Multi-mode ultrasonic fluid multi-parameter measurement device and method

Abstract

The present invention relates to a multi-modal ultrasonic fluid multi-parameter measurement device and method, the method comprising: sending a first and a second transmission signal, and correspondingly collecting a first and a second receiving signal; wherein the transmission signal will generate multiple modes when propagating in a pipeline; using a preset sampling model to collect sample signals from the corresponding receiving signals, specifically comprising: determining the spatiotemporal distribution characteristics of the mode through actual measurement results; determining the time intervals of different modal distributions; selecting corresponding sampling conditions through the sampling model, the sampling conditions including: the number of signal sampling points, and the signal sampling length; collecting sample signals from the receiving signal according to the sampling conditions; and finally, calculating the measurement volume under the multi-modal according to the sample signals. The present invention proposes a measurement method applied to a multi-modal scenario, which effectively improves the measurement accuracy under the multi-modal measurement system by accurately sampling and independently calculating each mode.

Description

Technical Field

[0001] The present invention relates to the field of ultrasonic measurement technology, and in particular to a multi-modal ultrasonic fluid multi-parameter measurement device and method. Background Art

[0002] Patent application CN111829601A discloses a synchronous measurement method and device, electronic device and storage medium for multi-state parameters of a fluid. The measurement method includes pre-constructing mathematical models of multiple state parameters, respectively, about the downstream propagation phase and the upstream propagation phase of a continuous sound wave at the actual flow velocity of a liquid fluid in a flowing state; obtaining the actual downstream propagation phase of the continuous sound wave in the liquid fluid in a flowing state; and the actual countercurrent propagation phase According to the actual downstream propagation phase Actual countercurrent propagation phase And the various mathematical models constructed are used to synchronously determine various state parameters.

[0003] In addition, classified from the ultrasonic measurement principle, the measurement methods of ultrasonic flow meters are mainly:

[0004] 1) Doppler shift technology

[0005] Doppler shift refers to the change in phase and frequency caused by the difference in propagation distance when the mobile station moves in a certain direction at a constant speed. The measurement principle of ultrasonic Doppler flowmeter is based on Doppler shift. In the ultrasonic Doppler flow measurement method, the ultrasonic transmitter is a fixed sound source, and the solid particles moving with the fluid act as "observers" with relative motion to the sound source. The frequency difference between the transmitted sound wave and the received sound wave is the Doppler shift of the sound wave caused by the movement of solid particles in the fluid. Since this frequency difference is proportional to the fluid flow velocity, the flow velocity can be obtained by measuring the frequency difference, and then the flow rate of the fluid can be obtained.

[0006] For example, patent application CN111337093A discloses an ultrasonic flow measurement method and device. The method is based on the pulse Doppler principle, utilizes the difference in Doppler frequency shift and amplitude of the echo signal between the gas and liquid phases, extracts the Doppler signal in the echo signal through the orthogonal demodulation method, and uses short-time Fourier transform to draw a time-frequency spectrum diagram. The bubble size in the measurement channel is then judged through the time-frequency spectrum diagram, thereby identifying the flow type of the fluid in the pipeline.

[0007] However, the existing ultrasonic Doppler flow measurement method also has certain defects. For example, it requires that the measured system (such as the fluid in the pipeline) should have a certain number of solid particles or bubbles that can reflect sound waves, so its application scenarios are very limited.

[0008] 2) Use single frequency sound waves for flow measurement

[0009] Patent application CN111337093A also discloses an ultrasonic flow measurement method and device, which calculates the overall flow rate by calculating the overall phase of the downstream and upstream flow, respectively. However, this method does not take into account the measurement error in a high-intensity vibration environment (or motion system).

[0010] Therefore, there is an urgent need for an ultrasonic measurement method that can improve measurement accuracy. Summary of the invention

[0011] The object of the present invention is to provide a multi-modal ultrasonic fluid multi-parameter measurement device and method, which can partially solve or alleviate the above-mentioned deficiencies in the prior art and can improve the accuracy of flow measurement by adopting a multi-modal calculation method.

[0012] In order to solve the above-mentioned technical problems, the present invention specifically adopts the following technical solutions:

[0013] A first aspect of the present invention is to provide a multi-modal ultrasonic fluid multi-parameter measurement method, comprising:

[0014] S201 uses a first probe and a second probe to send a first transmission signal and a second transmission signal respectively, and collects a first reception signal and a second reception signal correspondingly; wherein the first or second transmission signal generates at least two modes during the propagation process in the system to be measured;

[0015] S202 uses a preset sampling model to collect a sample signal from the corresponding received signal; wherein S202 includes:

[0016] (1) Determine the spatiotemporal distribution characteristics of the mode through the measured results of the signal;

[0017] (2) determining the time intervals of different modal distributions according to the spatiotemporal distribution characteristics;

[0018] (3) Selecting a corresponding sampling condition based on the sampling model and the time interval obtained in (2), wherein the sampling condition includes: the number of signal sampling points and the signal sampling length; wherein the sampling model includes:

[0019] H1∈(2 N-1 , 2 N );

[0020] H2=2 N ;

[0021] 2*M1<H2<M2;

[0022] Wherein, N is a natural number, H1 is the number of signal sampling points, H2 is the signal sampling length, M1 is the length of the mode received in the measured results, and M2 is the minimum time interval of the modal distribution;

[0023] (4) collecting a sample signal from the received signal according to the sampling condition;

[0024] S203 calculates the measurement volume corresponding to each mode according to the sample signal, and obtains the total volume of the system to be measured according to the measurement volume under each mode.

[0025] In some embodiments, before S201, the step further includes:

[0026] Sending a transmission signal, wherein the number of cycles of the transmission signal is a first set value;

[0027] receiving a received signal corresponding to the transmitted signal;

[0028] Determine whether the difference between the frequency of the received signal and the frequency of the transmitted signal falls within a preset frequency difference range. If so, select the number of cycles of the transmitted signal according to a third selection rule, wherein the third selection rule is: the number of cycles of the transmitted signal ≥ the first set value.

