CN101226070A - Method for detecting vortex street frequency based on heterodyne type accidental resonation - Google Patents
Method for detecting vortex street frequency based on heterodyne type accidental resonation Download PDFInfo
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Abstract
The invention discloses a vortex frequency detecting method based on a heterodyne random resonate. The method inputs the vortex signal into the heterodyne random resonate system, adjusts the frequency of the carrier signal continuously and analyzes the power spectrum and the power spectrum reciprocal of the output signal. The resonate spectrum peak then disposes an obvious process changing with the frequency, therefore the frequency of the resonate spectrum peak is taken conveniently and accurately, which is also called vortex signal frequency. The method is characterized in an effective increase of the signal-to-noise ration of the vortex signal, and the method is new in improving the adaptability of the vortex flow meter and detecting the frequency of the low-flow and weak vortex signals.
Description
Technical field
The present invention relates to a kind of vortex signal disposal route, especially, relate to a kind of vortex street frequency detecting method that in vortex shedding flow meter, uses based on the heterodyne system accidental resonance.
Background technology
Vortex shedding flow meter is based on the Karman vortex street principle and a kind of flowmeter of designing, has obtained developing rapidly since the seventies in 20th century, has been widely used in the measurement of gas, liquid and steam flow at present.Vortex shedding flow meter belongs to fluid oscillation type flowmeter in itself, and therefore when industry spot was used, the interference that pipeline and various device vibration cause can reduce measuring accuracy, influences measurement lower limit.Aspect the vortex signal processing, utilize the modern signal processing method that vortex shedding flowmeter signal is handled, from the signal that contains noise, accurately extract the vortex street frequency, to improve measuring accuracy, be one of current development of Vortex Flowmeter focus.The method that adopts is utilized the difference on signal and the noisiness mostly, comes attenuating noise by the mathematic(al) manipulation method, extracts useful signal, does not have the physical mechanism of noise and signal energy conversion, thereby is difficult to amplify the weak signal in the very noisy.Secondly, the output signal of vortex shedding flow meter is made up of two parts: the one, flow through the sinusoidal vortex signal that vortex shedder produces by fluid in the pipeline; The 2nd, by the noise signal that various interference cause, as pipe vibration, the turbulent flow pulsation reaches the interference of other equipment of industry spot etc.All these noises can cause that all the in-site measurement Signal-to-Noise reduces, and when serious interference or when low discharge is measured, even can't correctly record the vortex street frequency, have influenced the normal use of vortex shedding flow meter.
Summary of the invention
The objective of the invention is at the deficiencies in the prior art, a kind of vortex street frequency detecting method based on the heterodyne system accidental resonance is provided.
Purpose of the present invention is achieved through the following technical solutions: a kind of vortex street frequency detecting method based on the heterodyne system accidental resonance comprises the steps:
1), produces high and low two kinds of different frequency contents through process of heterodyning with the vortex signal input mixer;
2) output signal of frequency mixer remakes and uses stochastic resonance system, analyzes the power spectrum of stochastic resonance system output;
3) regulate the frequency of carrier signal continuously, power spectrum chart and power spectrum figure reciprocal thereof according to the stochastic resonance system output signal catch characteristic frequency, determine the vortex signal frequency.
Useful effect of the present invention is:
(1) by regulating the frequency of carrier signal continuously, very obvious variation process of feature will appear in the resonance spectrum peak of system's output vortex signal, record the vortex street frequency accurately thereby can make things convenient for.
(2) noisy vortex signal can effectively amplify vortex signal by accidental resonance, improves the signal to noise ratio (S/N ratio) of vortex signal, obtains the vortex street frequency exactly.
(3) this method can improve the on-the-spot adaptability of vortex shedding flow meter, and provides a kind of new method for vortex signal frequency detecting a little less than the low discharge.
(4) this method is applicable to that also other field relates to the Detection of Weak Signals in the very noisy, can widen the application of accidental resonance, has a good application prospect.
Description of drawings
Fig. 1 is a heterodyne system accidental resonance frequency detecting theory diagram of the present invention;
Fig. 2 is 3.43m for gathering flow
3/ h (low discharge) vortex signal time domain waveform figure;
Fig. 3 is 11.58m for gathering flow
3/ h (big flow) vortex signal time domain waveform figure;
Fig. 4 is primary flow signal low frequency part power spectrum chart after the heterodyne system stochastic resonance system;
Fig. 5 is that heterodyne system accidental resonance output power spectrum is with the frequency of carrier signal change curve;
Fig. 6 is that heterodyne system accidental resonance output power spectrum inverse is with the frequency of carrier signal change curve.
Embodiment
Vortex street frequency detecting method based on the heterodyne system accidental resonance of the present invention comprises the steps:
One,, produces high and low two kinds of different frequency contents through process of heterodyning with the vortex signal input mixer.With the vortex street frequency is that the vortex shedding flow meter output signal of f0 and carrier signal generator output signal that frequency is fc multiply each other in frequency mixer, and obtaining frequency is two signals of fc ± f0, and its neutralization fc+f0 frequently is a high frequency, and difference frequency Δ f=fc-f0 is a low frequency.
