Wireless ultrasonic flow measurement method and apparatus

Abstract

The application discloses a wireless ultrasonic flow measurement method and device, wherein reference waves are stored in devices at two ends of a river channel in advance, cross-correlation operation is performed on echo signals received by devices at two ends of an upstream and a downstream respectively and corresponding reference wave signals during actual flow measurement, and finally, a calculation result obtained by one of the devices is transmitted to the other device to calculate a final time difference, so that a large amount of original echo data does not need to be transmitted again, the requirements for software and hardware are low, and rapid and real-time accurate measurement of the river channel flow is more easily realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of flow measurement, in particular to a wireless ultrasonic flow measurement method and device. BACKGROUND

[0002] Most of the current ultrasonic time difference method flow measurement technologies adopt wired connection mode, and are widely used in pipeline and open channel flow measurement, but less used in natural river wide channels. With the development of technology, to solve the problem of high cost of installing over-river cable, more and more researches on wireless ultrasonic time difference method flow measurement system are carried out at home and abroad. The wireless ultrasonic time difference method flow measurement system ensures the synchronization of ultrasonic wave transmission and reception of the equipment at both ends of the main machine and the auxiliary machine through high-precision satellite timing, and realizes wireless transmission of data between the equipment at both ends through radio station, without laying over-river cable, simple engineering installation, and no influence on river navigation. Therefore, the wireless ultrasonic time difference method flow measurement is a new type of flow measurement technology which is planned to be widely promoted by water conservancy departments in the future, because it has high measurement accuracy, fast speed, convenient engineering installation, and can realize real-time online automatic flow measurement under long-term unattended condition.

[0003] The wireless ultrasonic time difference method flow measurement system measures the downstream propagation time t1 of ultrasonic wave at the upstream end of the river channel, and measures the upstream propagation time t2 of ultrasonic wave at the downstream end of the river channel, calculates the time difference Δt=t1-t2 of the downstream and upstream propagation of ultrasonic wave at both ends, and calculates the average flow velocity and flow of fluid according to the ultrasonic time difference Δt. The structure and flow measurement principle diagram of the wireless ultrasonic time difference method flow measurement system are shown in Figure 1 and Figure 2 .

[0004] The wireless ultrasonic time difference method flow measurement system calculates the flow according to the average laminar flow velocity and cross-sectional area, and the specific calculation method is as follows:

[0005]

[0006] In the formula:

[0007] Q──flow, m 3 / s;

[0008] α──flow velocity correction coefficient;

[0009] ──average laminar flow velocity, m / s;

[0010] S──cross-sectional area, m 2 ;

[0011] Where the cross-sectional area S is related to the water level, which can be determined by the water level cross-sectional area relationship, and the flow velocity correction coefficient α can be calibrated through later calibration, the key problem is how to accurately measure the average laminar flow velocity

[0012] Average laminar flow velocity in ultrasonic time difference method flow measurement system The calculation method is as follows:

[0013]

[0014] In the formula:

[0015] C──Speed of sound in stationary fluid, m / s;

[0016] Δt──Time difference of ultrasonic propagation between two ends, s;

[0017] L──Distance between ultrasonic transducers at both ends, m;

[0018] θ──Angle between ultrasonic propagation path and water flow direction, degree;

[0019] For wireless ultrasonic time difference method flow measurement system, the distance L between transducers and the ultrasonic transducer emission angle θ can be accurately determined according to engineering survey during measurement, and the speed of sound C can also be ensured by the accuracy of fluid temperature and other parameters and later correction work, so the accurate calculation of the time difference Δt of ultrasonic propagation between two ends of the river channel becomes the key to ensure the accuracy of flow velocity and flow measurement.

[0020] The traditional time difference calculation methods include threshold method and cross-correlation method. The threshold method mainly determines one or more adaptive threshold levels according to the collected echo signals, and the time when the detected echo signal amplitude reaches the threshold range (or the zero-crossing point after the threshold range) is the ultrasonic wave transit time. Then, the transit times obtained by the devices at two ends are subtracted to obtain the time difference. The threshold comparison method has certain applicability in scenes such as pipelines and open channels with good water conditions and less noise interference. However, for wide river channels, due to the influence of fluid noise, bubbles, floating objects and the like, the echo signal waveform often distorts or even has peak value missing phenomenon, the signal amplitude decreases and the threshold point cannot be normally detected, resulting in large errors or errors in the transit time measured by the device at one end or even both ends, so that the accurate ultrasonic time difference cannot be obtained. The cross-correlation method for calculating the ultrasonic wave flow time difference mainly performs cross-correlation operation on the echo signals received at both ends of the river channel, and finds the peak position of the cross-correlation operation, which is the time difference of ultrasonic wave propagation at both ends. Cross-correlation is used to represent the similarity between two signals, which is a function of two signals with respect to time. The position of the maximum peak of the cross-correlation function is the time difference between the two signals. Although the cross-correlation method for calculating the ultrasonic time difference is not easily affected by echo waveform distortion and amplitude fluctuation, and has certain inhibitory effect on interference noise in the echo signal, and the programming is simple and easy to implement, but since the wireless ultrasonic wave time difference flow measurement device is located on the upper and lower reaches of the river channel, real-time waveform data needs to be wirelessly transmitted to the other end for cross-correlation calculation. In actual measurement, a higher signal sampling rate and sampling length are required to accurately calculate the ultrasonic time difference at both ends. Higher sampling rate and sampling length will result in too large waveform data, and the collected waveform data is not easy to transmit quickly on both banks of the river. SUMMARY

[0021] One of the purposes of the present application is to provide a wireless ultrasonic wave flow measurement method to solve the problem of too large waveform data caused by the existing wireless ultrasonic wave flow measurement method, which makes it difficult to quickly transmit the collected waveform data on both banks of the river.

[0022] To achieve the above purpose, the technical scheme is as follows.

[0023] A wireless ultrasonic wave flow measurement method, comprising the following steps:

[0024] S1, constructing a reference wave r(t) using sampling data:

[0025]

[0026] In the formula, y(t) is the sampling signal of the echo received at the upstream end, x(t) is the sampling signal of the echo received at the downstream end, and Δτ is the time difference between x(t) and y(t); the range of t is (A, B), and A~B is the signal collection interval of the reference wave.

[0027] S2, storing the reference wave in the upstream end and the downstream end respectively;

[0028] S3, measuring the upstream end received echo signal y'(t) and the downstream end received echo signal x'(t);

[0029] S4, performing cross-correlation operation between the upstream end received echo signal y'(t) and the reference wave r(t) stored in the upstream end to obtain the cross-correlation function R ry (τ) of the upstream end received echo signal and the reference wave; performing cross-correlation operation between the downstream end received echo signal x'(t) and the reference wave r(t) stored in the downstream end to obtain the cross-correlation function R rx (τ) of the downstream end received echo signal and the reference wave;

[0030] S5, obtaining the time difference Δt = τ1- τ2 of the ultrasonic wave propagation between the upstream end and the downstream end; wherein τ1 is the value of τ corresponding to the maximum peak value of R rx (τ), and τ2 is the value of τ corresponding to the maximum peak value of R ry (τ); the range of τ is (0, 2(B-A));

[0031] S6, calculating the flow rate Q by using the following formula:

[0032]

[0033] In the formula: is the average laminar degree, C is the sound wave speed in the static fluid, Δt is the time difference of the ultrasonic wave propagation between the upstream end and the downstream end, L is the distance between the ultrasonic transducers at the upstream end and the downstream end, θ is the angle between the ultrasonic wave propagation path and the water flow direction, Q is the flow rate, α is the flow rate correction coefficient, and S is the cross-sectional area.

