Modeling And Simulation Research Of Dynamic Positioning System Of Semi-submersible Vessel

With the continuous development of shipbuilding industry and the human conquest of the sea journey continued, Dynamic Positioning System are used in more and more ships. Compared with the traditional anchor positioning, the Dynamic Positioning System can position without depth restriction and it is more accurate and flexible. With the continuous development of computer technology and simulation technology, the controller of the Dynamic Positioning System is also constantly upgrading. A good controller is essential to the Dynamic Positioning System.This paper introduces the advantages of the Dynamic Positioning System and its composition. According to the probability theory and random process theory, this paper establishes a complete model of sea conditions. It can descript and calculate the environment model accurately. The sea state model includes the characteristics of the sea breeze, the characteristics of waves and the characteristics of ocean current. And the sea state model also includes stress analysis of ships under the disturbance. The dynamic model and the kinematic model of the ship is also essential to the controller of the Dynamic Positioning System. This paper has established a comprehensive dynamic model and the kinematic model of the ship. It established a six degree dynamic equation model of the ship.The control of the motion of the ship is an integral part of the Dynamic Positioning System. This paper analyzes the technical characteristics of the propeller and its model. And also it analyzes the power distribution of each thruster during the course of the dynamic positioning. Then it analyzes several commonly used methods of the control of ship dynamic positioning. It includes fuzzy control, neural network control and H∞robust control. Based on the analysis of the advantages and disadvantages of each control method, a hybrid intelligent control algorithm which combined the fuzzy logic control and neural network control has been designed. We can also call it as the adaptive fuzzy inference control algorithm. This control strategy is fuzzy logic control which has the function of parameter adaptive. Because it used the connection structure of the neural network to express the system, it makes the training more convenient. Through the studying function of the artificial neural network, it can optimize the parameter in fuzzy logic control rules. And also it can optimize and improve the adaptive function of the system.The merits of the performance of the controller relates to the whole control system is good or bad. This article take the "TANANKOU" semi-submersible vessel as the simulation object. It make simulation research and test to the controller which was designed for the ship's Dynamic Positioning System. First it analyzes the forces and the track changes during the dynamic positioning in the absence of interference environment. Then it analyzes the forces and the track changes during the dynamic positioning in the interference environment. After the analysis can be the following conclusions:The controller of Dynamic Positioning System based on Adaptive Fuzzy Inference Control Algorithm has good control quality. The response time and rise time is in the required range. It has low overshoot and has certain anti-interference ability and robustness.