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1.
受损结构余度评估的半概率方法 总被引：3，自引：0，他引：3
本文给出了一种结构系统余度的度量定义，基于结构系统机构化失效概念和相当可靠性指数。本文提出了对受损结构安全评做的半概率方法。所示算例表明了本方法的有效性。 相似文献
2.
Various forms of recently appeared concepts of structure system redundancy are studied. A new measure for existing structure redundancy is proposed. By introducing the concept of structure system failure at the mechanism level and the concept of equivalent reliability index, the evaluation of safety criteria for existing offshore structures is developed. By employing the method presented in this paper, system redundancy has been evaluated for some numerical examples and satisfactory results have been drawn. 相似文献
3.
自治水下机器人机械手系统协调运动研究 总被引：1，自引：0，他引：1
简单描述了自治水下机器人搭载的三功能水下电动机械手的设计,鉴于自治水下机器人-机械手系统运动学冗余、内部可能干涉以及载体圆筒式外形等特点,将惩罚调节因子引入系统运动学伪逆矩阵,保证了关节在允许范围内运动,避免载体大幅度姿态变化及载体与机械手之间的干涉,同时采用梯度投影法优化海流作用下的系统推力。仿真表明,该算法在解决系统冗余度的同时,有效地协调多任务下的系统动作。 相似文献
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Yu Qing Xiao Xi
Lecturer 《中国海洋工程》1997,(2)
This paper is a survey of the state-of-the-art knowledge in structural redundancy measure andits application.The existing deterministic and probabilistic measures of structural redundancy are summa-rized.Emphasis is given to the discussion of their advantages and limitations.The application of damagetolerance concept in the design and maintenance of marine structures is also reviewed.Some most criticalproblems in structural redundancy are proposed for future research. 相似文献
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Despite rapid progress in improving mass-storage density and digital communication system performance, compression of hydroacoustic image data is still significant in many engineering and research areas since it can overcome data storage and transmission bandwidth limitations. In this paper, we present a novel and effective approach for lossless compression of hydroacoustic image data which consists of two stages. The first stage reduces the information redundancy. We propose several new techniques to remove redundancy between data samples, data blocks, and data frames. The second stage uses a newly developed cascade coding scheme. This simple scheme can achieve an efficiency of 97%. A decomposition algorithm is presented for finding the optimal cascade coding parameters. The algorithm decomposes a multivariable optimization problem into a series of one-variable optimizations. Our two-stage algorithm offers a compression ratio of 2-3 and provides an exact recovery of the original data. Because of its simplicity, the algorithm can be incorporated into a variety of echo sounder systems. The compression algorithms can also be implemented using low-level assembly language to meet the requirements of real-time applications 相似文献
7.
A new motion coordination algorithm for an autonomous underwater vehicle-manipulator system (UVMS) is proposed. This algorithm generates the desired trajectories for both the vehicle and the manipulator in such a way that the total hydrodynamic drag on the system is minimized. Resolution of kinematic redundancy of the system is performed at the acceleration level so that this algorithm can be incorporated into the system dynamics. The dynamics of the UVMS are modeled using a quasi-Lagrange approach. A state-space formulation of the system along with a model-based controller design for trajectory-following tasks that includes thruster dynamics is also presented. The computer simulation results demonstrate the effectiveness of this proposed method in reducing the drag on the system 相似文献
8.
The neural control of movement requires the ability to deal with changes, both in the environment and in the parameters that characterize the mechanical structure of the organism. Here we discuss the three types of coordinate representations that sensory and motor systems use to generate and control movements, and argue that the intrinsic redundancy of the musculoeskeletal system can be exploited to implement control signals that result in successful task completion while allowing for variance in trajectory parameters not relevant to the task. We also argue that muscle synergies activated through the stimulation of specific loci along the spinal cord provide evidence for the existence of a vocabulary of motor primitives that can be combined, either simultaneously or sequentially, to generate a broad repertoire of complex movements. 相似文献
9.