[0029] In some embodiments, it also includes:

[0030] Acquiring signal characteristics of the transmitted signal and the received signal;

[0031] It is determined whether at least two modes overlap with each other according to the signal characteristics. If not, S102 is executed. If yes, the number of cycles of the transmitted signal is reduced.

[0032] In some embodiments, the number of cycles of the transmitted signal is 50-100.

[0033] In some embodiments, the system to be measured includes: a pipe, and the diameter of the pipe is greater than 15 mm.

[0034] In some embodiments, S203 includes the steps of:

[0035] The first flow calculation model is used to calculate the measured volume in each mode; wherein the first flow calculation model is:

[0036] The measured volumes under each mode are averaged to calculate the average measured volume;

[0037] The total volume is calculated according to a second flow calculation model; wherein the second flow calculation model is:

[0038] Where t is time, is the average measurement volume, ΔQ V is the cumulative measurement error.

[0039] In some embodiments, the step of calculating the measured volume in each mode using the first flow calculation model includes:

[0040] Calculate the downstream phase difference and the upstream phase difference between the transmission signal and the corresponding reception signal in the first probe and the second probe respectively;

[0041] Calculate the downstream delay time and the upstream delay time corresponding to the first probe and the second probe respectively;

[0042] A phase calculation model is used to calculate the downstream phase and the upstream phase according to the downstream phase difference, the upstream phase difference and the downstream delay time and the upstream delay time respectively; and the first flow calculation model is used to calculate the volume to be measured according to the downstream phase and the upstream phase.

[0043] In some embodiments, the delay time calculation step includes:

[0044] Performing Fourier transform on the received signal and the transmitted signal respectively, so as to obtain a first Fourier transform complex value and a second Fourier transform complex value correspondingly;

[0045] performing conjugate point multiplication on the first Fourier transformed complex value and the second Fourier transformed complex value to obtain a third Fourier transformed complex value;

[0046] The corresponding delay time is read according to the third Fourier transform complex value, and the delay time is a position point corresponding to the maximum peak point in the corresponding Fourier transform complex value.

[0047] In some embodiments, the step of calculating the phase difference includes:

[0048] S21 performs Fourier transform on the transmission signal to obtain a first Fourier transform complex value, and finds the amplitude |F 发射 |The maximum value and the corresponding frequency position;

[0049] S22 performs Fourier transform on the received signal to obtain a second Fourier transform complex value, and obtains a corresponding Fourier transform complex value at the frequency position obtained in S21 in the second Fourier transform complex value;

[0050] S23, at the frequency position, using the real part and the imaginary part of the Fourier transform complex value corresponding to the first Fourier transform complex value at the frequency position to calculate the phase value of the transmitted signal, and using the real part and the imaginary part of the Fourier transform complex value corresponding to the second Fourier transform complex value at the same frequency position to calculate the phase value of the received signal;

[0051] S24 calculates a corresponding phase difference according to the phase value of the transmitted signal and the phase value of the received signal.

[0052] The present invention also provides a multi-modal ultrasonic fluid multi-parameter measurement device, comprising: a signal transmission and collection module, configured to respectively use a first probe and a second probe to send a first transmission signal and a second transmission signal, and correspondingly collect a first reception signal and a second reception signal; wherein the first or second transmission signal generates at least two modes during the propagation process in the system to be measured;

[0053] The sampling module is configured to collect a sample signal from the corresponding received signal using a preset sampling model; wherein the sampling module includes:

[0054] A measuring unit, configured to determine the spatiotemporal distribution characteristics of the mode through the measured results of the signal;

[0055] a time interval determination unit configured to determine time intervals of different modal distributions;

[0056] The sampling condition selection unit is configured to select a corresponding sampling condition according to the sampling model and the time interval, wherein the sampling condition includes: the number of signal sampling points and the signal sampling length; wherein the sampling model includes:

[0057] H1∈(2 N-1 , 2 N );

[0058] H2=2 N ;

[0059] 2*M1<H2<M2;

[0060] Wherein, N is a natural number, H1 is the number of sampling points, H2 is the signal sampling length, M1 is the length of the mode received in the measured results, and M2 is the minimum time interval of the modal distribution;

[0061] A sampling unit, configured to collect a sample signal from the received signal according to the sampling condition;

[0062] The multi-modal calculation module is configured to calculate the measurement volume corresponding to each mode according to the sample signal, and obtain the total volume of the system to be measured according to the measurement volume under each mode.

[0063] Beneficial technical effects:

[0064] In stark contrast to the traditional single-modal calculation approach, the present invention provides a method for calculating pipeline flow based on multi-modal information. This multi-modal calculation method can effectively improve the measurement accuracy of pipeline flow, and is particularly suitable for application scenarios such as aerospace where high-precision measurement is required (unlike the traditional single-modal calculation method, the present invention can more accurately capture the transmission characteristics of the signal and improve the accuracy of flow calculation by independently calculating multiple modes).

[0065] Furthermore, in order to improve the reliability of the multimodal calculation method, the present invention also restricts the number and length of signal sampling points in the signal sampling stage to accurately and effectively collect multimodal information.

[0066] Furthermore, in order to improve the applicability of the multimodal computing method, the present invention also proposes a restrictive signal transmission method, so that the generated multimodal information can be applicable to the multimodal computing method of the present invention through signal transmission adjustment. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, each element or part is not necessarily drawn according to the actual scale. Obviously, the drawings described below are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without paying creative labor.

[0068] Figure 1 It is a flow chart of a non-contact ultrasonic measurement method for strong vibration application in an exemplary embodiment of the present invention;

[0069] Figure 2 This is a schematic diagram of the measuring principle of the ultrasonic measuring meter;

[0070] Figure 3 A schematic diagram of the module structure of a non-contact ultrasonic measurement system for strong vibration applications in an exemplary embodiment of the present invention;

[0071] Figure 4 It is a schematic diagram of the signal characteristics of an ultrasonic flow meter;

[0072] Figure 5It is a flowchart of a multimodal computing method in an exemplary embodiment of the present invention. DETAILED DESCRIPTION

[0073] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0074] Herein, suffixes such as "module", "component" or "unit" used to represent elements are only used to facilitate the description of the present invention, and have no specific meanings by themselves. Therefore, "module", "component" or "unit" can be used mixedly.

