Double-frequency adaptive ultrasonic time difference method and system for measuring flow in open channel

Abstract

The application belongs to the field of intelligent water conservancy and measurement technology, and provides a double-frequency adaptive ultrasonic time difference method open channel flow measurement method and system. Among them, the left bank high-frequency ultrasonic probe and the left bank low-frequency ultrasonic probe are arranged on the left bank of the open channel, and the right bank high-frequency ultrasonic probe and the right bank low-frequency ultrasonic probe are arranged on the right bank of the open channel; and the line between the left bank high-frequency ultrasonic probe and the right bank high-frequency ultrasonic probe is parallel to the line between the left bank low-frequency ultrasonic probe and the right bank low-frequency ultrasonic probe. When measuring, the characteristics of high-frequency ultrasonic and low-frequency ultrasonic are comprehensively utilized to solve the problems of high-precision flow measurement, complex scene flow measurement with high sediment and large flow rate, and the problem of insufficient applicability of traditional single-frequency ultrasonic time difference method flow measurement in all scenes. In the application, the signal quality comprehensive score is compared with the low-frequency switching threshold and the high-frequency recovery threshold when selecting the ultrasonic probe, the frequent switching of high-frequency ultrasonic and low-frequency ultrasonic is avoided, and the reliability of the ultrasonic time difference method open channel flow measurement is improved.

Description

Technical Field

[0001] This invention belongs to the field of smart water conservancy and measurement technology, and particularly relates to a dual-frequency adaptive ultrasonic time-difference method and system for open channel flow measurement. Background Technology

[0002] Traditional ultrasonic time-of-flight (TOF) flow measurement systems for open channels involve installing ultrasonic probes on both the left and right banks of the channel. Each probe emits ultrasonic waves towards the probe on the opposite bank and simultaneously receives the waves emitted by the probe on the opposite bank. Knowing the time the opposite bank probe emits the ultrasonic waves, the propagation time from the opposite bank to the local bank can be calculated from the time the local probe receives the waves. Conversely, the propagation time from the local bank to the opposite bank can also be calculated. These two propagation times represent the downstream and upstream propagation times, respectively. The difference between these two times is related to the flow velocity in the open channel; by measuring these two propagation times, the flow velocity can be calculated.

[0003] Ultrasonic waves gradually attenuate as they propagate in water. When the open channel is wide and the propagation path is long, the signal received by the receiving probe may be too weak to be properly identified. Therefore, in practical applications, the maximum distance between the probes on the left and right banks is usually limited. Furthermore, as the sediment content of the water increases, the attenuation of ultrasonic waves also increases. When the sediment content increases to a certain level, the probe on the opposite bank may misinterpret the signal due to its weakness, leading to decreased flow measurement accuracy, data fluctuations, and in severe cases, complete signal interruption, making flow measurement impossible. These problems are particularly pronounced when the open channel is wide and the flow velocity varies greatly. Therefore, it is necessary to adopt corresponding technical methods to improve the adaptability of the ultrasonic time-of-flight flow measurement system to application scenarios with high sediment content, wide channels, and large flow velocity variations, thereby improving the accuracy and effectiveness of ultrasonic time-of-flight flow measurement in open channels. Summary of the Invention

[0004] This application provides a dual-frequency adaptive ultrasonic time-of-flight method and system for open channel flow measurement, in order to improve the adaptability of the ultrasonic time-of-flight flow measurement system to application scenarios such as high sediment content, large channel width, and large flow velocity variation, and to improve the accuracy and effectiveness of ultrasonic time-of-flight open channel flow measurement.

[0005] The dual-frequency adaptive ultrasonic time-difference method for open channel flow measurement provided in this application includes: during flow measurement, the system is first initialized: the left bank high-frequency ultrasonic probe (H) is activated. LF1 ) and right bank high-frequency ultrasound probe (H RF1 ); Then, in each measurement cycle, the overall signal quality score (Q) is obtained; Determine the overall signal quality score (Q) and the low-frequency handover threshold (Q). L ) and high-frequency recovery threshold (Q H The size relationship of ) If the currently operating device is a left bank high-frequency ultrasound probe (H) LF1 ) and right bank high-frequency ultrasound probe (H RF1 Based on the aforementioned size relationship, determine whether to shut down the left bank high-frequency ultrasound probe (H). LF1 ) and right bank high-frequency ultrasound probe (H RF1 And activate the left bank low-frequency ultrasound probe (H) LF2 ) and right bank low-frequency ultrasound probe (H RF2 ); If the currently operating device is a left bank low-frequency ultrasound probe (H) LF2 ) and right bank low-frequency ultrasound probe (H RF2 Based on the aforementioned size relationship, determine whether to turn off the left bank low-frequency ultrasound probe (H). LF2 ) and right bank low-frequency ultrasound probe (H RF2 And enable the left bank high-frequency ultrasound probe (H) LF1 ) and right bank high-frequency ultrasound probe (H RF1 ); Based on the current working left bank high-frequency ultrasound probe (H LF1 ) and right bank high-frequency ultrasound probe (H RF1 ) or left bank low-frequency ultrasound probe (H LF2 ) and right bank low-frequency ultrasound probe (H RF2 The received information is used to calculate the flow velocity of the water in the open channel based on the working principle of the ultrasonic time-of-flight method. Among them, the left bank high-frequency ultrasound probe (H LF1 ) and left bank low-frequency ultrasound probe (H LF2 ) are set on the left bank of the open channel, and high-frequency ultrasonic probes (H) are placed on the right bank. RF1 ) and right bank low-frequency ultrasound probe (H RF2 The high-frequency ultrasonic probe (H) is located on the right bank of the open channel; and on the left bank... LF1 ) and right bank high-frequency ultrasound probe (H RF1 The line connecting the two points is parallel to the left bank low-frequency ultrasound probe (H). LF2 ) and right bank low-frequency ultrasound probe (H RF2 The line connecting the two points forms an angle of 40 to 50 degrees with the direction of the flow velocity.

