Ultrasonic flow measurement method

Abstract

The invention belongs to the technical field of flow measurement, and particularly relates to an ultrasonic flow measurement method which remarkably improves measurement precision and system energy efficiency by intermittently updating zero flow velocity reference flight time and pre-storing zero flow velocity waveform data in combination with a correlation algorithm and a parabola interpolation technology. Compared with a traditional threshold value method and a TI scheme, the method abandons threshold value dependence, dynamic correlation matching is carried out by utilizing a standard waveform of factory calibration and a real-time signal, absolute flight time is calculated, and a wave hopping error caused by long-term signal degradation is effectively avoided; meanwhile, a pre-stored waveform template and a regular self-calibration mechanism suppress noise, temperature drift and transducer aging influences, breakthrough is achieved in the aspects of anti-interference performance, long-term reliability and low power consumption, and a high-cost-performance solution is provided for gas flow metering.

Description

Technical Field

[0001] The present invention belongs to the technical field of flow measurement, and particularly relates to an ultrasonic flow measurement method. Background Art

[0002] Currently, ultrasonic flow measurement technology is mainly based on the Time-of-Flight (TOF) algorithm. The flow velocity is calculated by measuring the time difference between the upstream (T12) and downstream (T21) propagation times of ultrasonic waves in the fluid. The core formula is: , : flow velocity, L is the straight-line distance between two transducers, is the angle between the straight line of the transducer and the pipeline, T12 is the upstream flight time of the transducer, T21 is the downstream flight time of the transducer. As Figure 1 shown, the existing technical methods and their disadvantages: Direct time measurement method (threshold method).

[0003] Principle: Directly measure T12 and T21 through a Time-to-Digital Converter (TDC) or threshold detection (such as the first-wave amplitude threshold). For example, Patent CN113835333A uses a coarse-fine counter and a synchronization module to calculate the flight time based on the time point when the received signal first exceeds a preset threshold.

[0004] Disadvantages: The signal amplitude is affected by factors such as fluid state and transducer aging, resulting in incorrect first-wave detection ("skipping waves") and significant measurement errors; the threshold is fixed and cannot adapt to the deterioration of signal quality during long-term use (such as a decrease in transducer sensitivity), and the measurement accuracy decays with the lifespan.

[0005] ADC sampling-related algorithms.

[0006] Principle: Collect the upstream and downstream received signals through an ADC and store them in the RAM; perform correlation operations and interpolation on the two groups of signals to calculate the time difference of flight time (dTof); perform interpolation calculations on the absolute flight times T12 and T21 by setting a threshold (such as 20% of the signal amplitude).

[0007] Disadvantages: The calculation of the absolute flight time depends on the threshold: the setting of the threshold has a great impact on the accuracy of T12 / T21. Long-term signal deterioration (such as increased noise and amplitude attenuation) leads to the failure of the threshold, and measurement errors accumulate; high power consumption: the correlation operation and interpolation algorithms are computationally complex, the digital processing time is long, which is not friendly to battery-powered instruments; lack of real-time performance: the absolute flight time needs to be calculated frequently, and the system cannot maintain low-power operation for a long time.

[0008] Existing methods all rely on thresholds or fixed algorithm parameters and are difficult to adapt to long-term signal deterioration, resulting in a decrease in measurement accuracy; complex operations (such as TI solutions) or high-frequency absolute time measurements (such as the threshold method) lead to excessive power consumption, restricting the application in battery-powered scenarios. Summary of the Invention

[0009] The object of the present invention is to provide an ultrasonic flow measurement method, which avoids relying on threshold calculation of the absolute flight time by intermittently updating the zero-flow-rate reference flight time, thereby reducing long-term measurement errors; and combines the pre-stored reference waveform with the correlation algorithm to reduce the real-time calculation amount and significantly reduce the system power consumption, so as to solve the problems proposed in the above background technology.

[0010] To achieve the above object, the present invention adopts the following technical solutions: An ultrasonic flow measurement method includes the following steps: Activate the upstream transducer to emit an ultrasonic signal, and receive the ultrasonic signal emitted by the upstream transducer through the downstream transducer to generate an upstream received signal, and store the processed upstream received signal in the first storage unit; Activate the downstream transducer to emit an ultrasonic signal, and receive the ultrasonic signal emitted by the downstream transducer through the upstream transducer to generate a downstream received signal, and store the downstream received signal in the second storage unit; Based on the signal data in the first storage unit and the second storage unit, calculate the relative flight time difference between the upstream and downstream signals; At every preset time interval, perform a correlation calculation on the pre-stored zero-flow-rate reference waveform data with the upstream received signal and the downstream received signal to update the reference flight time at zero flow rate; Calculate the gas flow velocity according to the relative flight time difference and the updated reference flight time.

