Dynamic modeling and simulation of mooring system for an unmanned underwater vehicle

To determine the kinematic performance of an unmanned underwater vehicle (UUV) attached to a mooring line and lurking on the seabed, a three-dimensional cable mathematical model that considers the effects of bending moments was established based on the Euler-Bernoulli beam theory. In addition, a quaternion-based cable attitude model was adopted as a substitute for the traditional Euler-angle form to eliminate the singular behavior under some special circumstances, namely, a drastic change in cable attitude or the existence of some specific uncertain Euler angles. The governing equations of the UUV, cable, and anchor were integrated by using appropriate boundary conditions to obtain the translational and rotational motion equations of the mooring system. Thereafter, the mathematical model of the mooring system was discretized by using the finite difference method, and the Newton-Raphson iterative method was employed to solve the difference equations. Application data from Hopland's towing experiment were extracted to validate the mathematical model. The results show that the modeling algorithm is accurate and efficient. Then, the UUV's position deviation and attitude change were simulated in periodically changing current to provide a theoretical principle for maintaining its normal working state.