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The prediction of dynamic crack propagation in brittle materials is still an important issue in many engineering fields. The remeshing technique based on scaled boundary finite element method（SBFEM） is extended to predict the dynamic crack propagation in brittle materials. The structure is firstly divided into a number of superelements, only the boundaries of which need to be discretized with line elements. In the SBFEM formulation, the stiffness and mass matrices of the super-elements can be coupled seamlessly with standard finite elements, thus the advantages of versatility and flexibility of the FEM are well maintained. The transient response of the structure can be calculated directly in the time domain using a standard time-integration scheme. Then the dynamic stress intensity factor（DSIF） during crack propagation can be solved analytically due to the semi-analytical nature of SBFEM. Only the fine mesh discretization for the crack-tip super-element is needed to ensure the required accuracy for the determination of stress intensity factor（SIF）. According to the predicted crack-tip position, a simple remeshing algorithm with the minimum mesh changes is suggested to simulate the dynamic crack propagation. Numerical examples indicate that the proposed method can be effectively used to deal with the dynamic crack propagation in a finite sized rectangular plate including a central crack. Comparison is made with the results available in the literature, which shows good agreement between each other. 相似文献
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Dynamic equivalence of the wind farm is a fundamental problem in the simulation of a power system connected with wind farms because it is unpractical to model every generator in a wind farm in detail. In this paper, an Equivalence Method based on the Output Characteristics （EMOC） is proposed, with which the wind farm composed of Squirrel-Cage Induction Generators （SCIGs） can be equivalent to one generator. By considering the diversity of wind generators and special operating characteristics of a wind farm, the equivalent generator based on EMOC responds accurately in various faults. No matter whether the wind farm is integrated in grid or just programmed, EMOC can be used to acquire an accurate equivalent generator. Simulation of the dynamic equivalence of an SCIG wind farm validated the method. 相似文献
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INTRODUCTION Structural damage detection technique addresses the problem of how to locate and detect damage that occurred in a structure by using the observed changes of its dynamic and static characteristics. In recent years, damage assessment of structure has drawn wide attention from various engineering fields. Gen-erally, the existing approaches proposed in this area can be clarified into two major categories: the dy-namic identification methods using dynamic test data and the static … 相似文献
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The capability automated warehouse in of a company to implement an an optimized way might be nowadays a crucial leverage in order to gain competitive advantage to satisfy the demand. The order picking is a warehouse function that needs to deal with the retrieval of articles from their storage locations. Merging several single customer orders into one, a picking order can increase efficiency of warehouse operations. The aim of this paper is to define throughout the use of ad-hoc genetic algorithm （GA） how better a warehouse can be set up. The paper deals with order batching, which has a major effect on efficiency of warehouse operations to avoid wastes of resources in terms of processes and to control possibility of unexpected costs in advance. 相似文献
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This paper proposes a simple and efficient distributed algorithm for calculating minimal dominating set in wireless sensor network. This method can avoid maintaining the connectivities between backbone hosts. Considering that the hosts in mobile networks have different characteristics, this paper proposes a method of calculating minimal dominating set with weight. The nodes can be chosen to form a minimal dominating set when the network topology changes. For the host switch on/off operation, the updating algorithm was provided. The change in the status of a host affects only the status of hosts in the restricted vicinity. Simulation results show that the proposed method can ensure fewer dominators but with higher weight to form the minimal dominating set and the nodes can be adaptive to the changes of network topology. 相似文献
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Image is not only an essential part,but also a major means to convey the implications in English poems.It is a literal and concrete representation of a sensory experience of an object.The rendering of images in English poems into Chinese can be guided by the dynamic equivalent translation theory put forward by Dr.Eugene A Nida.The theory emphasizes the roughly equivalent response of the target language receptors to the TL text to that of the source language receptors to the SL text.To achieve a Dynamic Equivalence,methods like Direct Translation,Addition,and Substitution can be employed in the translation of images in English poems. 相似文献
