The motion of a deep-sea remotely operated vehicle system Part 2: Analytical model

We developed a continuous linear-elastic one-dimensional analytic model tha t should accurately represent a vertically tethered system subject to surfa ce excitation. Our model accurately predicts: (a) the transfer function bet ween the motion of the ship and cage, (b) the transfer function between shi p motion and tension in the tether and (c) the natural frequency and its ha rmonics of the ROPOS deep-sea ROV system for depths between 0 and 1765 m up to moderately rough sea conditions. By solving the ship-cage motion transf er function for the onset of zero tension in the tether, we were able to pr edict the amplitude of ship motion that triggers a snap load. The solution to our model requires only two non-dimensional parameters representing the mass ratio of the cage and tether and the force ratio of drag to tension. T he predicted transfer function and natural frequency are not excessively se nsitive to the value of these parameters for the ROPOS ROV system. (C) 1999 Elsevier Science Ltd. All rights reserved.