Research On Dynamic Modeling And Techniques Of System Identification Of Underwater Vehicle

With the development of marine science and technology,the autonomous underwater vehicle(AUV)is being paid more and more attention.In the research on AUV,the accurate and applicable mathematical model is the key point of precise control,planning,prediction and simulation.As a consequence of the hydrodynamic coefficients contained in the mathematical model of AUV,which show strong coupling nonlinear characteristics,the way of acquiring accurate hydrodynamic coefficients has become one of the difficulties of the research.System identification has become an important mean of modern mathematical modeling and skill of modern test engineering,and obtained great achievements in the field of AUV in recent years.Due to the large amount of prior knowledge and the solid theoretical results,system models of some research objects have basic structures in general standards.For this type of system,the final system model can be obtained by identifying the parameters.Generally,for a given AUV,a dedicated set of simulation and control program combined with different application functions will be developed.Programs developed in this way are usually large,complex and not easy to write,and difficult to modify to apply on other AUVs.However,the idea based on modularization of MOOS(Mission Orientated Operating Suite)makes it simple to complete the development of such programs.Based on the change after the modification of AUV “Hailing”,this dissertation finished the following specific work:(1)The mathematical model of AUV was established.“Hailing” before and after modification was compared and the model to obtain the 6DOF kinematic and kinetic equations were established.Nonlinear equations of maneuvering motion of horizontal plane and vertical plane were obtained,which were applicable to the research of system identification.(2)Hydrodynamic coefficients of AUV were identified.With the data of the sea test of“Hailing” and the weighted least squares method(WLSM),hydrodynamic coefficients of“Hailing” were identified within horizontal plane and vertical plane and the major coefficients were analyzed.The results show that while different lengths of data group and different weight coefficients make the curves fluctuate in different levels,the overall trends are steady.(3)A simulation program was established to predict maneuverability.The model was completed with the hydrodynamic coefficients identified.Specific modules were redeveloped and combined to establish the simulation program,with which the maneuverability of“Hailing” was predicted.The result shows the characteristics of “Hailing” when turning with different rudder angles and submerging to a specific depth with different wing angles.