Research On Recoil Modeling Of Deepwater Drilling Riser System And Recoil Control

The recoil response of deepwater drilling risers can cause hazards to drilling platforms,pipe bodies,and subsea wellheads.Therefore,the research on recoil analysis and active control has become one of the important issues in the field of ocean engineering.In recent years,scholars have conducted in-depth research on the analysis and simulation of riser recoil response.However,there are few research results on the modeling and control of riser recoil systems.In this paper,the modeling of a deepwater drilling riser recoil system and several recoil control methods are studied.The specific contents are as follows:(1)The feedforward and feedback optimal recoil control method for riser recoil system is studied.Firstly,based on the finite series calculation model of the viscous resistance of drilling fluid,a continuous external system model of the viscous resistance of drilling fluid is obtained.Furthermore,the design method of the feedforward feedback optimal recoil controller is studied,and the existing conditions of the recoil controller are given.Secondly,combined with the idea of H_∞,the optimal guaranteed cost recoil controller is studied and the existing conditions of the controller are given.The simulation results show that the established external system model can describe the dynamic characteristics of the frictional force of the discharged fluid;The above two methods are superior to traditional optimal control methods in reducing backlash displacement.(2)The feedforward feedback discrete optimal control method for riser recoil system is studied.Firstly,a discrete exponential polynomial calculation model for the viscous resistance of drilling fluid is presented,and then a discrete external system model for viscous resistance is obtained.Secondly,the existing conditions of a feedforward feedback optimal recoil controller including the effects of platform heave motion and drilling fluid leakage are given.The recoil controller can be obtained by solving the Riccati equation and Stein equation.The simulation results show that the designed discrete feedforward optimal recoil controller can significantly suppress the recoil response of the riser and improve the safety of emergency evacuation of the riser;The Von Misses stress and spring elongation analysis results verify the effectiveness of the recoil controller.(3)The control method of riser recoil system based on time-delay feedback is studied.According to the viewpoint that time delay has a positive effect on certain systems.By introducing a time-delay signal into the control channel,a pure time-delay state feedback H_∞control method for riser recoil suppression is proposed.Using the Lyapunov-Krasovskii functional method,a sufficient condition for a delay H_∞recoil controller is obtained.The simulation results show that the designed delay H_∞controller can further reduce the riser recoil response by selecting an appropriate size of time delay.According to given the different time delay boundaries,the controllers with different control costs were obtained,and more options for the controllers are available.