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
Adaptive optics for extreme ultraviolet lithography : actuator design and validation for deformable mirror concepts
In the production of integrated circuits (e.g. computer chips), optical lithography is used to transfer a pattern onto a semiconductor substrate (wafer). For lithographic systems using light in the ultraviolet band (EUV) with a 13.5nm nm wavelength, only reflective optics with multi-layers can reflect that light by means of interlayer interference, but these mirrors absorb around 30% of the incident light. Depending on pattern and beam shape, there is a nonuniform light distribution over the surface of the mirrors. This causes temperature gradients and therefore local deformations, due to different thermal expansions. To improve the throughput (wafers per hour), there is a demand to increase the source power, that will increase these deformations even further. Active mirrors are a solution to correct these deformations by reshaping the surface. This thesis addresses the challenges to accurate deform a mirror with high repeatability, meeting the requirements for implementation in a lithographic illumination machine. The main design criteria are vacuum compatibility, actuator stroke and the distance between actuators. Four different experimental mirrors, with increasing complexity, are successfully designed, realized and validated. All mirrors are equipped with thermomechanical actuators to either bend, or axially deform them. These actuators are free from mechanical hysteresis and therefore have a high position resolution with high reproducibility. Extensive finite element analysis is done, to maximize actuator stroke and minimize input power. All mirrors are tested and validated with interferometer surface measurements and thermocouple temperature measurements. The first experimental mirror with one thermo-mechanical bending actuator is successfully built and tested (chapter 2). To obtain a high mirror deflection at a given inserted actuator power, aluminum is chosen as the actuator material. The mirror is made from Zerodur® like the mirrors in the first EUV lithographic demonstration machines. A mirror deformation of 4:7 nm/C is achieved, where the inserted actuator power is 0.044 C/mW, meaning 0:21 nm/mW. The measured characteristic time constant is 10 s, meaning that for a given input, 63% of the steady state stroke is reached within that time scale. All values are close to the predicted ones from the models and also meet the requirements for implementation. To further investigate the concept and to measure the mechanical and thermal actuator coupling, an experimental mirror with four actuators is designed, developed and validated (chapter 3). It is an extension of the mirror with one actuator. In a single actuator step-response, a mirror deflection of 3.4 nm/C is achieved. A design optimization is proposed and successfully tested which reduces the actuator coupling from 30% to 10%, while the mirror deflection at the same input is reduced to 55%. Actuator speed is demonstrated while simultaneously heating all actuators with 3mW, which correspond with a mirror deformation of 33 pm/s. When using an adaptive mirror in an EUV lithography system, actuator strokes of 1 nm/min are required. The demonstrated actuator speed of 33 pm/s = 2 nm/min meets that requirement. The third and fourth mirror have actuators placed perpendicular to the surface (chapter 4). By placing the actuators on a thin back plate, the force loop is localized and therefore a lower actuator coupling is achieved. The results obtained from the third mirror with 7 actuators are close to the predicted values from the static and thermal models. Based on these good results, this actuation principle is implemented in a smaller deformable mirror with 19 actuators inside a 25mm beam diameter. A linear relation between actuator power and temperature of 0.190 C/mW and between power and averaged interactuator stroke of 0.13 nm/mW is achieved. So, the successfully realized mirror deflection is 0:68 nm/ C and no hysteresis is observed. For both mirrors a support frame is developed, that minimizes introduced surface deformations by temperature variations. Thermal step responses are fitted and both heating and cooling characteristic time constants are 2:5 s. The thermal actuator coupling from an energized actuator to its direct neighbor is 6:0, to their neighbors it is 1:3%. The total actuator coupling is approximated around 10%, based on the good agreement between simulated and measured inter-actuator stroke. Finally, chapter 5 summarizes the main findings from the different deformable mirrors and compares them. Also, suggestions for future research are given for implementation into a lithographic machine.