文章在系统梳理国内外经济普查与调查制度的基础上,结合实际参与全国第一次海洋经济调查工作的具体情况,深入分析了现行海洋经济调查方案中存在的问题,针对涉海单位清查的底册冗余度较大、调查数据质量控制的方式有待强化、海洋经济调查组织实施的有效性及部分产业数据界限不清等问题开展了思考和分析,并从组织实施模式、涉海名录库管理、数据质量控制等环节,为管理部门优化海洋经济数据采集和分析的方式方法提出了优化海洋经济调查的组织实施模式、建立健全涉海名录库筛选和管理系统、强化和完善数据成果的质量控制方式等针对性的对策建议。 相似文献
10.
Plankis B.J. Horning M. Ponto N. Brown L.K. 《Oceanic Engineering, IEEE Journal of》2007,32(2):400-407
This paper presents the satellite-linked data acquisition and photogrammetry (SLiDAP) network, designed to conduct shore-based, close-range 3-D imaging in remote areas. The lack of communications and power infrastructure and ability to service the system requires periodic, synchronous operations of multiple semiautonomous elements with a high degree of reliability. The SLiDAP system uses an opportunistic network architecture based on four distinct levels of control, to accommodate unpredictable operational constraints and failures. The synchronization of periodic tasks in a distributed control and remotely operable network are highlighted, and measures to increase the reliability of system operations are discussed, including hardware redundancy, intelligent watchdog timer, software error tolerance, self-repair, and remote update capability. The characteristics of the SLiDAP system within the concept of autonomic computing are discussed. 相似文献
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A critical and potentially difficult problem for ocean-bottom observatories is the electrical power sub-system. While huge effort and expense has gone into development of land power grids and ocean communication cable power, the characteristics of ocean-bottom observatories require different strategies. Ocean-bottom observatories terminate on the ocean floor where large variable loads are installed, whereas commercial ocean-bottom cables terminate on land and normally have relatively fixed loads. Design considerations such as whether to use a constant current or constant voltage source, choice of voltage and current levels and cable capacitance and impedance are considered. Ocean-bottom observatory science requirements in the future will demand multiple loads along the cable, cable branches, fault protection and redundancy. The realities of high cable capacitance and the negative dynamic impedance of switching power supplies require that rapid load changes either be anticipated or prevented. Without proper control, rapid changes in load can result in instability and collapse of the power system. The strategy suggested in this paper requires that each load point (or junction box where science experiments will be attached to the system) be "smart" enough to keep load variations within tolerance bounds 相似文献
13.
As the exploration and exploitation of oil and gas proliferate throughout deepwater area,the requirements on the reliability of dynamic positioning system become increasingly stringent.The control objective ensuring safety operation at deep water will not be met by a single controller for dynamic positioning.In order to increase the availability and reliability of dynamic positioning control system,the triple redundancy hardware and software control architectures were designed and developed according to the safe specifications of DP-3 classification notation for dynamically positioned ships and rigs.The hardware redundant configuration takes the form of triple-redundant hot standby configuration including three identical operator stations and three real-time control computers which connect each other through dual networks.The function of motion control and redundancy management of control computers were implemented by software on the real-time operating system VxWorks.The software realization of task loose synchronization,majority voting and fault detection were presented in details.A hierarchical software architecture was planed during the development of software,consisting of application layer,real-time layer and physical layer.The behavior of the DP-3 dynamic positioning control system was modeled by a Markov model to analyze its reliability.The effects of variation in parameters on the reliability measures were investigated.The time domain dynamic simulation was carried out on a deepwater drilling rig to prove the feasibility of the proposed control architecture. 相似文献
14.
