自组织模糊控制能馈电子负载模拟策略

针对电子负载对响应快,控制准的测试性能需要,提出基于移相全桥隔离型拓扑的负载模拟电路,设计基于LEM传感器和LF353M的比例运算信号调理电路,并提出自组织型模糊控制的电流PI单闭环策略。对功率传递下的移相全桥电路作小信号等效电路模型并推理出输入电流与控制移相角的传递函数,并结合相位裕度稳定法设计PI校正器。最后,设计并通过自组织变论域改进模糊控制器,从而串联PI校正器进行参数智能调整。通过仿真验证和实验表明,在7 A的输入电流工况下,自组织模糊控制PI策略实现在7 ms内到达稳态,且稳态误差在3%以内,相比于常规PI与常规模糊控制,具有更良好的动态响应和稳态性能。     

单相光伏并网逆变器的两种定频滞环电流控制算法研究

传统的滞环电流控制算法具有实现简单、动态响应快、对负载参数变化不敏感、电流跟踪误差小等优点,但也存在开关频率随电流变化率变化而波动,造成网侧滤波电感设计困难、功率模块应力及开关损耗增大的不足.通过分析滞环电流控制算法的原理和开关频率波动的原因,提出了基于积分法的定频滞环电流控制算法和基于最小二乘法的定频滞环电流控制算法,无需额外模拟电路的优点,提高系统控制精度,并可以实现数字化.MATLAB仿真结果表明,这两种算法在实现滞环电流控制的同时保持定频,降低并网电流畸变率,无论电网稳定还是电网波动,都能较好地实现同步并网.     

基于弹性负载的地震模拟试验控制策略

传统地震模拟试验控制方法多将试件假定为刚性负载。针对该控制方法在实际应用中精度差的缺点,提出一种基于弹性负载的地震模拟控制策略,通过分析弹性试件力学模型,合理设置内环伺服控制参数,实现各种负载下系统传递特性的近似统一。在此基础上,优化外环振动控制辨识方法。振动台系统能在无预试验步骤情况下获得较高地震波形复现精度。试验表明：该控制策略无需预试验,在优化的伺服控制参数下,能在首帧地震模拟试验中获得85%以上的输入输出信号时域相关系数;经数帧试验,通过对系统驱动信号进行更新,地震模拟输入输出信号时域相关系数能稳定在90%以上。     

多间隙耦合腔注波互作用计算分析

根据空间电荷波理论,利用微波等效传输线的概念,建立了多间隙耦合腔中注波互作用的小信号计算模型。同时,还基于电子圆盘模型,建立了相应的一维大信号计算模型。依据模型编写了计算机程序进行了计算模拟,结果显示,小信号模型能较好地反映整管的增益频率特性。一维大信号模型能合理地模拟注波互作用的基本物理过程。另外利用电路反馈的理论,分析了多间隙耦合腔的稳定性,并利用奈奎斯特稳定判据给出了耦合腔稳定条件。     

外加电流阴极保护技术对海港工程钢筋混凝土结构的防护

为检验外加电流阴极保护技术在海港工程中的保护效果,设计了循环水系统和混凝土试块模型,以模拟钢筋混凝土海洋腐蚀状态,采用外加电流阴极保护技术对模型进行持续阴极保护。结果表明：设计的试验环境与实际工程环境相符;外加电流阴极保护技术可有效抑制钢筋腐蚀,且可对被保护结构实现长期、稳定的保护。     

基于有限集模型预测控制BPMSMS输出性能研究

针对无轴承电机支撑的永磁同步电主轴运行时的电流响应不灵敏、转矩脉动和转子振动等问题,提出基于有限集模型预测控制算法的BPMSMS控制策略。在完整的BPMSMS电压模型基础上,考虑转矩电流和转子位移的影响,进一步推导悬浮绕组模型预测电流方程,建立完整的无轴承永磁同步电主轴模型预测控制下的电流数学模型。根据使用的代价函数分别求出转矩控制和悬浮力控制的最优开关状态量,使得实际电流与参考电流误差更小,以此获得更好的转矩控制效果和转子振动抑制效果。仿真实验结果表明：在有限集模型预测控制下,BPMSMS具有更好的电流跟踪效果,转矩脉动小;在外加负载和干扰力时也能实现转子的稳定悬浮,系统鲁棒性较好。     

