Research On Modeling And Dynamic Positioning Control Of Semi-submersible Drilling Platform

With the rapid rise of ocean engineering,oil and gas exploitation is more and more inclined to the deep sea area.The semi-submersible drilling platform has the advantages of adapting to water depth,drilling depth and strong anti-interference ability.With the development of deep-sea strategy in China,the drilling platform positioning system economy and positioning capability requirements are also constantly improving.When the sea depth of about 1000 meters,the traditional mooring system has long been unable to meet the demand of deep sea positioning due to its long construction period and lack of positioning accuracy.The dynamic positioning system is flexible,adaptable and is not limited by depth and many other advantages,are widely used in deep-sea drilling platforms and ships.With the vast marine resources but subject to technical limitations in our country,strengthen the research and utilization of the dynamic positioning system is crucial for exploitation of marine resources.The research object is a deep-sea semi-submersible drilling platform in the South China Sea,which is used for hydrodynamic modeling and dynamic positioning control.To study the dynamic positioning of the semi-submersible drilling platform,we must first establish the correct model.In this paper,the hydrodynamic software AQWA based on the potential flow theory is used to calculate the frequency domain hydrodynamic coefficients of the drilling platform with the 3D frequency domain Green function method,including frequency domain added mass,radiation damping and response amplitude operator.The time-domain results are obtained by indirect time-domain method.The three degree of freedom motion mathematical model of the drilling platform is established by this result,and added the environmental interference,and then study the dynamic positioning of the model.In order to eliminate the deviation of ship position and heading angle caused by the disturbance with slowly varying environment,the dynamic positioning system adopts the linear quadratic optimal controller.The Kalman filter is used to filter the high frequency signal,and the weighting matrix of the linear quadratic optimal controller is optimized by genetic algorithm and the improved artificial bee colony algorithm respectively.The main contents of this paper are as follows: Firstly,the three degree of freedom mathematical model of semi-submersible drilling platform dynamic positioning system is studied from the kinematics and dynamics analysis,and the corresponding motion vector model is obtained by solving and converting the hydrodynamic coefficients of drilling platform calculated by AQWA software.Then the linear quadratic optimal controller is usedto carry out dynamic positioning control according to the linear simplified model.The Kalman filter was used to remove the environmental disturbance,and the dynamic positioning simulation of the drilling platform was carried out under the environment disturbance and no environment disturbance.The genetic algorithm and the improved artificial bee colony algorithm were used to optimize the LQR parameters respectively.Finally,the optimization results are compared and analyzed to verify the optimal performance of the designed controller.In short,the main work of this paper is to complete the related research on the semi-submersible drilling platform modeling and dynamic positioning control methods,focusing on the linear quadratic optimal control method in dynamic positioning system.