[0006] In one implementation, if the currently operating probe is a left-bank high-frequency ultrasound probe (H... LF1 ) and right bank high-frequency ultrasound probe (H RF1 ): Determine the overall signal quality score (Q) and the low-frequency handover threshold (Q). L ) and high-frequency recovery threshold (Q H The magnitude of the signal quality score (Q) is greater than the low-frequency handover threshold (Q). L The results of the left bank high-frequency ultrasound probe (H) were as follows:LF1 ) and right bank high-frequency ultrasound probe (H RF1 Continue working; Determine the overall signal quality score (Q) and the low-frequency handover threshold (Q). L ) and high-frequency recovery threshold (Q H The signal quality comprehensive score (Q) obtained from the magnitude relationship is less than the low-frequency handover threshold (Q). L The result is as follows: First, try to increase the ultrasonic excitation voltage. After the excitation voltage is increased, the system waits for one measurement cycle and then reacquires the current signal quality comprehensive score (Q). If the overall signal quality score (Q) is greater than or equal to the low-frequency handover threshold (Q) L ), left bank high-frequency ultrasound probe (H LF1 ) and right bank high-frequency ultrasound probe (H RF1 Continue working and record the current excitation voltage value as the new excitation voltage; If the overall signal quality score (Q) is still less than the low-frequency handover threshold (Q), L ), turn off the left bank high-frequency ultrasound probe (H LF1 ) and right bank high-frequency ultrasound probe (H RF1 And activate the left bank low-frequency ultrasound probe (H) LF2 ) and right bank low-frequency ultrasound probe (H RF2 ).

[0007] In one implementation, when the ultrasonic excitation voltage is increased... As the enhanced emission excitation voltage; Among them, U max U is the rated maximum excitation voltage of the ultrasonic probe; ΔU is the excitation voltage adjustment step, U current This represents the excitation voltage of the current ultrasonic probe.

[0008] In one implementation, if the currently operating probe is a left bank low-frequency ultrasound probe (H... LF2 ) and right bank low-frequency ultrasound probe (H RF2 ): If the overall signal quality score (Q) is less than or equal to the high-frequency recovery threshold Q H ), Left bank low-frequency ultrasound probe (H LF2 ) and right bank low-frequency ultrasound probe (H RF2 Continue working; If the overall signal quality score (Q) > the high-frequency recovery threshold (Q) H Turn off the left bank low-frequency ultrasound probe (HLF2) and the right bank low-frequency ultrasound probe (H). RF2 And enable the left bank high-frequency ultrasound probe (H) LF1 ) and right bank high-frequency ultrasound probe (H RF1 ).

[0009] In one implementation, the low-frequency switching threshold (Q) L ) less than the high-frequency recovery threshold (Q) H ), high-frequency recovery threshold (Q H ) and low-frequency switching threshold (Q L The difference between the two values ​​is the hysteresis interval (ΔQ). The initial value of the hysteresis interval (ΔQ) is in the range of 0.15-0.25, and it is then dynamically adjusted based on historical data.

[0010] In one implementation, the signal quality overall score (Q) is obtained by simultaneously collecting the following data in each measurement cycle: Right bank high-frequency ultrasound probe (H RF1 ) and left bank high-frequency ultrasound probe (H LF1 The voltage amplitude of the received ultrasonic signal is denoted as RSSI. H and RSSI R ; During the silent period of signal reception, ambient noise baseline (Noise) is collected. floor ), and calculate the signal-to-noise ratio (SNR) within the first pulse cycle; Left bank high-frequency ultrasound probe (H LF1 ) and left bank low-frequency ultrasound probe (H LF2 The corresponding frequencies are F1 and F2, respectively; the right bank high-frequency ultrasound probe (H RF1 ) and right bank low-frequency ultrasound probe (H RF2 The corresponding frequencies are F1 and F2, respectively; Fourier transform is performed on the received ultrasonic pulse train to extract the ratio of F1 and F2 energy to the energy of each harmonic, denoted as the signal waveform distortion rate (THD). The formula for calculating the signal waveform distortion rate (THD) is: ; Where V1 is the voltage amplitude of the fundamental frequency component, which is equal to the voltage amplitude of the current operating frequency F1 or F2, and the frequency of the fundamental frequency component is equal to the current operating frequency. n The voltage amplitude of the nth harmonic component is given, and its frequency is n times the fundamental frequency; N max The highest harmonic order; The current formula for calculating the overall signal quality score (Q) is: ; Among them, RSSI norm It is RSSI H and RSSI R The average value of the comprehensive processing results is taken: ; Then for RSSI avgNormalization yields RSSI norm ; Normalize the SNR to obtain the SNR norm ; Normalize the THD to obtain the THD. norm ; Among them, for RSSI H RSSI R SNR and THD are normalized, and the normalization adopts a linear mapping of the historical maximum and minimum values ​​to the [0,1] interval; α, β, and γ are weighting coefficients, with initial values ​​being preset empirical values, which are then dynamically optimized by the adaptive learning module.

