Deep water riser collision avoidance by top tension control

For tensioned riser arrays in deep waters interference between individual risers in strong ocean current is a key design and operational concern. The lateral deflections are likely to be large, and the risers may experience collision with fatigue or surface damage as a consequence. In this paper a system consisting of a tension leg platform (TLP), a pair of risers, environmental forces and hydrodynamic interaction is presented. The control system is described, and a set of control objectives with corresponding control strategies are suggested. The collision avoidance effects of the different control objectives are shown through simulations.