[0034] The above method pre-stores the reference wave in the devices at both ends of the river channel respectively, performs cross-correlation operation between the echo signals received at the upstream end and the downstream end and the corresponding reference wave signals during actual flow measurement, and finally only needs to transmit the operation result obtained by one of the devices to the other device to calculate the final time difference, without the need to transmit a large amount of original echo data, which has lower requirements for software and hardware and is easier to realize rapid and real-time accurate measurement of the river flow.

[0035] To solve the problem of the difference in the amplitude or waveform of the ultrasonic echo caused by different water levels, in some embodiments, the upstream end received echo sampling signal y(t) includes a plurality of echo sampling signals corresponding to different water level sections: y1(t), y2(t), …, y i (t), …, y n(t); the downstream end receives echo sampling signals x(t), which include multiple echo sampling signals corresponding to different water level segments: x1(t), x2(t), ..., x i (t), ..., x n (t); where n is the total number of water level segments and i is the sequence number of the water level segment; in step S4, the reference wave is the reference wave of the same water level segment as the upstream and downstream received echo signals.

[0036] To further improve measurement accuracy, in some embodiments, the cross-correlation operation in step S4 uses a generalized cross-correlation operation, which includes the following steps:

[0037] The generalized cross-correlation function R between the downstream received echo signal and the reference wave is calculated using the following formula. rx (τ):

[0038]

[0039] The generalized cross-correlation function R between the upstream received echo signal and the reference wave is calculated using the following formula. ry (τ):

[0040]

[0041] In the formula, G is the cross-power spectrum weighting function of the reference wave and the downstream received echo signal. rx (ω) represents the cross-power spectrum between the reference wave and the echo signal received downstream. G is the cross-power spectrum weighting function of the reference wave and the echo signal from the upstream receiver. ry (ω) represents the cross-power spectrum between the reference wave and the echo signal from the upstream receiver, where ω is the angular frequency of the reference wave.

[0042] To further improve measurement accuracy, in some embodiments, the cross-correlation operation in step S4 uses a generalized quadratic cross-correlation operation, including the following steps:

[0043] S41. Calculate the autocorrelation function R1 of the downstream received echo signal using the following formula. xx (τ):

[0044]

[0045] The autocorrelation function R1 of the upstream receiver echo signal is calculated using the following formula. yy (τ):

[0046]

[0047] The cross-correlation function R1 between the downstream received echo signal and the reference wave is calculated using the following formula. rx(τ) :

[0048]

[0049] The cross-correlation function R1 between the upstream received echo signal and the reference wave is calculated by the following formula ry (τ) :

[0050]

[0051] The generalized quadratic cross-correlation function R between the downstream received echo signal and the reference wave is calculated by the following formula rx (τ) :

[0052]

[0053] The generalized quadratic cross-correlation function R between the upstream received echo signal and the reference wave is calculated by the following formula ry (τ) :

[0054]

[0055] wherein, is the cross-power spectrum of the R1 rx (τ) and R1 xx (τ) signals, rx (ω) is the cross-power spectrum of the R1 rx (τ) and R1 xx (τ) signals, is the cross-power spectrum of the R1 ry (τ) and R1 yy (τ) signals, ry (ω) is the cross-power spectrum of the R1 ry (τ) and R1 yy (τ) signals, and ω is the angular frequency of the reference wave.

[0056] To verify the validity of the time difference measurement result, in some embodiments, S5 further comprises the following steps: if Δt≥0, then go to step S6; otherwise, repeat steps S3-S5 until the above condition is met.

[0057] To solve the problem that the calculation result is incorrect due to the influence of noise on the signal and further improve the accuracy of the cross-correlation method calculation, in some embodiments, S5 further comprises the following steps:

[0058] The envelope threshold method is used to calculate the transit time t x of the downstream received echo signal and the transit time t y of the upstream received echo signal, respectively.

[0059] If Δt≥0 and If yes, go to step S6; otherwise, repeat steps S3-S5 until the above condition is met.

[0060] wherein T0 is one ultrasonic wave period, Δt = τ1 - τ2, Δt' = t y -t x .

[0061] Based on the same inventive concept, the application further provides a wireless ultrasonic wave flow measuring device, comprising:

[0062] a first ultrasonic wave transducer arranged at the upstream of one side of the river channel and used for transmitting and receiving ultrasonic waves;

[0063] a first control unit arranged at the upstream of one side of the river channel and used for controlling the first ultrasonic wave transducer to transmit and receive ultrasonic waves;

[0064] a first operation unit arranged at the upstream of one side of the river channel and used for storing the reference wave r(t) and performing cross-correlation operation on the upstream end received echo signal y'(t) received by the first ultrasonic wave transducer and the reference wave r(t) stored in the first operation unit to obtain the cross-correlation function R ry (τ) of the upstream end received echo signal and the reference wave; and calculating the value of τ corresponding to the maximum peak value of R ry (τ), denoted as τ2. The range of τ is (0, 2(B-A));

[0065] a second ultrasonic wave transducer arranged at the downstream of the other side of the river channel opposite to the position of the first ultrasonic wave transducer and used for transmitting and receiving ultrasonic waves;

[0066] a construction unit used for constructing the reference wave r(t) according to the sampling data:

[0067]

[0068] wherein y(t) is the upstream end received echo sampling signal, x(t) is the downstream end received echo sampling signal, and Δτ is the time difference between x(t) and y(t); the range of t is (A, B), and A-B is the signal collection interval of the reference wave;

[0069] a second control unit arranged at the downstream of the other side of the river channel opposite to the position of the first ultrasonic wave transducer and used for controlling the second ultrasonic wave transducer to transmit and receive ultrasonic waves;

[0070] a second operation unit arranged at the downstream of the other side of the river channel opposite to the position of the first ultrasonic wave transducer and used for storing the reference wave r(t) and performing cross-correlation operation on the downstream end received echo signal x'(t) received by the second ultrasonic wave transducer and the reference wave r(t) stored in the second operation unit to obtain the cross-correlation function R rx (τ) of the downstream end received echo signal and the reference wave; and calculating the value of τ corresponding to the maximum peak value of Rrx (t) is the value of τ corresponding to the maximum peak, denoted as τ1;

[0071] the first calculation unit is configured to calculate the time difference Δt = τ1- τ2 of the ultrasonic wave propagation at the upstream and downstream ends according to τ1 and τ2; and

[0072] the second calculation unit is configured to calculate the flow rate Q according to the time difference Δt of the ultrasonic wave propagation at the upstream and downstream ends by the following formula:

[0073]

[0074]

[0075] In the formula, C is the speed of sound in the stationary fluid, L is the distance between the first ultrasonic transducer and the second ultrasonic transducer, θ is the angle between the ultrasonic wave propagation path and the water flow direction, Q is the flow rate, and α is the flow rate correction coefficient.

[0076] The first calculation unit is located at the upstream of one side of the river channel and in hard-wired communication with the first operation unit, or is located at the downstream of the other side of the river channel and in hard-wired communication with the second operation unit.

