Vibration Control of a Flexible Marine Riser with Time-Varying Length

In this paper, a flexible marine riser with varying length under the effects of ocean currents is investigated. The governing equations of the riser together with the drillship are developed using the extended Hamilton's principle. An approximated model using a modified Galerkin method is derived. The dynamical analysis of the system is performed with the approximated model developed. In addition, a boundary control is developed and implemented to suppress the transverse vibrations of the riser. Finally, the simulation results are shown to verify the vibration behavior of the system as well as the effectiveness of the proposed control algorithm.