Modal Reduction Based Tracking Control for Installation of Subsea Equipments∗

This paper proposes a control strategy for the deep sea installation of wellhead equipments hanged by flow line structures, named risers. A fundamental step of this operation is the positioning of the equipment over the wellhead, which can be costly, time-consuming, and unfeasible in bad weather conditions. The approach taken considers the riser structure an Euler-Bernoulli beam submerged in a fluid, whose top end is fixed in the offshore platform and the bottom end attached to a payload. A dynamic analysis is carried to identify the structure's most significant modes of vibration and create a reduced-order model. Then, a flatness-based approach is used for trajectory planning and tracking, resulting in a low complexity control structure. Numerical simulations are presented to validate the proposed controller and to analyse its performance in the presence of external perturbations.