[0011] Preferably, the pre-stored zero-flow-rate reference waveform data includes: The received waveform data from the upstream transducer to the downstream transducer at zero flow rate and its corresponding flight time TJ12, and the received waveform data from the downstream transducer to the upstream transducer at zero flow rate and its corresponding flight time TJ21.

[0012] Preferably, the calculation of the relative flight time difference between the upstream and downstream signals includes: Perform linear interpolation processing on the waveform data in the first storage unit and the second storage unit respectively with the pre-stored zero-flow-rate reference waveform data, and determine the flight time difference dt corresponding to the maximum correlation through parabolic interpolation.

[0013] Preferably, the parabolic interpolation includes: Perform interpolation operations on the three data points before and after the maximum correlation value to calculate the flight time difference dt.

[0014] Preferably, the preset time interval is 10 seconds to 60 seconds.

[0015] Preferably, the update of the reference flight time is performed through the formula: ; where TN12 is the absolute flight time of the current upstream signal, TN21 is the absolute flight time of the current downstream signal, is the absolute flight time difference, and Tn0 is the reference flight time.

[0016] Preferably, the calculation formula for the gas flow rate is: ; where L is the transducer spacing, θ is the angle between the ultrasonic propagation direction and the fluid flow direction, is the relative flight time difference between the upstream and downstream signals.

[0017] Preferably, the calculation formula for the relative flight time difference dTof is: ; where is the flight time of the upstream signal, is the flight time of the downstream signal.

[0018] Preferably, the calculation formulas for TN12 and TN21 are: , ; where dt is the flight time difference between the current waveform data and the pre-stored zero-flow-rate reference waveform data, and TJ12 and TJ21 are the pre-stored zero-flow-rate reference flight times respectively.

[0019] Preferably, the calculation formula for is: .

[0020] Technical effects and advantages of the present invention: An ultrasonic flow measurement method proposed by the present invention has the following advantages compared with the prior art: By intermittently updating the zero-flow-rate reference flight time and the pre-stored zero-flow-rate waveform data, and combining the correlation algorithm and the parabolic interpolation technique, the present invention significantly improves the measurement accuracy and system energy efficiency. Compared with the traditional threshold method and the TI scheme, this method abandons the threshold dependence, uses the factory-calibrated reference waveform and the real-time signal for dynamic correlation matching, calculates the absolute flight time, and effectively avoids the jump error caused by long-term signal degradation. At the same time, the pre-stored waveform template and the periodic self-calibration mechanism suppress the influence of noise, temperature drift and transducer aging, achieving breakthroughs in anti-interference, long-term reliability and low power consumption, and providing a high-cost-effective solution for gas flow measurement. Description of the Drawings

[0021] Figure 1 is a schematic diagram of ultrasonic flow measurement in the prior art; Figure 2 is the transceiver architecture diagram of the ultrasonic flow measurement of the present invention; Figure 3 It is the signal data acquisition flow chart of the present invention; Figure 4 It is the flow block diagram for calculating the time difference between two waveforms of the present invention; Figure 5 It is the flow chart of the flow velocity measurement operation of the present invention; Figure 6 It is the flow chart of the ultrasonic flow measurement method of the present invention. Specific embodiments

[0022] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The specific embodiments described here are only used to explain the present invention and are not used to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present invention.

[0023] The present invention provides an ultrasonic flow measurement method as shown in Figure 6 and includes the following steps: Activate the upstream transducer to transmit an ultrasonic signal, and receive the ultrasonic signal transmitted by the upstream transducer through the downstream transducer to generate an upstream received signal, and process and store the upstream received signal in the first storage unit; Activate the downstream transducer to transmit an ultrasonic signal, and receive the ultrasonic signal transmitted by the downstream transducer through the upstream transducer to generate a downstream received signal, and store the downstream received signal in the second storage unit; Based on the signal data in the first storage unit and the second storage unit, calculate the relative flight time difference between the upstream and downstream signals; specifically including: Perform linear interpolation processing on the waveform data of the first storage unit and the second storage unit respectively with the pre-stored zero flow velocity reference waveform data, and determine the flight time difference dt corresponding to the maximum correlation through parabolic interpolation. Further, the parabolic interpolation includes: performing interpolation operations on the three data points before and after the maximum correlation to calculate the flight time difference dt.

[0024] At every preset time interval (10 seconds to 60 seconds), perform correlation calculations on the pre-stored zero flow velocity reference waveform data with the upstream received signal and the downstream received signal to update the reference flight time under zero flow velocity; Further, the pre-stored zero flow velocity reference waveform data includes: the received waveform data from the upstream transducer to the downstream transducer under zero flow velocity and its corresponding flight time TJ12, and the received waveform data from the downstream transducer to the upstream transducer under zero flow velocity and its corresponding flight time TJ21.

