CN108548578A - A kind of ultrasonic echo signal characteristic peak recognition methods based on adaptive threshold - Google Patents
A kind of ultrasonic echo signal characteristic peak recognition methods based on adaptive threshold Download PDFInfo
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- CN108548578A CN108548578A CN201810270004.XA CN201810270004A CN108548578A CN 108548578 A CN108548578 A CN 108548578A CN 201810270004 A CN201810270004 A CN 201810270004A CN 108548578 A CN108548578 A CN 108548578A
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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
- G01F1/66—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 measuring frequency, phase shift or propagation time of electromagnetic or other waves, e.g. using ultrasonic flowmeters
- G01F1/667—Arrangements of transducers for ultrasonic flowmeters; Circuits for operating ultrasonic flowmeters
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Abstract
The present invention proposes a kind of ultrasonic echo signal characteristic peak recognition methods based on adaptive threshold.Existing recognition methods has blindness and inadaptability, is susceptible to and jumps wave phenomenon.The echo-signal that energy converter receives is filtered amplification by the present invention first, and the peak voltage signal of echo-signal is obtained using peak detection circuit.Then the step identification of echo-peak signal, while selected threshold value are carried out.It takes the intermediate value of peak value step as threshold value finally by judgement, and constantly updates storage echo-signal array so that threshold value can carry out adaptive adjustment to obtain the optimal value of real time threshold according to actual echo-signal.The present invention can be not only adjusted according to the variation of echo-signal amplitude, but also when current ultrasonic echo feature peak changes, adaptive threshold can also adjust in real time, this makes adaptive threshold have stronger adaptability compared to fixed threshold method.
Description
Technical field
The invention belongs to flow detection technical fields, are related to a kind of for the identification of ultrasonic flowmeter ultrasonic echo feature peak
Method.
Background technology
Ultrasonic flowmeter has the advantages that high-precision, low pressure loss, bidirectional measurement compared to other kinds of flowmeter.And
Signal processing is then the core technology of ultrasonic flowmeter.Domestic ultrasonic flowmeter is mainly measured by threshold level method super
The flight time of sound echo signal.After ultrasonic echo signal is more than the threshold voltage of setting, echo-signal was carried out
Zero detection, to measure the flight time of ultrasonic signal.Set threshold level is known as threshold value, is more than threshold value by first
Wave crest be known as characteristic peak, measure flight time of the time of a certain fixed zero crossing after characteristic peak as echo-signal, thus
Ensure the accuracy measured every time.
Threshold level method poor anti jamming capability, when echo-signal changes greatly, the amplitude of characteristic peak changes, and causes
System features peak identifies mistake so that the zero crossing of measurement is different, influences the accuracy measured, and this phenomenon is known as " jumping wave ".
Traditional threshold level method process is usually fixed threshold, judges characteristic wave, this recognition methods further according to threshold value position
There is certain limitation, is susceptible to and jumps wave phenomenon.
Invention content
The ultrasonic echo signal feature based on adaptive threshold that in view of the deficiencies of the prior art, the present invention proposes a kind of
Peak recognition methods.
Key step of the present invention is as follows：
Step 1：The echo-signal that energy converter receives is filtered amplification, is then obtained using peak detection circuit
The peak voltage signal of echo-signal.Select peak-peak and the immediate m echo data of set target amplitude as time
The reference of wave signal-data processing.According to m echo-signal for comparing record, setting initial threshold Th0。
Step 2：The step of echo-peak signal identifies.The maximum value of echo-peak signal is chosen first, then is determined each
Peak value plateau voltage size.Resolving power D is set, i.e., thinks two when the difference of two neighboring sampled point amplitude is less than resolving power D
Sampled point on same peak value step, otherwise when the difference of two neighboring sampled point amplitude be more than resolving power when then think to have occurred under
One peak value step.By peak value step recognition result, step array A=[A are obtained1,A2…Ak].Wherein k represents corresponding peak value
Step sum, wherein A1For the first peak value step, AkFor peak value step maximum value.Pass through each element divided by A in array Ak,
Obtain ratio array R=[R1,R2…1]。
On the one hand threshold value is chosen is selecting the maximum two peak value steps of difference in magnitude and by peak value from each peak value step
The fault-tolerance that threshold value is chosen is improved as threshold value in the midpoint of plateau voltage value；Another aspect threshold value will be close proximity to the ginseng of echo
Zero crossing is examined, the influence of whole amplitude fluctuations is reduced.
