机械制造专业毕业设计英文翻译.doc

机械制造专业毕业设计英文翻译

36
2020年4月19日
文档仅供参考

英文翻译
Chapter 4 portable rotating machinery vibration monitoring system design
With the modernization of enterprise device management, how to make equipment, continuous, reliable, safe and efficient operation to meet the requirements of modern enterprise management, is particularly important. The rotating mechanical equipment during operation of the vibration signals generated a lot of hidden information that can help people to correctly judge the various types of rotating machinery during operation of the state. Theory of vibration analysis and condition monitoring technology is inseparable organisms. Based on vibration analysis of rotating machinery condition monitoring system is to run the process of rotating machinery vibration information generated by the core to determine rotating machinery is running or the anomaly occurred.
4.1 The system works
The system works: The acquisition rotating machinery vibration sensor equipment running in the process of the vibration signals, after filtering hardware circuit amplification, A / D conversion, and then upload the data through the USB interface to a computer for processing; host computer can be the data collector sample rate, channel selection and so the corresponding parameter settings; through the application of the software for signal analysis and processing and analysis of paint-related waveforms; and then, through the relevant waveform analysis and spectrum analysis to determine the health status of machinery and equipment.
4.2 System Structure Diagram
Design concept of this system is the top-down design, the first device to achieve the overall planning function, and then divide the total work function to the hardware and software sub-modules to realize the system overall design block diagram shown in Figure 1.
4.3 Vibration speed sensor selection
Vibration sensor (Sensor) is a collection can be generated by rotating machinery vibration signals, according to a certain law of vibration signals are converted to their corresponding physical quantity or signal and another output device, is to achieve large-scale rotating machinery condition monitoring of an important link If there is no vibration sensor to the original vibration signals accurately capture and conversion, rotating machinery condition monitoring can not be achieved.
By collecting vibration signal of a different nature can be classified as follows: acceleration, velocity, displacement and so on. Vibration sensor selection must take into account sensor performance requirements; sensor static and dynamic characteristics. Vibration sensor static characteristics of the main parameters are: linearity, resolution and sensitivity. The dynamic characteristics of vibration sensors used it to respond to certain criteria to represent the input signal. As the rotating machinery vibration signals output sinusoidal signal, so the dynamic characteristics of sensors used to indicate the frequency response. Rotating machinery vibration test commonly used types of sensors are piezoelectric sensors and inertial rate sensors.
Piezoelectric sensors used for non-rotating components of the acceleration measurement. It is characterized by the use of a wide frequency range, usually 0.2 ~ 10k Hz, therefore, it is suitable for high-speed rotating machinery vibration tests. The quality of piezoelectric acceleration sensor is small, easy to install in mechanical equipment. However, piezoelectric sensors are high impedance, weak signal sensor, measuring the site vulnerable to electromagnetic, acoustic and thermal air currents and other interference, so that the output signal contains the part of non-vibration acceleration measurement points from a false signal.
Inertial speed sensor is a contact-type vibration sensor, it is absolutely vibration velocity of the detected objects into moving parts moving relative to the absolute speed of the shell, and then through an internal transformation to the relative vibration velocity transform parts of the electromotive force, namely, by measuring the electromotive force to calculate the speed of rotating machinery vibration. Inertial speed sensor that has high sensitivity and low output impedance, but also the output power of a strong signal, so it is not susceptible to electromagnetic interference afternoon, for more complex and requires a long lead on-site, still higher signal to noise ratio. The sensor's frequency range between 0.008 ~ 1KHz, no special pre-amplifier, install easy to use.
The system uses the VS Series Vibration velocity sensor shown in Figure 4-2, which measured bearing, chassis or structure of the vibration intensity and vibration intensity. Such sensors measure the vibration is relative to the absolute vibration of free space; its output voltage is proportional to the speed and vibration, so called velocity type vibration sensors. Can also convert the speed of traffic through the displacement of points re-display processing? This measurement can rotation or reciprocating body to conduct a comprehensive evaluation of working conditions, which directly installed on the machine outside, so maintenance is very convenient to use.

