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1.
带两控制器刚体飞行器的姿态镇定   总被引:2,自引:1,他引:2  
已知带两控制器的刚体飞行器系统不能被连续的纯状态反馈局部渐近镇定.有效的解 决方法包括时变反馈镇定方法和非连续反馈镇定方法.现有的时变反馈镇定方法设计均较为复 杂.已有的光滑时变反馈方法是非指数收敛的.本文通过引入辅助变量以及采用反馈线性化技术 设计出光滑时变的控制器.该方法设计简单且保证闭环系统状态是指数收敛的.仿真结果证明了 本文方法的有效性.  相似文献   

2.
非线性NARMAX模型的ARMAX模型全局线性化   总被引:7,自引:0,他引:7  
秦滨  韩志刚 《自动化学报》1997,23(3):332-337
提出了基于NARMAX模型的非线性系统的全局线性化方法.该方法用时变的 ARMAX模型近似描述非线性NARMAX模型.证明了这一线性化方法的有界性,并给出了 相应的实现方法.仿真结果说明了该方法的有效性.  相似文献   

3.
本文介绍一种采用S.M.A.R.T技术提高RAID数据可靠性的方法.阐述了S.M.A.R.T技术在RAID系统中的实现,给出了保障RAID数据高可靠性的执行流程,并且针对该方法进行了可靠性分析.分析结果表明了该方法的有效性.  相似文献   

4.
一、子程序设计 主程序与子程序间参数传递的方法 1.利用寄存器传递参数.该方法实现简单,调用方便. 2.利用内存单元传递参数.该方法优点是子程序要处理的数据或送出去的结果都有独立的存储单元,编写程序不易出错. 3.利用堆栈传递参数.该方法不占用寄存器和存储器单元.适用于参数较多且子程序有嵌套的情况.  相似文献   

5.
指数时间差分方法是近年来提出求解刚性常微分方程的一种新的数值计算方法.指数时间差分方法是一种积分方法,而不是经典的差分方法.利用指数时间差分方法求解扩散方程,如一维拟线性对流扩散方程和Allen-Cahn扩散方程.扩散方程在空间方向离散后转化成刚性常微分方程.用显式指数时间差分方法和相应阶的显式Runge-Kutta方法求解刚性常微分方程.数值结果表明显式指数时间差分方法具有相同阶的显式Runge-Kutta方法相应的精度,稳定性显著提高,而且能很好地模拟扩散方程的演化行为.指数时间差分方法可用于刚性常微分方程的数值计算.  相似文献   

6.
提出一种支持向量机(SVM)方法,通过图像的颜色和文本内容可有效地对大型图像数据库进行分类.为了评价此方法的性能.将它与人工神经网络中的方法进行了比较.实验证明这种方法比其他的方法更优越.  相似文献   

7.
基于GA和信息熵的文本分类规则抽取方法   总被引:1,自引:0,他引:1  
文本分类是文本数据挖掘中一个非常重要的技术.已经被广泛地应用于信息管理、搜索引擎、推荐系统等多个领域.现有的文本分类方法,大多是基于向量空间模型的算法.这些算法很难适用于大规模的文本数据集.为此,我们提出了一种基于遗传算法和信息熵的文本分类规则抽取方法.在该方法中,信息熵技术用来辅助遗传算法初始种群的生成.遗传算法和信息熵的有效集成.极大地提高了该混合方法的分类效率.实验结果表明.本文方法适用于大规模文本数据集:该方法提取规则的分类正确率较高.分类速度较快.  相似文献   

8.
本文中,提出了改进的再生核方法并求解了线性Fredholm型积分微分方程.首先构造了一个新的再生核希尔伯特空间并求解了其再生核.其次简要介绍了再生核方法.随后我们给出了改进的再生核方法.最后给出了四个数值算例.通过将本文的方法与CAS小波方法、微分变换法、改进的同伦摄动法、Runge-Kutta方法、传统的再生核方法进行比较,可知本文提出的方法具有精度高、计算速度快的优点.  相似文献   

9.
无线传感器网络分布式调度方法研究   总被引:10,自引:6,他引:4  
无线传感器网络(Wireless sensor network, WSN)是一个资源受限的网络系统.已提出了多种调度方法来提高网络性能. 本文归纳了WSN分布式调度方法的设计原则和分类方法,并按调度对象对调度方法进行了分类讨论. 详细论述了一些典型调度方法的内在机理,分析了每一类调度方法的特点. 对这些调度方法的设计目标和性能特点进行了对比.最后总结了WSN分布式调度方法的研究现状, 提出了该领域今后发展需要关注的重要因素.  相似文献   

