Ship Path Generation And Target Tracking Based On Automatic Control

With the development of the world economy,the tasks of the ship transportation industry have intensified.Automatic control can autonomously identify the environment,generate routes for ships and control them.The system can not only save human resources and avoid hidden safety hazards caused by human factors,but also improve system efficiency and meet the development requirements of today's shipping business.The ship's automatic control system is complex and contains many control problems.Three aspects of ship control related problems are studied in the thesis.They are ship's state estimation,path generation and tracking control.The environmental forces and ship's dynamics in the sea are studied.Irregular wind loads,wave loads,and current loads acting on the hull are simulated in detail.This mathematical model of ship in seaway is built to help further development of ship's path generation and tracking control strategy.Model-based state observer used by ship's dynamic positioning system are applied.Observer is one of the most important components for ship's navigation.The observer estimates ship's position,speed,and unknown forces on the vessel in real time and filtered first-order wave motion component,which is not favored by low frequency motion control.Ship's guidance system based on automatic control has also been studied.In terms of path generation,improvements to existing algorithms based on discrete artificial potential field algorithms are developed.For trajectory generation,the lineof-sight guidance law and polynomial curve interpolation method are investigated for different path types.In addition,the trajectory generation problem associated with limited ship's speed acceleration and jerk when traveling with minimum time is investigated.For the path following controller,we use a non-linear PID controller.The controller contains wind feedforward forces,acceleration-reference feedforward forces,proportion forces due to position deviation,forces due to speed deviation,as well as bias force rejection terms.Total control demand are allocated to each individual thruster by solving a quadratic programming problem with linearized objective function and constraints.Finally,with the aid of ship motion simulator,the ship state observer,guidance algorithm and tracking control are integrated,and the ship control simulation system is written in the Matlab.Simulation results are further discussed.