[0077] The device stores the reference waves in the devices at the two ends of the river channel in advance, respectively, and performs cross-correlation operation on the echo signals received at the upstream and downstream ends and the corresponding reference wave signals during actual flow measurement, and finally only needs to transmit the operation result obtained by one of the devices to the other device to calculate the final time difference, without the need to transmit a large amount of original echo data, and the requirements for software and hardware are low, and the rapid and real-time accurate measurement of the river flow is easier to achieve.

[0078] To solve the problem of the difference in the amplitude or waveform of the ultrasonic echo caused by different water levels, in some embodiments, the upstream end receives echo sampling signals y(t) including a plurality of echo sampling signals corresponding to different water level sections: y1(t), y2(t), …, y i (t), …, y n (t);

[0079] The downstream end receives echo sampling signals x(t) including a plurality of echo sampling signals corresponding to different water level sections: x1(t), x2(t), …, x i (t), …, x n (t);

[0080] The reference wave r(t) includes a plurality of reference waves corresponding to different water level sections: r1(t), r2(t), …, r i (t), …, r​n (t);

[0081] wherein n is the total number of water level segments, and i is the sequence number of water level segment;

[0082] The first operation unit is configured to perform cross-correlation operation on the reference wave r(t) of the same water level segment as the upstream end received echo signal y'(t) received by the first ultrasonic transducer;

[0083] The second operation unit is configured to perform cross-correlation operation on the reference wave r(t) of the same water level segment as the downstream end received echo signal x'(t) received by the second ultrasonic transducer.

[0084] To further improve the measurement accuracy, in some embodiments, the cross-correlation operation performed by the first operation unit and the second operation unit includes the following steps:

[0085] The generalized cross-correlation function R1(τ) of the downstream end received echo signal and the reference wave is calculated by the following formula: rx (τ):

[0086]

[0087] The generalized cross-correlation function R1(τ) of the upstream end received echo signal and the reference wave is calculated by the following formula: ry (τ):

[0088]

[0089] In the formula, is the cross-power spectrum weighting function of the reference wave and the downstream end received echo signal, G rx (ω) is the cross-power spectrum of the reference wave and the downstream end received echo signal, is the cross-power spectrum weighting function of the reference wave and the upstream end received echo signal, G ry (ω) is the cross-power spectrum of the reference wave and the upstream end received echo signal, and ω is the angular frequency of the reference wave.

[0090] To further improve the measurement accuracy, in some embodiments, the cross-correlation operation performed by the first operation unit and the second operation unit includes the following steps:

[0091] The autocorrelation function R1(τ) of the downstream end received echo signal is calculated by the following formula: xx (τ):

[0092]

[0093] The autocorrelation function R1(τ) of the upstream end received echo signal is calculated by the following formula: yy (τ):

[0094]

[0095] The cross-correlation function R1 between the downstream received echo signal and the reference wave is calculated using the following formula. rx (τ):

[0096]

[0097] The cross-correlation function R1 between the upstream receiver echo signal and the reference wave is calculated using the following formula. ry (τ):

[0098]

[0099] The generalized quadratic cross-correlation function R between the downstream received echo signal and the reference wave is calculated using the following formula. rx (τ):

[0100]

[0101] The generalized quadratic cross-correlation function R between the upstream receiver echo signal and the reference wave is calculated using the following formula. ry (τ):

[0102]

[0103] In the formula, R1 rx (τ) and R1 xx (τ) is the cross-power spectral weighting function of the signal, G rx (ω) is R1 rx (τ) and R1 xx (τ) Cross-power spectrum of the signal, R1 ry (τ) and R1 yy (τ) is the cross-power spectral weighting function of the signal, G ry (ω) is R1 ry (τ) and R1 yy (τ) is the cross-power spectrum of the signal, where ω is the angular frequency of the reference wave.

[0104] To verify the validity of the time difference measurement results, in some embodiments, the first calculation unit sends Δt to the second calculation unit when Δt≥0; otherwise, the first and second control units are executed repeatedly until the above conditions are met.

[0105] To address the problem of incorrect calculation results caused by signal noise and to further improve the accuracy of cross-correlation calculations, in some embodiments,

[0106] The first arithmetic unit is also used to calculate the transit time t of the echo signal received at the upstream end using the envelope threshold method.y ;

[0107] The second operation unit is also configured to calculate the time of flight t x ;

[0108] The first calculation unit sends Δt to the second calculation unit when Δt≥0 and , otherwise, the first and second control units are repeatedly executed until the above condition is met; wherein, T0 is an ultrasonic wave period, and Δt′=t y -t x .

[0109] The one or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:

[0110] 1. By pre-storing the reference waves in the devices at both ends of the river channel respectively, the correlation operation is performed between the echo signals received at both ends of the upstream and downstream and the corresponding reference wave signals during actual flow measurement, and finally the operation result obtained by one of the devices is transmitted to the other device to calculate the final time difference, without the need to transmit a large amount of original echo data, which has lower requirements for software and hardware and is easier to realize the rapid and real-time accurate measurement of the river channel flow.

[0111] 2. The problem of ultrasonic echo amplitude or waveform difference caused by different water levels is solved.

[0112] 3. The envelope threshold method is used to roughly calculate the time difference for verification, which further improves the accuracy of the correlation method calculation. SUMMARY

[0113] Figure 1 FIG. 1 is a structural schematic diagram of an existing wireless ultrasonic flow measurement system;

[0114] Figure 2 FIG. 2 is a schematic diagram of the principle of an existing wireless ultrasonic flow measurement method;

[0115] Figure 3 FIG. 3 is a flowchart of a wireless ultrasonic flow measurement method in an embodiment of the present application;

[0116] Figure 4 FIG. 4 is a signal waveform diagram of the reference wave r1(t) in an embodiment of the present application (original signals and filtered signals of the upstream and downstream received echoes);

[0117] Figure 5 FIG. 5 is a waveform diagram of the reference wave r1(t) and the downstream echo x1(t-27) and the upstream echo y1(t+27) constructed therefrom in an embodiment of the present application;

[0118] Figure 6A function waveform chart of a measured downstream echo and a reference wave r(t) and a self / cross-correlation function waveform chart thereof in an embodiment of the present application;

[0119] Figure 7 A function waveform chart of a measured downstream end generalized quadratic cross-correlation algorithm based on a reference wave r(t) in an embodiment of the present application;

[0120] Figure 8 A function waveform chart of a measured upstream echo and a reference wave r(t) and a self / cross-correlation function waveform chart thereof in an embodiment of the present application;

[0121] Figure 9 A function waveform chart of a measured upstream end generalized quadratic cross-correlation algorithm based on a reference wave r(t) in an embodiment of the present application;

[0122] Figure 10 A structural schematic diagram of a wireless ultrasonic flow measuring device in an embodiment of the present application. DETAILED DESCRIPTION

[0123] In order to better understand the above technical solutions, the above technical solutions will be described in detail below in combination with the drawings of the specification and specific embodiments.

