The Model Simplification And Hydrodynamic Coefficients Identification Research On Underwater Vehicle

The maneuverability of underwater vehicle is highly nonlinear, and the coupling is existed between the two planes. That is the key point of the underwater vehicle manipulating. Consequently, getting the hydrodynamic coefficients accurately plays a significant role in manoeuvring, the content of the study in this paper are as follows:Firstly, the simulation model of underwater vehicle movement is discussed. Starting with momentum theorem and analyzing the forces, the six DOF space motion equation of underwater vehicle is derived by using the Taylor's series and diffirential equation theories as the main math tools.Secondly, the research background of the the parameter identification in hydrodynamic coefficients is simulation and training, so the 108 hydrodynimic coefficients are analyzed in this paper. Because of lacking in the real navigation data, the complex hydrodynamic coefficients are unsuitability. It is necessary for us to simplify the coefficients in strctual and motion characteristics. Some dominant coefficients in standard equations are preserved, while others that is lesser effected are ignored.Thirdly, by studying the relations between the manoeuvring parameter and the hydrodynamic coefficients, the sensitive parameter of hydrodynamic coefficients is put forward. From the point of maneuverability, the sensitive parameters are determined in three types of representative maneuvering experiment which are horizontal-z form, horizontal constant rotary motion experiment and vertical trapezia- experiment respectively. Through the simulation experiment, the results are picked up, and some less sensitive parameters are eliminated.Finally, the principle and the design of extended kalman filter are studied, a part of one-order hydrodynamic coefficients are eatimated using nonlinear observer in EKF.