[0075] In this document, the terms "upper", "lower", "inner", "outer", "front", "back", "one end", "the other end" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0076] In this document, unless otherwise clearly specified and limited, the terms "installed", "provided with", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0077] Herein "and / or" includes any and all combinations of one or more of the associated listed items.

[0078] Herein, "plurality" means two or more than two, ie, it includes two, three, four, five, etc.

[0079] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0080] As used in this specification, the term "about" typically means + / - 5% of the stated value, more typically + / - 4% of the stated value, more typically + / - 3% of the stated value, more typically + / - 2% of the stated value, even more typically + / - 1% of the stated value, and even more typically + / - 0.5% of the stated value.

[0081] In this specification, some embodiments may be disclosed in a format of being within a certain range. It should be understood that such description of "being within a certain range" is only for convenience and brevity, and should not be interpreted as a rigid limitation on the disclosed range. Therefore, the description of the range should be considered to have specifically disclosed all possible sub-ranges and independent numerical values ​​within this range. For example, the range The description of should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within this range, for example, 1, 2, 3, 4, 5, and 6. The above rules apply regardless of the breadth of the range.

[0082] It is worth noting that the applicant has found that in the existing ultrasonic measurement methods, it is assumed that there is only one mode in the transmission process of the ultrasonic signal in the pipeline. However, the applicant has found that in the pulse wave measurement system, when the transmission signal is transmitted in the pipeline, the signal can generate multiple modes. And, especially when the number of transmission signal cycles is long, the number of modes can also increase. In this regard, the present application proposes a multi-modal calculation method for the multi-modal characteristics that can be generated in the pulse wave measurement system.

[0083] Embodiment 1

[0084] like Figure 5 As shown, the present invention proposes a multi-modal ultrasonic fluid multi-parameter measurement method, comprising:

[0085] S201 uses a first probe and a second probe to send a first transmission signal and a second transmission signal respectively, and collects a first reception signal and a second reception signal correspondingly; wherein the first or second transmission signal generates at least two modes during the propagation process in the system to be measured;

[0086] For example, in some embodiments, the ultrasonic flow meter is composed of a first probe and a second probe, firstly, a transmission signal is sent through the first probe, and a corresponding reception signal is received by the second probe. Secondly, the transmission signal is sent again by the second probe, and then the corresponding reception signal is received by the first probe.

[0087] For example, in some embodiments, the first probe includes: piezoelectric ceramic 1 and an acoustic wedge, and the second probe includes: piezoelectric ceramic 2 and an acoustic wedge.

[0088] S202 uses a preset sampling model to collect a sample signal from the corresponding received signal; wherein S202 includes:

[0089] (1) Determining the spatiotemporal distribution characteristics of the modes through the measured results of the signal; wherein the spatiotemporal distribution characteristics may be a mathematical relationship between the time delay of the signal and the signal amplitude, and the number of modes and the interval between the modes may be determined through the spatiotemporal distribution characteristics;

[0090] (2) determining the time intervals of different modal distributions according to the spatiotemporal distribution characteristics;

[0091] (3) Selecting a corresponding sampling condition based on the sampling model and the time interval obtained in (2), wherein the sampling condition includes: the number of signal sampling points and the signal sampling length; wherein the sampling model includes:

[0092] H1∈(2 N-1 , 2 N );

[0093] H2=2 N ;

[0094] 2*M1<H2<M2;

[0095] Wherein, N is a natural number, H1 is the number of signal sampling points, H2 is the signal sampling length, M1 is the length of the mode received in the measured results, and M2 is the minimum time interval of the modal distribution;

[0096] (4) collecting a sample signal from the received signal according to the sampling condition;

[0097] S203 calculates the measurement volume corresponding to each mode according to the sample signal, and obtains the total volume of the system to be measured according to the measurement volume under each mode.

[0098] In this embodiment, the sampling accuracy of multimodal information can be improved by selecting the number and length of signal sampling points through a sampling model.

[0099] See also Figure 4 As shown, Figure 4 The signal characteristics of the ultrasonic flowmeter are shown. Among them, the ultrasonic flowmeter is composed of 2 pairs of integrated ultrasonic probes. The signal characteristics of the ultrasonic flowmeter are composed of the characteristics of one pair of probes. Specifically, when one of the probes sends a sinusoidal pulse beam (a beam composed of multiple cycles), that is, when transmitting a signal, the corresponding other probe receives 6 ultrasonic modes with different propagation speeds (such as mode 1, mode 2...mode 6). In this embodiment, the signal data of the 6 modes are collected separately, and the measurement volumes under the 6 modes are calculated independently using the signal data of each mode, and finally the total volume of the flow in the pipeline is calculated together by the 6 measurement volumes.

[0100] by Figure 4 Taking the figure as an example, the signal acquisition method is further explained:

[0101] The transmission signal (i.e., the excitation signal) forms 6 significant modes, each of which corresponds to a different time delay. The time delay of the 6 modes reaches 450us, and the modes need to be segmented.

[0102] Specifically, the transmission signal can be segmented by using a window sliding method, which can be divided into the following steps:

[0103] The temporal and spatial distribution characteristics of the mode are determined by the measured results of the transmitted and received signals (such as obtaining Figure 4 The signal characteristic diagram shown);

[0104] After determining the time intervals of different modal distributions, you can configure the sampling window parameters. That is, the window time delay is less than the minimum time interval of the modality. At the same time, to ensure the accuracy of the subsequent algorithm, the window length must be greater than 2 times the length of the receiving mode ( Figure 4 For signals of 80 to 100 cycles, when the sound wave frequency is 5 MHz and the AD sampling rate is 100 MHz, the window length is preferably set to 2048, which can ensure the real-time performance of the subsequent signal processing algorithm.

