Multimode signal fusion and adaptive processing ultrasonic flowmeter and measuring method

Abstract

The invention relates to the technical field of fluid measurement, in particular to a multimode signal fusion and self-adaptive processing ultrasonic flowmeter and a measuring method. The multimode signal fusion and self-adaptive processing ultrasonic flowmeter comprises an ultrasonic transducer, a signal generation driving module, a signal receiving and conditioning module, a control module, a signal processing module, a signal quality evaluation module and a sound velocity calculation and compensation module. According to the method, the time difference method and Doppler method signals are fused, the self-adaptive processing strategy is adopted to improve the measurement precision of the low-flow-velocity fluid and the impurity-containing fluid, the measurement precision of the low-flow-velocity fluid can be remarkably improved, the adaptability to complex fluid is enhanced, the overall measurement reliability is improved, the Doppler method precision is optimized, and the intelligent degree is high.

Description

Technical Field

[0001] This invention relates to the field of fluid measurement technology, specifically to an ultrasonic flow meter, and more particularly to an ultrasonic flow meter and its measurement method that integrates time-of-flight and Doppler signals and employs an adaptive processing strategy to improve the measurement accuracy of low-velocity and impurity-containing fluids. Background Technology

[0002] Ultrasonic flow meters are widely used in industrial process control, energy metering, and water treatment due to their advantages such as non-contact operation, no pressure loss, and wide applicability. Mainstream technologies include the time-difference propagation method (TDAP) and the Doppler method.

[0003] Transit-Time (TRT) method: This method calculates flow velocity by measuring the time difference between the propagation of ultrasonic waves in the upstream and downstream directions. Its advantage is high accuracy for pure fluids, but it is very sensitive to flow velocity. At low flow velocities (e.g., <0.3 m / s), the time difference is extremely small, resulting in a significant decrease in measurement accuracy. Furthermore, it is sensitive to scale, air bubbles, or solid particles on the inner wall of the pipe, which can easily lead to signal attenuation or distortion.

[0004] Doppler flowmeter: This method calculates flow velocity by measuring the frequency shift caused by the reflection of ultrasonic waves from scattering bodies (such as bubbles or solid particles) in a fluid. Its advantages include relative sensitivity to low flow velocities in fluids containing a suitable amount of scattering bodies. Disadvantages include high requirements for fluid purity (sufficient scattering bodies), significant influence on measurement accuracy due to the concentration, size, and uniformity of the scattering bodies, and poor performance in pure liquids or high-concentration slurries.

[0005] Existing technologies typically employ a single measurement principle (pure time-of-flight method or pure Doppler method) or a simple combination thereof, making it difficult to simultaneously meet the high-precision measurement requirements of both pure liquids with low flow rates and fluids containing impurities. Especially under complex operating conditions where flow rates vary widely and fluid properties (such as purity) may change dynamically, single-mode flow meters often exhibit instability or insufficient accuracy. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides an ultrasonic flow meter and its measurement method based on multi-mode signal fusion and adaptive processing. The flow meter fuses time-difference and Doppler signals and employs an adaptive processing strategy to improve the measurement accuracy of low-velocity and impurity-containing fluids.

[0007] This invention provides an ultrasonic flow meter with multi-mode signal fusion and adaptive processing, including... At least one pair of ultrasonic transducers are installed in pairs on the outer or inner wall of the measuring pipe section of the ultrasonic flow meter for transmitting and receiving ultrasonic signals. The signal generation and driving module is connected to the ultrasonic transducer and is used to generate an excitation electrical signal that drives the ultrasonic transducer to emit ultrasonic waves. The signal receiving and conditioning module is connected to the ultrasonic transducer and is used to receive the ultrasonic echo signal sensed by the ultrasonic transducer and perform preprocessing. The control module is connected to the signal generation and driving module, enabling the ultrasonic transducer to alternately or simultaneously emit ultrasonic signals in time-difference mode and Doppler mode. The signal processing module is connected to the control module and the signal receiving and conditioning module respectively, and receives and processes the echo signals in the time difference method mode and the Doppler method mode. The signal quality assessment module is connected to the signal processing module and evaluates the quality parameters of the two signal modes in real time. The adaptive fusion decision module is connected to the signal quality assessment module. It receives the quality assessment results of the two modes of signals from the signal quality assessment module and dynamically decides the final flow rate output based on adaptive decision rules and fuzzy logic / weighted algorithm. The sound velocity calculation and compensation module is connected to the signal processing module. It calculates the fluid sound velocity based on the time difference method and uses it to update the sound velocity value in the Doppler flow velocity calculation.

