A hydrodynamic model for a tethered underwater robot and dynamic analysis of the robot in turning motion

Abstract

A new three-dimensional hydrodynamic model to simulate the hydrodynamic behavior of a tethered underwater robot system is proposed.In the model the governing equations of umbilical cable are derived from the balance of forces at a point of the cable,these equations are taken as the core part for robot's hydrodynamic model,the whole model can then be established by introducing the boundary conditions of the cable equations at the conjunction point between the lower end of cable and the underwater robot.In numerical simulation of this paper the hydrodynamic loading on main body of the robot and control forces issued from the running ducted thrusters are determined with computational fluid dynamics technique with their interactional effects being involved.The main characteristic of the model is that the model dynamic performance of tethered underwater robot system can be observed in a comprehensive point of view and some shortcomings in the existing hydrodynamic model can be overcome.These shortcomings include detached treatment to compositive portions of the robot system and insufficient investigation on the hydrodynamic performance of umbilical cable,robot main body and thrusters in an integral theoretical frame of the robot system.The numerical simulation of robot's turning motion under the effect of ducted thruster propul-sion indicates that the effective numerical simulation on the hydrodynamic behavior of tethered underwater robot can be conducted with the established model.