Step 3：N number of echo-signal is stored by first in first out, obtains N number of step array Ai=[A1i,A2i,…,
Aki], i ∈ [1, N], k are the peak value step sum of echo-signal；Obtain N number of ratio array R simultaneouslyi=[R1i,R2i..., 1], i
∈ [1, N], wherein R1i、R2i、R3iRatio, the second peak value platform of the first peak value step and peak-peak of respectively i-th echo
The ratio of the ratio of rank and peak-peak, third peak value step and peak-peak.Thus the average voltage of peak value step is obtainedj∈[1,k]：
Obtain the ratio average of each peak value step simultaneously
For the step array of current acquisition echo, sequentially compare to obtain the first elements A more than threshold valuep, p ∈
[1,k]。
As p=1 and judge to obtainFirst peak value step is lost, then takesAs first
Peak value step.
As p=2, then it is assumed that successfully identify the first peak value step.
The intermediate value of the first peak value step and the second peak value step that take acquisition echo is as threshold value, then it can thus be concluded that adaptive
Threshold value is：
Storage echo-signal array is constantly updated with the principle of first in first out so that threshold value can be believed according to actual echo
Number adaptive adjustment is carried out to obtain the optimal value of real time threshold.
Furtherly, this method further includes that the echo data after identifying and compensate for the first peak value step carries out jumping wave knowledge
Not, if R1(N+1)、R2(N+1)、R3(N+1)Indicate respectively the first, second, third peak value step of the echo-signal currently measured with most
The ratio of big peak value step.
WhenWhen, then present threshold value is in the first, second peak value step
Between, no jump wave.
WhenWhen, then present threshold value in the first peak value step and refers to step
Between, zero crossing is then postponed a cycle and reaches the time as true echo by zero crossing Forward a cycle backward.
WhenWhen, then present threshold value between second, third peak value step,
Zero crossing can integrally delay a cycle, then using zero crossing forward a cycle as true echo arrival time.
Compared with prior art, the present invention then uses the ultrasonic echo signal characteristic peak recognition methods of adaptive threshold,
According to the characteristic wave peak-settings threshold value of identification.Adaptive threshold can not only be adjusted according to the variation of echo-signal amplitude
It is whole, and when current ultrasonic echo feature peak changes, adaptive threshold can also adjust in real time, this makes adaptive threshold
There is stronger adaptability compared to fixed threshold method.
Description of the drawings
Fig. 1 is the ultrasonic flowmeter circuit diagram used in the embodiment of the present invention；
Fig. 2 is the flow chart of the ultrasonic echo signal characteristic peak recognition methods based on adaptive threshold；
Fig. 3 is original echoed signals and peak value step in the embodiment of the present invention；
Fig. 4 is peak voltage magnitude figure in the embodiment of the present invention；
Fig. 5 is that echo-signal jumps wave data processing principle figure in the present invention.
Specific implementation mode
The present invention is further described in detail below in conjunction with attached drawing.
The ultrasonic flowmeter circuit theory used in the present embodiment 8 parts as shown in Figure 1, be mainly made of：Monolithic
Machine, switch switching circuit, energy converter (A, B), signal preprocessing circuit, zero cross detection circuit, peak detection circuit, signal
Acquisition module.Wherein echo signal processing circuit plays the role of to ultrasonic echo signal filter and amplification.