[0011] This application also provides a dual-frequency adaptive ultrasonic time-difference method open channel flow measurement system, including: a left bank high-frequency ultrasonic probe (H LF1 ) and left bank low-frequency ultrasound probe (H LF2 The left bank high-frequency ultrasound probe (H) LF1 ) and left bank low-frequency ultrasound probe (H LF2 ) are set on the left bank of the open channel, and high-frequency ultrasonic probes (H) are placed on the right bank. RF1 ) and right bank low-frequency ultrasound probe (H RF2 The high-frequency ultrasonic probe (H) is located on the right bank of the open channel; and on the left bank... LF1 ) and right bank high-frequency ultrasound probe (H RF1 The line connecting the two points is parallel to the left bank low-frequency ultrasound probe (H). LF2 ) and right bank low-frequency ultrasound probe (H RF2 The line connecting the two points forms an angle of 40 to 50 degrees with the direction of the flow velocity; The data acquisition unit is used for system initialization during flow measurement: enabling the left bank high-frequency ultrasonic probe (H... LF1 ) and right bank high-frequency ultrasound probe (H RF1 Then, in each measurement cycle, the overall signal quality score (Q) is obtained; the overall signal quality score (Q) is compared with the low-frequency switching threshold (Q0). L ) and high-frequency recovery threshold (Q H The size relationship: If the currently operating probe is a left bank high-frequency ultrasound probe (H) LF1 ) and right bank high-frequency ultrasound probe (H RF1 Based on the aforementioned size relationship, determine whether to shut down the left bank high-frequency ultrasound probe (H). LF1 ) and right bank high-frequency ultrasound probe (H RF1 And activate the left bank low-frequency ultrasound probe (H) LF2 ) and right bank low-frequency ultrasound probe (H RF2 If the currently operating probe is a left bank low-frequency ultrasound probe (H...), then... LF2 ) and right bank low-frequency ultrasound probe (HRF2 Based on the aforementioned size relationship, determine whether to turn off the left bank low-frequency ultrasound probe (H). LF2 ) and right bank low-frequency ultrasound probe (H RF2 And enable the left bank high-frequency ultrasound probe (H) LF1 ) and right bank high-frequency ultrasound probe (H RF1 ); based on the current working left bank high-frequency ultrasound probe (H ); LF1 ) and right bank high-frequency ultrasound probe (H RF1 ) or left bank low-frequency ultrasound probe (H LF2 ) and right bank low-frequency ultrasound probe (H RF2 The received information is used to calculate the flow velocity of the water in the open channel based on the principle of ultrasonic time difference method.

[0012] In one embodiment, the dual-frequency adaptive ultrasonic time-difference method open channel flow measurement system further includes a water level sensing unit, which is connected to the data acquisition unit. The data acquisition unit calculates the water flow area based on the water level cross-sectional data and then calculates the cross-sectional flow rate based on the velocity area method.

[0013] In one implementation, the data acquisition unit determines the overall signal quality score (Q) and the low-frequency switching threshold (Q0). L ) and high-frequency recovery threshold (Q H When considering the size relationship: If the currently operating device is a left bank high-frequency ultrasound probe (H) LF1 ) and right bank high-frequency ultrasound probe (H RF1 ): Determine the overall signal quality score (Q) and the low-frequency handover threshold (Q). L ) and high-frequency recovery threshold (Q H The magnitude of the signal quality score (Q) is greater than the low-frequency handover threshold (Q). L The results of the left bank high-frequency ultrasound probe (H) were as follows: LF1 ) and right bank high-frequency ultrasound probe (H RF1 Continue working; Determine the overall signal quality score (Q) and the low-frequency handover threshold (Q). L ) and high-frequency recovery threshold (Q H The signal quality comprehensive score (Q) obtained from the magnitude relationship is less than the low-frequency handover threshold (Q). L The result is as follows: First, try to increase the ultrasonic excitation voltage. After the excitation voltage is increased, the system waits for 1 measurement cycle and then reacquires the current signal quality comprehensive score (Q). If the overall signal quality score (Q) is greater than or equal to the low-frequency handover threshold (Q) L ), left bank high-frequency ultrasound probe (H LF1 ) and right bank high-frequency ultrasound probe (HRF1 Continue working and record the current excitation voltage value as the new excitation voltage; If the overall signal quality score (Q) is still less than the low-frequency handover threshold (Q), L ), turn off the left bank high-frequency ultrasound probe (H LF1 ) and right bank high-frequency ultrasound probe (H RF1 And activate the left bank low-frequency ultrasound probe (H) LF2 ) and right bank low-frequency ultrasound probe (H RF2 ).

[0014] In one embodiment, when the data acquisition unit performs an ultrasonic excitation voltage boost... As the enhanced emission excitation voltage; Among them, U max U is the rated maximum excitation voltage of the ultrasonic probe; ΔU is the excitation voltage adjustment step, U current This represents the excitation voltage of the current ultrasonic probe.

[0015] The dual-frequency adaptive ultrasonic time-of-flight method and system for open channel flow measurement provided in this application comprehensively utilize the characteristics of high-frequency and low-frequency ultrasound, solving both the problem of high-precision flow measurement and the problem of flow measurement in complex scenarios with high sediment and high flow velocities. Therefore, it effectively addresses the problem of insufficient applicability of traditional single-frequency ultrasonic time-of-flight flow measurement systems across all scenarios. Furthermore, in this application, when selecting the ultrasonic probe, the signal quality comprehensive score (Q) and the low-frequency switching threshold (Q0) are used... L ) and high-frequency recovery threshold (Q H Compared with traditional methods, this avoids the frequent switching between high-frequency and low-frequency ultrasound, thereby improving the reliability of ultrasonic time-difference method for open channel flow measurement. Attached Figure Description

[0016] Figure 1 This is a schematic diagram showing the arrangement of the ultrasonic probes in Embodiments 1 and 2 of this application; Figure 2 This is a schematic diagram of the workflow of the dual-frequency adaptive ultrasonic time-difference method open channel flow measurement system in Embodiment 2 of this application; Figure 3 This is a schematic diagram of the dual-frequency adaptive ultrasonic time-difference method open channel flow measurement system in Embodiment 2 of this application.

