ABSTRACT:

Heave compensation system is necessary for the safety and the production efficiency as well as the component lifetime of the deep-sea mining system. Traditional heave compensation systems is a passive shock-absorbing system employing accumulator and high pressure air system, heave compensator cylinders, make-up units and so on, which need a much bigger shipboard space. To isolate the long lift pipeline with several thousand meters from the bending load induced by the irregular wave with reasonable deck space and energy consumption, a novel active heave compensation system of deep-sea mining based on dynamic vibration absorber was proposed in this paper. The dynamic models of the active heave compensation system with hydraulic actuator are established to investigate the performance of the active heave compensation system. And the feedback control was applied for the heave compensation system for increased effectiveness over a wider frequency band. The performance and the response of the proposed system with hydraulic actuator were simulated in time domain and frequency domain. The result shows that the active heave compensator based on dynamic vibration absorber with feedback controller can have the best performance of heave compensation and it is practical to isolate the lift pipe and its support platform from the ship motion induced by the irregular wave.

INTRODUCTION

With the decreasing of the mineral resources in the land and the increasing demand of the sustainable development of world economy, the deep-sea mining has been round the corner, driven by the ever increasing need for raw resources, especially copper. There are some entrepreneurial companies such as Nautilus and Neptune have exploration licenses covering vast areas of the seabed in the western Pacific targeting seafloor massive sulfide deposits (Scott, 2007). 1000m deep-sea poly-metallic nodule deep-sea mining system is indicated in Fig.1 (Liu, 2003).

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