Abstract Summary
Offshore Wind Turbines (OWT), nowadays, are designed with greater energy power capacities and thus they are comprised of components of larger dimensions in accordance with the increase in the energy demands worldwide. In order to install these larger OWTs, floating heavy lift vessels, operating under dynamic positioning, have been employed, increasing the efficiency of the operations. The methods of dissipating the undesired motion of the hanging loads play a decisive role in the safety and efficiency of installation. Various motion compensation and position control methods have been employed and tested in situ over the years, namely active tugger lines, gripper frames, crane motion compensators, etc. However, all of the current methods require mechanical equipment attached to payload as well as active human intervention. This fact, coupled with the delicate nature of positioning OWT components, the small error tolerances and the harsh offshore environment further highlight the paucity in research for a non-contact motion compensation technique for OWT installation. Such a technique would both contribute to the safety of the crew (by reducing the risk associated with human interventions offshore) and potentially reduce the required time for the overall procedure, a major factor for the efficiency and cost of the operation. The proposed technique is based on the magnetic interaction between the component and an electromagnetic actuator, involving both attractive and repulsive forces. To demonstrate the concept in a controlled environment, the dynamic behaviour of a magnetically controlled simple pendulum is studied both in a laboratory experiment and via numerical modelling. Special attention is paid to the study of the efficiency of the attained control and to the parameters of influence on the dynamic behaviour of the system. The system under consideration is strongly non-linear due to the distance-depended nature of the magnetic interaction force and the saturation control limits imposed by the physical actuator. This paper studies these effects and aims to optimize the performance of the contactless technique accordingly.
