Control Design And Numerical Simulation Of A Flexible Riser System

With the increasing demand for oil and gas resources,people are paying more and more attention to the exploitation of marine oil and gas resources.Being an indispensable transport component for connecting marine vessels and subsea wellheads,the flexible marine riser plays a pivotal role in marine oil and gas exploration.Due to the complexity of the marine environment,the flexible marine riser system is highly susceptible to vibrations caused by disturbing loads.This phenomenon of vibrational shifting not only affects the efficiency and performance of offshore oil and gas production systems and reduces production life,but also causes serious security accidents.In order to ensure the security of the riser system and improve productivity,this paper mainly studies the vibration reduction control of the flexible marine riser system.The details are as follows:1.In this paper,a proportional-differential boundary controller is designed to actively control the vibration of the riser system through the combination of boundary control technology and Lyapunov direct method.The design of the PD controller is simple,and the riser system has uniform boundedness under external disturbances.At the same time,the performance of the controller is verified by numerical simulation experiments,Which shows that the controller can effectively suppress the vibration of the riser system.2.This paper considers the influence of nonlinear input saturation,which is based on the fusion of the backstepping technique and boundary control theory and utilizing the auxiliary system to compensate for the input saturation nonlinearity.Consequently,a big-picture stable strategy is proposed to suppress the riser vibration.What's more,the stability of the control system is strictly verified by using Lyapunov stability theorem,and simulation experiments are carried out to verify the vibration damping performance of the controller.Furthermore,considering that the discontinuous symbol function is apt to cause input flutter problems in engineering,the design of the saturation function replaces the symbol function in the controller to improve the vibration control quality.3.In this paper,a boundary controller based on disturbance observer is developed for flexible riser system with input saturation.A boundary disturbance observer for time-varying boundary disturbances is designed and applied as a feedforward compensator for the riser system.At the same time,the backstepping technique is combined with the boundary control method,and the auxiliary system is used to compensate the input saturation nonlinearity.The Lyapunov stability theorem is used to prove its stability,and simulation experiments are carried out to verify the effectiveness of the controller.4.In this paper,an adaptive boundary controller for suppressing the vibration offset is proposed for the riser system with uncertain parameters or unknown parameters under input saturation.The backstepping technique and adaptive technology are used to design the controller based on the Lyapunov direct method.By introducing an auxiliary system to deal with the effect of input saturation,an adaptive law is designed to compensate for the uncertainty of system parameters,and a disturbance adaptive method is proposed to eliminate the effect of boundary disturbance.Utilizing the proposed control scheme,it can be ensured that the system state is uniformly bounded and converges to a small neighborhood of its equilibrium position.Finally,the effectiveness of the proposed controller is illustrated by numerical simulation.