Research On Predictive Control For Heave Compensation Of Dual Drawworks System Of Semi-submersible Drilling Platform

With the action of waves,the semi-submersible drilling platform have heave and other different forms of movement which affects the work efficiency of offshore drilling operations and in some serious cases,the drilling platform even cannot work.The problem mentioned above also reduce the life of drill bit and drill pipe,so it is necessary to adopt heave compensation device.There are different types of heave compensation device.Drawworks heave compensation as a new technology have been widely applied because of its advantages.With the increase of drilling depth,the market need powerful drill with intelligent control and high drilling efficiency,that is why dual drawworks system was invented.Compared with other countries,our research in this field has fallen behind,so the research of dual drawworks heave compensation system control technology and equipment have great significance.In this paper,the dual drawworks system of offshore drilling platform is taken as the object to be studied the working principle and control strategy of the heave compensation system.Aiming at the problems of large inertia and time delay in the heave compensation device,model predictive control is used to optimize the heave compensation effect.Firstly,referring to the parameters of 9000 m offshore drilling rig,the dual drawworks active heave compensation system was analyzed and the mathematical model of the system was established in this paper.A two-layer closed-loop control strategy of displacement and velocity for heave compensation system is proposed.Based on Simulink,the whole simulation model of heave compensation control system of dual drawworks is established,which provides the basis for the follow-up research of predictive control strategy.Secondly,the application of model predictive control algorithm in dual drawworks heave compensation system is studied and simulated.In this paper,the platform heave motion prediction data under different sea conditions are simulated based on P-M wave spectrum and standard sine.Then,according to the existing data,the platform heave motion prediction model is established based on Long Short-Term Memory network.Meanwhile,the prediction model is improved by wavelet multi-resolution analysis,and the prediction model outputs the future platform heave motion data which is used as the reference trajectory of MPC to realize predictive control.Based on the whole system simulation model built in Simulink,we verified the control effect of the model predictive control algorithm which used the state equation on the general model and the model with time delay.Furthermore,the gain scheduling model predictive control is used to improve the control ability of the time-varying model.Finally,the dual drawworks heave compensation test-bed is established.Then the joint test of MATLAB and PLC is realized by OPC communication and the control program is written to control the test-bed to simulate the heave motion of platform and drawworks’ heave compensation operation,and the actual control effect of the predictive control scheme is verified through the test.