CN111044110A - Gas ultrasonic flowmeter signal processing method based on similarity analysis - Google Patents
Gas ultrasonic flowmeter signal processing method based on similarity analysis Download PDFInfo
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- CN111044110A CN111044110A CN201911322066.1A CN201911322066A CN111044110A CN 111044110 A CN111044110 A CN 111044110A CN 201911322066 A CN201911322066 A CN 201911322066A CN 111044110 A CN111044110 A CN 111044110A
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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
- G01F1/662—Constructional details
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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
Abstract
The invention discloses a method for processing a gas ultrasonic flowmeter signal based on similarity analysis, which comprises the following steps of determining a characteristic wave, setting a threshold according to a certain proportion of a maximum peak value because the proportion of each peak in an echo signal to the maximum peak value is basically kept consistent, and marking a sine wave at which the amplitude of the echo signal reaches the threshold for the first time as the characteristic wave; analyzing the similarity, calculating the propagation time, recording the data after the characteristic wave, and analyzing the similarity of the two measurements to obtain the accurate propagation time; and step three, calculating the flow, and calculating the real-time flow according to the measured propagation time. The invention has the beneficial effects that: the DSP chip TMS320F28335 is used as a main control chip to complete excitation and collection of ultrasonic signals, real-time flow of gas is calculated by analyzing similarity of echo signals, instantaneity is high, and energy consumption is low.
Description
Technical Field
The invention relates to a signal processing method of a gas ultrasonic flowmeter, in particular to a signal processing method of the gas ultrasonic flowmeter based on similarity analysis, and belongs to the technical field of instruments and meters.
Background
In recent years, ultrasonic waves are receiving more and more attention in the technical field of detection, and particularly, a gas ultrasonic flow meter is widely applied to the natural gas measurement industry due to low pressure loss, large range ratio, bidirectional metering and low maintenance cost. The gas ultrasonic flowmeter is mainly based on a time difference method, and the time difference method is a measuring method for calculating flow information according to propagation time difference of ultrasonic waves under the conditions of forward flow and reverse flow in a measured medium. In the time difference method, the measurement of the propagation time of ultrasonic waves is a key of the entire flow meter. Three typical methods of measuring travel time are: threshold methods, cross-correlation methods and curve fitting methods.
The threshold method is the simplest and has strong real-time performance, but the accuracy of the method is not high; the cross-correlation method and the curve fitting method require a large amount of calculation, although the accuracy is high, the real-time performance is reduced, the energy consumption is increased, and the compensation is not realized.
Disclosure of Invention
The present invention is directed to a method for processing signals of a gas ultrasonic flowmeter based on similarity analysis, in order to solve the above-mentioned problems.
The invention realizes the purpose through the following technical scheme: a method for processing signals of a gas ultrasonic flowmeter based on similarity analysis comprises the steps of: the signal processing method comprises the following steps:
step one, determining characteristic waves, wherein because the proportion of each peak in an echo signal to a maximum peak value is basically kept consistent, a threshold value is set according to a certain proportion of the maximum peak value, and a sine wave at which the amplitude of the echo signal reaches the threshold value for the first time is recorded as the characteristic waves;
analyzing the similarity, calculating the propagation time, recording the data after the characteristic wave, and analyzing the similarity of the two measurements to obtain the accurate propagation time;
and step three, calculating the flow, and calculating the real-time flow according to the measured propagation time.
As a still further scheme of the invention: in the first step, a threshold is set and the characteristic wave is determined according to the threshold, and the method specifically comprises the following steps:
(1) searching two sine waves with the maximum proportion difference according to the characteristic that the proportion of each peak value and the maximum wave peak value of the echo signal is basically unchanged;
(2) and setting a threshold value according to the average value of the proportion of the two sine waves, and marking the sine wave in which the amplitude of the echo signal reaches the threshold value for the first time as a characteristic wave.
