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高频群脉冲电化学微小型加工中的反向电流与压力波 总被引:4,自引:2,他引:4
针对脉冲电化学加工,建立了反向电流和压力波的数学模型,提出了高频群脉冲电化学加工方法。结果表明,充分发挥反向电流作用的电源频率在10~24kHz之间,压力波频率在400~1333Hz之间。反向电流仅与电极本身有关,它决定了高频群脉冲电化学加工的主脉冲频率;压力波则除了电极外,还与电解质性质和流速、极间间隙和电压等有关,它决定了高频群脉冲电化学加工的调制脉冲频率。根据模拟结果设计的实验表明,良好的加工质量来源于高频群脉冲带来的较小极间间隙。 相似文献
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针对小间隙电解加工过程中极间间隙不稳定导致加工效率低下甚至发生短路等问题,以窄细槽电解加工过程为研究对象,提出自适应于工件蚀除速度的电极进给分段速加工方法。建立极间电流与加工深度之间的理论关系模型,采用单因素实验法对理论模型进行修正,使其反映实际加工过程。依据电解过程中深度与电流的变化规律,建立电极进给速度实时修正方程,实现电解过程不同进给速度段的划分。采用速度线性矢量混合算法,构建速度控制方程,实现各段速间的平稳过渡,保证电极进给速度变化时极间电流的稳定。实验结果表明,分段速进给控制方法能有效避免小间隙电解过程中由于进给速度与工件蚀除速度不匹配而导致的短路现象,有效保证窄细槽电解加工效率与轮廓精度。 相似文献
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为实现加工间隙的在线检测,建立间隙流场中流体运动的计算模型,分析作用在阴极面上的压力矢量分布, 并构建坐标系进行六维力分解,通过调整加工间隙及进口流速,建立阴极上的六维力与加工间隙之间的关系方程 式,用此关系式来实时检测加工间隙。 相似文献
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功率放大器与电磁铁作为电磁轴承系统的执行环节,是影响电磁轴承系统性能及体积的关键部件。为了减小功率损耗和易于实现系统控制,提出了一种带有电流负反馈的双极型PWM开关功率放大器,驱动脉宽信号由DSP产生,占空比可在线调节。通过对线圈和功放进行具体建模,并对其基本特性进行理论分析与仿真实验;为提高系统高频动态特性,提出了低偏置电流工作方式。研究结果表明,这种功放结构和工作方式对电磁轴承结构设计和控制器设计具有重大的指导意义和参考价值。 相似文献
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Estimating the harmonic parameters is fundamental requirement for signal modelling in a power supply system. In this study, exploration and exploitation in fractional adaptive signal processing (FrASP) is carried out for identification of parameters in power signals. We design FrASP algorithms based on recently introduced variants of generalized least mean square (LMS) adaptive strategies for parameter estimation of the model. The performance of the proposed fractional adaptive schemes is evaluated for number of scenarios based on step size and noise variations. Results of the simulated system for sufficient large number of independent runs validated the reliability and effectiveness of the given methods through different performance measures in terms of mean square error, variance account for, and Nash Sutcliffe efficiency. 相似文献
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基于ARMAV模型的结构参数辨识 总被引:4,自引:0,他引:4
根据激振信号{ft}和响应信号{xt}建立二维时序模型ARMAV(n,m,2),利用时序模型参数与模态参数的对应关系对结构进行模态参数辨识,识别出所有的模态参数,并根据时序模型参数进行功率谱估计。通过对电子机柜横梁的激振实验,表明用该种方法对结构参数的识别结果与理论值很吻合,可以在工程实际中对整个电子机柜结构进行参数识别,并可以得出功率谱图。 相似文献
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现有便携式心电采集系统需要低功耗高分辨率的模拟数字转换模块,虽然基于脉冲宽度调制的模拟信息转换器(AIC)可以有效降低系统的采样速率,但是该系统量化部分的转化时钟与量化精度成正比,因此存在功耗过高的问题。依据心电信号的能量不均衡特性,提出一种基于功率熵的精度可调时间-数字转换模块(TDC)设计方法。以能量最大化作为设计准则的基本思想,通过分析ECG信号的功率谱熵,确定系统观测向量所需的最小量化精度,实现AIC时间编码系统的优化设计。测试结果表明,该设计方法能够在压缩比为4,重构信噪比为38.91 dB,重构精度为0.36%的情况下,在采样心电信号的同时减少了80%的TDC内部时钟动态翻转,从而有效降低功耗。 相似文献
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Wu Gaoyang Zhang Zhijing Zhang Weimin Tang Xinglun 《Frontiers of Mechanical Engineering in China》2007,2(3):293-296
In the process of machining ultrathin metal structure parts, the signal composition of high frequency group pulse, the influence
of frequency to reverse current, and the design of the cathode in high frequency group pulse electrochemical machining (HGPECM)
are discussed. The experiments on process were carried out. Results indicate that HGPECM can greatly improve the characteristics
of the inter-electrode gap flow field, reduce electrode passivation, and obtain high machining quality. The machining quality
is obviously improved by increasing the main pulse frequency. The dimensional accuracy reaches 30–40 μm and the roughness
attained is at 0.30–0.35 μm. High frequency group pulse electrochemical machining can be successfully used in machining micro-parts.