[0124] Embodiment One

[0125] Referring to Figure 3 A wireless ultrasonic flow measuring method, comprising the following steps:

[0126] S1, constructing a reference wave r(t) by using sampling data:

[0127]

[0128] In the formula, y(t) is a sampling signal of a received echo at an upstream end, x(t) is a sampling signal of a received echo at a downstream end, Δτ is a time difference between x(t) and y(t); the range of t is (A, B), and A~B is a signal collection interval of the reference wave;

[0129] S2, storing the reference wave at the upstream end and the downstream end respectively;

[0130] S3, measuring a received echo signal y'(t) at the upstream end and a received echo signal x'(t) at the downstream end;

[0131] S4, performing a cross-correlation operation on the received echo signal y'(t) at the upstream end and the reference wave r(t) stored at the upstream end, to obtain a cross-correlation function R ry (τ) of the received echo signal at the upstream end and the reference wave; performing a cross-correlation operation on the received echo signal x'(t) at the downstream end and the reference wave r(t) stored at the downstream end, to obtain a cross-correlation function Rrx (τ);

[0132] S5, obtaining the time difference Δt = τ1-τ2 of the ultrasonic wave propagation at the upstream and downstream ends; wherein τ1 is the value of R rx (τ) is the value of τ corresponding to the maximum peak value, and τ2 is the value of R ry (τ) is the value of τ corresponding to the maximum peak value; the range of τ is (0, 2(B-A));

[0133] S6, calculating the flow rate Q by using the following formula:

[0134]

[0135] In the formula: is the average laminar flow degree, C is the sound wave speed in the static fluid, Δt is the time difference of the ultrasonic wave propagation at the upstream and downstream ends, L is the distance between the ultrasonic transducers at the upstream and downstream ends, θ is the angle between the ultrasonic wave propagation path and the water flow direction, Q is the flow rate, α is the flow rate correction coefficient, and S is the cross-sectional area.

[0136] When calculating τ1 and τ2, if τ1≥(B-A), the value of τ1 is updated as τ1-2(B-A); if τ2≥(B-A), the value of τ2 is updated as τ2-2(B-A).

[0137] The method can further include a step of verifying the validity of Δt: if Δt≥0, entering step S6; otherwise, repeating steps S3-S5 until the above condition is met.

[0138] The above method pre-stores the reference waves in the devices at the two ends of the river channel respectively, and performs cross-correlation operation on the echo signals received at the upstream and downstream ends and the corresponding reference wave signals respectively during actual flow measurement. Finally, only the operation result obtained by one of the devices needs to be transmitted to the other device to calculate the final time difference, without the need to transmit a large amount of original echo data, so that the requirements for software and hardware are low, and the river channel flow can be measured accurately and rapidly in real time.

[0139] Further, to solve the problem of the ultrasonic echo amplitude or waveform difference caused by different water levels, the upstream end received echo sampling signal y(t) includes a plurality of echo sampling signals corresponding to different water level sections: y1(t), y2(t), …, y i (t), …, y n (t);

[0140] The downstream end received echo sampling signal x(t) includes a plurality of echo sampling signals corresponding to different water level sections: x1(t), x2(t), …, x i (t), …, x n (t);

[0141] The reference wave r(t) includes a plurality of reference waves corresponding to different water level sections: r1(t), r2(t), …, r i (t), …, r n (t).

[0142] Wherein, n is the total number of water level sections, and i is the water level section number.

[0143] In step S4, the reference wave is the reference wave corresponding to the same water level section as the measured upstream and downstream received echo signals.

[0144] To further improve the measurement accuracy, the cross-correlation operation in step S4 can use generalized cross-correlation operation, or generalized quadratic cross-correlation operation.

[0145] Wherein, the specific steps of using generalized cross-correlation operation are as follows:

[0146] The generalized cross-correlation function R rx (τ) between the downstream end received echo signal and the reference wave is calculated by the following formula:

[0147]

[0148] The generalized cross-correlation function R ry (τ) between the upstream end received echo signal and the reference wave is calculated by the following formula:

[0149]

[0150] In the formula, is the cross-power spectrum weighting function of the reference wave and the downstream end received echo signal, G rx (ω) is the cross-power spectrum of the reference wave and the downstream end received echo signal, is the cross-power spectrum weighting function of the reference wave and the upstream end received echo signal, G ry (ω) is the cross-power spectrum of the reference wave and the upstream end received echo signal, and ω is the angular frequency of the reference wave.

[0151] The specific steps of using generalized cross-correlation operation are as follows:

[0152] S41, the autocorrelation function R1 xx (τ) of the downstream end received echo signal is calculated by the following formula:

[0153]

[0154] The autocorrelation function R1 yy (τ) of the upstream end received echo signal is calculated by the following formula:

[0155]

[0156] The cross-correlation function R1 between the downstream received echo signal and the reference wave is calculated using the following formula. rx (τ):

[0157]

[0158] The cross-correlation function R1 between the upstream receiver echo signal and the reference wave is calculated using the following formula. ry (τ):

[0159]

[0160] S42. Calculate the generalized quadratic cross-correlation function R between the downstream received echo signal and the reference wave using the following formula. rx (τ):

[0161]

[0162] The generalized quadratic cross-correlation function R between the upstream receiver echo signal and the reference wave is calculated using the following formula. ry (τ):

[0163]

[0164] In the formula, R1 rx (τ) and R1 xx (τ) is the cross-power spectral weighting function of the signal, G rx (ω) is R1 rx (τ) and R1 xx (τ) Cross-power spectrum of the signal, R1 ry (τ) and R1 yy (τ) is the cross-power spectral weighting function of the signal, G ry (ω) is R1 ry (τ) and R1 yy (τ) Cross-power spectrum of the signal, k is the weighting function correction coefficient, and the value of k ranges from 0.5 to 1. ω is the angular frequency of the reference wave.

[0165] Furthermore, to address the problem of incorrect calculation results caused by signal noise and to improve the accuracy of cross-correlation calculations, S5 also includes the following steps:

[0166] The transit time t of the downstream received echo signal was calculated using the envelope threshold method. x The transit time t of the echo signal received at the upstream end y ;

[0167] If Δt≥0 and If yes, go to step S6; otherwise, repeat steps S3-S5 until the above condition is met.

[0168] Wherein, T0 is an ultrasonic wave period, Δt = τ1-τ2, Δt' = t y -t x .

[0169] Wherein, the envelope threshold method specifically includes the following steps: taking the downstream as an example, the first four peak values (p1, p2, p3, p4) of the downstream terminal received echo signal x'(t) are extracted, and a dynamic threshold Th is set according to the peak value amplitude average value x =(p1+p2+p3+p4) / 4, the envelope transformation of x'(t) is performed to obtain the downstream echo envelope signal x''(t) = |x'(t) + jH[x'(t)]| (wherein H[x'(t)] is the Hilbert transformation of x'(t)), and the threshold point is found on the echo envelope signal through the threshold comparison method, so that the downstream ultrasonic wave transit time t x is obtained. The upstream is the same.

[0170] In order to further remove the noise in the signal, the upstream and downstream terminal received echo sampling signals are the data after filtering processing of the original echo sampling signals, and the upstream and downstream terminal received echo signals are the data after filtering processing of the original measured received echo signals.

[0171] Embodiment two

[0172] The following provides an optimal embodiment and brings in specific data for calculation to more clearly illustrate the technical solutions of the present application.

[0173] A wireless ultrasonic wave flow measurement method, comprising the following steps:

[0174] Step 1, according to the historical highest water level H of the river to be measured and the installation water level height h of the ultrasonic wave transducer, the water level is divided into n sections (n is flexibly selected according to the actual situation), and the water level range of each section is (H-h) / n;

[0175] In this embodiment, the actual installation water level height of the station transducer is about 29m, the historical highest water level of the river is about 37m, and the water level is divided into 16 sections, and the water level height of each section is 0.5m.