How It Works: VS Series Vibration Monitoring speed sensor is the use of magnetic induction principle to vibration signals converted into electrical signals. It is mainly from the magnetic circuit system, inertial mass, spring damping components. The sensor rigid shell secured to a magnet, inertial mass (coil component), with spring suspension components on the housing. Work, the sensor installed on the machine, the machine vibration when the working frequency range of the sensor, the coil and magnet relative movement, cutting magnetic field lines, on-line circle produces induced voltage, the voltage is proportional to the value of vibration velocity. Then match with the secondary instrument, which shows that the amount of vibration velocity or displacement size.
①sensitivity values are 80Hz, the speed of 18mm / s case determination of
② Amplitude linearity: "3%; transverse sensitivity ratio:" 5%
③ Direction: (provides for horizontal direction 0 °)
Vertical: 90 ° ± 10 °
Horizontal: 0 ° ± 10 °
④ Output Resistance: ≤ 450; Insulation resistance :> 20M
4.4 Hardware Design Module
4.4.1 Analog signal conditioning circuit
JP1 then collected the raw vibration sensors capture signal amplification through the filter into the analog circuit A / D chip for A / D conversion, in order to host computer for data processing.

1. Signal filtering
Vibration sensor will be a non-power rotating machinery vibration signals into electrical signals, but the vibration signals superimposed on the scene useless noise, these noise and vibration signals generated at the same time, some are mixed with the process of vibration signal transmission, the noise sometimes will be greater than the useful signal, thereby inundating useful signal. If you do not eliminate them, will be right behind the signal processing analysis to bring the error, and even sometimes lead to wrong conclusions, so the collected signal is filtered.
Generally divided into low-pass filters, high pass, band pass and band stop filter, its frequency response characteristics as shown in Figure 4-2.
Low-pass filter is the low-frequency signals while the high-frequency signals are not passed through the filter. High-pass filter and low-pass filter performance is just the opposite, namely, high-frequency signals through the low-frequency signal is not passed; band-pass filter is the frequency in a range of the signal through, while outside the scope of this Could not get it; band-stop performance and band-pass filter is the opposite, that is, within the scope of a certain frequency band signal is blocked, in which the signal outside the pass band. .

Field Dynamic collected vibration signals are often mixed with a lot of useless noise, for noise, its frequency is difficult to quantify given the size of the value of design as long as the filter when considering high-frequency interference signal suppression. According to Nyquist's Law, data collection devices for data acquisition frequency must be greater than twice the highest frequency vibration signal, the signal can not occur until the frequency aliasing phenomenon, the need to design a low-pass filter for vibration signal through, filter out some high-frequency interference . The simplest low-pass filter formed by capacitors and resistors, shown in Figure, A simple RC low-pass circuit, the general call it passive low-pass filter.
The low-pass filter

Figure 4-3 shows the RC low-pass filter circuit, the voltage loop equation:
Its gain

The availability of the actual gain of

Gain value is a function of frequency in the low frequency area Minimal, Signal pass; high frequency area Great, Signal unreasonable。 Unreasonable when they pass with the clinical point of time the frequency is defined as the cut-off frequency:
2．Signal amplification
In the rotating machinery vibration signals measurement, the sensor's output signal is very weak, generally can not be directly used to display, record, or conversion, the need for amplification, pairs of rotating machinery vibration signals measurement system uses the following characteristics of the amplifier requires :
①Frequency bandwidth, and can enlarge DC signal;
②High precision, good linearity;
③High input impedance, low output impedance
④Low drift, low noise;
⑤Powerful anti-common-mode interference。
IC op amp is composed of high-gain analog electronic devices, due to low prices, combined flexible and widely used. Analog signals can be proportional, integral, differential, and addition and subtraction and other operations. Figure 4-4 shows, LM324AD for Operational Amplifier chips, with the R22, and C4 composition amplifier circuit, the circuit set the capacitor C4 is the role of negative feedback: RFCF is not large, low-frequency signals will be fiction, virtually played the role of high-pass filter, which with the previous RC low-pass filter needed to band together fiction outside the high-frequency noise signal and low-frequency shaking signals at the same time by adjusting the value of C4,
Get a different gain.
In addition, R6, R15, R10, R22 four resistors form by the bipolar input op amp to convert a univocal input, in order to meet the requirements of AD-chip unspooled input, input range can be +5 V ~ 5V. To adapt to most of the voltage sensor output characteristics. VM intervention 2.5V voltage source, R93 access CH1 current source, can be adapted to current sensor, R85 and R14 for the protection of resistance.

