Motion Simulation of a Remotely Operated Vehicle (ROV)

Abstract

Maneuverability of the MURS 300 Mark II (a Remotely Operated Vehicle), developed for inspecting underwater parts of hydroelectric dam facilities, is discussed in this paper based on the results of the computer simulation and the water tank test.A mathematical model of the submersible operation is built on the equation of a six degree freedom motion of a rigid body. Gravity force, buoyancy, hydrodynamic forces and thrusts are considered as external forces in the model. Cable tension is not included because of its negligibly small force in calm water. Hydrodynamic forces, drag, lift, added mass and so on are determined by the wind tunnel test and the water tank test.Thrusts are also measured in a water tank test. Being equipped with neither tail wing nor stabilizer, ROVs are usually characterized with their relatively poor directional stability. If a step input of thrust is added, ROVs are unlikely to move on a straight track without supplemental manipulation of thrusters.An automatic heading control system can be a solution to improve directional stability of ROVs.In case of the MURS 300 Mark II, a step input of its foward thrust causes its ascending because of the center of its horizontal thrust located slightly below its gravity center unless an automatic depth control system is installed. Given a rectangular pulse thrust, the MURS 300 Mark II equipped with automatic heading and depth control systems automatically returns to an original place where an operator sets a joystick in a neutral position.This operational characteristic of the MURS 300 Mark II is quite useful for underwater structure inspections. The results of a full scale experiment performed in a water tank agree to and prove the computer simulation outputs.