[0105] Furthermore, in order to ensure that the ultrasonic measuring instrument can work stably under the stimulation of the transmission signal and at the same time enable the user to collect effective multi-modal information, a restrictive signal transmission method is provided in this embodiment for the multi-modal calculation method.

[0106] For example, in some embodiments, before S201, the step of:

[0107] Sending a transmission signal, wherein the number of cycles of the transmission signal is a first set value;

[0108] receiving a received signal corresponding to the transmitted signal;

[0109] Determine whether the difference between the frequency of the received signal and the frequency of the transmitted signal falls within a preset frequency difference range. If so, select the number of cycles of the transmitted signal according to a third selection rule, wherein the third selection rule is: the number of cycles of the transmitted signal ≥ the first set value.

[0110] In some embodiments, it also includes:

[0111] Obtain the signal characteristics of the transmitted signal and the received signal (such as obtaining Figure 4 The signal characteristic diagram shown);

[0112] It is determined whether at least two modes overlap with each other according to the signal characteristics. If not, S202 is executed. If yes, the number of cycles of the transmitted signal is reduced.

[0113] And, through Figure 4 It can be seen that after limiting the number of cycles of the mode, the modal distribution of the measured signal results is clearer. Figure 4 The signal characteristics of the transmitted signal and the received signal are also relatively consistent, which also shows that the measured results of the collected signals are effective and reliable.

[0114] In some embodiments, the number of cycles of the transmitted signal is 50-100.

[0115] In some embodiments, the system to be measured includes: a pipeline, and the diameter of the pipeline is greater than 15 mm. In this embodiment, in order to ensure the effectiveness of the multimodal calculation method, it is preferably applied to the measurement scenario of pipelines with a diameter greater than 15 mm.

[0116] Furthermore, the multimodal calculation method of the present invention is preferably applied to flow measurement of pipelines with a diameter greater than 20 mm.

[0117] In some embodiments, S203 includes the steps of:

[0118] The first flow calculation model is used to calculate the measured volume in each mode; wherein the first flow calculation model is:

[0119]

[0120] Q V represents the volume flow rate, R represents the pipe radius, represents the speed of sound wave propagation in solids, φ u represents the phase of the countercurrent, φ d represents the phase of the downstream, and θ1 represents the ultrasonic transducer.

[0121] The measured volumes under each mode are averaged to calculate the average measured volume;

[0122] The total volume is calculated according to a second flow calculation model; wherein the second flow calculation model is:

[0123] Where t is time, is the average measurement volume, ΔQ V is the cumulative measurement error.

[0124] In some embodiments, the step of calculating the measured volume in each mode using the first flow calculation model includes:

[0125] Calculate the downstream phase difference and the upstream phase difference between the transmission signal and the corresponding reception signal in the first probe and the second probe respectively;

[0126] Calculate the downstream delay time and the upstream delay time corresponding to the first probe and the second probe respectively;

[0127] A phase calculation model is used to calculate the downstream phase and the upstream phase according to the downstream phase difference, the upstream phase difference and the downstream delay time and the upstream delay time respectively; and the first flow calculation model is used to calculate the volume to be measured according to the downstream phase and the upstream phase.

[0128] In some embodiments, the delay time calculation step includes:

[0129] Performing Fourier transform on the received signal and the transmitted signal respectively, so as to obtain a first Fourier transform complex value and a second Fourier transform complex value correspondingly;

[0130] performing conjugate point multiplication on the first Fourier transformed complex value and the second Fourier transformed complex value to obtain a third Fourier transformed complex value;

[0131] The corresponding delay time is read according to the third Fourier transform complex value, and the delay time is a position point corresponding to the maximum peak point in the corresponding Fourier transform complex value.

[0132] In some embodiments, the step of calculating the phase difference includes:

[0133] S21 performs Fourier transform on the transmission signal to obtain a first Fourier transform complex value, and finds the amplitude |F 发射 |The maximum value and the corresponding frequency position;

[0134] S22 performs Fourier transform on the received signal to obtain a second Fourier transform complex value, and obtains a corresponding Fourier transform complex value at the frequency position obtained in S21 in the second Fourier transform complex value;

[0135] S23, at the frequency position, using the real part and the imaginary part of the Fourier transform complex value corresponding to the first Fourier transform complex value at the frequency position to calculate the phase value of the transmitted signal, and using the real part and the imaginary part of the Fourier transform complex value corresponding to the second Fourier transform complex value at the same frequency position to calculate the phase value of the received signal;

[0136] S24 calculates a corresponding phase difference according to the phase value of the transmitted signal and the phase value of the received signal.

[0137] Embodiment 2

[0138] The present invention also provides a multi-mode ultrasonic fluid multi-parameter measurement device, comprising:

[0139] The signal transmitting and collecting module is configured to respectively use the first probe and the second probe to send the first transmitting signal and the second transmitting signal, and correspondingly collect the first receiving signal and the second receiving signal; wherein the first or second transmitting signal generates at least two modes during the propagation process in the system to be measured;

[0140] The sampling module is configured to collect a sample signal from the corresponding received signal using a preset sampling model; wherein the sampling module includes:

[0141] A measuring unit, configured to determine the spatiotemporal distribution characteristics of the mode through the measured results of the signal;

[0142] a time interval determination unit configured to determine time intervals of different modal distributions;

[0143] The sampling condition selection unit is configured to select a corresponding sampling condition according to the sampling model and the time interval, wherein the sampling condition includes: the number of signal sampling points and the signal sampling length; wherein the sampling model includes:

[0144] H1∈(2 N-1 , 2 N );

[0145] H2=2 N ;

[0146] 2*M1<H2<M2;

[0147] Wherein, N is a natural number, H1 is the number of sampling points, H2 is the signal sampling length, M1 is the length of the mode received in the measured results, and M2 is the minimum time interval of the modal distribution;

[0148] A sampling unit, configured to collect a sample signal from the received signal according to the sampling condition;

[0149] The multi-modal calculation module is configured to calculate the measurement volume corresponding to each mode according to the sample signal, and obtain the total volume of the system to be measured according to the measurement volume under each mode.

