Ship Modeling And Course-keeping Based On ARX Model

The ship's course-keeping is the most basic research content in ship motion control,and it is the basis of ship track tracking control research.The motion of large ships is characterized by large inertia and slow response to rudder;nonlinear factors such as delay and relay characteristics exist in operation servo subsystem;vessel speed and ship loading will affect the parameters of ship motion model and even cause structural perturbation;the marine environment is particularly complex and changeable.These factors make ship coiarse control a complex nonlinear problem.At present,MMG(Maneuvering Modeling Group)model is mostly used as ship model in ship simulation research and engineering application.To build MMG model,a lot of complex experiments need to be designed to obtain many model parameters.For non-ship and marine engineering researchers,it is very difficult to build MMG model of ship.Therefore,this paper takes Ship Shihio Maru of Tokyo Ocean University as the controlled object,and indirectly constructs the ARX(AutoRegressive Model with eXogenous Variable)model with affine structure by using statistical modeling method.The least square method and Akaike information criterion are used to identify the model parameters and select the model order,and the long-term prediction performance of the model is used as the index to detect and compare the models.Compared with the direct modeling method,the indirect modeling method proposed in this paper can guarantee the stability or critical stability of the ARX model.In this paper,the long-term prediction performance of the optimal ARX model and the MMG model of Shijio Maru are compared.The results show that the forecasting ability of the indirect ARX model is comparable to that of the MMG model.In the research of course keeping control,PID control strategy,various fuzzy control strategies and LQR course control strategy based on ARX model are designed.In the NATLAB simulation experiment,the above control strategies can achieve ship course control.On this basis,the ARX model of the small surface unmanned ship experimental platform Wang Liang is established as the controlled object.Based on this model,simulation experiments and real ship experiments of various course control strategies are carried out.The results of simulation and real ship experiments show that these control strategies can effectively achieve ship course control.Through the analysis of the results of the real ship experiment it is found that the wind has a great influence on the ship's course.The influence of wind on the ship's course must be considered in the course of ship maneuvering.Therefore,an ARX model with rudder angle and wind force as input and yaw angle deviation as output is established to test its long-term prediction performance,compared with the ARX model without considering wind disturbance,a preliminary study is made on how to consider the wind effect in the model.