Research On Weather Optimal Dynamic Positioning For Ships With Nonlinear Model Predictive Control

With the more human activity in the ocean, the ship dynamic positioning technology is becoming increasingly importance has been attached. It couldn't be ignored which the consumed energy and emissions from the dynamic positioning ship or equipment running in the ocean for a long time. This paper takes the ship with dynamic positioning system as an object, for it's characteristics of nonlinear, large delay and strong coupling, studies the nonlinear model predictive control algorithm, and applies the algorithm to the ship dynamic positioning control system. Design controller of the ship dynamic positioning with the theory of weather optimal positioning control to reduce mechanical wear and tear, to achieve energy conservation and emissions reduction. The main work of the paper is as follows:1. For more accurate to describe the movement characteristics of the ship floating on the sea, giving consideration to maneuvering and seakeeping, the 6 DOF (Degree Of Freedom)unified state-space model for ship and the model of environment are established for the accurate description of the movement of the ship. First of all, the reference frame is set up for studying the characteristics of ship motion; Second, the unified state-space model for ship is established in the form of superposition of all forces; Then, the mathematical model of wind,wave and current is established; Finally, the main parameters of ship model S175 which used for simulation is provided, the program of the mathematical model is running to testify the model of ship and environment.2. Study the nonlinear model predictive control algorithm, and design the controller of the ship dynamic positioning. First of all, the math foundation is provided; Second, the mathematical model is simplified from 6 DOF to 3 DOF; Then, the nonlinear filter and observer of the environment are designed; The principle of the model predictive control is provided, and the controller of dynamic positioning with nonlinear model predictive control algorithm. The, stability of the controller is proved using the Lyapunov theorem. Finally, the simulation experiment was carried out to verify the advantage of the controller.3. Study two different theory of the weather optimal positioning control, and design the weather optimal positioning controller. First of all, the control strategy of weather optimal heading control which including zero sway control strategy and zero yaw control strategy is introduced; Second, according to the theory of ZPC-W (Zero Power Control Weathervane)and WOPC (Weather Optimal Positioning Control), the weather optimal positioning controllers are both designed; Finally, the simulation experiment was carried out to verify the effectiveness of the controller.Through the above research, the different weather optimal positioning controllers based the nonlinear model predictive control algorithm are realized. The simulation results show that the research method makes the dynamic positioning ship make a larger profit in the aspect of energy conservation and emissions reduction. All in all, this paper studies dynamic positioning for the future theoretical research and engineering application of the vessel, has a good reference value, and for the modern dynamic positioning technology reveals the broader prospects for development.