Two, the output signal of frequency mixer remakes and uses stochastic resonance system, analyzes the power spectrum of stochastic resonance system output.
Input to non-linear bistable system with frequency signal and difference frequency signal, when difference frequency signal delta f=fc-f0 frequency is low, in bistable system, form accidental resonance easily, the signal to noise ratio (S/N ratio) of output signal obviously improves, the signal power spectral amplitude ratio is also amplified and frequency signal fc+f0 will decay by bistable system.
Three, regulate the frequency of carrier signal continuously, power spectrum chart and power spectrum figure reciprocal thereof according to the stochastic resonance system output signal catch characteristic frequency, determine the vortex signal frequency.
Output frequency fc by continuous adjusting carrier signal generator, the frequency of difference frequency signal Δ f=fc-f0 becomes thereupon, the difference frequency resonance spectrum peak of non-linear bistable system output signal change procedure such as will occur suddenly disappearing again from small to large can accurately be measured the frequency of vortex signal in view of the above.
Specifically, whole detection method mainly is made up of carrier signal generator, frequency mixer, non-linear bistable system three bulks, and its theory diagram as shown in Figure 1.The effect of carrier signal generator is to produce the variable carrier signal of frequency f c, frequency mixer is used for realizing process of heterodyning, thus the vortex signal that is about to wait to ask frequency as input signal in frequency mixer with given frequency be the carrier signal of fc multiply each other obtain difference frequency with and two kinds of frequency signals frequently; Suppose that the vortex street frequency is f0, then frequency mixer output is that frequency is two signals of fc-f0 and fc+f0.Have only the frequency when the difference frequency signal lower, i.e. fc-f0=Af＜＜1 o'clock, could produce easy in bistable system the low frequency signal of formation accidental resonance.Signal to noise ratio (S/N ratio) obviously improved after difference frequency signal Δ f produced accidental resonance through bistable system, and amplitude is also amplified, and decays substantially behind bistable system with frequency fc+f0 signal.Therefore, the spectrum peak will appear at frequency Af place in the frequency spectrum of heterodyne system stochastic resonance system output signal.Can change the size of frequency Δ f neatly by regulating fc, the spectrum peak that occurs in frequency Δ f place is obviously given prominence to.But as carrier frequency fc=f0, promptly during Δ f=0, no longer there is low-frequency periodic signal in the input of bistable system, and the resonance spectrum peak of stochastic resonance system output will disappear thereupon.Can accurately measure the frequency of vortex signal in view of the above.
By the following examples content of the present invention is done further explanation.With this method the vortex shedding flow meter output signal is handled, with low discharge 3.43m
3/ h and general flow 11.58m
3/ h is an example.Fig. 2, Fig. 3 are respectively low discharge 3.43m
3/ h and general flow 11.58m
3The time-domain signal of/h, both compare, and at low discharge, time-domain signal is periodically obvious not as big flow, and vortex street periodic signal amplitude is little, is almost flooded by very noisy.For littler flow, its signal to noise ratio (S/N ratio) is lower, and this also is one of difficult point of current vortex flowmeter signals processing.After the heterodyne system stochastic resonance system, when fc=8.804Hz, signal low frequency part power spectrum has one obviously to compose the peak at difference frequency Δ f=0.004Hz place as shown in Figure 4 with primary flow signal.As seen the spectrum peak behind the heterodyne system accidental resonance is obvious, and signal to noise ratio (S/N ratio) is higher, is easy to accurate survey frequency.F0=fc-Δ f, therefore recording the vortex street frequency is 8.8Hz.Frequency f c when continuous adjusting carrier signal, particularly from less than 8.8Hz to greater than 8.8Hz the time, very responsive variation has appearred in the power spectrum peak of heterodyne system accidental resonance output, spectrum peak has occurred from rapid increase, the phenomenons such as arriving sharply increase again that suddenly disappears, as shown in Figure 5.Spectrum peak is asked reciprocal, and then Changing Pattern is just in time opposite, for the correct characteristic frequency of catching brings convenience this frequency values of 8.8Hz vortex street frequency to be detected just among Fig. 6.
Claims (4)
1. the vortex street frequency detecting method based on the heterodyne system accidental resonance is characterized in that, comprises the steps:
1), produces high and low two kinds of different frequency contents through process of heterodyning with the vortex signal input mixer.
2) output signal of frequency mixer remakes and uses stochastic resonance system, analyzes the power spectrum of stochastic resonance system output.
3) regulate the frequency of carrier signal continuously, power spectrum chart and power spectrum figure reciprocal thereof according to the stochastic resonance system output signal catch characteristic frequency, determine the vortex signal frequency.