[0176] Step 2, collect and record each section of water level reference wave to construct the required waveform data and perform filtering pretreatment. At least one ultrasonic wave measurement (ultrasonic wave signal transmission and reception between the upstream and downstream devices) is performed on the 16 sections of water level according to the water level condition of the river to be measured for constructing the reference wave, and the downstream terminal received echo sampling signals X1(t), X2(t), …, X i (t), …, X 16(t); the echo signal received at the upstream end is Y1(t), Y2(t),..., Y i (t),..., Y 16 (t); the collected echo signals are subjected to Butterworth filtering to reduce frequency noise interference, and the processed wave signals are respectively denoted as x1(t), x2(t),..., x i (t),..., x 16 (t), y1(t), y2(t),..., y i (t),..., y 16 (t). Generally, the short-term amplitude of the river water level does not change greatly, so the process can be carried out in steps according to the water level change of the measuring station, that is, the measurement is recorded when a certain water level appears, and the water level section that does not appear can be temporarily processed.

[0177] Taking the first water level (the river water level to be measured is usually located in the first and second sections) as an example, a 1Msps, 5V acquisition system is used to collect and record a group of downstream and upstream original echo signals X1(t), Y1(t) when the river water level is 29.20m, the recording time range is 140000μs-143000μs, and the data x1(t), y1(t) of the original echo signals X1(t), Y1(t) subjected to Butterworth filtering are used as the reference wave required data signal for constructing r1(t). The collected downstream and upstream original echo signals X1(t), Y1(t) and the filtered preprocessed signals x1(t), y1(t) are as shown in Figure 4 .

[0178] Step 3, constructing the reference wave corresponding to the first water level (29.0m-29.5m). The downstream and upstream propagation speeds of ultrasonic waves are affected by the water flow rate, so there is a time shift Δτ between the echo signals x1(t) and y1(t), that is, the time difference between the time when the ultrasonic wave is received by the transducers at the upstream and downstream ends when collecting the echo, which can be calculated by aligning the waveform data. According to the upstream and downstream waveform data collected and recorded in step 2, Δτ=54μs can be calculated, so when the flow rate is 0 in this water level interval, the ultrasonic waveforms received at the upstream and downstream ends are respectively x1(t-27), y1(t+27), x1(t-27)≈y1(t+27). In order to reduce the echo difference caused by the inconsistency between the upstream and downstream equipment, x1(t-27) and y1(t+27) are averaged, and is taken as the reference wave corresponding to the first water level (29.0m-29.5m) of the river. The reference wave r1(t) and the partial data curves of the downstream echo x1(t-27) and the upstream echo y1(t+27) are as shown in Figure 5As shown, the reference wave r1(t) data is stored in the processing equipment on both sides of the river channel in advance, so that the ultrasonic time difference measurement and calculation of the water level of the first section of the river channel (29.0m-29.5m) can be performed.

[0179] Step 4, the measured downstream end receiving echo signal x1'(t) is autocorrelated to obtain the function R1 xx (τ), the x1'(t) and the water level corresponding reference wave signal r1(t) are cross-correlated to obtain R1 rx (τ), and the envelope threshold method is used to roughly calculate the upstream ultrasonic transit time t x , then the generalized quadratic cross-correlation operation is performed on R1 xx (τ) and R1 rx (τ), and the recording time constant τ1 is obtained.

[0180] In the embodiment, the measured water level is 29.35m, the time range for collecting and storing the waveform data is 140000μs-143000μs, and the corresponding reference wave r1(t) is selected.

[0181] wherein,

[0182]

[0183] Generalized quadratic cross-correlation operation:

[0184]

[0185] That is, the mutual power spectrum operation is performed on the signals R1 xx (τ) and R1 rx (τ) in the frequency domain, so as to strengthen the signal correlation part and suppress the interference noise, and finally the inverse Fourier transform is performed to the time domain, and the time coordinate corresponding to the maximum peak value of the time domain R rx (τ) is the time difference τ1 of the downstream echo signal relative to the reference wave, and if it is necessary to make the signal peak value more sharp and prominent, the Hilbert transform processing can be performed on the signal R rx (τ) inversely transformed to the time domain.

[0186] In the embodiment, the curve graphs of the downstream echo signal and the envelope signal and the corresponding reference wave signal r1(t) and the cross-correlation R rx (τ) and the autocorrelation R xx (τ) operation waveform curve graphs are shown in Figure 6 The first four peak values (2948mV, 3516mV, 4763mV, and 4813mV) of the collected downstream echo signal are extracted, and the dynamic threshold Th x=4010mV, and simultaneously perform envelope transformation on the signal to obtain the downstream echo envelope signal. The downstream ultrasonic transit time t is then roughly calculated using the threshold method. x =142278μs. The downstream function waveform (after Hilbert transform) based on the generalized second-order cross-correlation algorithm of the reference wave r1(t) is as follows: Figure 7 As shown in the figure, R is at τ1 = 5557 μs. rx (τ) is the peak value, and τ1 is located on the right half axis of the function curve (τ1>3000μs). Therefore, the value of τ1 is updated to τ1-2×(143000-140000)=-443μs. Record the updated value τ1.

[0187] Similarly, the measured upstream received echo signal and its corresponding water level reference wave signal are processed in the same way. The curves of the upstream received echo signal and envelope signal versus the reference wave signal r1(t), and their cross-correlation and autocorrelation waveforms are shown below. Figure 8 As shown, the first four peak values ​​of the upstream echo signal (3133mV, 4256mV, 4918mV, and 4948mV, respectively) are extracted, and a dynamic threshold Th is set based on the average peak amplitude. y =4314mV. A rough calculation using the threshold method was performed on the upstream echo envelope signal to obtain the upstream ultrasonic wave transit time t. y =142323μs. The function waveform curve (after Hilbert transform) of the generalized second-order cross-correlation algorithm based on the reference wave r1(t) at the upstream end is as follows: Figure 9 As shown, by Figure 9 It can be seen that R is at τ2=5501μs ry (τ) is the peak value, and τ2 is located on the right half axis of the function curve (τ2>3000μs). Therefore, the value of τ2 is updated to τ2-2×(143000-140000)=-499μs. Record the updated value of τ2.

[0188] Step 5: Calculate the ultrasonic flow measurement time difference and determine the validity of the data. Based on the numerical results obtained in Step 4, calculate the ultrasonic transmission time difference Δt between the two ends of the measurement: Δt = τ1 - τ2 = (-443) - (-499) = 56 μs. Based on the upstream and downstream ultrasonic transit times, roughly calculate the time difference Δt′ = t y -t x =142323-142278=45μs, satisfying Δt≥0, (In this implementation scheme, T0≈67μs), the data is valid, the ultrasonic propagation time difference Δt is 56μs, and the calculation is complete.

[0189] Step 6: Substitute the calculated time difference Δt into the formula based on other known parameters from this implementation process. The average laminar velocity of the river channel can be calculated The measured actual flow velocity of the river channel is consistent.

[0190] The ultrasonic flow measurement time difference calculation method provided by the application is used for continuous measurement of a certain station for a period of time, and the calculated data results are shown in Table 1. The data results calculated by the method are stable and reliable, high in accuracy, fast in response, and suitable for wide river channel wireless time difference method flow measurement application.

