CN113029258A - Vortex street flow meter digital signal processing system based on vortex street amplitude-frequency characteristic anti-interference - Google Patents
Vortex street flow meter digital signal processing system based on vortex street amplitude-frequency characteristic anti-interference Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
- G01F1/05—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects
- G01F1/20—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects by detection of dynamic effects of the flow
- G01F1/32—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects by detection of dynamic effects of the flow using swirl flowmeters
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Abstract
The invention relates to a vortex street flowmeter, in particular to an anti-interference digital signal processing system of the vortex street flowmeter based on the amplitude-frequency characteristic of the vortex street. The measuring range ratio of the vortex shedding flowmeter is increased, and the pulse leakage phenomenon in high and low flow velocity stages is avoided. The piezoelectric sensor comprises a main control unit and a piezoelectric sensor; the piezoelectric sensor is connected with the input end of the program-controlled charge amplifier, the output end of the program-controlled charge amplifier is connected with the input end of the program-controlled narrow-band filter, the output end of the program-controlled narrow-band filter is connected with the input end of the program-controlled amplifier a, the output end of the program-controlled amplifier a is connected with the input end of the program-controlled amplifier b, the output end of the program-controlled amplifier b is connected with the program-controlled trigger, and the program-controlled trigger is respectively connected with the main control unit and.
Description
Technical Field
The invention relates to a vortex street flowmeter, in particular to an anti-interference digital signal processing system of the vortex street flowmeter based on the amplitude-frequency characteristic of the vortex street.
Background
The vortex street flowmeter is a flow meter designed based on the Karman vortex street principle. The frequency of the vortex is in direct proportion to the flow speed of the fluid within a certain Reynolds number range. Accordingly, by detecting the vortex frequency and knowing the cross-sectional area of the pipe, the volumetric flow rate of the fluid can be determined.
The existing vortex shedding flowmeter has the problems of low lower limit measuring capability, poor linearity, poor anti-electromagnetic and vibration interference capability, pulse output 'pulse leakage' and the like. Compared with the traditional amplifying, filtering, shaping and pulse output, the FFT is adopted to improve the measurement performance of the vortex street when the signal-to-noise ratio is larger. But when the signal-to-noise ratio is <1, an FFT will yield an erroneous measurement.
Therefore, how to identify effective signals of the vortex street is very important, and a high-quality vortex street signal processing system is urgently needed.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides an anti-interference vortex street flowmeter digital signal processing system based on the vortex street amplitude-frequency characteristic. The technical scheme includes that the piezoelectric sensor comprises a main control unit and a piezoelectric sensor; the piezoelectric sensor is connected with the input end of a program-controlled charge amplifier, the output end of the program-controlled charge amplifier is connected with the input end of a program-controlled narrow-band filter, the output end of the program-controlled narrow-band filter is connected with the input end of a program-controlled amplifier a, the output end of the program-controlled amplifier a is connected with the input end of a program-controlled amplifier b, the output end of the program-controlled amplifier b is connected with a program-controlled trigger, and the program-controlled trigger is respectively connected with a main control unit and a pulse control output;
purifying the identified effective vortex street signal by a program-controlled narrow-band filter, and setting a threshold value of a program-controlled trigger according to the real-time amplitude variation range of the purified vortex street signal to effectively convert the vortex street signal into pulses; the effective extraction of the vortex street signal is realized.
Furthermore, the output end of the program-controlled charge amplifier is also connected with the input end of a program-controlled high-pass filter, the output end of the program-controlled high-pass filter is connected with the input end of a program-controlled low-pass filter, the output end of the program-controlled low-pass filter is connected with the input ends of the two stages of program-controlled amplifiers, and the output ends of the two stages of program-controlled amplifiers are connected with the main control unit.
Furthermore, the main control unit is respectively connected with the human-computer interface unit and the WDT watchdog circuit, the human-computer interface unit comprises an LCM display screen, keys, a word stock and a memory, the support for the Chinese and English menus can be realized through the word stock, and the memory is used for accessing parameters.
Further, the main control unit is connected with a power management circuit for switching the battery and the external power supply.
Further, the main control unit is connected with the output interface circuit.
