Nonlinear Mathematics Modeling and Analysis of the Vectored Thruster Autonomous Underwater Vehicle in 6-DOF Motions

The new type of autonomous underwater vehicle (AUV) is equipped with rudders and vectored thrusters, which are combined to control the directions to realize multi-motion modes in different control modes at high speed and low speed respectively. Euler angle representation is used to establish 6-DOF kinematic model according to the structural and kinetic characteristics. In order to achieve the satisfactory performance with arbitrary angles, the quaternion method is used to solve the problem of existence of singularities when the pitch angles are degree . Then nonlinear dynamic equations with 6-DOF of the vehicle are deduced based on the Newton second law and Lagrangian approach respectively. The dynamic models of the two methods are the same, which shows that the dynamic model of the vehicle is accurate and it lays a foundation for the control system design. Moreover, the Runge-Kutta algorithm is used to solve the dynamic equations, which clears up the difficulties of the computation and the display of coupled nonlinear motion equations. The kinematic model and dynamic model are proved to be valid through the computation and analysis of the spatial movement's capability, which shows that the maneuverability of the vehicle equipped with rudders and vectored thrusters is greatly enhanced.