[0150] Furthermore, in some embodiments, the system further comprises:

[0151] The signal period adjustment module is configured to obtain the signal characteristics of the transmitted signal and the received signal; determine whether there are at least two modes overlapping each other according to the signal characteristics, if not, perform signal sampling, and if so, reduce the number of periods of the transmitted signal.

[0152] The system in this embodiment can implement any step in the above method, which will not be described in detail here.

[0153] It can be understood that the ultrasonic measurement mainly includes: signal transmission, signal collection and signal calculation stages. The preferred signal calculation method in the present invention will be described below through embodiments three and four.

[0154] Embodiment 3

[0155] See also Figure 1 As shown, the present invention provides a non-contact ultrasonic measurement method for strong vibration applications, comprising the steps of:

[0156] S101: Acquire a downstream signal and an upstream signal, wherein the downstream signal includes: a first transmission signal and a first reception signal corresponding thereto, and the upstream signal includes: a second transmission signal and a second reception signal corresponding thereto;

[0157] In some embodiments, the same number of data points are collected for the transmitted signal and the received signal.

[0158] S102 calculates the downstream phase difference and the upstream phase difference between the transmitted signal and the corresponding received signal in the downstream signal and the upstream signal respectively;

[0159] S103 calculates the downstream delay time and the downstream delay time of the downstream signal and the upstream signal respectively;

[0160] S104 uses a phase calculation model to calculate the downstream phase and the upstream phase according to the downstream phase difference, the upstream phase difference, the downstream delay time, and the upstream delay time; wherein the phase calculation model includes:

[0161]

[0162]

[0163] Among them, Int represents the phase ambiguity number, τ0 represents the delay time, and f represents the signal frequency. represents the phase difference, and φ represents the phase.

[0164] S105 calculates the volume flow to be measured according to the phase of the downstream flow and the phase of the upstream flow. The calculation model of the volume flow is:

[0165]

[0166] Among them, Q V represents the volume flow rate, R represents the pipe radius, represents the speed of sound wave propagation in solids, φ u represents the phase of the countercurrent, φ d represents the downstream phase, θ1 represents the angle between the normal direction of the ultrasonic transducer (or ultrasonic probe) and the normal direction of the pipe wall (e.g. Figure 2 shown).

[0167] Ultrasonic measurement principle Figure 2 As shown in the figure, the piezoelectric ceramic in the ultrasonic probe (mainly including piezoelectric ceramic sheets and acoustic wedges) is connected to the pipe wall through the acoustic wedge, and the sound wave propagation path can be extended by changing the position of the acoustic wedge. The angle between the normal direction of the ultrasonic transducer (that is, the ultrasonic probe) and the normal direction of the pipe wall is θ1, and the thickness of the pipe wall is h w , the distance between the sound wedges is L, the ultrasonic transducer is on the plane of the pipe axis, and the measured pipe radius is R. Considering that the pipe wall and the ultrasonic sound wedge are made of the same material, the ultrasonic wave propagates at the same speed in the sound wedge and the pipe wall, and there is no angle change. On the inner wall of the pipe, due to the inconsistent propagation speed of sound waves in different media, the refraction angle θ2 is caused. Among them, it can be assumed that the fluid flow field is a uniform flow field

[0168] The applicant has noticed that if the ultrasonic flowmeter operates in a strong vibration environment such as caused by the operation of an engine, the ultrasonic flowmeter vibrates along with the pipe wall vibration. When the ultrasonic flowmeter is used as a transmitting sound source, the vibrating ultrasonic flowmeter becomes a moving sound source, causing Doppler frequency shift.

[0169] In a strong vibration environment, the Doppler frequency shift phenomenon in the signal acquisition data is very obvious, but the traditional phase difference calculation method is difficult to eliminate the influence of the Doppler frequency shift. Therefore, the present invention proposes a phase difference solution method for performing correlation calculation on the transmitted signal and the received signal for phase difference measurement in a strong vibration environment. By performing correlation calculation on the transmitted signal and the received signal, the influence of the Doppler frequency shift on the flow measurement can be eliminated to a certain extent.

[0170] For example, in some embodiments, S102 includes the steps of:

[0171] S21 performs Fourier transform on the transmission signal to obtain a first Fourier transform complex value, and finds the amplitude |F 发射 |The maximum value and the corresponding frequency position;

[0172] S22 performs Fourier transform on the received signal to obtain a second Fourier transform complex value, and obtains a corresponding Fourier transform complex value at the frequency position obtained in S21 in the second Fourier transform complex value;

[0173] S23, at the frequency position, using the real part and the imaginary part of the Fourier transform complex value corresponding to the first Fourier transform complex value at the frequency position to calculate the phase value of the transmitted signal, and using the real part and the imaginary part of the Fourier transform complex value corresponding to the second Fourier transform complex value at the same frequency position to calculate the phase value of the received signal;

[0174] S24 calculates a corresponding phase difference according to the phase value of the transmitted signal and the phase value of the received signal.

[0175] For example, in some embodiments, the first transmission signal is first subjected to a Fourier transform, and the Fourier transform amplitude |F 发射 | maximum value and the corresponding frequency position. At the same time, the first received signal is subjected to a corresponding Fourier transform F 接收 , find the Fourier transform value of the first received signal at the frequency position of the maximum amplitude point of the first transmitted signal, and use the real and imaginary parts of the Fourier transform at the same frequency position to obtain the phase value of the first transmitted signal and the first received signal, that is, φ = atan (F imag / F real ), the phase delay (i.e., phase difference) can be obtained by subtracting the phase of the first transmitted signal from the phase of the first received signal.

[0176] In this embodiment, the signal phase is calculated according to the co-frequency position of the transmitted signal and the received signal, which can effectively alleviate the signal detection error generated in a high-intensity vibration environment.

[0177] In addition, traditional delay algorithms usually use time domain convolution methods, but the amount of data calculation in the time domain convolution method is very high and the hardware consumption is large. In this regard, this application proposes a frequency domain product calculation method based on multi-level evaluation to reduce the amount of calculation and hardware consumption while improving the calculation reliability.