As a still further scheme of the invention: in the second step, the similarity of the two measurements is analyzed to obtain the propagation time, and the specific steps comprise:
(1) recording three continuous positive zero-crossing points after the characteristic wave as candidate propagation time, sampling and storing four continuous periods of data from the first positive zero-crossing point, and normalizing the stored data;
(2) and analyzing the two continuous echo signal data to find out the state with the maximum similarity, and then selecting the correct propagation time from the three candidate propagation times.
As a still further scheme of the invention: the gas ultrasonic flowmeter uses a DSP chip TMS320F28335 as a main control chip.
The invention has the beneficial effects that: the signal processing method of the gas ultrasonic flowmeter based on the similarity analysis is reasonable in design, the DSP chip TMS320F28335 is used as a main control chip, excitation and collection of ultrasonic signals are completed, real-time flow of gas is calculated by analyzing the similarity of echo signals, instantaneity is high, and energy consumption is low.
Drawings
FIG. 1 is a schematic diagram of the ratio of the fifth and sixth peaks to the maximum peak amplitude according to the present invention;
FIG. 2 is a schematic diagram of data selection according to the present invention;
FIG. 3 is a hardware schematic of the flow meter system of the present invention;
fig. 4 is a schematic flow chart of the signal processing of the flowmeter of the invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1 to 4, a method for processing a signal of a gas ultrasonic flowmeter based on similarity analysis includes the following steps:
step one, determining characteristic waves, wherein because the proportion of each peak in an echo signal to a maximum peak value is basically kept consistent, a threshold value is set according to a certain proportion of the maximum peak value, and a sine wave at which the amplitude of the echo signal reaches the threshold value for the first time is recorded as the characteristic waves;
analyzing the similarity, calculating the propagation time, recording the data after the characteristic wave, and analyzing the similarity of the two measurements to obtain the accurate propagation time;
and step three, calculating the flow, and calculating the real-time flow according to the measured propagation time.
Further, in the embodiment of the present invention, in the first step, setting a threshold and determining the characteristic wave according to the threshold specifically includes the following steps:
(1) searching two sine waves with the maximum proportion difference according to the characteristic that the proportion of each peak value and the maximum wave peak value of the echo signal is basically unchanged;
(2) and setting a threshold value according to the average value of the proportion of the two sine waves, and marking the sine wave in which the amplitude of the echo signal reaches the threshold value for the first time as a characteristic wave.
The two adjacent sine waves with the maximum difference between the amplitude and the maximum wave amplitude are the fifth wave and the sixth wave, and the DN100 flowmeter is collected at 0m and 60m3/h、100m3/h、150m3/h、200m3/h、250m3/h、300m3/h、350m3/h、400m3/h、450m3/h、550m3/h、650m3In 50 sets of ultrasonic echo signals at/h flow rate point, the average value of the ratio of the fifth wave amplitude to the maximum peak amplitude is 0.343 and the sixth wave is 0.518, as shown in fig. 1, and therefore the threshold coefficient is set to 0.43 which is (0.343+ 0.518)/2.
Further, in the embodiment of the present invention, in the second step, the similarity between the two measurements is analyzed to obtain the propagation time, and the specific steps include:
(1) recording three continuous positive zero-crossing points after the characteristic wave as candidate propagation time,the time values of the three positive zero crossings are denoted in turn by t1、t2、t3From t1Sampling and storing four continuous periods of DATA at the beginning of time, normalizing the stored DATA, recording the DATA as DATA1, performing the same processing on the next arriving ultrasonic signal, and recording the DATA as DATA 2;
(2) and analyzing the two continuous echo signal data to find out the state with the maximum similarity, and then selecting the correct propagation time from the three candidate propagation times.
The normalized data is calculated according to the following formula:
in the formula, N represents the data quantity; v1iDATA representing the first three cycles in DATA 1; v2iDATA representing the last three cycles in DATA 1; v3iDATA representing the first three cycles in DATA 2; v4iDATA representing the last three cycles in DATA 2; r1The correlation between the first three periods of DATA in DATA1 and the first three periods of DATA in DATA 2; r2The correlation between the first three periods of DATA in DATA1 and the last three periods of DATA in DATA 2; r3Representing the degree of correlation between the last three cycles of DATA in DATA1 and the first three cycles of DATA in DATA 2. R1、R2、R3Smaller values represent a higher correlation between the two data.
