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991.
在利用概率因果网络模型进行汽轮机故障诊断过程中,传统的基于简约覆盖理论的求算方法不能直接得到诊断问题的解,而且当故障节点较多或网络层次较多时,存在着"组合爆炸"、计算量呈指数速度增加等问题;对此,基于群智能理论,建立汽轮发电机组故障诊断系统概率因果网络群智能算法模型,给出基本的群运算法则及改进方法,将焦点放在有限空间的诊断推理上,并实现并行处理,很好地解决了传统算法中的问题;最后一个应用实例验证了此方法的优越性及工程实用性。 相似文献
992.
舰船电子装备综合诊断中的IETM设计与应用技术研究 总被引:3,自引:3,他引:0
交互式电子技术手册是装备保障信息化技术研究和应用的热点之一,IETM不仅作为一种电子手册,实现了技术手册的数字化,而且它具有交互功能,实现了技术手册的智能化;更为重要的是.IETM的数据格式采用了国际通用的成熟标准,从根本上为实现数据的互操作性和共享性,实现数据的网络集成化提供了可能;本文结合舰船电子装备IETM通用要求和实施要点,介绍了武器装备IETM通用开发平台中涉及的关键技术及应用方向,阐述了IETM数据的标准化技术、多数据源导入技术、IETM动态数据交换技术、故障分析技术等关键技术,提出了适应武器装备维修保障需求的IETM通用开发平台解决方案. 相似文献
993.
针对带有挠性太阳帆板卫星的姿态控制问题,设计了基于支持向量机的逆模型控制律,采用模态分析方法对姿态模型进行简化处理;首先设计了基于支持向量机的恒衰减因子逆模型控制律,分别在无干扰、阶跃干扰和周期性干扰三种情况下进行仿真;考虑执行机构的力矩输出有限,在对恒衰减因子取不同值下的仿真结果进行分析的基础上,又分别设计了衰减因子取分段函数形式及输入限幅的控制律;仿真结果显示,设计的控制律能够使系统具有好的稳定效果和动态品质,有效地减小了挠性模态振动对姿态控制的影响,并对扰动具有一定的抑制能力。 相似文献
994.
Design and Verification of Enhanced Secure Localization Scheme in Wireless Sensor Networks 总被引:2,自引:0,他引:2
He Daojing Cui Lin Huang Hejiao Ma Maode 《Parallel and Distributed Systems, IEEE Transactions on》2009,20(7):1050-1058
In this paper, we focus on the need for secure and efficient localization for wireless sensor networks in adversarial settings. An attack-resistant and efficient localization scheme is developed, which extends the scheme proposed in [1]. The method offers strong defense against not only distance reduction attacks but also distance enlargement attacks. Furthermore, our method does not employ any device-dependent variables, hence yields more accurate localization. An attack-driven model is also specified using Petri net. It provides a formal method for the verification of our scheme when considering distance enlargement attacks. The state analysis shows that the potential insecure states are unreachable, implying that the model can offer strong defense against these attacks. To the best of our knowledge, it is the first time that the Petri net has been introduced to validate security scheme for wireless sensor networks in the literature. 相似文献
995.
The robust stochastic stability, stabilization and H∞ control for mode‐dependent time‐delay discrete Markovian jump singular systems with parameter uncertainties are discussed. Based on the restricted system equivalent (r.s.e.) transformation and by introducing new state vectors, the singular system is transformed into a standard linear system, and delay‐dependent linear matrix inequalities (LMIs) conditions for the mode‐dependent time‐delay discrete Markovian jump singular systems to be regular, causal and stochastically stable, and stochastically stable with γ‐disturbance attenuation are obtained, respectively. With these conditions, robust stabilization problem and robust H∞ control problem are solved, and the LMIs sufficient conditions are obtained. A numerical example illustrates the effectiveness of the method given in the paper. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
996.