[0017] Icon labels: 100 - Left bank of the open channel; 200 - Right bank of the open channel. Detailed Implementation

[0018] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. The principles and features of the present invention are described below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0019] Example 1: This embodiment provides a dual-frequency adaptive ultrasonic time-of-flight method for open channel flow measurement, in which two ultrasonic probes are respectively set on the left and right banks of the open channel. Specifically: Reference Figure 1 Left bank high-frequency ultrasound probe H LF1 and the left bank low-frequency ultrasound probe H LF2 A high-frequency ultrasonic probe H was installed 100 meters on the left bank of the open channel and on the right bank. RF1 and the right bank low-frequency ultrasound probe H RF2 The high-frequency ultrasonic probe H is set at 200 meters on the right bank of the open channel; and on the left bank... LF1 and the right bank high-frequency ultrasound probe H RF1 The line connecting them is parallel to the left bank low-frequency ultrasound probe H. LF2 and the right bank low-frequency ultrasound probe H RF2 The angle between the line connecting the two channels and the direction of water flow in the open channel is 40 to 50 degrees. The angle should be as close as possible to 45 degrees, but not necessarily exactly 45 degrees, so as to ensure that the time difference of ultrasonic wave propagation with and against the current is close to the maximum, which is beneficial to improving the measurement accuracy of low flow velocities.

[0020] During flow measurement, this embodiment follows these steps: S100 System Initialization: Enable Left Bank High-Frequency Ultrasonic Probe H LF1 With right bank high-frequency ultrasound probe H RF1 In this embodiment, the left bank high-frequency ultrasound probe H is activated. LF1 With right bank high-frequency ultrasound probe H RF1 Previously, after the system powered on, both the master unit and the slave unit performed self-tests, including: The clock synchronization unit locks onto the satellite signal, preparing for the synchronization of the measurement time reference between the two sides of the strait. Locking onto the satellite signal is the first step in achieving synchronization of the time reference between the two sides of the strait. Then, the master and slave units continue to perform a handshake through the data short transmission unit to achieve synchronization of the measurement time reference between the two sides of the strait. The data short transmission unit establishes a LoRa communication link and confirms that bidirectional communication is normal. Ultrasonic probe impedance detection to determine if the probe is online; The water level sensing unit reads the initial water level.

[0021] S200: Real-time acquisition of signal quality parameters: Subsequently, in each measurement cycle, the overall signal quality score Q is obtained; S300: Determine the current signal quality level: Determine the overall signal quality score Q and the low-frequency handover threshold (Q). L and high-frequency recovery threshold Q H Size relationship: Scenario A: Currently in high-frequency mode (fundamental frequency F1): If the currently operating probe is a left-bank high-frequency ultrasound probe H LF1 and the right bank high-frequency ultrasound probe H RF1 Based on the aforementioned size relationship, determine whether to shut down the left bank high-frequency ultrasound probe H. LF1 and the right bank high-frequency ultrasound probe H RF1 And the left bank low-frequency ultrasound probe H was activated. LF2 and the right bank low-frequency ultrasound probe H RF2 ; Scenario B: Currently in low-frequency mode (fundamental frequency F2): If the currently operating probe is a left-bank low-frequency ultrasound probe H LF2 and the right bank low-frequency ultrasound probe H RF2 Based on the aforementioned size relationship, determine whether to shut down the left bank low-frequency ultrasound probe H. LF2 and the right bank low-frequency ultrasound probe H RF2 And the left bank high-frequency ultrasound probe H was activated. LF1 and the right bank high-frequency ultrasound probe H RF1 ; Based on the current working left bank high-frequency ultrasonic probe H LF1 With right bank high-frequency ultrasound probe H RF1 Or left bank low-frequency ultrasound probe H LF2 and the right bank low-frequency ultrasound probe H RF2 The received information is used to calculate the flow velocity of the water in the open channel based on the principle of ultrasonic time difference method.

[0022] When the working device is the left bank high-frequency ultrasonic probe H LF1 With right bank high-frequency ultrasound probe H RF1 At that time, the voltage of the excitation signal emitted by both is U1. Left bank high-frequency ultrasonic probe H LF1 H-direction high-frequency ultrasonic probe on the right bank RF1 Transmitting ultrasonic signals, the left bank high-frequency ultrasonic probe H LF1 High-frequency ultrasonic probe H emitted to the right bank RF1 The reception time is T L1 Right bank high-frequency ultrasonic probe H RF1 High-frequency ultrasonic probe H on the left bank LF1 Right bank high-frequency ultrasound probe H RF1 High-frequency ultrasonic probe H emitted to the left bank LF1 The reception time is T R1To obtain the start time of the ultrasonic probe's signal transmission on the opposite bank, this embodiment employs a synchronous clock technique. Based on this technique, given the known time of the ultrasonic wave transmission from the opposite bank's probe, the propagation time of the ultrasonic wave from the opposite bank to this bank can be calculated based on the time when the probe on this bank receives the ultrasonic wave. Conversely, the propagation time from this bank to the opposite bank can also be calculated. These two propagation times represent the downstream and upstream propagation times of the ultrasonic wave over the same distance, respectively. The difference between these two times is related to the flow velocity of the water in the open channel. By measuring these two propagation times, the flow velocity can be calculated. In practical applications, water temperature is usually also measured to correct for errors in flow velocity calculation caused by variations in the ultrasonic wave's propagation speed at different water temperatures. This invention does not discuss water temperature measurement or the use of water temperature for flow velocity error correction.

[0023] When the working device is the left bank low-frequency ultrasound probe H LF2 and the right bank low-frequency ultrasound probe H RF2 At that time, the voltage of the excitation signal emitted by both is U2, which is the same as that of the left bank high-frequency ultrasonic probe H. LF1 With right bank high-frequency ultrasound probe H RF1 The calculation principles and processes are the same during operation, so I will not repeat them here.