[0008] Furthermore, the time difference mode signal is a short pulse train or a broadband signal with specific encoding, used to measure the propagation time difference, and the Doppler mode signal is a narrowband signal of a long continuous wave or a long pulse train, used to detect Doppler frequency shift.

[0009] Furthermore, the signal processing module includes a time difference processing channel and a Doppler processing channel; The time difference method processing channel receives and processes the echo signal in the time difference method mode, accurately measures the ultrasonic wave propagation time t_AB downstream and t_BA upstream, calculates the time difference Δt=t_BA-t_AB, and calculates the time difference method flow velocity V_tt according to the formula V=(K*L^2*Δt) / (2*D*cosθ*t_AB*t_BA), where V is the flow velocity, K is the calibration coefficient, L is the sound path, D is the pipe diameter, and θ is the angle between the sound velocity and the pipe axis. The Doppler processing channel receives and processes echo signals in Doppler mode, extracts the spectrum of the echo signal, identifies the main Doppler frequency shift Δf, and calculates the Doppler flow velocity V_dop according to the formula V_dop=(C*Δf) / (2*f0*cosα), where V_dop is the Doppler flow velocity, C is the speed of sound, f0 is the transmission frequency, and α is the angle between the speed of sound and the direction of the flow velocity.

[0010] Corresponding to the time difference method processing channel and the Doppler method processing channel mentioned above, the sound velocity calculation and compensation module uses the ultrasonic wave downstream propagation time t_AB and upstream propagation time t_BA measured by the time difference method to calculate the fluid sound velocity C=2L / (t_AB +t_BA), and uses this sound velocity in the calculation formula of the Doppler method flow velocity V_dop.

[0011] Furthermore, the signal quality assessment module evaluates the quality parameters of the time difference method mode, including signal-to-noise ratio, signal amplitude, and confidence level of transit time measurement. The signal quality assessment module evaluates the quality parameters of the Doppler mode, including echo intensity, signal-to-noise ratio of the spectrum, significance and width of the main peak of the spectrum, and stability of the center of gravity of the spectrum.

[0012] Furthermore, the adaptive decision-making rules of the adaptive fusion decision-making module include: Rule 1: Prioritize high-confidence time difference method: If the signal quality assessment result of the time difference method is excellent, and the flow rate |V_tt| is greater than the set low flow rate threshold V_low, then the flow rate V_tt of the time difference method shall be used as the final output flow rate V_out. Rule 2, poor signal quality of low flow rate or time difference method: If the signal quality assessment result of the time difference method is poor, or |V_tt| is less than or equal to the low flow rate threshold V_low, and the signal quality assessment result of the Doppler method is excellent, the Doppler method flow rate V_dop is used as the final output flow rate V_out. Rule 3, Signal Fusion or Special Processing: If the signal quality of both modes is barely usable, then the two flow velocities are weighted and fused based on their respective quality assessment scores. V_out = W_tt * V_tt + W_dop * V_dop, where W_tt and W_dop are weighting factors, W_tt + W_dop = 1, and the weighting factors are proportional to the signal quality; If the signal quality in both modes is extremely poor, an error / invalid flag will be output, or historical data will be used for prediction, and a maintenance alarm signal will be issued.

