Research On Dynamic Modeling And Hydrodynamic Parameters Identification For Auv

The 21st century is the century that man investigate, develop and utilize the sea. With the increase of developing and utilizing the sea and military affairs, more and more researchers apply themselves to the development of autonomous underwater vehicle(AUV) which can explore the underwater circumstance and accomplish the special missions. It represents the develop direction of underwater vehicle. However, AUV is a highly nonlinear and time-varying dynamic system, thus it is very important to establish a accurate model for the control,prediction and simulation of the AUV. But the accurate model largely depends on the hydrodynamic parameters, so the research of hydrodynamic parameters is becoming more important.After introducing the open-frame AUV prototype named "CRanger-01", the paper studies the problems of dynamic modeling and hydrodynamic parameters identification of AUV.Based on analyzing the kinematics and the dynamics effecting on AUV, a dynamic model of six degree-of-freedom(DOF) is established. A simplified model is obtained aiming at an open-frame structure and design characteristics. A hydrodynamic experiment has been carried out for the identification of dynamic model of the thrusters, which is carried out in a water tank.A least-square(LS) technique is utilized to estimate the hydrodynamic parameters of AUV. The Horizontal movement and vertical movement of AUV are simulated, then the surge,sway,heave,pitch and yaw DOF are identified respectively.With a view to the difficulty of the traditional hydrodynamic parameters experiments and theoretical calculation methods for AUV and the drawback of optimum results tending to local optimization of the ever identification methods, a genetic algorithm(GA) based hydrodynamic parameters identification method of AUV is presented. This method has a better robustness and can find the globally optimal point without the initial values of parameters. On the analysis of the realization methods of hydrodynamic parameters identification by using GA, the horizontal movement and vertical movement of "CRanger-01" are identified, then 38 hydrodynamic parameters of surge,sway,heave,pitch and yaw DOF are obtained.In order to verify the reliability of the dynamic model of "CRanger-01", the motion simulation system is established at the same initial values and the same thrust. Compared with the actual values, the identification errors are in the allowable range and are greatly reduced compared to using LS. It further demonstrates that GA can identify the hydrodynamic parameters of AUV effectively and can provide a reference for engineering practice.