频率计

The effect of tribology factors on bearing vibration is studied experimentally. AR model and WPT are used to processing the normal arid abnormal signals. The results are as follows:1. The vibration of ball bearings is caused by the tribology action of contact pairs of ball and ring races and has the essential of tribo-dynamics. Any factors affecting the tribology characteristics of contact pairs will affect vibration and noise of bearings consequently.2. Vibration characteristics of bearing keep almostly unchanged with the increasing of axial load expecting the increasing of nature frequencies. When radial load increasing with axial load unchanged, nature frequencies keep unchanged but some new vibration peaks appears in the spectrum.3. Vibration amplitudes are damped and nature frequency are enhanced with sufficient lubrication. Vibration and noise of bearings increase obviously and roar can happen and the contact surfaces scratch slightly under insufficient and unclean lubrication state. Bearing will be disabled in a few minutes without any lubrication.4. Bearing vibration is unstable under low speed. With the speed increasing, the vibration become stable and natural frequencies increase slightly but the amplitudes increase apparently.5. Bearing vibration can be excited only by some harmonics ofwaviness without lubrication and by all harmonics with lubrication based on the theoretical analysis.6. The nature frequencies of ball bearings decrease with the increasing sizes. When international clearance increasing, nature frequencies decrease in radial and increase in axial and angular and the amplitudes increase in radial and decrease in axial and angular. When the number of balls increasing, nature frequencies increase and amplitudes decrease. When the pitch diameter increasing, axial nature frequency increase and others nearly keep no change. When outer race groove curvature radius increasing, nature frequencies increase in radial and decrease in axial and angular and amplitudes keep no change in radial and increase in axial and angular. When inner race groove curvature radius increasing, nature frequencies decrease and amplitudes increase.7. The distortion in amplitude and frequency components of bearing vibration signals picked up by the present probe measurement method is founded and right conclusions cannot be achieved by the signals. When accelerometer is rigidly screwed with steel stud onto a flat outer surface of a ball bearing, vibration signal can be got without distortion and the reliability of research on bearing vibration is assured.8. AR model is suitable for large samples of bearing vibration signals, square root of length of samples can be used as the upper limitation of order determination and the FPE order selection criterion is effective. Many advantages of AR spectrum are founded over the classical based on FFT.9. Time-Frequency analysis is necessary for abnormal noise of ball bearings. WPT overcomes the principle shortcomings of STFT and proved to be a best tool to process the abnormal signals.

理论分析和试验研究表明： 1球轴承振动是钢球—滚道接触副中的各种摩擦学作用引起的，具有摩擦动力学的本质，任何对接触副的摩擦学特性有影响的因素都将对球轴承的振动和噪声特性产生影响； 2中心轴向载荷作用下，载荷增大使球轴承的固有振动频率升高，载荷越大同样的载荷增幅引起的频率升幅减小，足够大的中心轴向载荷作用下载荷的变化对球轴承振动的频率特性不会产生明显的影响； 3轴向和径向联合载荷作用下，径向载荷不大时球轴承振动的固有频率基本不变，但是可能引起变刚度激励的非线性振动，出现新的频峰，过大的径向载荷将使部分钢球脱离接触，使球轴承的振动和噪声呈现不稳定状态； 4润滑对球轴承的振动和噪声特性有重要的影响，良好的润滑对振动有明显的抑制作用，润滑不充分时，振动和噪声的水平会有明显增高，一定条件下还会激发接触副中的谐振，发出啸声，造成接触表面的伤害，无润滑干接触时，短时的运转就会损伤接触副表面，使振动和噪声迅速增大，并随时可能引发严重的磨损和卡滞失效；接触副润滑良好时，油膜的"刚化效应"使球轴承振动的固有频率有所提高，润滑剂中含有弥散性污浊时，振动的幅度总体升高，但弥散性污浊不会改变球轴承振动的频率特性；浙江大学博士学位论文：球轴承振动的研究 5低速时，球轴承振动的基本特征呈现不稳定状态，随着转速的提高，球轴承振动的频率特性趋于稳定，固有频率频峰升高； 6理论分析表明，干接触时钢球和滚道表面波纹度的某些谐波分量能激励球轴承的振动，振动的幅值与谐波幅值成正比，实际球轴承中钢球的分布不可能完全均匀，波纹度的激励作用会随时发生；润滑接触的分析表明，波纹度的任意谐波分量均能激励球轴承的振动； 7球轴承的几何和结构参数分析表明，球轴承尺寸越大，径向、轴向和角振动的固有频率越低；钢球中心圆直径增大，球轴承的径向和轴向振动的固有频率基本不变，角振动的固有频率有所上升，振动的幅频特性基本不变；径向游隙加大使球轴承的径向振动固有频率降低，轴向和角振动的固有频率有所升高，径向振动幅频特性的幅值升高，而轴向和角向降低；钢球的数量增多使球轴承振动的固有频率上升，幅频特性的幅值下降，径向振动的幅值下降最为明显；外圈沟曲率半径系数增大使球轴承径向振动的固有频率升高，轴向和角振动的固有频率降低，径向幅频特性基本不变，轴向和角向幅频特性幅值升高；内圈沟曲率半径系数增大使径向、轴向和角振动固有频率均下降，振动幅频特性的幅值均有升高； 8试验对比表明，传感器采用探针式安装时，由于探针接触副接触特性的影响，钡(量得到的球轴承振动信号有失真，采用专门设计和制作的试验球轴承，以固定式安装加速度计，首次测量得到了球轴承振动的真实信号，通过对振动信号的分析，验证了球轴承振动的理论模型； 9)基于时间序列分析的AR模型适用于大样本球轴承振动信号的分析，以样本长度的均方根值作定阶上界，FPE做判阶准则，给出的AR谱光滑，频率分辨率高，是球轴承振动分析的简便而可靠的手段； 10以时频域分析的小波包变换分析球轴承异音信号能够比较好地定位和聚焦异音发生的时间，时间间隔，频率范围，同样是球轴承振动分析的可靠的手段，可用作球轴承故障诊断技术。