[0013] The present invention also provides a measurement method for an ultrasonic flow meter based on the above-mentioned multi-mode signal fusion and adaptive processing, comprising the following steps: S1. The control module controls the ultrasonic transducer to alternately or simultaneously transmit time-difference mode signals and Doppler mode signals. S2. Receive the echo signals corresponding to the time difference mode signal and the Doppler mode signal through the signal receiving and conditioning module; S3. The time difference method echo signal is processed through the time difference method processing channel of the signal processing module, and the time difference method flow velocity V_tt is calculated. S4. The Doppler echo signal is processed through the Doppler processing channel of the signal processing module, and the Doppler flow velocity V_dop is calculated. S5. Evaluate the quality of the time difference method signal and the Doppler method signal respectively through the signal quality evaluation module; S6. The adaptive fusion decision module applies preset adaptive decision rules based on the signal quality evaluated in step S5 and the flow velocity values ​​V_tt and V_dop calculated in steps S3 and S4. S7. Calculate the sound velocity C using the sound velocity calculation and compensation module based on the time difference method, and use it to update the sound velocity value in the Doppler flow velocity calculation. S8. Output the final flow rate V_out and / or the calculated volumetric flow rate and cumulative flow rate.

[0014] In summary, the present invention has the following beneficial effects: I. Significantly improves the accuracy of low flow rate measurement: In the low-velocity region (<0.3 m / s or even lower) where the accuracy of the traditional time difference method decreases, it automatically switches to the Doppler method, which is more sensitive to low flow rates (when the fluid contains scattering bodies), effectively expanding the low-end measurement capability of the flow meter; II. Enhanced adaptability to complex fluids: When the fluid contains scatterers such as bubbles and solid particles, which cause the time-of-flight method signal to degrade, it can automatically switch to the scatterer-dependent Doppler method to ensure the continuity of measurement. In pure fluids, it can maintain high-precision time-of-flight method measurement and is robust to changes in fluid properties. 3. Improve overall measurement reliability: Through real-time signal quality assessment, unreliable data is not forced to be output when the signal quality is poor. The adaptive fusion mechanism ensures that the best or second-best measurement result can be selected in most operating conditions. IV. Optimize the accuracy of the Doppler method: The sound velocity parameters in the Doppler method calculation are updated in real time using the high-precision time difference method sound velocity measurement results, which reduces the measurement error of the Doppler method caused by the change of sound velocity; V. High level of intelligence: The adaptive decision-making process simulates the judgment logic of experts, enabling the flow meter to cope with complex working conditions more intelligently. Attached Figure Description

[0015] Figure 1 This is a system structure block diagram of the ultrasonic flow meter with multi-mode signal fusion and adaptive processing according to the present invention; Figure 2 This is a flowchart of the measurement method of the present invention; Figure 3 This is a flowchart of the adaptive fusion decision-making process of the present invention. Detailed Implementation

[0016] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0017] like Figure 1 The ultrasonic flow meter shown includes an ultrasonic transducer, a signal generation and driving module, a signal receiving and conditioning module, a control module, a signal processing module, a signal quality assessment module, and a sound velocity calculation and compensation module.

[0018] Specifically, the ultrasonic transducer has at least one pair (T1, T2), which are installed in pairs on the outer or inner wall of the measuring pipe section of the ultrasonic flow meter for transmitting and receiving ultrasonic signals. Preferably, an ultrasonic transducer with integrated transceiver is used.

[0019] Specifically, the signal generation and driving module is connected to the ultrasonic transducer and is used to generate an excitation electrical signal that drives the ultrasonic transducer to emit ultrasonic waves.

[0020] Specifically, the signal receiving and conditioning module is connected to the ultrasonic transducer and is used to receive the ultrasonic echo signal sensed by the ultrasonic transducer and perform preprocessing such as amplification and filtering.