[0178] For example, in some embodiments, S103 includes the steps of:

[0179] S31 performs Fourier transform on the received signal and the transmitted signal respectively to obtain a first Fourier transform complex value and a second Fourier transform complex value correspondingly;

[0180] S32 performs conjugate point multiplication on the first Fourier transform complex value and the second Fourier transform complex value to obtain a third Fourier transform complex value;

[0181] S33 reads a corresponding delay time according to the third Fourier transform complex value, where the delay time is a position point corresponding to the maximum peak point in the corresponding Fourier transform complex value.

[0182] In some embodiments, S33 includes the steps of:

[0183] Determine whether the signal strength in the third Fourier transform complex value belongs to a second strength threshold range; for example, determine whether the signal strength is greater than or equal to 1010 dBm.

[0184] If yes, then execute the steps:

[0185] Using a frequency domain low-pass filtering method to filter the third Fourier transform complex value, and correspondingly obtain a fourth Fourier transform complex value;

[0186] Find the maximum peak point in the fourth Fourier transform complex value, and use the position point corresponding to the maximum peak point as the delay time;

[0187] If not, then perform the following steps:

[0188] Performing an inverse Fourier transform on the third Fourier transform complex value to obtain a fifth Fourier transform complex value;

[0189] Squaring the fifth Fourier transform complex value, and performing Fourier transform on the squared fifth Fourier transform complex value to obtain a sixth Fourier transform complex value;

[0190] The sixth Fourier transform complex value is filtered by using a frequency domain low-pass filtering method, and the seventh Fourier transform complex value is obtained by using an inverse Fourier transform again;

[0191] The maximum peak point in the seventh Fourier transform complex value is found, and the position point corresponding to the maximum peak point is used as the delay time. Furthermore, high-precision delay information of the downstream signal and the upstream signal is calculated by successive Fourier transforms and signal processing cross processing.

[0192] In this embodiment, in order to address the delay measurement error caused by Doppler frequency shift, especially in high-intensity vibration environments, a collaborative processing method based on intensity verification and multi-level Fourier transform is proposed to accurately calculate high-precision delay information for different vibration environments.

[0193] Furthermore, the frequency domain product method in this embodiment can implement parallel computing in a field programmable logic device (FPGA), thereby reducing hardware consumption.

[0194] Furthermore, in order to improve the accuracy of flow measurement, the present invention also proposes a restrictive signal transmission method to limit key features such as signal transmission frequency and number of cycles, thereby improving the accuracy and reliability of subsequent data collection and calculation.

[0195] In some embodiments, before S101, the method further includes:

[0196] sending a transmit signal at a first frequency;

[0197] receiving a received signal corresponding to the transmitted signal;

[0198] Determine whether the signal strength of the received signal falls within a first strength threshold range; if so, determine the second frequency according to a first selection rule, where the first selection rule requires that the second frequency be greater than or equal to the first frequency; correspondingly, send the corresponding first or second transmission signal at the second frequency in S101.

[0199] For example, in some embodiments, when applied to the flow measurement of the fuel supply pipeline of the engine, if the signal strength (such as the signal-to-noise ratio) of the received signal is greater than or equal to 10 dBm, the current actual transmission frequency can be used as the minimum transmission frequency in the actual measurement process.

[0200] That is to say, before the flow measurement is performed in this embodiment, the frequency of the transmitted signal can be selected through a pre-test to ensure the accuracy of subsequent signal acquisition and phase and delay calculation.

[0201] Preferably, in some embodiments, ultrasonic waves of one frequency are used as the transmission signal.

[0202] In some embodiments, the number of cycles of the transmitted signal satisfies a second selection rule, and the second selection rule is:

[0203]

[0204] The signal sampling rate (also known as sampling speed or sampling frequency) refers to the number of samples extracted from a continuous signal to form a discrete signal per unit time. The signal sampling length is used to represent the total length of the sample points collected during the sampling process (or the length of the discrete signal obtained by the collection).

[0205] In some embodiments, before S101, the method further includes:

[0206] Sending a transmission signal, wherein the number of cycles of the transmission signal is a first set value;

[0207] receiving a received signal corresponding to the transmitted signal;

[0208] Determine whether the difference between the frequency of the received signal and the frequency of the transmitted signal falls within a preset frequency difference range. If so, select the number of cycles of the transmitted signal according to a third selection rule, wherein the third selection rule is: the number of cycles of the transmitted signal ≥ the first set value.

[0209] For example, in some embodiments, before performing actual flow measurement, the steps include:

[0210] After the actual transmission frequency of the transmission signal (equivalent to the second frequency) is selected, a pulse wave of 30 cycles (equivalent to the first set number) is sent in advance at the selected transmission frequency, and it is determined whether the current received signal is at the same frequency as the transmission signal. If so, the number of cycles of the actual transmission signal can be set to be greater than or equal to 30.

[0211] Different from the traditional Doppler measurement technology, the present invention uses the ultrasonic probe as a moving sound source for measurement, and correspondingly proposes a time delay and phase combination measurement method based on a restrictive excitation mode. On the one hand, it can ensure that the ultrasonic probe can work stably at the excitation frequency through a specific excitation mode, and on the other hand, it can combine the transmission and reception signals for correlation calculation, so as to obtain the flow in the pipeline in a vibrating state through comprehensive calculation of time delay and phase.

[0212] Specifically, the present invention can limit two characteristics of the transmission signal, such as the number of cycles and the frequency, during the pre-test phase to ensure that the ultrasonic probe can work stably at the excitation frequency and that the ultrasonic wave can ensure the accuracy of subsequent delay and phase calculations.

[0213] For example, in some embodiments, the present invention usually sets the number of cycles to be greater than or equal to 50 through the second and third selection rules to ensure that the transmission signal and the reception signal have the same frequency.