[0024] This embodiment constructs an adaptive ultrasonic time-of-flight flow measurement method that dynamically applies different ultrasonic frequencies and dynamically adjusts the excitation voltage of the excitation signal. This method effectively improves the system's adaptability to complex application scenarios while maintaining the accuracy of ultrasonic wireless time-of-flight flow measurement in open channels. It addresses the problem of insufficient adaptability in complex scenarios such as wide channels, large variations in sediment content, and large flow velocity fluctuations.

[0025] When the water is relatively clear and the current is slow, activate the left bank H. LF1 and right bank H RF1 High-frequency probes are used for measurement. Compared to low-frequency ultrasound, high-frequency ultrasound has advantages such as better directivity and higher time-difference resolution, enabling the acquisition of stable and highly accurate flow data. During periods of high flooding, water bodies typically have high sediment content and high flow velocities. At this time, the attenuation problem of high-frequency ultrasound becomes more prominent, and the received signal strength weakens accordingly. When the signal strength weakens to a predetermined threshold, the data acquisition unit will automatically activate the left bank H... LF2 and right bank H RF2 Low-frequency probes are used for measurement. Compared to high-frequency ultrasound, although low-frequency ultrasound has lower time-difference resolution and lower flow measurement accuracy, it has advantages such as better penetration and stronger resistance to sediment, allowing for stable flow data in high-flood applications. High-frequency ultrasound solves the problem of high-precision flow measurement, while low-frequency ultrasound solves the problem of flow measurement in complex scenarios with high sediment and high flow velocities. The flexible application of both achieves a balance between high measurement accuracy and stability in high-flood flow measurement, effectively addressing the lack of applicability of traditional single-frequency ultrasonic time-difference flow measurement systems across all scenarios.

[0026] Furthermore, this application utilizes a comprehensive signal quality score Q and a low-frequency switching threshold Q when selecting an ultrasound probe. L and high-frequency recovery threshold Q H Compared to other methods, this avoids the frequent switching between high-frequency and low-frequency ultrasound, thus improving the reliability of ultrasonic time-difference method for open channel flow measurement.

[0027] In S300, for case A: If Q≥Q L That is, to determine the overall signal quality score Q and the low-frequency switching threshold Q. L and high-frequency recovery threshold Q H The signal quality score Q obtained from the magnitude relationship is greater than the low-frequency switching threshold Q. L When the result is good, it indicates a good signal, and the left bank high-frequency ultrasound probe H LF1 and the right bank high-frequency ultrasound probe H RF1 Continue working and return to S200 for the next cycle of measurement; If Q<Q L That is, to determine the overall signal quality score Q and the low-frequency switching threshold Q. L and high-frequency recovery threshold Q H The magnitude relationship indicates that the overall signal quality score Q is less than the low-frequency handover threshold Q. L The result is as follows: First, an attempt is made to increase the ultrasonic excitation voltage. After the excitation voltage is increased, the system waits for one measurement cycle and then reacquires the current signal quality comprehensive score Q. At this point, if the overall signal quality score Q is greater than or equal to the low-frequency handover threshold Q L This indicates that the excitation voltage boost is effective, thus maintaining the H of the left bank high-frequency ultrasonic probe. LF1 and the right bank high-frequency ultrasound probe H RF1 Continue working, record the current excitation voltage value as the new excitation voltage, and return to S200 for the next cycle of measurement; At this point, if the overall signal quality score Q is still less than the low-frequency handover threshold Q L This indicates that the excitation voltage increase has reached its upper limit or the effect is not significant, so the left bank high-frequency ultrasonic probe H should be turned off. LF1 and the right bank high-frequency ultrasound probe H RF1 And activate the left bank low-frequency ultrasound probe H LF2 and the right bank low-frequency ultrasound probe H RF2 .

[0028] In this embodiment, the excitation voltage is increased first before switching frequencies, thereby preserving the accuracy of high-frequency measurements.

[0029] For case B in S300: If the overall signal quality score Q is less than or equal to the high-frequency recovery threshold QH This indicates that the signal quality has not yet reached the high-frequency recovery condition, so the left bank low-frequency ultrasound probe H... LF2 and the right bank low-frequency ultrasound probe H RF2 Continue working and return to S200 for the next cycle of measurement; If the overall signal quality score Q is greater than the high-frequency recovery threshold Q H This indicates a significant improvement in signal quality; therefore, the left bank low-frequency ultrasound probe H should be turned off. LF2 and the right bank low-frequency ultrasound probe H RF2 And enable the left bank high-frequency ultrasound probe H LF1 and the right bank high-frequency ultrasound probe H RF1 Then return to S200 for the next cycle of measurement.

[0030] In this embodiment, the low-frequency switching threshold Q L Less than the high-frequency recovery threshold Q H High-frequency recovery threshold Q H With low-frequency switching threshold Q L The difference is the hysteresis interval ΔQ. The initial value of the hysteresis interval ΔQ is in the range of 0.15-0.25, and then it is dynamically adjusted according to historical data. By setting the hysteresis interval ΔQ, frequent frequency switching can be avoided.

[0031] Furthermore, in this embodiment, the excitation voltage is increased first before switching frequencies to preserve the accuracy of high-frequency measurements.

[0032] In this embodiment, when the ultrasonic excitation voltage is increased... by As the enhanced emission excitation voltage; Among them, U max U is the rated maximum excitation voltage of the ultrasonic probe; ΔU is the excitation voltage adjustment step, U current This represents the excitation voltage of the current ultrasonic probe.