[0021] Specifically, the control module (MCU) is connected to the signal generation and driving module, enabling the ultrasonic transducer to alternately or simultaneously transmit ultrasonic signals in time-difference mode and Doppler mode. The time-difference mode signal is usually a short pulse train or a broadband signal with a specific code, used to measure the propagation time difference. The Doppler mode signal is usually a narrowband signal of a long continuous wave or a long pulse train, used to detect the Doppler frequency shift.

[0022] Specifically, the signal processing module (SPU) is connected to the control module and the signal receiving conditioning module respectively, and receives and processes the echo signals in the time difference method mode and the Doppler method mode, including the time difference method processing channel and the Doppler method processing channel. The time difference method processing channel receives and processes the echo signal in the time difference method mode, accurately measures the ultrasonic wave propagation time t_AB downstream and t_BA upstream, calculates the time difference Δt=t_BA-t_AB, and calculates the time difference method flow velocity V_tt according to the formula V=(K*L^2*Δt) / (2*D*cosθ*t_AB*t_BA), where V is the flow velocity, K is the calibration coefficient, L is the sound path, D is the pipe diameter, and θ is the angle between the sound velocity and the pipe axis. The Doppler processing channel receives and processes echo signals in Doppler mode, extracts the spectrum of the echo signals, identifies the main Doppler frequency shift Δf, and calculates the Doppler flow velocity V_dop according to the formula V_dop=(C*Δf) / (2*f0*cosα), where V_dop is the Doppler flow velocity, C is the speed of sound, f0 is the transmission frequency, and α is the angle between the speed of sound and the direction of the flow velocity. This channel needs to have strong noise suppression and spectrum analysis capabilities.

[0023] Specifically, the signal quality assessment module (SQA) is connected to the signal processing module and evaluates the quality parameters of the two signal modes in real time. The SQA module evaluates the quality parameters of the time difference method mode, including signal-to-noise ratio, signal amplitude, and confidence level of transit time measurement (such as waveform correlation and transit time jitter). The SQA module evaluates the quality parameters of the Doppler method mode, including echo intensity, signal-to-noise ratio of the spectrum, significance and width of the main peak of the spectrum (reflecting the uniformity of scatterer distribution), and stability of the spectral centroid.

[0024] Specifically, the adaptive fusion decision module (AFDM) is connected to the signal quality assessment module, receives the quality assessment results of the two modes of signals from the signal quality assessment module, receives the currently calculated time difference flow velocity V_tt and Doppler flow velocity V_dop, and dynamically decides the final flow velocity output based on preset adaptive decision rules and fuzzy logic / weighted algorithm. The adaptive decision rule is as follows: Rule 1: Prioritize high-confidence time difference method: If the signal quality assessment result of the time difference method is excellent (e.g., high SNR, high confidence), and the flow rate |V_tt| is greater than the set low flow rate threshold V_low, then the flow rate V_tt of the time difference method shall be used as the final output flow rate V_out. In this case, the Doppler method result can be used only for auxiliary verification or ignored. Rule 2, Poor Signal Quality Due to Low Flow Rate or Time Difference Method: If the signal quality assessment result using the time difference method is poor (e.g., low SNR, low confidence), or |V_tt| is less than or equal to the low flow rate threshold V_low, then If the Doppler signal quality assessment result is excellent (e.g., strong echo, clear spectrum), the Doppler flow velocity V_dop is used as the final output flow velocity V_out. If the Doppler signal quality is also poor, then proceed to rule three; Rule 3, Signal Fusion or Special Processing: If the signal quality of both modes is barely usable, then the two flow velocities are weighted and fused based on their respective quality assessment scores. V_out = W_tt * V_tt + W_dop * V_dop, where W_tt and W_dop are weighting factors, W_tt + W_dop = 1, and the weighting factors are proportional to the signal quality; If the signal quality of both modes is extremely poor, an error / invalid flag will be output, or historical data will be used for prediction (such as Kalman filtering), and a maintenance alarm signal will be issued. Among them, the dynamically updated low flow rate threshold V_low can be fine-tuned based on historical measurement data, fluid type (preset or learned), ambient temperature and other factors.