[0025] Calculate the gas flow velocity based on the relative flight time difference and the updated reference flight time.

[0026] Specifically, the update of the reference flight time is through the formula: ; where TN12 is the absolute flight time of the current upstream signal, TN21 is the absolute flight time of the current downstream signal, is the absolute flight time difference, and Tn0 is the reference flight time.

[0027] Furthermore, the calculation formula for the gas flow velocity is: ; where L is the transducer spacing, θ is the angle between the ultrasonic propagation direction and the fluid flow direction, is the relative flight time difference between the upstream and downstream signals. The calculation formula of is:

[0028] Furthermore, the calculation formula for the relative flight time difference dTof is: ; where is the flight time of the upstream signal, is the flight time of the downstream signal.

[0029] Furthermore, the calculation formulas for TN12 and TN21 are: , ; where dt is the flight time difference between the current waveform data and the pre-stored zero-flow-rate reference waveform data, and TJ12 and TJ21 are the pre-stored zero-flow-rate reference flight times respectively.

[0030] Specifically, the transducer transmitting and receiving architecture in this embodiment is as Figure 2 shown. The leftmost is the upstream transducer. The downstream transducer and the flow channel form a flow channel module. One end of the upstream transducer is connected to capacitor C1 and resistor R1. R1 is connected to the chip transmitting port TX_UP, and the other end of the transducer is grounded. The other end of C1 is connected to the chip receiving pin RX_UP. One end of the downstream transducer is connected to capacitor C2 and resistor R2. R2 is connected to the chip transmitting port TX_DN, and the other end of the transducer is grounded. The other end of C2 is connected to the chip receiving pin RX_DN. RX_UP and RX_DN are connected to a multiplexer. The multiplexer selects RX_UP or RX_DN to output to a variable gain amplifier through the control signal SEL. The output of the variable gain amplifier is connected to a low-pass filter. The output of the low-pass filter is connected to an ADC digital-to-analog conversion circuit. The output of the ADC is connected to a digital signal processing module. The TX_sig output by the digital signal processing module is connected to an output driving circuit. The control signal sel of the output driving circuit selects the TX_sig signal and outputs it to TX_UP or TX_DN.

[0031] The acquisition of received waveform data is as follows Figure 3 As shown, after the data acquisition starts, the upstream transducer emits a signal. Then, the receiving link is turned on. The downstream transducer receives the ultrasonic signal emitted by the upstream transducer. The receiving link converts the received signal into a digital signal through an ADC, and after CIC decimation filtering processing, stores it in the storage circuit RAM0. Then, the chip is turned off, and after waiting for a period of time (set here to 15 ms) to completely stop the transducer, the chip is restarted. The downstream transducer emits a signal, the upstream transducer receives the ultrasonic signal emitted by the downstream transducer, the receiving link converts the received signal into a digital signal through an ADC, and after CIC decimation filtering processing, stores it in the storage circuit RAM1. The data acquisition ends.

[0032] The calculation of the time difference between two waveforms is as follows Figure 4 As shown, first, the data of the two waveforms to be calculated are output to the Figure 4 random access memory circuits RAM_t0 and RAM_t1. The calculation process starts. The digital arithmetic module linearly interpolates the data in RAM_t0 and RAM_t1, then correlates the two sets of data, finds the maximum value of the correlation and performs parabolic interpolation on the three points before and after it, and calculates the time difference dt through the position of the interpolated data.

[0033] The working process of the implementation method of the entire flow velocity measurement calculation is as follows Figure 5 As shown, after the flow velocity measurement starts, initialization is first performed, setting A = 0, and setting the timing time for periodic operation. Here, the total time for one measurement, including the sleep and acquisition calculation time of the chip, is set to 1 second. After the timing starts, the data acquisition is carried out according to the Figure 3 process, and the data is stored in the storage circuits RAM0 and RAM1. After the data acquisition is completed, data processing and calculation are performed.

[0034] The processing process is as follows: When A = 0, calculate the square of the flight time at zero flow velocity at this time , first store RAM0 in RAM_t0 and RAM2 in RAM_t1. RAM2 stores the received waveform data of the ultrasonic wave emitted from the upstream transducer to the downstream transducer and stored through two receiving channels when the flow velocity is zero at the factory of the measurement module. TJ12 is the flight time of the waveform stored in RAM2. Calculate the waveform time difference dt between RAM0 and RAM2 according to the Figure 4 process, and through the formula , calculate TN12; Similarly, first store RAM1 in RAM_t0 and RAM3 in RAM_t1. RAM3 stores the received waveform data saved by the downstream transducer transmitting to the upstream transducer and received through two channels at zero flow velocity when the measurement module leaves the factory. TJ21 is the flight time of the waveform stored in RAM3. Calculate the waveform time difference dt between RAM1 and RAM3 according to the process of Figure 4 . Calculate TN21 through the formula TN21 = dt + TJ21. After obtaining TN12 and TN21, calculate the square of the flight time at zero flow velocity at this time .