10.
传统的奖学金评定方法是按照学生总成绩的高低作为评定依据.把一个多因数的问题简单化,使它成为一个单一的问题来处理.这种方法显然不合理.针对这个问题.采用基于模糊划分的模糊C-均值方法.对学生进行奖学金评定.为评审人员提供了一种比较科学、公正的评审方法.  相似文献   

11.
Youmans RJ  Ohlsson S 《Ergonomics》2008,51(4):441-475
The operation of machines typically requires attention to instruments that signal the state of the machine. One safeguard against primary instrument malfunction is to provide backup instruments, but this works only if the operators react to malfunction by switching attention to the backups. Little is known about the effect of negative outcomes or feedback on allocation of attention to backup instruments. Four experiments demonstrated that prior practice causes operators of a simulated machine to adapt to instrument malfunction by changing to a suboptimal decision rule rather than by reallocating attention to a different set of instruments. This fallacy appears linked to the operators' failures to notice feedback that they should switch during the simulations and operators' failures to correctly interpret outcome feedback following the simulations. The results raise theoretical questions and warn interface designers not to overrate backup instruments.  相似文献   

12.
《Ergonomics》2012,55(4):441-475
The operation of machines typically requires attention to instruments that signal the state of the machine. One safeguard against primary instrument malfunction is to provide backup instruments, but this works only if the operators react to malfunction by switching attention to the backups. Little is known about the effect of negative outcomes or feedback on allocation of attention to backup instruments. Four experiments demonstrated that prior practice causes operators of a simulated machine to adapt to instrument malfunction by changing to a suboptimal decision rule rather than by reallocating attention to a different set of instruments. This fallacy appears linked to the operators' failures to notice feedback that they should switch during the simulations and operators' failures to correctly interpret outcome feedback following the simulations. The results raise theoretical questions and warn interface designers not to overrate backup instruments.  相似文献   

13.
This article is devoted to the numerical solution of the inviscid two-layer shallow water system. This system may lose the hyperbolic character when the shear between the layer is big enough. This loss of hyperbolicity is related to the appearance of shear instabilities that leads, in real flows, to intense mixing of the two layers that the model is not able to simulate. The strategy here is to add some extra friction terms, which are supposed to parameterize the loss of mechanical energy due to mixing, to get rid of this difficulty. The main goal is to introduce a technique allowing one to add locally and automatically an ??optimal?? amount of shear stress to make the flow to remain in the hyperbolicity region. To do this, first an easy criterium to check the hyperbolicity of the system for a given state is proposed and checked. Next, we introduce a predictor/corrector strategy. In the predictor stage, a numerical scheme is applied to the system without extra friction. In the second stage, a discrete semi-implicit linear friction law is applied at any cell in which the predicted states are not in the hyperbolicity region. The coefficient of this law is calculated so that the predicted states are driven to the boundary of the hyperbolicity region according to the proposed criterium. The numerical scheme to be used at the first stage has to be able to advance in time in presence of complex eigenvalues: we propose here a family of path-conservative numerical scheme having this property. Finally, some numerical tests have been performed to assess the efficiency of the proposed strategy.  相似文献   

14.
One's model of skill determines what one expects from neural network modelling and how one proposes to go about enhancing expertise. We view skill acquisition as a progression from acting on the basis of a rough theory of a domain in terms of facts and rules to being able to respond appropriately to the current situation on the basis of neuron connections changed by the results of responses to the relevant aspects of many past situations. Viewing skill acquisition in this ways suggests how one can avoid the problem currently facing AI of how to train a network to make human-like generalizations. In training a network one must progress, as the human learner does, from rules and facts to wholistic responses. As to future work, from our perspective one should not try to enhance expertise as in traditional AI by attempting to construct improved theories of a domain, but rather by improving the learner's access to the relevant aspects of a domain so as to facilitate learning from experience.  相似文献   

15.
防火墙作为网络安全设备越来越多地应用于局域网络与公用网络的互联中,具有服务代理、包过滤、入侵检测等功能。防火墙作为一个网络互连设备,在组建网络中还有着局域网与Internet互联、隐藏防火墙外网IP地址、隐藏内部网络、IP地址重定向、安全访问控制以及构建VPN等应用。文中结合某单位的局域网规划设计就防火墙的应用作了重要的阐述。  相似文献   