[0025] Specifically, the sound velocity calculation and compensation module (SCCM) is connected to the signal processing module. It calculates the fluid sound velocity based on the time difference method and uses it to update the sound velocity value in the Doppler flow velocity calculation. The sound velocity calculation and compensation module uses the ultrasonic wave propagation time t_AB and the counter-current propagation time t_BA measured by the time difference method to calculate the fluid sound velocity C=2L / (t_AB +t_BA), and uses this sound velocity in the calculation formula of the Doppler flow velocity V_dop to improve the accuracy of the Doppler method. At the same time, the sound velocity can also be used to assist in the judgment of fluid composition or temperature.

[0026] Combination Figure 2 As shown, the measurement method of the ultrasonic flow meter with multi-mode signal fusion and adaptive processing includes the following steps: S1. The ultrasonic transducer is controlled by the control module (MCU) to alternately or simultaneously transmit time-difference mode signals and Doppler mode signals; S2. Receive the echo signals corresponding to the time difference mode signal and the Doppler mode signal through the signal receiving and conditioning module; S3. The time difference method echo signal is processed by the time difference method processing channel of the signal processing module (SPU) to calculate the time difference method flow velocity V_tt; S4. The Doppler echo signal is processed through the Doppler processing channel of the signal processing module (SPU) to calculate the Doppler flow velocity V_dop; S5. Evaluate the quality of the time difference method signal and the Doppler method signal respectively through the signal quality assessment module (SQA); S6. The Adaptive Fusion Decision Module (AFDM) applies preset adaptive decision rules based on the signal quality evaluated in step S5 and the flow velocity values ​​V_tt and V_dop calculated in steps S3 and S4. Figure 3 As shown, If the time difference method has good signal quality and |V_tt|>V_low, then V_tt is selected as the final flow rate V_out; If the time difference method has poor signal quality or |V_tt| <= V_low: If the Doppler signal quality is good, then V_dop is selected as the final flow velocity V_out; If the Doppler signal quality is poor: if the quality of both is barely usable, then V_tt and V_dop are fused with a weight of 0.5 each to obtain V_out; If both are of extremely poor quality, an error flag will be output or a predicted value will be used, and an alarm will be triggered.

[0027] S7. Calculate the sound velocity C using the sound velocity calculation and compensation module (SCCM) based on the time difference method, and use it to update the sound velocity value in the Doppler flow velocity calculation. S8. Output the final flow rate V_out and / or the calculated volumetric flow rate and cumulative flow rate.

[0028] The following example illustrates this point, using a clamp-on ultrasonic flow meter with a DN50 pipe diameter as an example.

[0029] Ultrasonic transducers (T1, T2): center frequency 1MHz, installed using V-shaped reflection method (θ≈60°).

[0030] Control module (MCU): Control signal generator. In every 100ms cycle: the first 40ms transmits a time difference method signal (5-cycle 1MHz sine pulse train), the middle 20ms are silent (receiving time difference method echo), and the last 40ms transmits a Doppler method signal (continuous wave 1MHz).

[0031] Signal Processing Unit (SPU): Time difference method channel: Use cross-correlation algorithm to accurately measure t_AB and t_BA, and calculate V_tt; Doppler method channel: The echo signal is bandpass filtered (center 1MHz, bandwidth 50kHz), mixed, and lowpass filtered to obtain the difference frequency signal. FFT spectrum analysis (1024 points) is performed to find the main peak and calculate Δf. The sound velocity C provided by SCCM is used to calculate V_dop.

