Active control of flexible marine risers

In this article, active control of flexible marine riser angle and the reduction of forced vibration under a time-varying distributed load are considered using boundary control approach. A torque actuator is introduced in the upper riser package and a boundary control law is designed to generate the required signal for riser angle control and vibration reduction with guaranteed closed-loop stability. Exponential stability can be achieved under the free vibration condition. The proposed control is simple, implementable with actual instrumentation, and is independent of system parameters, thus possessing stability robustness to variations in parameters. The design is based on the partial differential equations of the system, thus avoiding some drawbacks associated with the traditional truncated-model-based design approaches. Numerical simulations are provided to verify the effectiveness of the approach presented.