Comparison of R1、R2、R3Size and according to the following formula
The correct propagation time is selected. The algorithm of the above formula is: if R is1And if the correlation degree is the lowest, the correlation degree of the first three periods in the DATA1 and the first three periods in the DATA2 is considered to be the highest, no wave error occurs in the current measurement, and the time value t of the second positive zero-crossing point after the characteristic wave is selected2Is the transit time; if R is2At a minimum, the first three cycles in DATA1 are considered to be in phase with the last three cycles in DATA2The degree of correlation is highest, the threshold value arrival time in the measurement is advanced by one period, and the time value t of the third positive zero crossing point after the characteristic wave is selected3Is the transit time; in the same way as R3And if the correlation degree is the lowest, the correlation degree of the last three periods in the DATA1 and the first three periods in the DATA2 is considered to be the highest, the threshold value reaching time in the measurement is delayed by one period, and the time value t of the first positive zero crossing point after the characteristic wave is selected1To transit time
Further, in the embodiment of the present invention, in the third step, according to:
calculating the flow;
wherein β is the included angle between transducer and pipe wall, k is flow correction coefficient, Δ t is the forward and reverse travel time difference, tuFor forward travel time, tdIs the propagation time of the return; d is the diameter of the pipeline.
Further, in the embodiment of the present invention, the gas ultrasonic flow meter uses a DSP chip TMS320F28335 as a main control chip.
The working principle is as follows: when the signal processing method of the gas ultrasonic flowmeter based on the similarity analysis is used, the DSP chip TMS320F28335 is used as a main control chip to complete excitation and collection of ultrasonic signals, and the real-time flow of gas is calculated by analyzing the similarity of echo signals.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.
Claims (4)
1. A method for processing signals of a gas ultrasonic flowmeter based on similarity analysis comprises the steps of: the signal processing method comprises the following steps:
step one, determining characteristic waves, wherein because the proportion of each peak in an echo signal to a maximum peak value is basically kept consistent, a threshold value is set according to a certain proportion of the maximum peak value, and a sine wave at which the amplitude of the echo signal reaches the threshold value for the first time is recorded as the characteristic waves;
analyzing the similarity, calculating the propagation time, recording the data after the characteristic wave, and analyzing the similarity of the two measurements to obtain the accurate propagation time;
and step three, calculating the flow, and calculating the real-time flow according to the measured propagation time.
2. The method for processing the signal of the gas ultrasonic flowmeter based on the similarity analysis as claimed in claim 1, wherein: in the first step, a threshold is set and the characteristic wave is determined according to the threshold, and the method specifically comprises the following steps:
(1) searching two sine waves with the maximum proportion difference according to the characteristic that the proportion of each peak value and the maximum wave peak value of the echo signal is basically unchanged;
(2) and setting a threshold value according to the average value of the proportion of the two sine waves, and marking the sine wave in which the amplitude of the echo signal reaches the threshold value for the first time as a characteristic wave.
3. The method for processing the signal of the gas ultrasonic flowmeter based on the similarity analysis as claimed in claim 1, wherein: in the second step, the similarity of the two measurements is analyzed to obtain the propagation time, and the specific steps comprise:
(1) recording three continuous positive zero-crossing points after the characteristic wave as candidate propagation time, sampling and storing four continuous periods of data from the first positive zero-crossing point, and normalizing the stored data;
(2) and analyzing the two continuous echo signal data to find out the state with the maximum similarity, and then selecting the correct propagation time from the three candidate propagation times.
4. The method for processing the signal of the gas ultrasonic flowmeter based on the similarity analysis as claimed in claim 1, wherein: the gas ultrasonic flowmeter uses a DSP chip TMS320F28335 as a main control chip.
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