[0032] Signal Quality Assessment (SQA): Time difference method: Calculate the cross-correlation peak height (SNR proxy) and calculate the standard deviation (confidence level) of the upstream and downstream transit time measurements. Doppler method: Calculate the ratio of the amplitude of the main peak to the average amplitude of the noise floor in the FFT spectrum (SNR), and calculate the full width at half maximum (FWHM) of the main peak (reflects the distribution of the scatterer; the narrower the width, the better the quality).

[0033] Adaptive Fusion Decision Making (AFDM): Set the initial V_low to 0.2 m / s.

[0034] Normalized quality factor: Q_tt=min(1, SNR_tt / SNR_tt_threshold)*min(1, (1-StdDev_tt / StdDev_max)) (value 0~1); Q_dop=min(1,SNR_dop / SNR_dop_threshold)*min(1,(FWHM_min / FWHM)) (value 0~1, the smaller FWHM is, the better the quality).

[0035] Decision-making rules: If Q_tt>0.8 and |V_tt|>V_low->V_out=V_tt; Otherwise, if Q_dop > 0.7, then V_out = V_dop; Otherwise, if Q_tt > 0.4 and Q_dop > 0.4, then V_out = (Q_tt * V_tt + Q_dop * V_dop) / (Q_tt + Q_dop). Otherwise, output a "weak signal" alarm, and keep the previous valid value of V_out (or set it to NaN).

[0036] Sound velocity calculation (SCCM): C=2L / (t_AB+t_BA), updated once per time difference method measurement cycle, used for Doppler method calculation in the next cycle.

[0037] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape, principle and application direction of this application should be covered within the scope of protection of this application.

Claims

1. An ultrasonic flow meter with multi-mode signal fusion and adaptive processing, characterized in that, include At least one pair of ultrasonic transducers are installed in pairs on the outer or inner wall of the measuring pipe section of the ultrasonic flow meter for transmitting and receiving ultrasonic signals. The signal generation and driving module is connected to the ultrasonic transducer and is used to generate an excitation electrical signal that drives the ultrasonic transducer to emit ultrasonic waves. The signal receiving and conditioning module is connected to the ultrasonic transducer and is used to receive the ultrasonic echo signal sensed by the ultrasonic transducer and perform preprocessing. The control module is connected to the signal generation and driving module, enabling the ultrasonic transducer to alternately or simultaneously emit ultrasonic signals in time-difference mode and Doppler mode. The signal processing module is connected to the control module and the signal receiving and conditioning module respectively, and receives and processes the echo signals in the time difference method mode and the Doppler method mode. The signal quality assessment module is connected to the signal processing module and evaluates the quality parameters of the two signal modes in real time. The adaptive fusion decision module is connected to the signal quality assessment module. It receives the quality assessment results of the two modes of signals from the signal quality assessment module and dynamically decides the final flow rate output based on adaptive decision rules and fuzzy logic / weighted algorithm. The sound velocity calculation and compensation module is connected to the signal processing module. It calculates the fluid sound velocity based on the time difference method and uses it to update the sound velocity value in the Doppler flow velocity calculation.

2. The ultrasonic flow meter with multi-mode signal fusion and adaptive processing according to claim 1, characterized in that: The time difference mode signal is a short pulse train or a broadband signal with specific encoding, used to measure the propagation time difference; the Doppler mode signal is a narrowband signal of a long continuous wave or a long pulse train, used to detect Doppler frequency shift.

3. The ultrasonic flow meter with multi-mode signal fusion and adaptive processing according to claim 1, characterized in that, The signal processing module includes a time difference processing channel and a Doppler processing channel; The time difference method processing channel receives and processes the echo signal in the time difference method mode, accurately measures the ultrasonic wave propagation time t_AB downstream and t_BA upstream, calculates the time difference Δt=t_BA-t_AB, and calculates the time difference method flow velocity V_tt according to the formula V=(K*L^2*Δt) / (2*D*cosθ*t_AB*t_BA), where V is the flow velocity, K is the calibration coefficient, L is the sound path, D is the pipe diameter, and θ is the angle between the sound velocity and the pipe axis. The Doppler processing channel receives and processes echo signals in Doppler mode, extracts the spectrum of the echo signal, identifies the main Doppler frequency shift Δf, and calculates the Doppler flow velocity V_dop according to the formula V_dop=(C*Δf) / (2*f0*cosα), where V_dop is the Doppler flow velocity, C is the speed of sound, f0 is the transmission frequency, and α is the angle between the speed of sound and the direction of the flow velocity.