[0191] Table 1: Continuous measurement and calculation data results of a certain station flow measurement stage

[0192]

[0193]

[0194] Example Three

[0195] As Figure 10 shown, a wireless ultrasonic flow measurement device includes:

[0196] A first ultrasonic transducer is arranged on the upstream side of the river channel and used for transmitting and receiving ultrasonic waves.

[0197] A first control unit is arranged on the upstream side of the river channel and used for controlling the first ultrasonic transducer to transmit and receive ultrasonic waves.

[0198] A first operation unit is arranged on the upstream side of the river channel and used for storing a reference wave r(t), performing cross-correlation operation on the upstream end received echo signal y'(t) received by the first ultrasonic transducer and the reference wave r(t) stored in the first operation unit, and obtaining the cross-correlation function R ry (τ) of the upstream end received echo signal and the reference wave. ry When R y (τ) is the maximum peak value, the corresponding τ value is recorded as τ2. The range of τ is (0, 2(B-A)); and the envelope threshold method is used to calculate the transit time t

[0199] A second ultrasonic transducer is arranged on the downstream side of the other side of the river channel opposite to the position of the first ultrasonic transducer and used for transmitting and receiving ultrasonic waves.

[0200] A construction unit is used for constructing the reference wave r(t) according to the sampling data:

[0201]

[0202] In the formula, y(t) is the upstream end received echo sampling signal, x(t) is the downstream end received echo sampling signal, Δτ is the time difference between x(t) and y(t); the range of t is (A, B), and A~B is the signal collection interval of the reference wave.

[0203] a second control unit, arranged at a downstream position of the river relative to the first ultrasonic transducer, for controlling the second ultrasonic transducer to emit and receive ultrasonic waves;

[0204] a second operation unit, arranged at a downstream position of the river relative to the first ultrasonic transducer on the other side of the river, for storing the reference wave r(t), and performing cross-correlation operation between the downstream-end received echo signal x'(t) received by the second ultrasonic transducer and the reference wave r(t) stored in the second operation unit to obtain a cross-correlation function R rx (τ) of the downstream-end received echo signal and the reference wave; rx (τ) as the value of τ corresponding to the maximum peak value, denoted as τ1; and for calculating the transit time t x of the downstream-end received echo signal by using envelope threshold method;

[0205] a first calculation unit, for calculating the time difference Δt = τ1-τ2 of ultrasonic wave propagation between the upstream and downstream ends according to R ry (τ) R rx (τ); when Δt≥0 and , sending Δt to the second calculation unit, otherwise repeating the first and second control units until the above condition is met;

[0206] wherein, τ1 is the value of τ corresponding to the maximum peak value of R ry (τ), and τ2 is the value of τ corresponding to the maximum peak value of R rx (τ), τ is in the range of (0, 2(B-A)), T0 is an ultrasonic wave period, and Δt' = t y -t x ; and

[0207] a second calculation unit, for calculating the flow rate Q according to the time difference Δt of ultrasonic wave propagation between the upstream and downstream ends by the following formula:

[0208]

[0209] wherein: is the average laminar flow degree, C is the speed of sound in the stationary fluid, L is the distance between the first ultrasonic transducer and the second ultrasonic transducer, θ is the angle between the ultrasonic wave propagation path and the water flow direction, Q is the flow rate, α is the flow rate correction coefficient, and S is the cross-sectional area.

[0210] In the embodiment, the first operation unit is in an auxiliary machine, and the auxiliary machine is located at an upstream position of the river on one side. The second operation unit, the construction unit, the first calculation unit and the second calculation unit are integrated in a main machine, and the main machine is located at a downstream position of the river on the other side. The main machine and the auxiliary machine communicate wirelessly.

[0211] Further, the upstream end receives echo sample signals y(t) including a plurality of echo sample signals corresponding to different water level sections: y1(t), y2(t), …, y i (t), …, y n (t);

[0212] The downstream end receives echo sample signals x(t) including a plurality of echo sample signals corresponding to different water level sections: x1(t), x2(t), …, x i (t), …, x n (t);

[0213] The reference wave r(t) includes a plurality of reference waves corresponding to different water level sections: r1(t), r2(t), …, r i (t), …, r n (t);

[0214] Wherein, n is the total number of water level sections, and i is the water level section number;

[0215] The first operation unit is configured to perform cross-correlation operation on the reference wave r(t) of the same water level section as the upstream end received echo signal y'(t) received by the first ultrasonic transducer;

[0216] The second operation unit is configured to perform cross-correlation operation on the reference wave r(t) of the same water level section as the downstream end received echo signal x'(t) received by the second ultrasonic transducer.

[0217] The cross-correlation operation performed by the first operation unit and the second operation unit can be generalized cross-correlation operation, including the following steps:

[0218] The generalized cross-correlation function R rx (τ) between the downstream end received echo signal and the reference wave is calculated by the following formula:

[0219]

[0220] The generalized cross-correlation function R ry (τ) between the upstream end received echo signal and the reference wave is calculated by the following formula:

[0221]

[0222] In the formula, is the cross-power spectrum weighting function of the reference wave and the downstream end received echo signal, G rx (ω) is the cross-power spectrum of the reference wave and the downstream end received echo signal, is the cross-power spectrum weighting function of the reference wave and the upstream end received echo signal, G ry(ω) is the cross-power spectrum of the reference wave and the upstream receiving end echo signal, and ω is the angular frequency of the reference wave.

[0223] The cross-correlation operation performed by the first operation unit and the second operation unit can also be a generalized quadratic cross-correlation operation, including the following steps:

[0224] The autocorrelation function R1 of the downstream end received echo signal is calculated by the following formula xx (τ) :

[0225]

[0226] The autocorrelation function R1 of the upstream receiving end echo signal is calculated by the following formula yy (τ) :

[0227]

[0228] The cross-correlation function R1 of the downstream end received echo signal and the reference wave is calculated by the following formula rx (τ) :

[0229]

[0230] The cross-correlation function R1 of the upstream receiving end echo signal and the reference wave is calculated by the following formula ry (τ) :

[0231]

[0232] The generalized quadratic cross-correlation function R of the downstream end received echo signal and the reference wave is calculated by the following formula rx (τ) :

[0233]

[0234] The generalized quadratic cross-correlation function R of the upstream receiving end echo signal and the reference wave is calculated by the following formula ry (τ) :

[0235]

[0236] In the formula, is the autocorrelation function R1 rx (τ) of the downstream end received echo signal, and R1 xx (τ) is the autocorrelation function of the upstream receiving end echo signal, and G rx (ω) is the cross-power spectrum of the autocorrelation function R1 rx (τ) of the downstream end received echo signal and the autocorrelation function R1 xx (τ) of the upstream receiving end echo signal, is the cross-power spectrum of the autocorrelation function R1 ry (τ) of the downstream end received echo signal and the autocorrelation function R1 yy (τ) of the upstream receiving end echo signal, and Gry (ω) is R1 ry (τ) is R1 yy (τ) is the cross power spectrum of the signal, ω is the angular frequency of the reference wave.

[0237] Further, if Δt≥0, the first computing unit sends Δt to the second computing unit, otherwise, the first and second control units are repeatedly executed until the above condition is met.