Yan Zhang Laurence T. Yang Jianhua Ma Jun Zheng 《Journal of Network and Computer Applications》2009,32(2):483-489
As a fundamental component in wireless networks, location management consists of two operations: location update and paging. These two supplementary operations enable the mobile user ubiquitous mobility. However, in case of failed location update, a significant consequence is the obsolete location identity in the network databases and thereafter the incapability in establishing the valid route for the potential call connection, which will seriously degrade the network quality-of-service (QoS). This issue is not theoretically studied in the literature. In this paper, we perform a quantitative analysis of the location management effect on QoS in the wireless networks. The metrics call blocking probability and the average number of blocked calls are introduced to reflect the QoS. For the sake of general applicability, the performance metrics are formulated with the relaxed tele-traffic parameters. Namely, the call inter-arrival time, cell residence time, location area residence time and location update inter-arrival time follow a general probability density function. The formulae are additionally specified in the static and several dynamic location management mechanisms. Numerical examples are presented to show the interaction between the performance metrics and location management schemes. The discussions on the sensitivity of tele-parameters are also given. 相似文献
997.
A cable-driven parallel manipulator is a manipulator whose end-effector is driven by a number of parallel cables instead of
rigid links. Since cables always have more flexibility than rigid links, a cable manipulator bears a concern of possible vibration.
Thus, investigation of vibration of cable manipulators caused by cable flexibility is important for applications requiring
high system stiffness or bandwidth. This paper provides a vibration analysis of general 6-DOF cable-driven parallel manipulators.
Based on the analysis of the natural frequencies of the multibody system, the study demonstrates that a cable manipulator
can be designed stiff enough for special applications like the cable-manipulator based hardware-in-the-loop simulation of
contact dynamics. Moreover, under an excitation, a cable may vibrate not only in its axial direction, but also in its transversal
direction. The paper also analyzes the vibration of cable manipulators caused by cable flexibilities in both axial and transversal
directions. It is shown that the vibration of a cable manipulator due to the transversal vibration of cables can be ignored
comparing to that due to the axial flexibility of cables. 相似文献
998.
Flexible-body modeling with geometric nonlinearities remains a hot topic of research by applications in multibody system dynamics
undergoing large overall motions. However, the geometric nonlinear effects on the impact dynamics of flexible multibody systems
have attracted significantly less attention. In this paper, a point-surface impact problem between a rigid ball and a pivoted
flexible beam is investigated. The Hertzian contact law is used to describe the impact process, and the dynamic equations
are formulated in the floating frame of reference using the assumed mode method. The two important geometric nonlinear effects
of the flexible beam are taken into account, i.e., the longitudinal foreshortening effect due to the transverse deformation,
and the stress stiffness effect due to the axial force. The simulation results show that good consistency can be obtained
with the nonlinear finite element program ABAQUS/Explicit if proper geometric nonlinearities are included in the floating
frame formulation. Specifically, only the foreshortening effect should be considered in a pure transverse impact for efficiency,
while the stress stiffness effect should be further considered in an oblique case with much more computational effort. It
also implies that the geometric nonlinear effects should be considered properly in the impact dynamic analysis of more general
flexible multibody systems. 相似文献
999.
The robust stability and robust stabilization for time‐delay discrete singular systems with parameter uncertainties is discussed. A delay‐dependent linear matrix inequality (LMI) condition for the time‐delay discrete systems to be nonsingular and stable is given. Based on this condition and the restricted system equivalent transformation, the delay‐dependent LMI condition is proposed for the time‐delay discrete singular systems to be admissible. With this condition, the problems of robust stability and robust stabilization are solved, and the delay‐dependent LMI conditions are obtained. Numerical examples illustrate the effectiveness of the method given in the paper. Copyright © 2009 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society 相似文献
1000.
一种基于多Agent的分布式入侵检测系统设计 总被引:1,自引:0,他引:1
在分析现有基于Agent的入侵检测系统的基础上,提出了一种基于多Agent分布式入侵检测系统模型。该模型采用了分布检测、分布响应的模式,各Agent之间具有良好的相对独立性。通过多Agent技术的思想建立系统总体结构,给出了模型的各个组成部分,并对结构中各种Agent与中心控制台的功能设计进行了分析。同时对涉及到特征匹配算法、动态选举算法、协同算法进行了初步的设计与分析。系统可充分利用各Agent的协同完成入侵检测任务,实时响应,可有效地改进传统IDS。 相似文献