Modeling of active heave compensation system of deep-sea mining based on dynamic vibration absorber and its H∞ robust control
The heave compensation system is vital for the deep-sea mining system undergoes excessive vibrations due to irregular wave loads for both normal operating and extreme conditions. To ensure its safety and operation efficiency, a novel active heave compensation system of deep-sea mining based on dynamic vibration absorber was proposed in this paper. The three-degree-of-freedom dynamic models of active heave compensation system based on dynamic vibration absorber in irregular wave are established. A H∞ Robust controller is designed for active heave compensation system by applying robust loop shaping control. The performance of H∞ robust controller and its robustness stability of the system are simulated and analyzed in frequency domain. The results show that the performance of the system in wave energy concentrated frequency domain of China's deep-sea mining field was improved by the concentrated weighting of acceleration output. And it also shows that the designed H∞ controller is perfect in system robustness stability against some parameter fluctuations of the system model. Therefore the designed active heave compensation system is practical to isolate the lift pipe and its support platform from the significant vibration of the ship motion induced by the irregular wave.
Deep-ocean Mining Technology: Learning Curve I
The recent state of technological development in the countries that have joined deep-ocean mining since the ’90s is reviewed in terms of readiness for the development of a commercial mining technology. Previous R&D work performed on deep-ocean mining technology and systems is used as a baseline for review. The review includes discussions on most of the technical issues that have been already identified in the literature for manganese nodule production system design. While recent technological developments do not yet appear to identify new issues, it is likely that more issues remain to be identified and solved. The realization of a costeffective commercial deep-ocean mining system will take much longer than is claimed. The commercialization of deep-ocean resources would require a pool of experts, technical innovation and cost-effective technology, plus costand technology-sharing among the countries and/or companies. More clearly defined guidelines or regulations at the early stages can save time and cost for the system and technological development for commercialization. More importantly, a decision needs to be made to build on previous achievements and move forward, thus also saving time and funds. This paper follows Chung (1999). ___________ *The ISOPE assumes no responsibility for the statements expressed by the author. DEEP-OCEAN MINERALS OF INTEREST Our primary minerals of present interest in the deep seafloor are manganese nodules and cobalt-rich manganese crusts, the former from a depth of 800 to 3,000 m, and the latter from a depth of 3,000 to 6,000 m. Essential metals from the nodules and crusts are for use in steel, aircraft, military equipment, machinery and cutting tools. PREVIOUS DEVELOPMENTS One of the greatest technological innovations in ship and deep-ocean technology of this century is the deep-ocean mining system with the Hughes Glomar Explorer (Fig. 1): A huge “moon pool” (270 ft or 82.3 m long) can be opened and closed in the bottom of the ship hull in the middle of the ocean. It deploys and retrieves a large, remotely controlled, self-propelled seafloor miner with 6,000-m long-pipe system through the moon pool for operation on the 6,000-m-deep seafloor. Its pipe handling and deployment are automated. What was done in the '70s? The U.S.-based international consortia carried out their R&D programs in the '70s as private enterprises and claimed their respective manganese nodule areas in the Pacific Ocean. Most of what we have heard regarding the deep-ocean mining technologies and systems for exploration, nodule recovery and processing took place in the '70s. These data are kept proprietary, and most of the data or documents have not been made available to the public. Most of the claims of deep-ocean mining R&D by the international consortia are made orally, with little documented proof made available in the public domain. The Lockheed−Dutch Shell-Amoco−Bos Khalis Consortium (OMCO, Ocean Minerals Co.), OMCO/Lockheed. Lockheed /OMCO developed large-scale test mining system(s) with the Hughes Glomar Explorer and conducted at-sea tests in the Pacific Ocean in 1976 and 1978 (Figs. 1 and 6). Also, it conducted exploration surveys and processing research. Further, the Lockheed/OMCO team developed a Proceedings of The Fifth (2003) Ocean Mining Symposium Tsukuba, Japan, September 15-19, 2003 Copyright © 2003 by The International Society of Offshore and Polar Engineers ISBN 1-880653-61-3
Algorithms for Linear-Quadratic Optimization
Linear-quadratic optimization problems Newton algorithms Schur and generalized Schur algorithms structure-preserving algorithms. Appendices: Comparison of Riccati solvers notation and abbreviations.