4. The ultrasonic flow meter with multi-mode signal fusion and adaptive processing according to claim 3, characterized in that, The sound velocity calculation and compensation module uses the time difference method to measure the ultrasonic wave propagation time t_AB downstream and t_BA upstream to calculate the fluid sound velocity C=2L / (t_AB +t_BA), and uses this sound velocity in the Doppler flow velocity V_dop calculation formula.

5. The ultrasonic flow meter with multi-mode signal fusion and adaptive processing according to claim 1, characterized in that, The signal quality assessment module evaluates the quality parameters of the time difference method mode, including signal-to-noise ratio, signal amplitude, and confidence level of transit time measurement. The signal quality assessment module evaluates the quality parameters of the Doppler mode, including echo intensity, signal-to-noise ratio of the spectrum, significance and width of the main peak of the spectrum, and stability of the center of gravity of the spectrum.

6. The ultrasonic flow meter with multi-mode signal fusion and adaptive processing according to claim 1, characterized in that, The adaptive decision rules of the adaptive fusion decision module include: Rule 1: Prioritize high-confidence time difference method: If the signal quality assessment result of the time difference method is excellent, and the flow rate |V_tt| is greater than the set low flow rate threshold V_low, then the flow rate V_tt of the time difference method shall be used as the final output flow rate V_out. Rule 2, poor signal quality of low flow rate or time difference method: If the signal quality assessment result of the time difference method is poor, or |V_tt| is less than or equal to the low flow rate threshold V_low, and the signal quality assessment result of the Doppler method is excellent, the Doppler method flow rate V_dop is used as the final output flow rate V_out. Rule 3, Signal Fusion or Special Processing: If the signal quality of both modes is barely usable, then the two flow rates are weighted and fused according to their respective quality assessment scores: V_out = W_tt * V_tt + W_dop * V_dop, where W_tt and W_dop are weighting factors, W_tt + W_dop = 1, and the weighting factors are proportional to the signal quality. If the signal quality in both modes is extremely poor, an error / invalid flag will be output, or historical data will be used for prediction, and a maintenance alarm signal will be issued.

7. A measurement method for an ultrasonic flowmeter based on the multi-mode signal fusion and adaptive processing described in any one of claims 1-6, characterized in that, Includes the following steps: S1. The control module controls the ultrasonic transducer to alternately or simultaneously transmit time-difference mode signals and Doppler mode signals. S2. Receive the echo signals corresponding to the time difference mode signal and the Doppler mode signal through the signal receiving and conditioning module; S3. The time difference method echo signal is processed through the time difference method processing channel of the signal processing module, and the time difference method flow velocity V_tt is calculated. S4. The Doppler echo signal is processed through the Doppler processing channel of the signal processing module, and the Doppler flow velocity V_dop is calculated. S5. Evaluate the quality of the time difference method signal and the Doppler method signal respectively through the signal quality evaluation module; S6. The adaptive fusion decision module applies preset adaptive decision rules based on the signal quality evaluated in step S5 and the flow velocity values ​​V_tt and V_dop calculated in steps S3 and S4. S7. Calculate the sound velocity C using the sound velocity calculation and compensation module based on the time difference method, and use it to update the sound velocity value in the Doppler flow velocity calculation. S8. Output the final flow rate V_out and / or the calculated volumetric flow rate and cumulative flow rate.

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