Furthermore, the main control unit adopts an ARM CORTEX M4F kernel MCU to amplify, filter, sample and digitally process the signals output by the piezoelectric sensor, and identifies the vortex street signals through amplitude-frequency characteristics; and purifying the vortex street signal by a program-controlled hardware narrow-band tracking filter, and converting the threshold self-adaptive trigger into a pulse signal for outputting and measuring.
Furthermore, the main control unit is connected with a temperature sensor and a pressure sensor, and the temperature sensor and the pressure sensor are connected with the main control unit through a 16-bit ADC module.
Compared with the prior art, the invention has the beneficial effects.
The invention provides an anti-interference digital signal processing system of a vortex street flowmeter based on vortex street amplitude-frequency characteristics, wherein an identified vortex street effective signal is purified by a hardware program-controlled narrow-band tracking filter. The amplitude of the vortex street signal is greatly fluctuated, and the threshold value of the hardware program control threshold value self-adaptive trigger is set according to the real-time amplitude variation range of the purified vortex street signal, so that the vortex street signal is effectively converted into pulses; the effective extraction of vortex street signal has been realized, the effect of anti-interference such as electromagnetism, vibration is reached. The measuring range ratio of the vortex shedding flowmeter is increased, and the phenomenon of pulse leakage in high and low flow velocity stages is solved.
Drawings
The invention is further described with reference to the following figures and detailed description. The scope of the invention is not limited to the following expressions.
Fig. 1 is a block diagram of the signal processing of the present invention.
Fig. 2 is a schematic diagram of the signal processing flow of the present invention.
FIG. 3 is a circuit diagram of the flow measurement circuit of the present invention.
Fig. 3a-3d are enlarged views of a portion of fig. 3.
FIG. 4 is a circuit diagram of a temperature measuring circuit and a pressure measuring circuit according to the present invention.
Fig. 4a-4c are enlarged views of a portion of fig. 4.
FIG. 5 is a circuit diagram of the MCU, human interface, WDT circuit of the present invention.
Fig. 5a-5e are enlarged views of a portion of fig. 5.
Detailed Description
In a first specific embodiment, as shown in fig. 1, 2, 3, 4, and 5, the digital signal processing system of a vortex shedding flowmeter based on the anti-interference vortex shedding amplitude-frequency characteristic of the present invention includes a programmable charge amplifier, a programmable high-pass filter, a programmable low-pass filter, a two-stage programmable amplifier, a programmable narrow-band filter, a programmable amplifier a, a programmable amplifier b, a programmable trigger, a pulse control output circuit, a main control unit, a temperature sensor, and a pressure sensor measurement unit, which are sequentially connected to a piezoelectric sensor, and a control signal of the main control unit is further respectively connected to the programmable charge amplifier, the programmable high-pass filter, the programmable low-pass filter, the two-stage programmable amplifier, the programmable narrow-band filter, the programmable amplifier a, the programmable amplifier b, the programmable trigger, and the pulse control.
The digital signal processing system of the vortex street flowmeter based on the anti-interference vortex street amplitude-frequency characteristic adopts amplitude-frequency characteristic identification, tracking filtering, threshold value self-adaptation and gain self-adaptation technologies, and is designed by applying an ARM CORTEX M4F kernel MCU with low power consumption and high performance and a low power consumption peripheral chip. The effective extraction of vortex street signal is realized to reach the effect of anti-interference such as electromagnetism, vibration. The measuring range ratio of the vortex shedding flowmeter is increased, and the phenomenon of pulse leakage in high and low flow velocity stages is solved.
According to a statistical rule obtained by a large amount of data and long-time analysis, the noise frequency is distributed in the whole vortex street signal frequency range, the signal energy is far larger than the noise energy at the higher frequency of the vortex street signal, and the signal and the noise energy are close to each other at the lower frequency of the vortex street signal, so that the signal is completely submerged in the noise.
The signal amplitude (a), the density (ρ) and the flow velocity (v) satisfy the relation:
A∝ρv2 (1)
it can be seen that for the same fluid at the same temperature, the density is a constant value, and the signal amplitude is proportional to the square of the flow rate.
Thus, we can write the above equation as:
A＝Kρv2 (2)
wherein: a: vortex street signal amplitude, K: the self-defined coefficient, ρ: density of fluid, v: the flow rate of the fluid.
