Vibration control of 2-D variable-length flexible riser systems with unknown boundary disturbance

The riser system is subject to vibration due to marine environmental loads, which can affect the efficiency of the system or even destroy it. This paper proposes a solution for the vibration control problem of a 2-D variablelength flexible riser based on PDE model. Firstly, a disturbance observer is developed to estimate and offset the unknown disturbance in the feedback loop. Based on the above method, an effective boundary controller is designed to realize the elastic suppression goal of the 2-D variable-length flexible riser. Secondly, when considering the asymmetric output constraints, a time adjustment function is introduced to develop a new controller based on the barrier Lyapunov function, which realizes the control objective of suppressing the boundary vibration of the flexible riser within specified constraints in a finite time. Finally, the effectiveness of the controller is verified by simulation examples.