[0033] In this embodiment, the signal quality comprehensive score Q is obtained by simultaneously collecting the following data in each measurement cycle: Right bank high-frequency ultrasound probe H RF1 and the left bank high-frequency ultrasound probe H LF1 The voltage amplitude of the received ultrasonic signal is denoted as RSSI. H and RSSI R ; During the silent period of signal reception, ambient noise is collected. floor And calculate the signal-to-noise ratio (SNR) during the first pulse cycle; specifically: ; in, V signalThis represents the amplitude of the excitation voltage of the ultrasonic probe. V noise For environmental noise base floor The amplitude. Before calculating the signal-to-noise ratio, the signal is first filtered to eliminate interference from environmental factors.

[0034] Left bank high-frequency ultrasound probe H LF1 and the left bank low-frequency ultrasound probe H LF2 The corresponding frequencies are F1 and F2, respectively; right bank high-frequency ultrasound probe H RF1 and the right bank low-frequency ultrasound probe H RF2 The corresponding frequencies are F1 and F2, respectively. A Fourier transform is performed on the received ultrasonic pulse train, and the ratio of the energy of F1 and F2 to the energy of each harmonic is extracted and denoted as the signal waveform distortion rate (THD). The formula for calculating the signal waveform distortion rate (THD) of F1 is: ; Where V1 is the voltage amplitude of the fundamental frequency component (frequency equal to the current operating frequency F1 or F2), and its frequency is equal to the current operating frequency. n Let N be the voltage amplitude of the nth harmonic component, with a frequency that is n times the fundamental frequency. max The highest harmonic order (usually 5-7) is the THD value. The higher the THD value, the more severe the waveform distortion and the worse the signal quality.

[0035] In the above formula, the upper limit of the summation sign is ∞. In practice, it is usually N. max The values ​​are taken as 5-7. F1 and F2 have different fundamental frequencies, harmonic frequencies, and voltage amplitudes. The distortion in the high-frequency mode F1 is mainly caused by scattering from suspended particles, while the distortion in the low-frequency mode F2 is mainly caused by bubbles, boundary reflections, and cavitation effects. The typical range for THD is approximately 5%-15% for the high-frequency mode and approximately 3%-10% for the low-frequency mode.

[0036] This embodiment selects three parameters—RSSI, SNR, and THD—to comprehensively evaluate signal quality from the dimensions of signal strength, anti-interference capability, and waveform distortion degree. Among them, the signal waveform distortion rate (THD) is a key parameter that distinguishes it from traditional solutions. It can provide early warning when the presence of bubbles, suspended particles, or turbulence in the water causes waveform distortion, avoiding flow measurement errors caused by incorrect identification of the first pulse.

[0037] A multi-dimensional weighted scoring model is used to normalize the above parameters and calculate the current signal quality score Q. The formula for calculating the current signal quality comprehensive score Q is as follows: ; Among them, RSSI norm It is RSSI H and RSSI R The overall processing results are as follows. The average value is taken: ; Then for RSSI avg Normalization yields RSSI norm This is mainly because the left and right bank probes receive signals from the opposite bank respectively, and the signal strength may be asymmetrical (e.g., due to water flow disturbances or installation deviations). Taking the average value can more objectively reflect the overall signal quality. Normalization is performed separately for each bank. ; RSSI min and RSSI max It is the highest value in historical records.

[0038] Normalize the SNR to obtain the SNR norm ; Normalize the THD to obtain the THD. norm ; For RSSI H RSSI R SNR and THD are normalized, and the normalization adopts a linear mapping of the historical maximum and minimum values ​​to the [0,1] interval; α, β, and γ are weighting coefficients, with initial values ​​being preset empirical values, which are then dynamically optimized by the adaptive learning module.

[0039] The adaptive learning module is optimized based on the initial values, and the rationality of the initial values ​​directly affects the convergence speed and system stability. As shown in Table 1, the initial values ​​of the weight coefficients α, β, and γ are set to 0.35, 0.3, and 0.35, respectively. These initial values ​​were determined through laboratory simulations of signal quality assessment tests under different sand concentrations and flow velocities. RSSI, as a direct indicator of signal strength, is given the highest weight; SNR and THD, reflecting anti-interference capability and waveform distortion degree, respectively, are given medium weights.

[0040] Table 1

[0041] By combining multiple parameters such as RSSI, SNR, and THD, a weighted scoring function is constructed to achieve accurate quantification of signal quality; a higher Q value indicates better signal quality and higher reliability of current measurement.

[0042] The dual-frequency adaptive ultrasonic time-of-flight flow measurement method provided in this embodiment also includes S400, adaptive learning and parameter optimization: During normal operation, the system continuously records switching events and environmental parameters to build a historical database. At regular intervals (e.g., every 24 hours), the system invokes a lightweight machine learning model to optimize the following parameters: S400.1 Threshold Dynamic Adjustment: Based on historical handover success rates, the low-frequency handover threshold (Q) is dynamically adjusted. L ) and high-frequency recovery threshold (Q H ): ; ; Among them, P success P represents the handover success rate over the past 24 hours. target Let λ be the target success rate, and λ be the adjustment coefficient.

[0043] P success The success rate of switching over the past 24 hours is calculated as follows: ; in, This represents the total number of times the switch was triggered in the past 24 hours. This represents the number of successful switching attempts. A successful switching attempt means that the target probe is successfully activated and three consecutive test pulses can be transmitted and received normally. In practical engineering applications, switching may fail due to the following reasons: hardware failure, i.e., the probe to be activated is damaged or the communication link is interrupted; communication timeout, i.e., the handshake between the master and slave fails; clock synchronization failure, i.e., the GPS / BeiDou signal is lost, resulting in inconsistent time bases between the two sides; power supply problems, i.e., insufficient power supply prevents the probe from being properly excited.