Then according to the Karman vortex street formula:
f＝Stv/d (3)
wherein: f: frequency of vortex, St: strouhal number, v: flow rate of fluid, d: the frontal width of the vortex generator.
Substituting equation (3) into equation (2) can result in:
d＝0.28*D (5)
finishing to obtain: a ═ Amρf2D2 (6)
Wherein: a: amplitude (V), A) of vortex street signalm: defined amplitude-frequency coefficient, ρ: density of fluid (kg/m)3)，f：Frequency of vortex (Hz), D: inner diameter (m) of the pipe.
As can be seen from the above, AmThe two parameters can be regarded as constants in any vortex shedding flowmeter only according to the size of the vortex shedding flowmeter body and the characteristics of the piezoelectric sensor. Therefore, the amplitude-frequency coefficient of each vortex street flowmeter can be determined by calibrating the flowmeter in the production process. All experiments were performed according to the verification procedure of JJJG 1029-2007 vortex shedding flowmeter. When the vortex shedding flowmeter is actually applied, the pipe diameter is known, the density can be calculated, and AmAnd (5) calibrating to obtain the frequency which accords with the amplitude-frequency characteristic in the signal frequency spectrum as the flow measurement frequency.
In the second embodiment, the hardware circuit of the present invention is divided into: flow measurement circuit, temperature measurement circuit, pressure measurement circuit, man-machine interface, power management, output interface circuit.
As shown in fig. 3, 3a, 3b, 3c, and 3d, the vortex street flow signal collected by the piezoelectric sensor enters the charge amplifier for pre-amplification, and the output of the charge amplifier is divided into two paths.
And the channel 1 enters a subsequent program-controlled narrow-band tracking filter to filter and purify the vortex street signals, and the program-controlled threshold self-adaptive Schmitt trigger converts the purified vortex street signals into pulses to be measured and output.
And the path 2 enters a subsequent filtering amplification link consisting of program-controlled high-pass, program-controlled low-pass and two-stage program-controlled amplification, the program-controlled high-pass and low-pass filters effectively filter interference signals outside the frequency range of the field flow signal according to the parameters set by the vortex street converter, and the two-stage program-controlled amplifier is self-adaptive to the change of the amplitude of the field flow signal, so that the amplitude is kept within a certain amplitude range, and is converted into digital quantity through the ADC, and the reliability of subsequent digital signal processing is ensured.
As shown in fig. 4, 4a, 4b, and 4c, the signals of the temperature and pressure sensors are processed by a special 16-bit ADC, U12: the ADS1148 is matched with a peripheral circuit to carry out amplification, filtering and acquisition and is communicated with the MCU through the SPI interface.
As shown in fig. 5, 5a, 5b, 5c, 5d, and 5e, the main control chip is a CORTEXM4F core MCU: MSP432P 401R; the man-machine interface part comprises an LCM display screen, keys, a word stock and an FRAM ferroelectric memory, the support to the English menu can be realized through the word stock, and the memory is used for accessing parameters.
The WDT watchdog circuit has the advantages that a program pointer is wrong due to the fact that the work of a single chip microcomputer is interfered by an external electromagnetic field, a dead cycle is caused, the whole system controlled by the single chip microcomputer is in a stagnation state, and unpredictable results are caused. The watchdog regularly checks the running condition of the MCU, and once an error occurs, a reset signal is sent to the MCU to restart the whole system.
The invention adopts the software and hardware technologies of amplitude-frequency characteristic identification, tracking filtering, threshold value self-adaption, gain self-adaption, low power consumption and the like to amplify, filter, sample and process digital signals output by the piezoelectric sensor, identifies vortex street signals through the amplitude-frequency characteristic, purifies the vortex street signals sequentially through the programmable hardware narrowband tracking filter, converts the threshold value self-adaption trigger into pulse signals to output and measure, and can realize the accurate measurement of the vortex street flowmeter by applying the vortex flowmeter digital signal processing system based on the vortex street amplitude-frequency characteristic anti-interference.