It is illustrated in figure 2 the ultrasonic echo signal characteristic peak recognition methods flow chart based on adaptive threshold, this method
Shown in steps are as follows：
Step 1：The echo-signal that energy converter receives is filtered amplification, is then obtained using peak detection circuit
The peak voltage signal of echo-signal is illustrated in figure 3 original echoed signals and peak value step in the present embodiment.Select maximum peak
The reference that value is handled with the immediate m echo data of set target amplitude as echo signal data.It is returned in the present embodiment
Wave signal data stores number m=100, and initial threshold Th is set by Germicidal efficacy0=1.65V.
Step 2：The step of echo-peak signal identifies, chooses the maximum value of echo-peak signal first, then passes through peak value
The voltage value of step determines each peak value plateau voltage size.Resolving power D is set, this reality as known to Fig. 4 peak voltage magnitude figures
It is 0.02V to apply peak voltage magnitude fluctuation range in example, therefore resolving power D=0.03V is arranged, i.e., when two neighboring sampled point width
The difference of value thinks two sampled points on same peak value step when being less than resolving power D=0.03V, otherwise works as two neighboring sampled point
The difference of amplitude then thinks next peak value step occurred when being more than resolving power.
By peak value step recognition result, step array A=[A are obtained1,A2…Ak].Wherein k represents corresponding peak value step
Sum, wherein A1For the first peak value step, AkFor peak value step maximum value.Pass through each element divided by A in array Ak, obtain
Ratio array R=[R1,R2…1]。
On the one hand threshold value is chosen is selecting the maximum two peak value steps of difference in magnitude and by peak value from each peak value step
The fault-tolerance that threshold value is chosen is improved as threshold value in the midpoint of plateau voltage value；Another aspect threshold value will be close proximity to the ginseng of echo
Zero crossing is examined, the influence of whole amplitude fluctuations is reduced.
Step 3：N number of echo-signal is stored by first in first out, N=10 is taken in the present embodiment, obtains 10 number of steps
Group Ai=[A1i,A2i,…,Aki], i ∈ [1,10], k are the peak value step sum of echo-signal；Obtain 10 ratio arrays simultaneously
Ri=[R1i,R2i..., 1], i ∈ [1,10], wherein R1i、R2i、R3iThe the first peak value step and maximum peak of respectively i-th echo
The ratio of the ratio of value, the ratio of the second peak value step and peak-peak, third peak value step and peak-peak.Thus it obtains each
The average voltage of a peak value stepj∈[1,k]：
Obtain the ratio average of each peak value step simultaneously
For the step array of current acquisition echo, sequentially compare to obtain the first elements A more than threshold valuep, p ∈
[1,k]。
As p=1 and judge to obtainFirst peak value step is lost, then takesAs first
Peak value step.
As p=2, then it is assumed that successfully identify the first peak value step.
The intermediate value of the first peak value step and the second peak value step that take acquisition echo is as threshold value, then it can thus be concluded that adaptive
Threshold value is：
Storage echo-signal array is constantly updated with the principle of first in first out so that threshold value can be believed according to actual echo
Number adaptive adjustment is carried out to obtain the optimal value of real time threshold.
Step 4：Echo data after identifying and compensate for the first peak value step carries out jumping wave identification, if R1(N+1)、
R2(N+1)、R3(N+1)The the first, second, third peak value step and peak-peak step of the echo-signal currently measured are indicated respectively
Ratio.
WhenWhen, then present threshold value is in the first, second peak value step
Between, no jump wave.
WhenWhen, then present threshold value in the first peak value step and refers to step
Between, zero crossing is then postponed a cycle and reaches the time as true echo by zero crossing Forward a cycle backward.
WhenWhen, then present threshold value between second, third peak value step,
Zero crossing can integrally delay a cycle, then using zero crossing forward a cycle as true echo arrival time.
