Research On Control Algorithm Of Auto Area Keeping For Dynamic Positioning System

This paper is based on the ocean science exploring ship of Ocean 1. Beyond the work of analysis of ordinary dynamic positioning (DP) fuzzy controller, research on auto area keeping when inputs contain errors that can't be neglected, energy as index function, is probed into.The marine environmental forces acting on the vessel are the wind, the current and the waves. The motion control system of a dynamic positioning system is a nonlinear, coupling, time-delay complicate system. It's difficult to control the system effectively using the conventional control method. As an intellect control method, fuzzy logic control is very suitable control for such a complicate system. In this thesis fuzzy control method is applied to DP system. It has solved the problems such as accurate position-keeping, searching for most favorable heading (MFH), auto area keeping control, and has acquired satisfied control effect.In this thesis the author achieved fuzzy control to DP system on the basis of simulation system of ship's motion. After analyzing the principles of optimizing basic fuzzy controller, a new method for optimization is proposed .The distribution of membership function of input and output can be adjusted by three parameters, which makes the control result approach to optimal. The method is simple and practicable, and is proved to be effective. And it will be of assist to design a fuzzy controller. When keeping MFH, the force acting on the vessel in the sway direction is lest, this will be of great importance for saving on energy. A technique of searching for MFH based on fuzzy logic is brought up, which adjusts the heading according to the lateral movement of the vessel. The technique is independent from measurement values and mathematic formula of environment factors, combining the acquiring for MFH and control, attaining fast response and a high degree of accuracy.A control method is brought up that is most fit for auto area keeping in comparison with several other control plans. The plan keeps the heading of the vessel close to mean MFH, and does not keeping controlling the sway direction and surge direction. When there is random error in input data, if position-keeping plan is applied, thrusters will change working status in high frequency that will lead to sever thrust wear and energy waste. And if the heading is not kept, it will be hard to control the vessel, or bring about heavy cost while adjusting the head.It shows that it's feasible to apply fuzzy logic control to dynamic positioning...