[0035] When A is not equal to 0, skip the measurement . Directly measure the time difference dTof between the waveforms stored in RAM0 and RAM1; first store RAM1 in RAM_t0 and RAM1 in RAM_t1, and calculate the waveform time difference dt between RAM0 and RAM1 according to the process of Figure 4 . Let dTof = dt, calculate the flow velocity and output it.

[0036] The above is a single flow velocity measurement. Then judge whether A is equal to 30. If it is equal to 30, set A = 0; if A is equal to 30, set A = A + 1; the module enters the sleep state, judge whether the timer reaches the preset timing time (here it is 1 second). If it reaches, re-time and start a new measurement, and so on.

[0037] In summary, the present invention significantly improves the measurement accuracy and system energy efficiency by intermittently updating the zero flow velocity reference flight time and pre-stored zero flow velocity waveform data, combined with the correlation algorithm and parabolic interpolation technology. Compared with the traditional threshold method and TI scheme, this method abandons the threshold dependence, uses the factory-calibrated reference waveform and real-time signal for dynamic correlation matching, calculates the absolute flight time, and effectively avoids the skip error caused by long-term signal deterioration; at the same time, the pre-stored waveform template and regular self-calibration mechanism suppress the influence of noise, temperature drift and transducer aging, achieving breakthroughs in anti-interference, long-term reliability and low power consumption, and providing a cost-effective solution for gas flow measurement.

[0038] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An ultrasonic flow measurement method, characterized in that, Including the following steps: Exciting the upstream transducer to transmit an ultrasonic signal, and receiving the ultrasonic signal transmitted by the upstream transducer through the downstream transducer to generate an upstream received signal, and processing and storing the upstream received signal in the first storage unit; Exciting the downstream transducer to transmit an ultrasonic signal, and receiving the ultrasonic signal transmitted by the downstream transducer through the upstream transducer to generate a downstream received signal, and storing the downstream received signal in the second storage unit; Calculating the relative flight time difference between the upstream and downstream signals based on the signal data in the first storage unit and the second storage unit; At every preset time interval, performing a correlation calculation between the pre-stored zero-flow-rate reference waveform data and the upstream received signal and the downstream received signal to update the reference flight time at zero flow rate; Calculating the gas flow rate according to the relative flight time difference and the updated reference flight time; 2. The ultrasonic flow measurement method according to claim 1, characterized in that The pre-stored zero-flow-rate reference waveform data includes: The received waveform data from the upstream transducer to the downstream transducer at zero flow rate and its corresponding flight time TJ12, and the received waveform data from the downstream transducer to the upstream transducer at zero flow rate and its corresponding flight time TJ21.

3. A method for ultrasonic flow measurement according to claim 1, characterized in that, The calculating of the relative flight time difference between the upstream and downstream signals includes: Performing linear interpolation processing on the waveform data in the first storage unit and the second storage unit respectively with the pre-stored zero-flow-rate reference waveform data, and determining the flight time difference dt corresponding to the maximum correlation through parabolic interpolation; 4. The ultrasonic flow measurement method according to claim 3, wherein, The parabolic interpolation includes: Performing interpolation operations on the three data points before and after the maximum correlation to calculate the flight time difference dt; 5. A method for ultrasonic flow measurement according to claim 1, characterized in that, The preset time interval is 10 seconds to 60 seconds; 6. The ultrasonic flow measurement method according to claim 1, characterized in that The update of the reference flight time is through the formula: ; Among them, TN12 is the absolute flight time of the current uplink signal, and TN21 is the absolute flight time of the current downlink signal. is the absolute flight time difference, and Tn0 is the reference flight time.

7. The ultrasonic flow measurement method according to claim 1, characterized in that The calculation formula for the gas flow rate is as follows: ; where L is the transducer spacing, and θ is the angle between the ultrasonic propagation direction and the fluid flow direction, which is the relative flight time difference between the upward and downward signals.

8. An ultrasonic flow measurement method according to claim 7, characterized in that, The calculation formula for the relative time-of-flight difference dTof is as follows: ; Among them, is the flight time of the uplink signal, is the flight time of the downlink signal.

9. An ultrasonic flow measurement method according to claim 6, characterized in that, The calculation formulas for TN12 and TN21 are as follows: , ; Wherein, dt is the flight time difference between the current waveform data and the pre-stored zero-flow-rate reference waveform data, and TJ12 and TJ21 are the pre-stored zero-flow-rate reference flight times respectively.

10. The ultrasonic flow measurement method according to claim 6, characterized in that, The said The calculation formula is: .

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