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In machining processes, errors of rough in dimension, shape and location lead to changes in processing quantity, and the material of a workpiece may not be uniform. For these reasons, cutting force changes in machining, making the machining system deformable. Consequently errors in workpieces may occur. This is called the error reflection phenomenon. Generally, such errors can be reduced through repeated processing while using appropriate processing quantity in each processing based on operator‘s experience.According to the theory of error reflection, the error reflection coefficient indicates the extent to which errors of rough influence errors of workpieces. It is related to several factors such as machining condition, hardness of the workpiece, etc. This non-linear relation cannot be worked out using any formula. RBF neural network can approximate a non-linear function within any precision and be trained fast. In this paper, non-linear mapping ability of a fuzzy-neural network is utilized to approximate the non-linear relation. After training of the network with swatch collection obtained in experiments, an appropriate output can be obtained when an input is given. In this way, one can get the required number of processing and the processing quantity each time from the machining condition. Angular rigidity of a machining system,hardness of workpiece, etc., can be input in a form of fuzzy values. Feasibility in solving error reflection and optimizing machining parameters with a RBF neural network is verified by a simulation test with MATLAB. 相似文献
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1IntroductionPath planning of autonomous mobile robot is pivotaltechnique for machine intelligence,which ai ms to finda non-collision path frominitial position to objectiveposition according to evaluation functions in anobstacle space[1].It can be described as travelersalesman problem(TSP),a typical combinationopti mization problem,which belongs to the well-known NP-hard opti mization[2].The mathematicaldefinition can be regarded as a mapG=(V,E),where eachlinee∈Ehas a nonnegative powerω(… 相似文献
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文强 《柳州职业技术学院学报》2021,(1)
执行元件工作是自动变速器形成动力挡位的基础,而自动变速器换挡是通过执行元件的切换来实现的,因此,执行元件的工作状态直接影响着自动变速器的动力传递。U340E自动变速器有8个执行元件,执行元件数量增多,变速器出故障的概率增加。通过对执行元件的故障分析,可以缩小自动变速器的故障范围,以便快速诊断出自动变速器的某类故障,缩减故障诊断时间,降低维修成本。 相似文献
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张娜 《新疆教育学院学报》2006,22(4):106-109
针对一类非线性系统给出一种基于学习方法的突变故障诊断方法,这种方法的思想是通过在线逼近器(诸如神经网络、模糊逻辑网络等)的自适应学习估计故障的大小。设计了一个观测器,以此来检测、辨识和诊断一类非线性系统动态系统的故障。从理论上,给出了故障检测的鲁棒性分析和敏感性分析,最后给出了检测时间上界。 相似文献
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邱浩 《深圳职业技术学院学报》2007,6(4):12-16
针对控制系统故障诊断中存在的不可测干扰，利用一种基于广义逆的未知输入观测器进行故障诊断，并将此方法用于汽车发动机电控系统执行器的故障检测问题。该观测器对控制系统的状态进行重构，通过判断由系统的真实输出和其估计值之间的残差是否超过阈值来检测故障。仿真结果表明，该方法原理简单，对汽车发动机电控系统执行器故障的诊断准确有效。 相似文献
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在对现有的变压器保护进行分析的基础上,针对差动保护在反映匝间故障时灵敏度不足的问题,结合电流电压的变压器保护理论的分析,提出了一种基于损耗功率的变压器匝间故障主保护方案。该方案实时计算有功损耗与无功损耗之间的比值,故障时该比值将发生较大的突变,通过该特征,可检测到轻微匝间故障。 相似文献
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In recent years, fault detection and isolation(FDI) technologies have been developing rapidly.Among them the observer-based fault detection andisolation technology for nonlinear systems are the mostattractive research areas, and lots of promising resultscan be found in survey papers[1]. Generally, thereare several kinds of strategies for observer-based FDIin nonlinearsystems such as unknown inputs observer-based FDI[2], and adaptive observer-based FDI[3]. Insome cases, fault accommodation… 相似文献
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Active suspension control of a one-wheel car model using single input rule modules fuzzy reasoning and a disturbance observer 总被引：1，自引：0，他引：1
YOSHIMURAToshio TERAMURAItaru 《浙江大学学报(A卷英文版)》2005,6(4):251-256
INTRODUCTION Research and development of active suspensionsystems for car models are increasing much in recentyears because the active suspension systems offergood riding comfort to passengers of high speedground transportation. Investigation of linear activesuspension systems has been mainly developed basedon optimal control theory assuming that the car modelis described by a linear or approximately linear sys-tem (Hác, 1986; Hrovat, 1993; Yoshimura and Su-gimoto, 1990). However,… 相似文献
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研究了一类离散时滞系统的变结构控制问题．在未知系统状态的条件下,首先设计了系统的状态观测器,然后基于该观测器并结合Lyapunov稳定性理论设计系统的变结构控制器．所得条件均以线性矩阵不等式形式出现,使得该结论应用十分方便． 相似文献
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针对一类含有状态时滞和扰动的非线性不确定系统,研究了一种基于状态估计的执行器故障诊断方法。在通过变换得到等价系统的基础上,构造全阶时滞观测器(TDO),削弱外扰影响,并利用神经网络设计的故障估计器在线估计出系统故障,实现多通道诊断,最后采用域值处理技术提高故障估计的鲁棒性。仿真示例表明了该方法的有效性。 相似文献
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To investigate the robust fault detection(RFD) observer design for linear uncertain systems,the H_ index and H ∞ norm are used to describe this observer design as optimization problems.Conditions for the existence of such a fault detection observer are given in terms of matrix inequalities.The solution is obtained by new iterative linear matrix inequality(ILMI) algorithms.The RFD observer design over finite frequency range in which D f does not have full column rank for a system is also considered.Numerical example demonstrates that the designed fault detection observer has high sensitivity to the fault and strong robustness to the unknown input. 相似文献