mode, to ensure the delicate alignment required for bolted connections. This paper introduces a contactless technique to control the torsional vibrations of a rigid cylinder using electromagnetic interaction between two magnets, incorporating magnetically-imposed damping and active control algorithms. The magnetically-imposed dissipation is achieved by introducing nonlinear damping into the system, i.e. by controlling the orientation of the field exerted by the electromagnetic actuator. Leveraging the nonlinear coupling of the interaction between the magnets and the modification of the stable equilibrium position, the results show a satisfactory active control performance (low residual error and swift response). The key parameters for control efficiency are identified as the separation distance between the magnets, the fluctuation step of the actuator’s magnetic field, and the magnetically-induced stiffness relative to the inherent stiffness of the system. Consequently, the proposed method lays a promising foundation for a non-contact control technique, particularly valuable in offshore wind turbine installations.

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Current offshore wind turbine installation and positioning methods require mechanical equipment attached on the lifted components and human intervention. The present paper studies the development of a contactless motion compensation technique by investigating a magnetically controlled pendulum. The technique involves the interaction of a magnetic pendulum with an electromagnetic actuator. Two control modes are considered: the imposition of a desired motion to the mass and the motion attenuation of a prescribed pivot excitation. The numerical model is validated and calibrated against experiments and demonstrates excellent predictive capabilities. The control exerted is effective for a broad range of excitation frequencies and amplitudes. Important parameters associated with the performance of the technique such as the separation distance of the magnets and the saturation of the controller are identified. The controllability regions for effective control depending on the characteristics of the excitation are derived. The force amplitude of the contactless actuator is comparable to currently-used active tugger line control systems, but with the additional advantage of both attractive and repulsive forces. The findings of this paper illuminate the path for the further development of a non-contact control technique which has the potential to increase the efficiency of offshore wind installations.

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Europe has set an ambitious target to increase the offshore wind power capacity to approximately 30 GW by 2026. With nearshore locations already allocated, future wind farms must be installed in deeper waters, pushing the operational limits of currently used jack-up vessels. Utilizing existing floating heavy-lift vessels presents a viable alternative. This paper disseminates data gathered during the full-scale testing campaign of a floating installation of an offshore wind turbine tower. For this purpose, novel time-synchronized motion-tracking units were developed. Analysis of the obtained data reveals that approximately 96% of the motion response of the tower is due to wave action and 3% to vortex-induced vibrations caused by the presence of a passive tugger line, which shifted one of the system's natural frequencies towards the tower's vortex-shedding frequency. Next to wind and wave-induced motion, the data reveal that the hoisting itself induces tower vibrations, accounting for less than 1% of the tower motion response. The collected data offer a distinctive perspective on this type of installation, which is unlikely to be replicated at model scale due to the scaling limitations associated with the interdependence of waves and wind. The data can be used to validate motion control strategies to enhance the efficiency, safety, and workability of floating offshore wind turbine installations.

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An experiment has been performed on a magnetic pendulum, which interacts with an electromagnet. The free non-linear vibrations of the pendulum-magnet system are studied to identify and analyse the system’s characteristics. Due to the presence of the electromagnet, a modulation of the pendulum’s natural frequency is observed. A mathematical model is formulated that is able to reproduce the experimental results.@en

The present study introduces a magnetic PD control technique for the case of a simple pendulum driven by a sinusoidal motion of its pivot. The results attained demonstrate a good control performance for all the excitation cases of pivot point motion considered. The motion of the mass of the pendulum is successfully attenuated even when the pivot excitation is at the natural frequency of the pendulum. Furthermore, a fixed desired position can be achieved with small error and no saturation of the actuation present at steady-state. The initial distance between the magnet and the mass that ensures an efficient motion control is derived analytically and is validated by numerical simulations. The magnetic control method proposed serves as promising foundation for a non-contact position control technique for offshore wind turbine installation purposes.@en

The present study introduces a modified version of PD Control for the case of a magnetically controlled pendulum. The response was observed in both experimental and numerical simulations taking into consideration the non-linearity posed by the system. The modified PD controller was compared to the simple counterpart for further concrete justification of its superiority. The results attained highlight the benefits of the modified PD control in all facets of control performance, namely the efficiency, the accuracy of the representation of the interaction, the sensitivity on alterations of the control gains as well as the prediction of the experimental response by the numerical simulation. Thus, the control method proposed can serve as a promising foundation for the further development of a non-contact position control technique for offshore wind turbine installation purposes. @en