[0214] Embodiment 4

[0215] like Figure 3As shown, the present invention also provides a non-contact ultrasonic measurement system for strong vibration applications, including:

[0216] The signal acquisition module 10 is configured to acquire a downstream signal and an upstream signal, wherein the downstream signal includes: a first transmission signal and a first reception signal corresponding thereto, and the upstream signal includes: a second transmission signal and a second reception signal corresponding thereto;

[0217] The phase difference calculation module 20 is configured to calculate the downstream phase difference and the upstream phase difference between the transmitted signal and the corresponding received signal in the downstream signal and the upstream signal respectively;

[0218] The delay time calculation module 30 is configured to respectively calculate the downstream delay time and the upstream delay time of the downstream signal and the upstream signal; wherein the delay time calculation module includes:

[0219] The first transform unit 31 is configured to perform Fourier transform on the received signal and the transmitted signal respectively, so as to obtain a first Fourier transform complex value and a second Fourier transform complex value correspondingly;

[0220] A conjugate point multiplication unit 32 is configured to perform conjugate point multiplication on the first Fourier transform complex value and the second Fourier transform complex value to obtain a third Fourier transform complex value;

[0221] The delay time calculation unit 33 is configured to read the corresponding delay time according to the third Fourier transform complex value, wherein the delay time is a position point corresponding to the maximum peak point in the corresponding Fourier transform complex value;

[0222] The phase calculation module 40 is configured to respectively calculate the downstream phase and the upstream phase according to the downstream phase difference, the upstream phase difference, the downstream delay time and the downstream delay time using a phase calculation model;

[0223] The volume flow calculation module 50 is configured to calculate the volume flow to be measured according to the phase of the downstream flow and the phase of the upstream flow.

[0224] In some embodiments, the system further comprises:

[0225] The first pre-transmission module 60 is configured to send a transmission signal at a first frequency; receive a reception signal corresponding to the transmission signal; determine whether the signal strength of the reception signal falls within a first strength threshold range, and if so, determine a second frequency according to a first selection rule, wherein the first selection rule requires that the second frequency is greater than or equal to the first frequency; correspondingly, send the corresponding first or second transmission signal at the second frequency.

[0226] In some embodiments, the number of cycles of the transmitted signal satisfies a second selection rule, and the second selection rule is:

[0227]

[0228] In some embodiments, the system further comprises:

[0229] The second pre-transmission module 70 is configured to send a transmission signal, and the number of cycles of the transmission signal is a first set value; receive a received signal corresponding to the transmission signal; determine whether the difference between the frequency of the received signal and the frequency of the transmission signal belongs to a preset frequency difference range, and if so, select the number of cycles of the transmission signal according to a third selection rule, and the third selection rule is: the number of cycles of the transmission signal ≥ the first set value.

[0230] In some embodiments, the phase difference calculation module includes:

[0231] The transmission signal calculation unit 21 is configured to perform Fourier transform on the transmission signal to obtain a first Fourier transform complex value, and find the amplitude |F 发射 |The maximum value and the corresponding frequency position;

[0232] A received signal calculation unit 22 is configured to perform Fourier transform on the received signal to obtain a second Fourier transform complex value, and obtain a corresponding Fourier transform complex value at a frequency position obtained in the transmitted signal calculation unit in the second Fourier transform complex value;

[0233] The phase value calculation unit 23 is configured to calculate the phase value of the transmitted signal at the frequency position using the real part and the imaginary part of the Fourier transform complex value corresponding to the first Fourier transform complex value at the frequency position, and calculate the phase value of the received signal using the real part and the imaginary part of the Fourier transform complex value corresponding to the second Fourier transform complex value at the same frequency position;

[0234] The phase difference calculation unit 24 is configured to calculate the corresponding phase difference according to the phase value of the transmitted signal and the phase value of the received signal.

[0235] In some embodiments, the delay time calculation unit includes:

[0236] a judgment subunit configured to judge whether the signal strength in the third Fourier transform complex value belongs to the second strength threshold range; if so, start the first delay calculation subunit, which is configured to filter the third Fourier transform complex value by using a frequency domain low-pass filtering method to obtain a fourth Fourier transform complex value accordingly;

[0237] Find the maximum peak point in the fourth Fourier transform complex value, and use the position point corresponding to the maximum peak point as the delay time; if not, start the second delay calculation subunit, which is configured to perform an inverse Fourier transform on the third Fourier transform complex value to obtain a fifth Fourier transform complex value; square the fifth Fourier transform complex value, and perform Fourier transform on the squared fifth Fourier transform complex value to obtain a sixth Fourier transform complex value; use frequency domain low-pass filtering to filter the sixth Fourier transform complex value, and use inverse Fourier transform again to obtain a seventh Fourier transform complex value; find the maximum peak point in the seventh Fourier transform complex value, and use the position point corresponding to the maximum peak point as the delay time.

[0238] Furthermore, compared with the standard sidetone phase measurement method that uses multiple frequency sound waves, the present invention solves the problem of precision measurement by using only one frequency sound wave.

[0239] The present invention combines the advantages of pulse wave and continuous wave. It only needs to send once to solve the problem. The traditional measurement mode needs to send pulse wave first and then send continuous wave, and the operation process is relatively complicated.

[0240] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0241] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus a necessary general hardware platform, and of course by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, a magnetic disk, or an optical disk), and includes a number of instructions for a computer terminal (which can be a mobile phone, a computer, a server, or a network device, etc.) to execute the methods described in each embodiment of the present invention.

[0242] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation modes, which are merely illustrative rather than restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are within the protection of the present invention.