[0238] In operation, the first unit constructs the reference wave r(t) of different water levels according to the sampling data, and stores the reference wave r(t) in the first and second computing units. The reference wave in the second computing unit is sent by the host to the auxiliary machine and stored in the second computing unit.

[0239] In measurement, the first control unit controls the first ultrasonic transducer at the upstream end to send ultrasonic waves to the second ultrasonic transducer at the downstream end, and the second control unit controls the second ultrasonic transducer at the downstream end to receive the ultrasonic waves, to obtain the downstream received echo signal x'(t) and send it to the second computing unit at the downstream end. At the same time, the second control unit controls the second ultrasonic transducer at the downstream end to send ultrasonic waves to the first ultrasonic transducer at the upstream end, and the first control unit controls the first ultrasonic transducer at the upstream end to receive the ultrasonic waves, to obtain the upstream received echo signal y'(t) and send it to the first computing unit at the upstream end.

[0240] After receiving the upstream received echo signal y'(t), the first computing unit at the upstream end performs cross-correlation operation (generalized cross-correlation operation or generalized quadratic cross-correlation operation) on y'(t) and the reference wave r(t) of the same water level as y'(t) stored in the first computing unit, to obtain the cross-correlation function R ry (τ) of the upstream received echo signal and the reference wave, and then calculates the value of τ corresponding to the maximum peak value of R ry (τ), denoted as τ2. At the same time, the first computing unit calculates the transit time t y of the upstream received echo signal using envelope threshold method according to the upstream received echo signal y'(t). Then τ2 and t y are sent to the first computing unit at the downstream end through wireless communication. After receiving the downstream received echo signal x'(t), the second computing unit at the downstream end performs cross-correlation operation (generalized cross-correlation operation or generalized quadratic cross-correlation operation) on x'(t) and the reference wave r(t) of the same water level as x'(t) stored in the second computing unit, to obtain the cross-correlation function R rx (τ) of the downstream received echo signal and the reference wave, and then calculates the value of τ corresponding to the maximum peak value of R rx(t) is the value of τ corresponding to the maximum peak, denoted as τ1. Meanwhile, the second calculation unit calculates the transit time t of the downstream end received echo signal x'(t) according to the envelope threshold method x . Then τ1 and t x are sent to the first calculation unit of the downstream end.

[0241] After receiving τ1 and τ2, the first calculation unit of the downstream end calculates the time difference Δt = τ1-τ2 of the upstream and downstream ultrasonic wave propagation, and judges the validity of Δt. If Δt≥0 and then the first calculation unit sends Δt to the second calculation unit, otherwise sends instructions to the first and second control units to reacquire x'(t) and y'(t) until the above conditions are met. Wherein, T0 is an ultrasonic wave period, Δt' = t y -t x .

[0242] The second computer unit of the downstream end is used to calculate the flow rate Q according to the time difference Δt of the upstream and downstream ultrasonic wave propagation through the following formula:

[0243]

[0244] Wherein: is the average laminar flow, C is the speed of sound in the stationary fluid, L is the distance between the first ultrasonic transducer and the second ultrasonic transducer, θ is the angle between the ultrasonic wave propagation path and the flow direction, Q is the flow rate, α is the flow rate correction coefficient, and S is the cross-sectional area.

[0245] Finally, it should be pointed out that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A wireless ultrasonic current measurement method, comprising the following steps: S1. Construct a reference wave r(t) using the sampled data: In the formula, y(t) is the echo sampling signal received at the upstream end, x(t) is the echo sampling signal received at the downstream end, Δτ is the time difference between x(t) and y(t); the range of t is (A, B), where A~B is the signal acquisition interval of the reference wave; S2. Store the reference wave at the upstream and downstream ends respectively; S3. Measure the echo signal y'(t) received at the upstream end and the echo signal x'(t) received at the downstream end; S4. Perform a cross-correlation operation between the upstream received echo signal y'(t) and the reference wave r(t) stored at the upstream end to obtain the cross-correlation function R between the upstream received echo signal and the reference wave. ry (τ); Perform a cross-correlation operation between the downstream received echo signal x'(t) and the reference wave r(t) stored at the downstream end to obtain the cross-correlation function R between the downstream received echo signal and the reference wave. rx (τ); S5. Obtain the time difference Δt = τ1 - τ2 between the upstream and downstream ultrasonic wave propagation; where τ1 is the time difference between the upstream and downstream ultrasonic waves. rx (τ) is the value of τ corresponding to the maximum peak value, and τ2 is R. ry (τ) is the value of τ corresponding to the maximum peak value; the range of τ is (0, 2(BA)); S6. Calculate the flow rate Q using the following formula: In the formula: Let C be the average laminar flow rate, Δt be the acoustic velocity in the static fluid, L be the time difference between the upstream and downstream ultrasonic waves, θ be the distance between the upstream and downstream ultrasonic transducers, θ be the angle between the ultrasonic wave propagation path and the water flow direction, Q be the flow rate, α be the velocity correction coefficient, and S be the cross-sectional area.

2. The wireless ultrasonic current measurement method according to claim 1, characterized in that: The upstream end receives echo sampling signals y(t), which include multiple echo sampling signals corresponding to different water level segments: y1(t), y2(t), ..., y i (t), ..., y n (t); The downstream end receives echo sampling signals x(t), which include multiple echo sampling signals corresponding to different water level segments: x1(t), x2(t), ..., x i (t), ..., x n (t); The reference wave r(t) includes multiple reference waves corresponding to different water level segments: r1(t), r2(t), ..., r i (t), ..., r n (t); Where n is the total number of water level segments, and i is the sequence number of the water level segment; In step S4, the reference wave is a reference wave in the same water level segment as the upstream and downstream received echo signals.

3. The wireless ultrasonic current measurement method according to claim 1 or 2, characterized in that, The cross-correlation operation in step S4 includes the following steps: The generalized cross-correlation function R between the downstream received echo signal and the reference wave is calculated using the following formula. rx (τ): The generalized cross-correlation function R between the upstream received echo signal and the reference wave is calculated using the following formula. ry (τ): In the formula, G is the cross-power spectrum weighting function of the reference wave and the downstream received echo signal. rx (ω) represents the cross-power spectrum between the reference wave and the downstream received echo signal. G is the cross-power spectrum weighting function of the reference wave and the echo signal from the upstream receiver. ry (ω) represents the cross-power spectrum between the reference wave and the echo signal from the upstream receiver, where ω is the angular frequency of the reference wave.

4. The wireless ultrasonic current measurement method according to claim 1 or 2, characterized in that, The cross-correlation operation in step S4 includes the following steps: S41. Calculate the autocorrelation function R1 of the downstream received echo signal using the following formula. xx (τ): The autocorrelation function R1 of the upstream receiver echo signal is calculated using the following formula. yy (τ): The cross-correlation function R1 between the downstream received echo signal and the reference wave is calculated using the following formula. rx (τ): The cross-correlation function R1 between the upstream receiver echo signal and the reference wave is calculated using the following formula. ry (τ): S42. Calculate the generalized quadratic cross-correlation function R between the downstream received echo signal and the reference wave using the following formula. rx (τ): The generalized quadratic cross-correlation function R between the upstream receiver echo signal and the reference wave is calculated using the following formula. ry (τ): In the formula, R1 rx (τ) and R1 xx (τ) is the cross-power spectral weighting function of the signal, G rx (ω) is R1 rx (τ) and R1 xx (τ) Cross-power spectrum of the signal, R1 ry (τ) and R1 yy (τ) is the cross-power spectral weighting function of the signal, G ry (ω) is R1 ry (τ) and R1 yy (τ) is the cross-power spectrum of the signal, where ω is the angular frequency of the reference wave.