2. the vortex street frequency detecting method based on the heterodyne system accidental resonance according to claim 1, it is characterized in that, described step (1) is specially: with the vortex street frequency is that the vortex shedding flow meter output signal of f0 and carrier signal generator output signal that frequency is fc multiply each other in frequency mixer, obtaining frequency is two signals of fc ± f0, its neutralization fc+f0 frequently is a high frequency, and difference frequency Δ f=fc-f0 is a low frequency.
3. the vortex street frequency detecting method based on the heterodyne system accidental resonance according to claim 1, it is characterized in that, described step (2) is specially: input to non-linear bistable system with frequency signal and difference frequency signal, when difference frequency signal delta f=fc-f0 frequency is low, in bistable system, form accidental resonance easily, the signal to noise ratio (S/N ratio) of output signal obviously improves, and the signal power spectral amplitude ratio is also amplified and frequency signal fc+f0 will decay by bistable system.
4. the vortex street frequency detecting method based on the heterodyne system accidental resonance according to claim 1, it is characterized in that, described step (3) is specially: by the output frequency fc of continuous adjusting carrier signal generator, the frequency of difference frequency signal Δ f=fc-f0 becomes thereupon, the difference frequency resonance spectrum peak of non-linear bistable system output signal change procedure such as will occur suddenly disappearing again from small to large can accurately be measured the frequency of vortex signal in view of the above.
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Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102322940A (en) * | 2011-08-15 | 2012-01-18 | 中国计量学院 | Vortex street frequency detection method based on random energy resonance |
| CN105093243A (en) * | 2014-05-08 | 2015-11-25 | 北京大学 | GNSS carrier loop circuit tracking method based on stochastic resonance algorithm |
| CN105571659A (en) * | 2016-01-21 | 2016-05-11 | 中国计量学院 | Vortex frequency stochastic resonance control and detection method based on standard deviation |
| CN106500779A (en) * | 2016-12-27 | 2017-03-15 | 中国计量大学 | The vortex signal detection means of the accidental resonance with feedforward controller |
| CN108683623A (en) * | 2018-03-29 | 2018-10-19 | 中国人民解放军战略支援部队信息工程大学 | Faint OFDM sub-carrier numbers method of estimation based on accidental resonance |
| CN109905090A (en) * | 2019-02-27 | 2019-06-18 | 武汉深海蓝科技有限公司 | A kind of feature extracting method and system of the nonperiodic signal based on accidental resonance |
| CN110554293A (en) * | 2018-05-31 | 2019-12-10 | 广东电网有限责任公司 | partial discharge signal processing device |
| US11598657B2 (en) | 2018-12-14 | 2023-03-07 | Endress+Hauser Flowtec Ag | Measurement system for measuring a flow parameter of a fluid flowing in a pipe |
| CN107941288B (en) * | 2017-12-27 | 2023-07-21 | 武汉新烽光电股份有限公司 | Flowmeter based on frequency mixing |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN200986450Y (en) * | 2006-11-13 | 2007-12-05 | 浙江大学 | Differential pressure vortex quality and flux measurement signal processing equipment |
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Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102322940A (en) * | 2011-08-15 | 2012-01-18 | 中国计量学院 | Vortex street frequency detection method based on random energy resonance |
| CN102322940B (en) * | 2011-08-15 | 2013-07-10 | 中国计量学院 | Vortex street frequency detection method based on random energy resonance |
| CN105093243A (en) * | 2014-05-08 | 2015-11-25 | 北京大学 | GNSS carrier loop circuit tracking method based on stochastic resonance algorithm |
| CN105571659A (en) * | 2016-01-21 | 2016-05-11 | 中国计量学院 | Vortex frequency stochastic resonance control and detection method based on standard deviation |
| CN105571659B (en) * | 2016-01-21 | 2018-05-15 | 中国计量学院 | A kind of vortex street frequency accidental resonance control detection method based on standard deviation |
| CN106500779A (en) * | 2016-12-27 | 2017-03-15 | 中国计量大学 | The vortex signal detection means of the accidental resonance with feedforward controller |
| CN107941288B (en) * | 2017-12-27 | 2023-07-21 | 武汉新烽光电股份有限公司 | Flowmeter based on frequency mixing |
| CN108683623A (en) * | 2018-03-29 | 2018-10-19 | 中国人民解放军战略支援部队信息工程大学 | Faint OFDM sub-carrier numbers method of estimation based on accidental resonance |
| CN108683623B (en) * | 2018-03-29 | 2020-09-08 | 中国人民解放军战略支援部队信息工程大学 | Estimation method of weak OFDM subcarrier number based on stochastic resonance |
| CN110554293A (en) * | 2018-05-31 | 2019-12-10 | 广东电网有限责任公司 | partial discharge signal processing device |
| US11598657B2 (en) | 2018-12-14 | 2023-03-07 | Endress+Hauser Flowtec Ag | Measurement system for measuring a flow parameter of a fluid flowing in a pipe |
| CN109905090A (en) * | 2019-02-27 | 2019-06-18 | 武汉深海蓝科技有限公司 | A kind of feature extracting method and system of the nonperiodic signal based on accidental resonance |
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