[0044] To ensure the method works properly, There is a lower threshold. There is an upper limit threshold.

[0045] This embodiment uses a dynamic threshold adjustment mechanism to adaptively optimize and switch thresholds based on changes in environmental factors such as water sediment content and flow velocity. This ensures that the system switches to low-frequency mode in a timely manner when water quality is poor and resumes high-frequency mode in a timely manner when the environment improves, thereby improving the accuracy of flow measurement in all scenarios.

[0046] In this embodiment, λ = 0.005-0.02, with a preferred value of 0.01, which is an empirical engineering value selected based on the considerations shown in Table 2.

[0047] Table 2

[0048] In this embodiment, the adjustment coefficient λ is set to 0.01. This value was determined through laboratory simulations of switching success rates under different sediment concentrations and flow velocities. An excessively large λ would cause drastic threshold fluctuations, affecting system stability; an excessively small λ would result in slow threshold convergence, failing to adapt to environmental changes in a timely manner. λ=0.01 allows for smooth convergence to the optimal threshold within a 24-hour update cycle, balancing system response speed and stability.

[0049] A further optimized implementation of this embodiment is: Firstly, adaptive λ (dynamic adjustment coefficient) includes: λ is dynamically adjusted based on the historical handover success rate variance. ; in The standard deviation of the handover success rate. λ is the adjustment coefficient. When the switching success rate fluctuates greatly, increasing λ speeds up the response; when the fluctuation is small, decreasing λ maintains stability.

[0050] Secondly, the confidence interval for the handover success rate includes: When the number of samples switched is insufficient, the threshold will not be updated temporarily. Total number of switches in the past 24 hours If the number of samples is less than the minimum number of samples (e.g., 10 times), the threshold will not be dynamically adjusted to avoid incorrect adjustments caused by small samples.

[0051] S400.2 Excitation Voltage Reference Value Update: This method records the average excitation voltage during stable operation in both high-frequency and low-frequency modes, and updates it to the reference excitation voltage for each mode: High-frequency mode reference excitation voltage update: Record continuous and stable measurements in high-frequency mode (overall signal quality score Q ≥ high-frequency recovery threshold Q). H The average excitation voltage over 10 or more measurement cycles is updated using an exponential smoothing method. .

[0052] Low-frequency mode reference power update: Record the average excitation voltage during continuous stable measurements in low-frequency mode (signal quality comprehensive score Q is stable at a medium level and there is no switching trigger, for more than 10 measurement cycles), and update it using the exponential smoothing method. ; Where, λ U This is a smoothing coefficient, ranging from 0.7 to 0.9, with a preferred value of 0.8, used to balance the influence of historical reference values ​​and the current stable voltage. and These are the average excitation voltages during stable operation in high-frequency and low-frequency modes, respectively.

[0053] Record the average excitation voltage during stable operation in high-frequency mode, and update it to the new reference excitation voltage U. base,F1 This reduces power consumption while ensuring measurement reliability.

[0054] While low-frequency probes offer stronger penetration and higher rated maximum excitation voltage, in practical applications, excessively high transmit power (requiring a larger excitation voltage) can lead to problems such as excessive power consumption, accelerated probe aging, and sidelobe reflection interference. Therefore, adaptive updates to the power reference are also necessary in low-frequency mode to minimize transmit power and optimize overall system performance while ensuring signal quality.

[0055] By updating the adaptive excitation voltage reference, the system can reduce power consumption, extend equipment life, and reduce reflection interference caused by excessively strong signals while ensuring measurement reliability.

[0056] This embodiment enables the system to have long-term environmental adaptability by optimizing the weighting coefficients, thresholds, and voltage references online.

[0057] The dual-frequency adaptive ultrasonic time-of-flight method for open channel flow measurement provided in this embodiment also includes S500: data upload and remote configuration, specifically including: The host unit uploads data such as flow rate, water level, flow rate, signal quality comprehensive score Q, current frequency mode, and excitation voltage for each measurement cycle to the cloud platform via 4G / 5G network; The cloud platform can remotely distribute configuration parameters (such as weighting coefficients, thresholds, excitation voltage adjustment steps, etc.) to enable remote optimization and upgrades of the system.

[0058] Example 2: This embodiment provides a dual-frequency adaptive ultrasonic time-of-flight method open channel flow measurement system, referring to... Figure 1 Left bank high-frequency ultrasound probe H LF1 and the left bank low-frequency ultrasound probe H LF2 A high-frequency ultrasonic probe H was installed 100 meters on the left bank of the open channel and on the right bank. RF1 and the right bank low-frequency ultrasound probe H RF2 The high-frequency ultrasonic probe H is set at 200 meters on the right bank of the open channel; and on the left bank... LF1 and the right bank high-frequency ultrasound probe H RF1 The line connecting them is parallel to the left bank low-frequency ultrasound probe H. LF2 and the right bank low-frequency ultrasound probe H RF2 The angle between the line connecting the two channels and the direction of water flow in the open channel is 40 to 50 degrees. The angle should be as close as possible to 45 degrees, but not necessarily exactly 45 degrees, so as to ensure that the time difference of ultrasonic wave propagation with and against the current is close to the maximum, which is beneficial to improving the measurement accuracy of low flow velocities.

