Boundary Iterative Learning Control Design And Numerical Simulation For Marine Flexible Riser System

As one of the most important energy sources,the petroleum is often regarded as the key of industry.It is obvious that the petroleum occupies an important position in the development of modern industry.The marine riser,as an important connecting device between the submarine wellhead and the offshore platform,is easy to be influenced by the complex environment and will result in a vibration displacement.Thus,with the further exploration of offshore oil and gas resources,the abatement issue of marine riser system got the extensive concern of academic filed.In this paper,the vibration damping problem of marine flexible riser system is studied,the specific contents are as follows:i.In this paper,a boundary iterative control method is proposed for marine flexible riser system.The iterative learning law is used as the feedforward part,and the last control output is used as the next control input to realize the tracking task quickly.As the feedback part,the traditional boundary control is used to realize the stabilization of the system.In the design of iteration terms,the discrete time domain and the continuous time domain are combined.Firstly,the positive definite function is constructed in the discrete domain,then transformed into the lyapunov function in the continuous domain.The iterative learning law in the continuous time domain is designed to avoid the phenomenon of finite discontinuity in the discrete time domain.The gait of reverse design makes the controller more systematic and structured,reduced the difficulty of controller design.ii.In this paper,a boundary iterative control method with parameter adaptive law is designed for Marine flexible riser systems to dispose the uncertain parameters.Firstly,the current parameters and operating indexes of the system are identified and compared with the expected performance indexes.Then,the adaptive law design is carried out according to the lyapunov stability principle,so as to achieve the goal of compensating for the influence of uncertain parameters on system stability without the accurate system parameter values.iii.In this paper,stability analysis and numerical simulation are carried out for the two control methods proposed.According to the lyapunov stability principle,it is proved that the vibration amplitude of the riser decreases exponentially to a bounded range.By adopting finite difference method to system model,the function of the controller is applied in MATLAB.The result shows that output can obtain stability in a limited time under the action of the controller,the tracking performance and versatility are certificated in the meantime.