Open-Loop Vibration Control of an Underwater System: Application to Refueling Machine

This paper addresses a residual vibration control problem of the refueling machine (RM) that transports fuel rods in water to their desired locations in the nuclear reactor. A hybrid lumped-mass and distributed-parameter model of the RM is considered for investigation of the transverse vibrations (caused by trolley movement) of a fuel rod in water. Simulations and experiments reveal that the hydrodynamic force causes a large deflection of the rod in water as compared with in air, which must be suppressed to avoid damage to the rod's fissile material. A new command-shaping method for suppression of the flexible rod's residual vibrations in water is developed, which considers both a similitude law relating the maximum endpoint deflection of the rod in water to the maximum trolley velocity and a constraint on the rod's maximum endpoint deflection during its transport. The simulation and experimental results show that the proposed underwater-command-shaping method can effectively suppress the vibrations of the flexible rod operating in water.