电寿命试验固态负载及其控制策略设计

针对低压电器电寿命试验装置中传统模拟负载的不足,该文设计一种交流固态负载并对其电流控制策略进行研究。首先根据电寿命试验要求,对交流固态负载的关键环节电流发生单元进行拓扑结构设计,并阐述其工作原理;其次,结合试验电流的生成要求,提出基于二阶广义积分锁相环(SOGI-PLL)与改进无差拍的控制策略;在此基础上进行仿真及样机验证。结果表明所设计的交流固态负载具备进行电寿命试验所需的电流模拟功能,相比于其他控制方法,所提控制策略生成的试验电流的性能指标更佳,且结合触点状态检测实现电流发生单元的实时启停,保证负载设计的独立性。     

负载电流法在基于振动信号分析法监测变压器铁心状况中的应用分析

振动法能够有效的诊断变压器运行中潜伏的故障。由于振动法在检测出故障的同时还能够检测铁心的状况,为其进行充分的研究开辟了门路。文中提到了一种负载电流法,在不空载运行变压器的情况下,能够取得变压器铁心振动信号基频成分。通过模拟变压器实际运行的情况,观察不同空载和负载电流情况下变压器本体的震动加速信号,分析拟合的负载电流与振动加速信号基频成分的关系曲线。实验得出,负载电流为零时变压器振动信号基频成分的幅值与空载情况时变压器振动信号基频成分差异不大。由此可以看出,振动分析方法用于提取变压器铁心振动信号的基频成分是可行的。最后,对铁心故障采用负载电流法监测,发现该方法不失为初步判定铁心状况的有效方法。     

电力电缆电力传送实验平台测试系统设计

为研究高效安全传送绿色电力的方法,设计电力传送实验平台测试系统。该系统以S3C2440A微处理器为核心构建嵌入式测试电路,该电路通过MIK-DZU-400 V电压变送器、HD-T101-300A电流变送器、MIK-ST500温度变送器等集成模块实现电力电压、电流及电缆温度的感知与调理。基于Linux操作系统,在Qtopia2.2.0集成开发环境中设计嵌入式测试软件,该测试软件主要包括电力电压、电流及电缆温度信号的采集与保存模块,电力电缆热特征参数分析模块、通信模块、电力电缆寿命疲劳分析模块接口、电缆动态增容传输分析功能接口、电力传送控制模块接口。在上位机PC中利用Visual C++6.0 MFC模块开发上位机分析处理软件。实验表明:测试系统能够感知电缆温度、电力电压和电流,能够基于电缆热路模型分析电力电缆热特征参数,能够通过接口开放地添加电力电缆寿命、疲劳分析、电力传送动态控制等新方法。     

基于Stacking融合模型的PHEV复合储能系统实时能量分配策略

为了解决插电式混合动力汽车单一电池低比功率、无法响应暂态功率需求的问题,设计了电池和超级电容并联式复合储能系统。同时针对采用动态规划法优化负载电流分配时缺乏实时性的问题,利用不同驱动工况下动态规划优化的结果构成训练集进行训练,并综合GRU网络以及XGBoost算法,提出了一种Stacking集成学习框架下多模型融合的能量分配策略。仿真结果表明,与仅使用单一电池的储能系统相比,基于Stacking融合模型的实时能量分配系统在UDDS和US06两种循环工况下,电池峰值电流分别降低了48.7%和50.8%,有效削弱了电池的峰值电流,提升了电池的整体性能。     

Press load monitor

The article describes the design and use of an instrument which displays the peak frame load during a single operating stroke of a press. It consists of a strain gauge link permanently bolted to the frame of each press to which a portable electronic unit is connected. The technique of using a strain gauge link eliminates the problems encountered when a load cell is used, or when a strain gauge system is bonded directly to the machine frame.     

Embedded beam under equivalent load induced from a surface moving load

Summary The paper is concerned with a specific problem in the study of an infinite beam embedded in a two-parameter elastic foundation (Vlazov-layer) under the equivalent load induced from a surface load moving normal to its length. Expressions for the deflection, flexural moment, and shear in the infinite beam are presented in an integral form. Numerical results are given for the deflection and flexural moment induced in the embedded beam due to the action of the moving load.With 5 Figures     

Random load sequences and stochastic crack growth based on measured load data

This paper addresses the modeling of random fatigue load sequences based on real measured loads, which represents a key step in stochastic damage tolerance. Discrete-time Markov chains and hidden Markov chains are investigated to model sequences of max–min stresses. The parameters of these models are inferred from in-flight measured loads of a given fleet of fighter aircrafts. The accuracy of the two models is assessed based on the statistical properties of a parameter representative of the crack growth under variable amplitude loads, which accounts for load interactions and retardation/acceleration effects. This parameter obtained with the PREFFAS crack closure model represents the maximum stress of a constant amplitude load sequence supposedly equivalent in terms of crack extension to the variable amplitude sequence. The statistical properties of this parameter corresponding to variable amplitude load sequences generated with these models are compared to those of sequences randomly sampled from the measured loads. The Hidden Markov Model appears to be the most appropriate and accurate model. It is then used in a stochastic analysis of a crack initiating at a hole of a skin-stringer panel in a fighter aircraft. This illustrative example explores the effects of the scatter in both loads and material properties (here through the crack growth rate) on the stochastic crack growth.     

