Active Control of Slender Structures for Marine Applications

The project is a part of a larger project at CeSOS that aims to incorporate control theory and new material technologies into design and control of marine structures and systems. The main problem to be considered in this project is the collision between tensioned risers in an array. Clashing of tensioned risers is primarily considered as a deepwater problem (>1000m) and when the risers have to be located relatively close to each other due to small space. For deep water problems a tension leg platform (TL P) with tensioned risers is probably the only feasible solution for production with well heads at the platform. This configuration is considered for future field development at the Norwegian continental shelf and is a relevant research challenge for Stato il. Tensioned risers are today kept in an almost constant tension by a heave compensated mechanism on a TLP. Risers in an array subjected to current and wave loads, will experience varying environmental loads and hence various drag forces, depending on w here they are placed in the array. Today all the risers in the array are heave compensated individually, and the heave compensation of one riser does not take into account the impact from the neighbouring risers. A collaboration with MARINTEK is establish ed for the simulation of the system. During the research stay at MIT, the main focus will be at the mathematical modelling of the system. The research group working with Prof. Triantafyllou at the Center for Ocean Engineering, MIT, is specialized in math ematical modelling and control of slender, flexible marine structures. Joining this group will give valuable inputs which will be made use of in the modelling described above.