Research On Generalized Predictive Control Algorithm In Ship Position Of Replenishment Ship

When the ships underway or platforms offshore run out of the consume substances such as fuel, food and fresh water, etc., they need replenishment at sea. In modern wars, replenishment at sea is also regarded as a very important part of naval logistics, and navy around the world have paid more and more attention to underway replenishment at sea. It is required that the replenishment ship and receiving ship must keep the same forward speed and the same direction, at the same time they also have to keep a certain distance, while under the complex ocean environment and the disturbance of replenishment equipment.The replenishment ship with dynamic positioning system is researched. First, based on the separated modeling method, a 3-DOF maneuvering motion mathematic ship model have been established, including disturbing forces which are caused by wind, wave and ocean current, meanwhile based on the elasticity, the mathematic model of supply instruments highline constant tension system is established during transverse navigation. Forces of cableway supply point and received point are calculated, max deflection of the line and motion characteristics of the cargo on line are deep analysed.Secondly, based on maneuvering motion model of replenishment ship, we get the low frequency motion model and high frequency motion model, and a Kalman filtering method is used to separate the low frequency signals and high frequency signals as well as to get the optimal low frequency signals of the replenishment ship motion.Then we derive predictive model which is required in the generalized predictive control.Finally, in the process of replenishment, the ship positions of the replenishment ship and the receiving ship are analyzed. When the replenishment ship is sailing close to the receiving ship from a long distance, the method of generalized predictive adaptive control is adapted to control the heading of the replenishment ship, so that the replenishment ship can close to the receiving ship quickly; When both ships are relatively static or in the process of replenishment, the method of multivariable generalized predictive control is adapted to control the ship position of the replenishment ship.The simulation by VC++ and MATLAB verifies that the method of generalized predictive adaptive control adapted to control the heading of the replenishment ship is better than the method of adaptive PID, and aslo verifies that the controller based on multivariable generalized predictive control is valid for controlling the ship position of the replenishment ship. The result shows that the control system can ensure the replenishment accomplished safety and smoothly.