Design Of Nonlinear Fuzzy Controller For Ship Track Keeping

With the continuous strengthening of world economic integration,international freight transport has become more frequent.Goods that transported in this way not only has a huge amount,but also has a high economic value.In order to better achieve the purpose of safe and economic transportation,a nonlinear fuzzy track keeping controller is designed in this paper.Firstly,the NFAD(nonlinear feedback and decoration)technique is used for ship course keeping control to verify its effectiveness.The mathematical model of yupeng ship is established.The model has a nonlinear feedback compensation term and takes the characteristics of steering gear into consideration.The conformity between the established nonlinear ship model and real ship is verified by carrying out turning circle simulation test in hard starboard.Then NFAD technique is used in the design of fuzzy PID controller.The theoretical analysis proves that the influence of this technique on steady state,dynamic state and output of the system is within a reasonable range.The simulation results show that control performance of fuzzy PID is improved by NFAD technique.After adjusting the parameters of ship model,the simulation experiment is carried out again,it is proved that the designed controller can achieve course keeping control,and has the effect of energy saving and robustness.By using the improved LOS(Line of Sight)trajectory guidance algorithm and fuzzy control technique,and replacing the fixed value with variable distance,a track keeping controller is designed and simulated.In view of the phenomenon that ship will drift outward when turning at large angles,a new steering strategy is proposed,which is determine the optimal starting turning point by setting an inner tangential circle.The key of this method is to determine the radius of the inner tangential circle at large angles.Through some simulation test,we found,when steering radius is 3.2 times of length of Mariner ship,track keeping control effect is ideal.On this basis,a nonlinear fuzzy track keeping controller is designed by introducing NFAD technique.The simulation results show that the controller can still achieve good control effect in extreme circumstance,and can greatly reduce the average rudder angle.By using NFAD technique,a nonlinear fuzzy track keeping controller is designed,this controller can achieve the effect of track keeping control well in straight-line navigation stage,small-angle and large-angle turning steering,and can also achieve energy-saving in this process.The goal of designing a safe and economical track keeping controller is realized.