Motion Planning and Tracking of Subsea Structures

This article uses an active control dedicated to the positioning of subsea structures like flow lines. This kind of operation consists in connecting the bottom end of a very long pipeline to the wellhead, by dynamically modifying the pipeline top end position, which is linked to a Dynamically Positioned Vessel (DPV). Such long pipelines are usually called risers, because they are used to rise the drilling mud or the hydrocarbons from the wellhead to the platform. Nowadays this operation is often done manually. The use of an active control intends to reduce the operation time, and to make it possible even under bad weather conditions. The considered subsea structure can be aproximated as a cable submerged in a flow and modelled by the Bernoulli cable equation, completed with a damping factor, that linearly depends on the structure speed. This article tests previous works regarding the tracking system used to follow the reference trajectory of the motion planning considering the Euler-Bernoulli beam equation for large rotations, that is the most used model to define the dynamic behavior of this kind of structures.