The measurement of seismometer transfer function is implemented mainly in the low-frequency part, and transfer function in the high-frequency part is obtained with analysis and calculation.

本文对宽频带地震计的频率特性测试是在地震计的低频段进行，对于地震计高频段的频率特性采用理论分析计算获得。

FPGA-based realization of the digital frequency meter, text in all the source code, for reference purposes only.

详细说明：基于FPGA数字频率计的实现，文中有所有的源代码，仅供参考。

It is uses the modular unit to construct the system, carries on the digital frequency meter design and the development new method.

它是采用模块化单元构建系统，进行数字频率计设计与开发的新方法。

The frequency- meter also has a simple structure, low cost, high accuracy and simple operation,reduce the cost of the product and facilitate the design and development of new product and so on.

该频率计具有结构简单、价格低、精度高、操作简单、并且降低产品的成本，有利于新产品的设计与研制、等特点。

Constitute a digital frequency meter for each module are given in more detail the design of methods and procedures for a complete design and simulation results.

对构成数字频率计的每一个模块，给出了较详细的设计方法和完整的程序设计以及仿真结果。

This article mainly describes the design of digital frequency method and the steps that the frequency meter from the main amplifier.

本文主要介绍设计数字频率计的方法和步骤。

Mz and other precision frequency meter.

Mz等精度频率计。

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主要经营项目有：1、锂电池保护板、动力类（电动工具、电动车、航模）类锂电池保护板；2、开关电源、适配器、充电器；3、大功率音响、功放、通讯电源、逆变电源；4、太阳能电池方案、充电器方案、便携电源；5、特种电源/智能电源以及电源管理系统；6、LED驱动，各种高频电子电路的设计，更新解难/电路设计等；公司拥有艾德克斯8514C电子负载、泰克TDS2014B四通道示波器、泰克电流探头、功率仪/高压测试仪、频谱分析议、频率计、信号发生器、高低温环境控制室等先进设备和一批专业素质高、干劲十足的科研技术、设计人才；有能力做到全方位、一体化的完美服务。

The introduction of some products are as follows: First, Taiwan's electronic devices Aosta Product:(self-produced self-marketing) program-controlled voltage insulation tester, grounding resistance, leakage current, micro-resistance tester, electrical parameters of the test Transformer parameters meter, insulation resistance tester, electronic load, on-machine, cable tester, variable frequency power supply, LCR Bridge, frequency meter, mV table, the standard signal generator, oscilloscope, signal generator, signal generator, digital multimeter, distortion device, before shaking device, spectrum analyzer, capacitance meter, inductance meter, modulation device, Sweep Signal Generator, Telephone Analyzer, Calibrator Table III, EMC Electric Tester, regulated power supply and so on.

现将部分产品介绍如下：程控耐压绝缘测试仪、接地电阻、泄漏电流、微电阻测试仪、电参数测试变压器参数测量仪、绝缘电阻测试仪、电子负载、导通机、排线测试仪、变频电源、LCR电桥、频率计、毫伏表、标准信号源、示波器、信号发生器、信号源、数字万用表、失真仪、抖摆仪、频谱分析仪、电容测量仪、电感测量仪、调制度仪、扫频信号发生器、电话分析仪、三用表校准仪、EMC电测仪、稳压电源等。

He and Nina moved to California and lived at 2005 Ivar Street, Apt.

他和Nina搬到加州，并在2005年伊瓦尔街，公寓生活。

Droperidol （ potently inhibits transfected HERGchannels and this is the probable mechanism for QT prolongation.

氟哌利多有效地抑制了转染的 HERG 钾通道，可能是 QT 间期延长的机制。