Research On Course Control Based On Improved Smith Predictive Fuzzy PID

With the development and utilization of oceanic resources,the bulk goods trade between countries mostly depends on ship transportation.Due to the uncertainty of the external environment and the status quo of large-scale development of ships,people have gradually put forward new expectations and ’requirements on the level of intellectualization of ship navigation under the purpose of fully guaranteeing the economy and safety of ship transportation.In recent years;the emergence of intelligent algorithm has solved many control problems.However,due to the lag between practice and theory,most ships still use PID autopilot.However,PID autopilot is not ideal in terms of control accuracy or robustness.Therefore,it is necessary to study the intelligent control and accelerate the use of the intelligent rudder.Based on the ship maneuvering and the theory of control,this paper designs a course control system which compensates for the time delay of steering gear.Based on the analysis of the structure and composition of the ship motion control system,the first-order Nomoto nonlinear response ship motion model and the transfer function equation of the steering gear with time delay are established.In order to solve the adverse effects of the time-delay problem on the steering gear system and improve the control performance of the course.controller in all aspects,the Smith predictive control algorithm which can effectively improve the time-delay problem is selected.The control quality of the controller is improved by compensating the lagging part of the system.At the same time,in order to further improve the defects of control quality weakening or even failure of traditional Smith prediction controller in the case of model mismatch,based on ’the structural improvement of traditional Smith prediction controller by C.C.Hang,the adaptive control rate was studied through simulation analysis.Therefore,when the model is not fully matched,Smith predicted that the controller can still be highly adaptive and can change the parameters of the controller in real time according to the response characteristics and state of the control system,so as to solve the problem of controller stability degradation when the model is mismatched.Besides the disturbance of wind,wave and current,it is inevitable to have some other uncertain external factors when the ship is sailing,which makes the motion model of the ship have uncertainty with the uncertainty of the disturbance.While fuzzy control has a good control effect on the external interference and parameter change.The intelligent control method of fuzzy control can significantly improve the adaptive and anti-interference performance of the control by using a certain principle to set the PID parameters in real time.For the problem of low control precision caused by fewer control rules when the response of the system is in small deviation,the variable theory domain is used to design the fuzzy control domain from the conventional fixed value to the adaptive value,so as to improve the control system precision.In this paper,Matlab software platform is used for programming to conduct simulation research.The results show that the control algorithm has good steady-state and dynamic response characteristics under both the uncertain interference of external factors and the perturbation of the model.It shows that the fuzzy-PID control algorithm based on Smith can control the course well and provide a good reference for the design of.the intelligent ship’s course controller.