It should be understood that the detailed description of the present invention is only for illustrating the present invention and is not limited by the technical solutions described in the embodiments of the present invention, and those skilled in the art should understand that the present invention can be modified or substituted equally to achieve the same technical effects; as long as the use requirements are met, the method is within the protection scope of the invention.
Claims (7)
1. The anti-interference vortex street flowmeter digital signal processing system based on the vortex street amplitude-frequency characteristic is characterized by comprising a main control unit and a piezoelectric sensor; the piezoelectric sensor is connected with the input end of a program-controlled charge amplifier, the output end of the program-controlled charge amplifier is connected with the input end of a program-controlled narrow-band filter, the output end of the program-controlled narrow-band filter is connected with the input end of a program-controlled amplifier a, the output end of the program-controlled amplifier a is connected with the input end of a program-controlled amplifier b, the output end of the program-controlled amplifier b is connected with a program-controlled trigger, and the program-controlled trigger is respectively connected with a main control unit and a pulse control output;
purifying the identified effective vortex street signal by a program-controlled narrow-band filter, and setting a threshold value of a program-controlled trigger according to the real-time amplitude variation range of the purified vortex street signal to effectively convert the vortex street signal into pulses; the effective extraction of the vortex street signal is realized.
2. The digital signal processing system for a vortex shedding flowmeter with anti-interference function based on vortex shedding amplitude-frequency characteristic as claimed in claim 1, wherein the output end of the programmable charge amplifier is further connected with the input end of a programmable high-pass filter, the output end of the programmable high-pass filter is connected with the input end of a programmable low-pass filter, the output end of the programmable low-pass filter is connected with the input end of the two-stage programmable amplifier, and the output end of the two-stage programmable amplifier is connected with the main control unit.
3. The digital signal processing system of the vortex shedding flowmeter with anti-interference and vortex shedding amplitude-frequency characteristics according to claim 1, wherein the main control unit is respectively connected with a human-computer interface unit and a WDT watchdog circuit, the human-computer interface unit comprises an LCM display screen, keys, a word bank and a memory, support for Chinese and English menus can be realized through the word bank, and the memory is used for parameter access.
4. The vortex shedding flowmeter digital signal processing system based on the vortex shedding amplitude-frequency characteristic interference resistance of claim 1, wherein the main control unit is connected with a power management circuit for switching a battery and an external power supply.
5. The vortex street amplitude frequency characteristic interference rejection-based vortex shedding flowmeter digital signal processing system according to claim 1, wherein said main control unit is connected to an output interface circuit.
6. The anti-interference vortex street flowmeter digital signal processing system based on the vortex street amplitude-frequency characteristic is characterized in that the main control unit adopts an ARM CORTEX M4F kernel MCU to amplify, filter, sample and digitally process the signals output by the piezoelectric sensor, and identifies the vortex street signals through the amplitude-frequency characteristic; and purifying the vortex street signal by a program-controlled hardware narrow-band tracking filter, and converting the threshold self-adaptive trigger into a pulse signal for outputting and measuring.
7. The digital signal processing system of the vortex shedding flowmeter with anti-interference function based on the vortex shedding amplitude-frequency characteristic as claimed in claim 1, wherein the main control unit is connected with a temperature sensor and a pressure sensor, and the temperature sensor and the pressure sensor are connected with the main control unit through a 16-bit ADC conversion module.
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| CN205642490U (en) * | 2016-05-19 | 2016-10-12 | 辽宁聚焦科技有限公司 | Many reference amounts vortex street mass flow meter based on HART agreement |
| WO2017143649A1 (en) * | 2016-02-23 | 2017-08-31 | 合肥工业大学 | Kalman filter-based vortex flowmeter anti-transient shock interference signal processing method and system |
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2021
- 2021-02-05 CN CN202110161619.0A patent/CN113029258A/en active Pending
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1230686A (en) * | 1999-01-08 | 1999-10-06 | 合肥工业大学 | Digital signal processing system of vortex street flowmeter |
| CN101476906A (en) * | 2009-01-21 | 2009-07-08 | 合肥工业大学 | Anti-strong fixed interference digital signal processing system of vortex street flowmeter |
| CN102322904A (en) * | 2011-06-11 | 2012-01-18 | 杭州电子科技大学 | Vortex shedding flow meter based on self-adaptive fast Fourier transformation |
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