4.4.2 Unit Design and Implementation of ADC
1．Select analog-digital conversion of basic technical indicators
(1)Conversion time and the maximum sampling frequency of
Sampling frequency chosen is too high will increase the amount of data and lead to follow-up analysis and processing workload increased dramatically. According to sampling theorem, the sampling frequency as long as the signal processing is greater than twice the highest frequency, we can not lose the information contained in the original signal. In practical work, generally selected, so that can determine the sampling interval, the analog-digital conversion modules, must be completed within the sampling interval T conversion. Therefore, conversion time and the maximum sampling frequency of these two indicators is very important.
(2)Conversion bit
Select the number of bits in the ADC, it is necessary according to its measurement range and accuracy required to determine the median conversion. The practical application of some of ADC, its end figures are not reliable, need to give up, so that measurement accuracy is reduced by half, this should be the choice when the ADC to be fully considered. Also, be sure to enable measurement of the signal through the op-amp circuit, its voltage amplitude at the ADC within the scope of work.
(3)Sample Channel
ADC sampling channel is also able to input analog signals into large ones. In selecting analog-digital conversion
Device, we should take this into account, that is, parallel input channels simultaneously, or the order of the serial input.
2．ADC cell design
(1)ADC chip select
Based on the above choice of analog-digital conversion of basic technical indicators, data acquisition system used as the ADS8361 chip ADC module, ADS8361 is the production of It’s ADS8361 is a dual-channel, four-way, analog differential input, 16-bit A / D conversion precision device; it to be divided into two four-channel differential inputs are connected to a stand-alone converter, and can complete pairs of signals collected at the same time, the maximum conversion rate of up to 500kHz, which 2μs completing a second A / D sampling, sampling after the data from the serial access on the output. It operates in the 50kHz frequency has a strong anti-interference ability,
Particularly suitable for high sampling rate data acquisition requirements of occasions, ADS8361 using SSOP-24 package. In addition, ADS8361 also provides high-speed dual serial interface can be effective in reducing software overhead, and power consumption is very low, only 150mW.
Shown in Figure 4-5, the chip ADS8361 has two internal sample-hold devices. Allowed to enter the four-channel differential signal with a 2.5V internal reference voltage output (pin directly to the output +2.5 v), the input signal range is (if using the internal reference voltage, then the input signal range of-2.5v ~ +2.5 v) 4 analog input .
The photo shows the pin diagram ,4-6 in which the chip-select signal, BGND digital manner, CLOCK is the clock input, CONVST pin is the A / D conversion pulse input pin, Ml, M0, A0 pin used to select sampling channel and data channels; RD pin to read the data pins.

The photo shows the pin diagram ,4-6 in which the chip-select signal, BGND digital manner, CLOCK is the clock input, CONVST pin is the A / D conversion pulse input pin, Ml, M0, A0 pin used to select sampling channel and data channels; RD pin to read the data pins.
Acquisition circuit works: VA + is positive that the output number, VA-inverting signal output terminal for the REF for the reference voltage input, CD4053 access multiplexer switch; ADS8361 The CS pin is the chip select terminal, Ml,
M0, A0 pin used to select the sample channel and data channel; RD pin to read the data pins, CONVST pin is the A / D conversion pulse, in use with the CONVST pin RD should be connected, CLOCK pin with the input sampling clock, DATAA, DATAB is the serial data output; the other seven Lu acquisition signal [(VB +, VB-), (VC +, VC-), (VD +, VD-), (VE +, VE-), (VF +, VF-), (VG +, VG-), (VH +, VH-)] the collection of the same principle with the first channel to achieve 8-channel vibration signals A / D converter;