16.
Relevance feedback (RF) is a technique that allows to enrich an initial query according to the user feedback. The goal is to express more precisely the user’s needs. Some open issues arise when considering semi-structured documents like XML documents. They are mainly related to the form of XML documents which mix content and structure information and to the new granularity of information. Indeed, the main objective of XML retrieval is to select relevant elements in XML documents instead of whole documents. Most of the RF approaches proposed in XML retrieval are simple adaptation of traditional RF to the new granularity of information. They usually enrich queries by adding terms extracted from relevant elements instead of terms extracted from whole documents. In this article, we describe a new approach of RF that takes advantage of two sources of evidence: the content and the structure. We propose to use the query term proximity to select terms to be added to the initial query and to use generic structures to express structural constraints. Both sources of evidence are used in different combined forms. Experiments were carried out within the INEX evaluation campaign and results show the effectiveness of our approaches.  相似文献   

17.
This research compared grasps to real surfaces with grasps to virtual surfaces, and used virtual surfaces to examine the role of cues to surface shape in grasp. The first experiment investigated the kinematics of overhand grasps to real and virtual objects. The results showed that, compared with grasps to real surfaces, grasps to virtual objects were different in the deceleration phase of the grasp movement and were more variable in their endpoint position. The second experiment used several measures to examine the relationship between the visual perception of a surface and the decision to grasp the surface with either an over-or underhand grasp. It was found that visual perception of the surface was consistent with the grasping decision. The third experiment used virtual surfaces to examine how the removal of visual cues to shape affected the decision to switch from over- to underhand grasp. Results showed that the orientation at which the decision switched was dependent on the visual information content. Overall, the results showed that subtle differences existed between the reach to grasp movements towards real and virtual surfaces and that the decision to choose between grasp types was dependent on the visual information used to depict the virtual surface. These results are discussed in relation to the design and use of input devices to enable manipulation of three-dimensional objects in virtual worlds.  相似文献   

18.
Holonic manufacturing systems (HMS) is based on the notion of holon, an autonomous, cooperative and intelligent entity to provide a econfigurable, flexible and decentralized manufacturing environment to respond to changing needs and opportunities. A set of holons that cooperate to achieve a goal forms a holarchy. How to design a mechanism to form a holarchy to achieve a goal while minimizing the overall cost is a challenge. The objectives of this paper are to propose models and develop collaborative algorithms to guide the holons to form a holarchy to coherently move toward the desired goal state ultimately. We adopt contract net protocol (CNP) to model mutual selection of holons in forming a holarchy. We formulate a holarchy optimization problem to minimize the cost subject to the feasibility constraints. To analyze the feasibility of a holarchy, a Petri net (PN) model is proposed. As classical PN models do not take into account the cost involved in firing transitions, we augment the PN model with cost functions in the problem formulation. Due to the distributed architecture of HMS, the internal structure of each potential holarchy that acts as bidder in CNP is not available to the manager. A key issue is to determine the feasibility of a holarchy without constructing the whole PN model of the given hierarchy. We study the feasible conditions for a holarchy and propose a collaborative algorithm to analyze the feasibility and award contracts to holons without constructing the whole model of a holarchy.  相似文献   

19.
Previous research has found isoinertial strength testing to be superior to isometric and isokinetic strength testing for prediction of task performance. The purpose of this study was to investigate tests on an isoinertial lifting machine (ILM) and their ability to predict performance on actual lifting tasks. Sixteen male subjects performed two lifting tasks: maximum box lift to truck-bed height of 1.35 m; and 'speed lifts' of 60 concrete blocks (each 22.7 kg) to the same height. These performance tests were compared to three ILM tests: a maximal lift to 1.83 m, a second maximal lift to 1.52 m, and an endurance test that entailed 60 timed ILM lifts of 22.7 kg to 1.83 m. Pearson product-moment correlations between ILM tests and performance tasks varied from r = 0.55 to 0.71. Therefore, the isoinertial test protocols employed in this study were able to account for only 30% to 50% of the variance in the performance of maximal lifting and endurance tasks. In was concluded that prediction of maximal lifting ability or endurance ability using an ILM might be enhanced by closer approximation of specific task variables, or by inclusion of dynamic parameters to measure technique.  相似文献   

20.
目前,数据库为了保证运行安全需要进行在线更新,由于大量的数据要在短时间之内完成加载,那么计算机很难直接对其表决。针对这种问题,我们提出针对数据库的实时状态表决,而不是对数据库直接表决,并基于这种表决方法设计出相应的算法,有效解决数据量过大的问题。  相似文献   

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