The Research On Ship Dynamic Positioning System Controller Based On Fuzzy Predictive Control

The dynamic positioning system is a ship device which can control the vessel on arequired position by means of active thrust. Nowadays, because human put more and moreattention on the exploitation of marine resource, so the development of dynamic positioningtechnology has become increasingly important.Ship dynamic positioning system is a complicated non-linear system, which hasmulti-variable, strong coupling, heavy inertia and the environmental disturbance. The earlycontrol method，for example PID，already can’t meet the demand of precision for shipdynamic positioning system. Fuzzy predictive control as a hybrid intelligent control methodhas good control effect for the control of complex systems.In the use of dynamic positioning system to locate the ship, the filtering effect of thefilter has a great impact on the positioning accuracy. A major drawback of Kalman filter-based estimators is the necessity of linearization about a set of pre-defined yaw angles. Inthat case, the global stability can not be guaranteed. In this paper a nonlinear observer usingSDRE equation is introduced. Compared with Kalman observer, the new observer’sadvantage is eliminating the need for ship motion equations linearized process, therebyreducing the amount of computation.Fuzzy predictive control, depending on the expansions can be divided into fuzzycontrol and predictive control the core of the fuzzy predictive control algorithm. In thispaper these two fuzzy predictive control algorithms were studied and the results applied tothe design of the ship dynamic positioning system controller.In the study of fuzzy predictive control as the core of predictive control, select DMCcontrol based on the T-S fuzzy model as the specific object of study, focused on theidentification problem for T-S fuzzy model. After the study of the DMC control based on theT-S fuzzy model, this algorithm is applied to controller design for Dynamic PositioningSystem.In the study of fuzzy predictive control as the core of fuzzy control, improve theconventional fuzzy control, changed it from the” post adjustment” to “pre-control”. Theinput of the fuzzy control is the output of the predictive model, which is predictive error andpredictive change rate. In other words, in the use of predictive model, the controller canpredictive the next time error and to take preventive measures before it produces. Finallythis fuzzy predictive control algorithm is applied to the controller design for Dynamic Positioning System, the simulation results indicate that under different sea conditions, thefuzzy predictive controller designed in this paper is very effective, can make the vessel fromactual position to the desired position in a shot time and then stable at the anchor.