| Most deep sea drilling platform and self-propelled semi-submersible ship are equipped with dynamic positioning system(DP) in order to improve the accuracy and security during work, meanwhile saving the cost. With the wide needs of the offshore oil and gas in recently years, DPS technology is more and more concern by many country. China's dynamic positioning system technology independent research is carried off.Self-propelled semi-submersible vessel motion model is built on the basis of S-surface theory. A LS-SVM controller was designed which can meet the DPS2 requirements in part 6 chapter 7 of DNV's ?Rules for classification of ships?,and also do the optimization works of data filtering and thrust allocation, then the simulation experiments were carried out. The simulation experiment contains many usual affect elements to make the datas close to the sea circumstance as possible as we can, the results proves that the controller and the simulation system is feasible, the main research contents are as follows:(1) A 50000 ton semi-submersible vessels linear mathematical model of low-frequency motion is established, while including the establishment of winds, waves and currents and other second-order model of environmental interference.(2) The high-frequency signal does not affect the positioning of ship,so design a Kalman filter to remove the high-frequency signal measured by various sensors avoid unnecessary waste of energy. Due to the uncertainty of the statistical properties of the interference noise will affecrt the accuracy of Kalamn filter, design a adaptive Kalman filter to measurement noise, the simulation experiment shows that the filter designed in this paper has a high precision and can prevent the filter divergence effectively.(3)A thrust allocation strategy is proposed base on the propulsion engineering configuration and the distribution characteristics of the self-propelled semi-submersible vessel its own,establish relevant target constraint,change target equation by weights,to ensure the existence of feasible solutions,the simulation experiment shows that this method is more economical and practical.(4) Take the low-frequency linear semi-submersible vessel motion model as a predictive model, designed a LS-SVM S-surface controller for the DP-2 dynamic positioning system, it has a higher accuracy and faster convergence compared with traditional S surface controller.(5) Design and implementation a semi-physical simulation system for the 50000 ton self-propelled semi-submersible vessel. And the dynamic positioning control system simulation experiment is carried out in this simulation system. Simulation results proves the S-surface dynamic positioning control system is feasibility and effectiveness. |
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