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Translated from Transactions of Beijing Institute of Technology, 2006, 26(7): 585–588 [译自: 北京理工大学学报] 相似文献
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振动台功率谱复现算法 总被引:1,自引:0,他引:1
传统的振动控制技术将初始辨识的系统频率响应函数贯穿使用于振动控制的过程中;针对液压振动台系统的时变特性,提出使用基于最小均方误差(least mean square,简称LMS)的自适应算法在线辨识系统的频响函数.平滑周期图功率谱估计法相对现代谱估计法分辨率较低,提出自回归(auto-regressive,简称AR)模型法对振动系统响应信号进行功率谱估计,利用尤利-沃克(Yule-Walker)方程求解AR模型参数,并给出AR模型阶次确定的方法.利用自行开发的基于DSP和ARM多处理器信号处理系统对功率谱复现进行软硬件仿真.结果表明,此方法对振动台功率谱进行复现,复现精度优于传统功率谱复现算法. 相似文献
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A Study on Electrochemical Micromachining for Fabrication of Microgrooves in an Air-Lubricated Hydrodynamic Bearing 总被引:1,自引:1,他引:1
Y.-H. Moon E.-S. Lee J.-W. Park 《The International Journal of Advanced Manufacturing Technology》2002,20(10):720-726
A specially built electrochemical micromachining/pulsed electrochemical micromachining (EMM/PECM) cell, a electrode tool filled
with non-conducting material, a electrolyte flow control system and a small and stable gap control unit, are developed to
achieve accurate dimensions for spindle recesses. Two electrolytes, aqueous sodium nitrate and aqueous sodium chloride are
applied in this study. The former electrolyte has better machinability than the latter because of its ability to change appropriately
to the transpassive state without forming pits on the surface of the workpiece. It is easier to control the machining depth
precisely by micrometer with pulse current than direct current. This paper also presents an identification method for the
machining depth by the in-process analysis of the machining current and interelectrode gap size. The interelectrode gap characteristics,
including pulse current, effective volumetric electrochemical equivalent and electrolyte conductivity variations, are analysed,
based on the model and experiments.
ID="A1"Correspondance and offprint requests to: E.-S. Lee, Department of Mechanical Engineering, Inha University, 253, Yonghyun-Dong, Nam-Gu, Incheon, 402–751, Korea. E-mail:
leees@inha.ac.kr 相似文献
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Determination of the reflector type from an image reconstructed using echo signals measured with ultrasonic antenna arrays 总被引:1,自引:0,他引:1
E. G. Bazulin 《Russian Journal of Nondestructive Testing》2014,50(3):141-149
The application of the digital image focusing (DFA) method to the determination of the types of detected reflectors is considered. For this purpose two antenna arrays (AAs) are used, which are placed on opposite sides of the reflector and using which echo signals are recorded in three acoustic channels in the double-scanning mode. The first and second acoustic channels transmit and receive echo signals using the first and second AA, respectively, and the third channel is tuned so that the first AA transmits pulses and the second AA receives echo signals. Using signals in each channel, many partial images can be reconstructed in a common coordinate system according to different acoustic schemes with allowance for both multiple reflections from irregular boundaries of a tested object and effects of transformation of the wave types. Combining partial images makes it possible to obtain a high-quality image, in which the entire boundary of the reflector is seen and using which an attempt to automate the procedure of evaluating the reflector size and determining its type was made. Such an approach allows one to reduce the subjective influence of an operator on the testing results. It is shown that in order to increase the image resolution, the spectrum of echo signals can be extrapolated by the spectrum splitting method jointly with the construction of an AR model of their spectrum. The results of model experiments that confirm the possibility of determining the reflector type are presented. 相似文献
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从理论上对5种常用自回归模型时序识别系统的判别函数分类性能进行了定性分析,同时定量地比较了它们对试验摩擦振动状态的分类概率。指出了它们各自的特点,对其分类能力进行了评价,在常用的5种判别函数中,Kullback-Leibler信息量适用的范围广,分类性能好,在状态信号特征信息不充分时,应优先选用。反之,应根据信号特征,选择相应的判别函数。本文的分析有助于为自回归模型时序识别系统选择适当的判别函数。 相似文献