Study on Dynamic Behavior of Unmanned Surface Vehicle-Linked Unmanned Underwater Vehicle System for Underwater Exploration

When the unmanned underwater vehicle (UUV) is operated alone, its mission performance is limited due to energy limitation, navigation errors so on. In order to solve these problems, an unmanned surface vehicle (USV)-linked-UUV is proposed. This paper focuses on the motion analysis of the vehicles and umbilical cable (UC) coupling system to investigate the interaction between USV-UC-UUV dynamic behavior in the ocean environment. For this, a new dynamic modeling method for investigating a multi-body dynamics system consisting of an USV moving on the water surface, an UC, and an UUV is employed. First, the structure and hardware composition of the proposed system are presented. The USV and UUV are modeled as rigid-body vehicles, and the flexible UC is discretized using the catenary equation. The motion equations of both vehicles USV and UUV are combined with the governing equations of the flexible UC dynamics. In order to solve the nonlinear coupled dynamics of the vehicles and flexible UC, the 4th-order Runge–Kutta numerical method is implemented. In modeling of the flexible UC dynamics, the mathematical dynamic equations of the UC are firstly performed using the catenary equation method. Then, in order to solve a two-point boundary value problem of the catenary equation, the shooting method is applied. The interactions between the dynamics of the flexible UC and the mobilities of both vehicles USV and UUV are investigated through numerical simulations in the time domain. Through the computer simulation, the behavior of the complete USV-UC-UUV operating under the number of different physical circumstances can be predicted and thence analyzed. The cases when the USV-UC-UUV maneuvers in a variety of motion operation modes are studied to conduct a systematic motion analysis. Both the variation of the cable forces and moment at the tow points and the configuration of the cable in the water are investigated. The simulation results may serve as a useful tool to improve the performance of the vehicles that operate under the effects of the UC in the water are investigated