5. The wireless ultrasonic current measurement method according to claim 1 or 2, characterized in that, S5 also includes the following steps: If Δt≥0, proceed to step S6; otherwise, repeat steps S3 to S5 until the above conditions are met.

6. The wireless ultrasonic current measurement method according to claim 1 or 2, characterized in that, S5 also includes the following steps: The transit time t of the downstream received echo signal was calculated using the envelope threshold method. x The transit time t of the echo signal received at the upstream end y ; If Δt≥0 and Then proceed to step S6; otherwise, repeat steps S3 to S5 until the above conditions are met. Where T0 is one ultrasonic cycle, Δt = τ1 - τ2, Δt ′ =t y -t x .

7. A wireless ultrasonic flow measurement device, characterized in that, include: The first ultrasonic transducer is located upstream on one side of the river and is used to transmit and receive ultrasonic waves. The first control unit is located upstream on one side of the river channel and is used to control the first ultrasonic transducer to transmit and receive ultrasonic waves. The first processing unit, located upstream on one side of the river channel, stores the reference wave r(t). It performs a cross-correlation operation between the upstream echo signal y'(t) received by the first ultrasonic transducer and the reference wave r(t) stored in the first processing unit to obtain the cross-correlation function R between the upstream echo signal and the reference wave. ry (τ); calculate R ry (τ) is the value of τ corresponding to the maximum peak value, denoted as τ2; the range of τ is (0, 2(BA)); The second ultrasonic transducer is located downstream of the first ultrasonic transducer on the other side of the river and is used to transmit and receive ultrasonic waves. The construction unit is used to construct the reference wave r(t) based on the sampled data: In the formula, y(t) is the echo sampling signal received at the upstream end, x(t) is the echo sampling signal received at the downstream end, Δτ is the time difference between x(t) and y(t); the range of t is (A, B), where A~B is the signal acquisition interval of the reference wave; The second control unit is located downstream of the first ultrasonic transducer on the other side of the river and is used to control the second ultrasonic transducer to transmit and receive ultrasonic waves. The second processing unit, located downstream of the first ultrasonic transducer on the other side of the river, stores the reference wave r(t). It performs a cross-correlation operation between the downstream echo signal x'(t) received by the second ultrasonic transducer and the stored reference wave r(t) to obtain the cross-correlation function R between the downstream echo signal and the reference wave. rx (τ); calculate R rx (τ) is the value of τ corresponding to the maximum peak value, denoted as τ1; The first calculation unit is used to calculate the time difference Δt = τ1 - τ2 between the upstream and downstream ultrasonic wave propagation based on τ1 and τ2; and The second calculation unit is used to calculate the flow rate Q based on the time difference Δt between the upstream and downstream ultrasonic waves, using the following formula: In the formula: Let C be the average laminar flow rate, C be the velocity of sound in the still fluid, L be the distance between the first and second ultrasonic transducers, θ be the angle between the ultrasonic propagation path and the direction of water flow, Q be the flow rate, α be the velocity correction coefficient, and S be the cross-sectional area. The first computing unit communicates wirelessly with the second computing unit. The first computing unit is located upstream on one side of the river and communicates with the first computing unit via hardwire, or it is located downstream on the other side of the river and communicates with the second computing unit via hardwire.

8. The wireless ultrasonic flow measuring device according to claim 7, characterized in that: The upstream end receives echo sampling signals y(t), which include multiple echo sampling signals corresponding to different water level segments: y1(t), y2(t), ..., y i (t), ..., y n (t); The downstream end receives echo sampling signals x(t), which include multiple echo sampling signals corresponding to different water level segments: x1(t), x2(t), ..., x i (t), ..., x n (t); The reference wave r(t) includes multiple reference waves corresponding to different water level segments: r1(t), r2(t), ..., r i (t), ..., r n (t); Where n is the total number of water level segments, and i is the sequence number of the water level segment; The first arithmetic unit is used to perform cross-correlation calculation on the reference wave r(t) of the same water level segment as the upstream echo signal y'(t) received by the first ultrasonic transducer; The second arithmetic unit is used to perform cross-correlation calculation on the reference wave r(t) of the same water level segment as the downstream echo signal x'(t) received by the second ultrasonic transducer.

9. The wireless ultrasonic flow measuring device according to claim 7 or 8, characterized in that, The cross-correlation operation performed by the first arithmetic unit and the second arithmetic unit includes the following steps: The generalized cross-correlation function R between the downstream received echo signal and the reference wave is calculated using the following formula. rx (τ): The generalized cross-correlation function R between the upstream received echo signal and the reference wave is calculated using the following formula. ry (τ): In the formula, G is the cross-power spectrum weighting function of the reference wave and the downstream received echo signal. rx (ω) represents the cross-power spectrum between the reference wave and the downstream received echo signal. G is the cross-power spectrum weighting function of the reference wave and the echo signal from the upstream receiver. ry (ω) represents the cross-power spectrum between the reference wave and the echo signal from the upstream receiver, where ω is the angular frequency of the reference wave.

10. The wireless ultrasonic flow measurement device according to claim 7 or 8, characterized in that, The cross-correlation operation performed by the first arithmetic unit and the second arithmetic unit includes the following steps: The autocorrelation function R1 of the downstream received echo signal is calculated using the following formula. xx (τ): The autocorrelation function R1 of the upstream receiver echo signal is calculated using the following formula. yy (τ): The cross-correlation function R1 between the downstream received echo signal and the reference wave is calculated using the following formula. rx (τ): The cross-correlation function R1 between the upstream receiver echo signal and the reference wave is calculated using the following formula. ry (τ): The generalized quadratic cross-correlation function R between the downstream received echo signal and the reference wave is calculated using the following formula. rx (τ): The generalized quadratic cross-correlation function R between the upstream receiver echo signal and the reference wave is calculated using the following formula. ry (τ): In the formula, R1 rx (τ) and R1 xx (τ) is the cross-power spectral weighting function of the signal, G rx (ω) is R1 rx (τ) and R1 xx (τ) Cross-power spectrum of the signal, R1 ry (τ) and R1 yy (τ) is the cross-power spectral weighting function of the signal, G ry (ω) is R1 ry (τ) and R1 yy (τ) is the cross-power spectrum of the signal, where ω is the angular frequency of the reference wave.

11. The wireless ultrasonic flow measurement device according to claim 7 or 8, characterized in that, When Δt≥0, the first calculation unit sends Δt to the second calculation unit; otherwise, the first and second control units are executed repeatedly until the above conditions are met.

12. The wireless ultrasonic flow measurement device according to claim 7 or 8, characterized in that: The first arithmetic unit is also used to calculate the transit time t of the echo signal received at the upstream end using the envelope threshold method. y ; The second arithmetic unit is also used to calculate the transit time t of the downstream received echo signal using the envelope threshold method. x ; The first calculation unit is in the case where Δt≥0 and If T0 is the time limit, Δt is sent to the second calculation unit; otherwise, the execution of the first and second control units is repeated until the above conditions are met. Here, T0 is one ultrasonic cycle, and Δt... ′ =t y -t x .

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