Claims

1. A multi-modal ultrasonic fluid multi-parameter measurement method, characterized in that: include: S201 uses a first probe and a second probe to send a first transmission signal and a second transmission signal respectively, and collects a first reception signal and a second reception signal correspondingly; wherein the first or second transmission signal generates at least two modes during the propagation process in the system to be measured; S202 uses a preset sampling model to collect a sample signal from the corresponding received signal; wherein S202 includes: (1) Determine the spatiotemporal distribution characteristics of the mode through the measured signal results; (2) determining the time intervals of different modal distributions according to the spatiotemporal distribution characteristics; (3) Selecting a corresponding sampling condition based on the sampling model and the time interval obtained in (2), wherein the sampling condition includes: the number of signal sampling points and the signal sampling length; wherein the sampling model includes: H1∈(2 N-1 ，2 N )； ； ； Wherein, N is a natural number, H1 is the number of signal sampling points, H2 is the signal sampling length, M1 is the length of the mode received in the measured result, and M2 is the minimum time interval of the modal distribution; (4) collecting the sample signal from the received signal according to the sampling condition; S203 calculates the measurement volume corresponding to each of the modes according to the sample signal, and obtains the total volume of the system to be measured according to the measurement volume under each of the modes; wherein the measurement volume under each mode is calculated using a first flow calculation model; wherein the first flow calculation model is: ;in, Represents the measured volume, represents the pipe radius, represents the speed of sound wave propagation in solids, Indicates the phase of countercurrent, represents the downstream phase, Indicates the angle between the normal direction of the probe and the normal direction of the pipe wall; The measured volumes under each mode are averaged to calculate the average measured volume; The total volume is calculated according to a second flow calculation model; wherein the second flow calculation model is: ； Where t is time, is the average measured volume, is the cumulative measurement error.

2. The method according to claim 1, characterized in that Before S201, the steps include: Sending a transmission signal, wherein the number of cycles of the transmission signal is a first set value; receiving a received signal corresponding to the transmitted signal; Determine whether the difference between the frequency of the received signal and the frequency of the transmitted signal falls within a preset frequency difference range. If so, select the number of cycles of the transmitted signal according to a third selection rule, wherein the third selection rule is: the number of cycles of the transmitted signal ≥ the first set value.

3. The method according to claim 2, characterized in that Also includes: Acquiring signal characteristics of the transmitted signal and the received signal; It is determined according to the signal characteristics whether at least two of the modes overlap with each other. If not, S202 is executed. If so, the number of cycles of the transmitted signal is reduced.

4. The method according to claim 3, characterized in that The number of cycles of the transmission signal is 50-100.

5. The method according to claim 1, characterized in that The system to be measured includes: a pipeline, and the diameter of the pipeline is greater than 15 mm.

6. The method according to claim 5, characterized in that The step of using the first flow calculation model to calculate the measurement volume under each mode includes: Calculate the downstream phase difference and the upstream phase difference between the transmission signal and the corresponding reception signal in the first probe and the second probe respectively; Calculate the downstream delay time and the upstream delay time corresponding to the first probe and the second probe respectively; A phase calculation model is used to calculate the downstream phase and the upstream phase according to the downstream phase difference, the upstream phase difference and the downstream delay time and the upstream delay time respectively; and the first flow calculation model is used to calculate the volume to be measured according to the downstream phase and the upstream phase.

7. The method according to claim 6, characterized in that The calculation steps of the delay time include: Performing Fourier transform on the received signal and the transmitted signal respectively, so as to obtain a first Fourier transform complex value and a second Fourier transform complex value correspondingly; performing conjugate point multiplication on the first Fourier transformed complex value and the second Fourier transformed complex value to obtain a third Fourier transformed complex value; The corresponding delay time is read according to the third Fourier transform complex value, and the delay time is a position point corresponding to the maximum peak point in the corresponding Fourier transform complex value.

8. The method according to claim 6, characterized in that The calculation steps of phase difference include: S21 performs Fourier transform on the transmission signal to obtain a first Fourier transform complex value, and finds the amplitude |F 发射 |The maximum value and the corresponding frequency position; S22 performs Fourier transform on the received signal to obtain a second Fourier transform complex value, and obtains a corresponding Fourier transform complex value at the frequency position obtained in S21 in the second Fourier transform complex value; S23 calculates the phase value of the transmitted signal using the real part and the imaginary part of the Fourier transform complex value corresponding to the first Fourier transform complex value at the frequency position, and calculates the phase value of the received signal using the real part and the imaginary part of the Fourier transform complex value corresponding to the second Fourier transform complex value at the same frequency position; S24 calculates a corresponding phase difference according to the phase value of the transmitted signal and the phase value of the received signal.

9. A multi-modal ultrasonic fluid multi-parameter measurement device, characterized in that: include: The signal transmitting and collecting module is configured to respectively use the first probe and the second probe to send the first transmitting signal and the second transmitting signal, and correspondingly collect the first receiving signal and the second receiving signal; wherein the first or second transmitting signal generates at least two modes during the propagation process in the system to be measured; The sampling module is configured to collect a sample signal from the corresponding received signal using a preset sampling model; wherein the sampling module includes: A measuring unit, configured to determine the spatiotemporal distribution characteristics of the mode through the measured results of the signal; a time interval determination unit configured to determine time intervals of different modal distributions; A sampling condition selection unit is configured to select a corresponding sampling condition according to the sampling model and the time interval, wherein the sampling condition includes: the number of signal sampling points and the signal sampling length; wherein the sampling model includes: H1∈(2 N-1， 2 N )； ； 2*M1<H2<M2; Wherein, N is a natural number, H1 is the number of signal sampling points, H2 is the signal sampling length, M1 is the length of the mode received in the measured results, and M2 is the minimum time interval of the modal distribution; A sampling unit, configured to collect a sample signal from the received signal according to the sampling condition; The multimodal calculation module is configured to calculate the measurement volume corresponding to each mode according to the sample signal, and obtain the total volume of the system to be measured according to the measurement volume under each mode; wherein the measurement volume under each mode is calculated using a first flow calculation model; wherein the first flow calculation model is: ;in, Represents the measured volume, represents the pipe radius, represents the speed of sound wave propagation in solids, Indicates the phase of countercurrent, represents the downstream phase, Indicates the angle between the normal direction of the probe and the normal direction of the pipe wall; The measured volumes under each mode are averaged to calculate the average measured volume; The total volume is calculated according to a second flow calculation model; wherein the second flow calculation model is: ； Where t is time, is the average measured volume, is the cumulative measurement error.

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