Numerical optimization of a cage-mounted passive heave compensation system

Heave compensation systems are used to increase the safe operating sea-states of vertically tethered systems, as well as, decrease the tension in the tether and the motion of the underwater platform. However, the characteristics of the heave compensator must be carefully chosen or operating problems may be exacerbated. In this paper, a discrete representation of a deep-sea remotely operated vehicle system with a passive cage-mounted heave compensator is used within a sequential quadratic programming optimization routine to choose the stiffness and damping characteristics that minimize the tension in the tether and platform motion. Using the optimal values of the stiffness and damping, the rms cage motion and rms tension were significantly decreased over all operating depths and sea-states.