Influence of load biaxiality on the fracture load of center cracked sheets

Analysis of the problem of a plane infinite elastic body with a centrally located crack subject to uniform biaxial load along the remote outer boundaries, indicates that loads applied parallel to the crack influence the value of the critical (fracture) tensile load applied perpendicular to it, with the Poisson ratio of the material determining the characteristics of this influence. Experimental information from specially designed biaxial test programs, obtained by the authors and also from the published data of other investigators, shows that, while tensile loads parallel to the crack raise the critical value of perpendicular load for an aluminum alloy, they have a reverse effect on the critical load for plexiglass (polymethylmethacrylate or PMMA), in qualitative agreement with the predictions of the analysis.

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Résumé On analyse le problème d'un corps élastique plan infini comportant une fissure centrale soumise à une contrainte biaxiale le long de ses bords éloignés. L'analyse montre que les charges appliquées parallèlement à la fissure influencent la valeur de la contrainte critique de rupture en traction appliquée perpendiculairement à elle, les caractéristiques de cette influence étant régies par le rapport de Poisson du matériau. Des informations expérimentales venant de programme d'essais en condition biaxiale spécialement conçu et recueillies par les auteurs et par la littérature publiée par d'autres chercheurs montrent que tandis que les contraintes de traction parallèles à la fissure accroissent la valeur critique de la charge perpendiculaire dans le cas d'un alliage aluminium, elles ont un effet inverse sur la charge critique dans le cas du plexiglas (polyméthyleméthacrylate ou PMMA), ceci étant en accord qualitatif avec les prédictions de l'analyse.

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No menclature 2 crack length - (x, y), (r, ), (, ) rectangular, polar, elliptic coordinates, respectively - z x +iy, complex variable - t _jk ,e _jk components of the stress and strain tensors, respectively - T _k ,u _k ,b _k components of the surface traction, displacement and body force vectors, respectively - t _xx ,t _xy ,t _yy rectangular stress components - t ,t ,t elliptic stress components - u _x ,u _y ;u ,u rectangular and elliptic displacement components, respectively - U elastic strain energy per unit thickness - W work of forces applied to the body per unit thickness - P, V potential energies per unit thickness - surface energy per unit thickness - R bound region of thex-y plane - C ₁,C ₂ closed boundary curves ofR - , , , sectionally holomorphic functions of the complex variablez - E Young's modulus - k applied load biaxiality ratio,t _xx ()/t _yy () - stress applied to the outer boundary surface - µ elastic shear modulus - Poisson's ratio - surface energy density per unit area - (3-)/(1+) for plane stress, (3-4) for plane strain     

基于形函数方法快速识别结构动态荷载的试验验证

在动态荷载识别中常常由于矩阵的病态性影响识别的精度,利用有限元理论中的形函数逼近荷载曲线,将识别离散的荷载历程转化为计算有限的形函数权重,从而显著改善反卷积法识别荷载中存在的采样时间长或采样频率高时数值求解困难的问题;并能改善反问题的病态性,提高对噪音的鲁棒性。一个连续梁的数值算例比较验证了该方法在5%的高斯噪声影响下能精确地识别未知荷载。悬臂梁试验中,通过实测的结构动态响应,在移动时间窗内利用荷载形函数方法可以实现激励的在线识别。     

Behaviour of structural fibre composite sandwich panels under point load and uniformly distributed load

An innovative fibre composite sandwich panel made of glass fibre reinforced polymer skins and a modified phenolic core material was developed for building and other structural applications. The behaviour of this new generation sandwich panel was studied with reference to the main fibre orientation in floor applications, so that the effect due to erroneous installation could be evaluated. The two- and four-edge supported sandwich panels with different fibre orientations and fixity systems between panel and joist were tested under point load and uniformly distributed load (UDL) to determine their strength and failure mechanisms. The results of this experimental investigation show that the panels behave similarly under both loading conditions. Moreover, the fixity does not have a major effect on its failure mode and deflection.