For autonomous manipulation in water, an underwater vehicle-manipulator system (UVMS) should be able to generate trajectori9es for the vehicle and manipulators and track the planned trajectories accurately. In this paper, for trajectory generation, we suggest a performance index for redundancy resolution. This index is designed to minimize the restoring moments of the UVMS during manipulation, and it is optimized without impeding the performance of a given task. As a result, the restoring moments of the UVMS are decreased, and control efforts are also reduced. For tracking control of the UVMS, a nonlinear H∞ optimal control with disturbance observer is proposed. This control is robust against parameter uncertainties, external disturbances, and actuator nonlinearities. Numerical simulations are presented to demonstrate the performance of the proposed coordinated motion control of the UVMS. The results show that control inputs for tracking are reduced, and the UVMS can successfully track generated trajectories. 相似文献
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Chu Liangcheng Qu Naisi Guo Yonggang Lu Min Ph.D. Dalian University of Technology Dalian
Associate Professor Dalian University of Technology Dalian
Assistant M.S. Dalian University of Technology Dalian
Engineer Bohai Oil Company Tianjin 《中国海洋工程》1993,(4)
- Theoretically speaking, it is impossible to make the differential equation of motion uncoupled for the natural modes of a system in consideration of the attached water. The hydro-elastic structure is equal to the, non-proportional damping system. In this paper a perturbation analysis method is put forward. The structure motion equation is strictly solved mathematically, and the non-proportional damping problem is transformed into a series of proportional damping ones in the superposition form. The paper also presents the calculation formula of the dyanamic response of the structure being subjected to harmonic and arbitrary load. The convergence of the proposed method is also studied in this paper, and the corresponding convergence conditions are given. Finally, the proposed method is used to analyze the displacement response of a real offshore platform. The calculation results show that this method has the characteristics of high accuracy and fast convergence. 相似文献
17.
N. Vedachalam R. Ramesh V. Bala Naga Jyothi V. Doss Prakash G. A. Ramadass 《Marine Georesources & Geotechnology》2013,31(5):525-538
ABSTRACTReliable power supply, precise position determination and effective communication are the key requirements for strategic autonomous underwater vehicles (AUV) involved in long duration scientific missions, search operations and when operated as a swarm. The paper presents the challenging range of AUV developed for deep water, Polar and intervention applications; demanding technical requirements for strategic AUV; reliability modeling done on the lithium-ion batteries to identify the redundancy requirements for achieving near-zero failures; navigation model to estimate the achievable level of position accuracies using the state-of-the-art navigation system; limitations in underwater communication; and their importance in realizing vehicle autonomy and swarm intelligence. It is identified that a strategic grade Doppler velocity- aided inertial navigation system could provide position accuracies of about 0.5% of the distance travelled when navigated using sea bottom or ice reference, and a 38?kWh lithium-ion battery pack requires about 7% redundant battery capacity to achieve a failure probability of <?1% in a period of 1 year. 相似文献
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在分析遥感影像中提取的线状目标的基础上,利用样条插值函数,对提取的线状目标矢量化表示进行了研究。主要过程包括目标的分解、插值点的选取、插值函数的选择、特征点的增加等。实验结果表明,提出的方法能有效地表示提取的线状目标,减少数据冗余,具有好的光滑性。 相似文献
19.
The study investigates the effect of the salinity gradient on the functional composition, functional diversity and functional redundancy of soft-bottom communities in the south-western Baltic Sea. For this purpose, three different areas were selected and compared using a biological trait approach. Functional diversity was calculated by using Rao's Quadratic Entropy as a measure and functional redundancy by the ratio between functional and species diversity.Despite a high variability due to different other occurring environmental gradients, a clear shift in functional composition was visible using the BTA approach. The changes were most distinct for the traits, longevity and larvae type if the analyses were based on the biomass of the species, whereas abundance-based analyses tend to show less clear results.Along the same gradient, functional diversity and functional redundancy tended to increase if biomass data were used in the analysis. On the other hand no changes could be observed in the functional diversity when the abundance of the species was used.The result of the BTA showed a trend from long-lived and highly specialised species towards short-lived ubiquitous species with decreasing salinity. However, dominance of ubiquitous species in brackish waters seems to buffer the functional loss. Therefore it can be followed that by gaining functional redundancy the robustness of the benthic ecosystem to environmental changes increases. 相似文献
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本系统是为玉米高产、稳产栽培试验研究而编制的。作者着重介绍数据库管理系统与应用程序包之间交互作用,数据库的条件检索方法以及整个系统的结构和功能。研究过程中证实,使用本系统大大提高了工作效率。 相似文献