Time measurement module in the present embodiment uses DTC-GP22, is calculating ultrasonic echo signal arrival time process
In can measure continuous 3 echo periods simultaneously；Three zero crossing t can be obtained as Fig. 5 jumps wave data processing principle figure1、t2、t3,
When without jump wave i.e. in the case of threshold value 2, t2For echo arrival time, by t0=(t1+t2+t3)/3 as echo arrival time with
Improve the stability measured；
When there is 1 situation of threshold value, by t3As true echo arrival time；
When there is 3 situation of threshold value, then by t1As true echo arrival time.
Claims (2)
1. a kind of ultrasonic echo signal characteristic peak recognition methods based on adaptive threshold, feature include the following steps：
Step 1：The echo-signal that energy converter receives is filtered amplification, then obtains echo using peak detection circuit
The peak voltage signal of signal；Peak-peak is selected to believe as echo with the immediate m echo data of set target amplitude
The reference of number processing；According to m echo-signal for comparing record, setting initial threshold Th0；
Step 2：The step of echo-peak signal identifies：The maximum value of peak signal is chosen first, then passes through each peak value step
Voltage value determine each peak value plateau voltage size；By peak value step recognition result, step array A=[A are obtained1,A2…
Ak]；Wherein k represents corresponding peak value step sum, A1For the first peak value step, AkFor peak value step maximum value；Pass through array A
In each element divided by Ak, obtain ratio array R=[R1,R2…1]；
Threshold value is chosen：The maximum two peak value steps of difference in magnitude are selected from each peak value step and make the midpoint of peak value step
For threshold value；To reduce the influence of whole amplitude fluctuations close proximity to the reference zero crossing of echo simultaneously；
Step 3：N number of echo-signal is stored by first in first out, obtains N number of step array Ai=[A1i,A2i,…,Aki], i ∈
[1, N], while obtaining N number of ratio array Ri=[R1i,R2i..., 1], wherein R1i、R2i、R3iThe first of respectively i-th echo
Peak value step and the ratio of peak-peak, the ratio of the second peak value step and peak-peak, third peak value step and peak-peak
Ratio；Thus the average voltage of peak value step is obtained
Obtain the ratio average of each peak value step simultaneously
For the step array of current acquisition echo, sequentially compare to obtain the first elements A more than threshold valuep, p ∈ [1,
k]；
As p=1 and judge to obtainFirst peak value step is lost, then takesAs the first peak value
Step；
As p=2, then it is assumed that successfully identify the first peak value step；
The intermediate value of the first peak value step and the second peak value step that take acquisition echo is as threshold value, then it can thus be concluded that adaptive threshold
For:
Constantly update storage echo-signal array with the principle of first in first out so that threshold value can according to actual echo-signal into
The adaptive adjustment of row is to obtain the optimal value of real time threshold.
2. a kind of ultrasonic echo signal characteristic peak recognition methods based on adaptive threshold according to claim 1,
It is characterized in that：Further include carrying out jumping wave identification to echo data, to prevent signal in measuring from jumping error caused by wave, specifically：
Echo data after identifying and compensate for the first peak value step carries out jumping wave identification, if R1(N+1)、R2(N+1)、R3(N+1)Point
The ratio of the first, second, third peak value step and peak-peak step of the echo-signal currently measured is not indicated；
WhenWhen, then present threshold value between the first, second peak value step,
Without jump wave；
WhenWhen, then present threshold value is in the first peak value step and with reference between step,
Zero crossing, then is postponed a cycle and reaches the time as true echo by zero crossing Forward a cycle backward；
WhenWhen, then present threshold value is between second, third peak value step, zero passage
Point can integrally delay a cycle, then using zero crossing forward a cycle as true echo arrival time.
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| TWI790714B (en) * | 2021-08-17 | 2023-01-21 | 桓達科技股份有限公司 | Method of determining characteristic time reference wave of acoustic signal of ultrasonic flowmeter |
| CN114111972A (en) * | 2021-10-29 | 2022-03-01 | 浙江威星智能仪表股份有限公司 | Method for automatically adjusting echo of ultrasonic meter |
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