[0059] The dual-frequency adaptive ultrasonic time-difference method open channel flow measurement system also includes a data acquisition unit for system initialization during flow measurement: enabling the left bank high-frequency ultrasonic probe H. LF1 With right bank high-frequency ultrasound probe H RF1Then, in each measurement cycle, the overall signal quality score Q is obtained; the overall signal quality score Q is compared with the low-frequency switching threshold Q. L and high-frequency recovery threshold Q H Size relationship: If the currently operating probe is the left bank high-frequency ultrasound probe H LF1 and the right bank high-frequency ultrasound probe H RF1 Based on the aforementioned size relationship, determine whether to shut down the left bank high-frequency ultrasound probe H. LF1 and the right bank high-frequency ultrasound probe H RF1 And the left bank low-frequency ultrasound probe H was activated. LF2 and the right bank low-frequency ultrasound probe H RF2 If the currently operating probe is the left bank low-frequency ultrasound probe H... LF2 and the right bank low-frequency ultrasound probe H RF2 Based on the aforementioned size relationship, determine whether to shut down the left bank low-frequency ultrasound probe H. LF2 and the right bank low-frequency ultrasound probe H RF2 And the left bank high-frequency ultrasound probe H was activated. LF1 and the right bank high-frequency ultrasound probe H RF1 Based on the current working left bank high-frequency ultrasonic probe H LF1 With right bank high-frequency ultrasound probe H RF1 Or left bank low-frequency ultrasound probe H LF2 and the right bank low-frequency ultrasound probe H RF2 The received information is used to calculate the flow velocity of the water in the open channel based on the principle of ultrasonic time difference method.

[0060] This embodiment constructs an adaptive ultrasonic time-of-flight flow measurement system that dynamically applies different ultrasonic frequencies and dynamically adjusts the excitation voltage of the signal. This system effectively improves the adaptability of the system in complex application scenarios while maintaining the accuracy of ultrasonic wireless time-of-flight flow measurement in open channels. It addresses the problem of insufficient adaptability in complex scenarios such as wide channels, large variations in sediment content, and large flow velocity fluctuations.

[0061] When the water is relatively clear and the current is slow, activate the left bank H. LF1 and right bank H RF1 High-frequency probes are used for measurement. Compared to low-frequency ultrasound, high-frequency ultrasound has advantages such as better directivity and higher time-difference resolution, enabling the acquisition of stable and highly accurate flow data. During periods of high flooding, water bodies typically have high sediment content and high flow velocities. At this time, the attenuation problem of high-frequency ultrasound becomes more prominent, and the received signal strength weakens accordingly. When the signal strength weakens to a predetermined threshold, the data acquisition unit will automatically activate the left bank H... LF2 and right bank H RF2Low-frequency probes are used for measurement. Compared to high-frequency ultrasound, although low-frequency ultrasound has lower time-difference resolution and lower flow measurement accuracy, it has advantages such as better penetration and stronger resistance to sediment, allowing for stable flow data in high-flood applications. High-frequency ultrasound solves the problem of high-precision flow measurement, while low-frequency ultrasound solves the problem of flow measurement in complex scenarios with high sediment and high flow velocities. The flexible application of both achieves a balance between high measurement accuracy and stability in high-flood flow measurement, effectively addressing the lack of applicability of traditional single-frequency ultrasonic time-difference flow measurement systems across all scenarios.

[0062] Furthermore, in this application, when selecting an ultrasound probe, the signal quality comprehensive score Q and the low-frequency switching threshold Q are used. L and high-frequency recovery threshold Q H Compared to other methods, this avoids the frequent switching between high-frequency and low-frequency ultrasound, thus improving the reliability of ultrasonic time-difference method for open channel flow measurement.

[0063] Reference Figure 3 In this embodiment, the data acquisition unit includes a master unit and a slave unit, which are installed on the left bank and right bank respectively. The master unit transmits signals to the left bank H via signal cables. LF1 (or H) LF2 The probe sends an excitation signal, H LF1 (or H) LF2 After receiving the excitation signal, the probe resonates and emits ultrasonic signals outward. The H on the right bank... RF1 (or H) RF2 After receiving the ultrasonic signal, it is transmitted to the slave unit via a signal cable. The slave unit captures the rising edge of the first received ultrasonic pulse, records the rising edge time T2, and combines it with the excitation signal transmission time T1 of the master unit to calculate the propagation time T of the ultrasonic pulse from the master-side ultrasonic probe to the slave-side ultrasonic probe. L =T2-T1. Similarly, the slave unit sends a signal cable to the right bank H. RF1 (or H) RF2 The probe sends an excitation signal, H RF1 (or H) RF2 After receiving the excitation signal, the probe resonates and emits ultrasonic signals outward. The H signal on the left bank... LF1 (or H) LF2 After the probe receives the ultrasonic signal, it transmits it to the host unit via a signal cable. The host unit captures the rising edge of the first received ultrasonic pulse and then calculates the propagation time T of the ultrasonic wave from the slave-side ultrasonic probe to the host-side ultrasonic probe. R .

[0064] The data acquisition unit can also control the transmitted signal strength based on the received signal strength, thereby further enhancing the system's adaptability in scenarios with high sediment content and high flow velocity. When the sediment content decreases and the flow velocity decreases, the received signal strength will gradually increase. When the signal strength increases to a predetermined threshold, the data acquisition unit will then appropriately reduce the transmitted signal strength to prevent interference caused by excessive ultrasonic signal reflection and oscillation.

[0065] The data short transmission unit, employing a LoRa module, has one set on each side. It is used by the master unit to send synchronization commands to the slave unit, enabling both units to obtain the ultrasonic signal transmission time in conjunction with the clock synchronization unit. The data short transmission unit is also used by the slave unit to send T... L The propagation time measurement results are used to enable the host unit to calculate the time difference of ultrasonic signal propagation upstream and downstream.

[0066] The clock synchronization unit, employing a GPS + BeiDou module, has one set on each side of the clock. It can output periodic synchronization pulses at regular intervals, and the pulse interval can be flexibly adjusted as needed. Under normal circumstances, the master unit and the slave unit simultaneously receive the synchronization pulse at the same time. After receiving the synchronization pulse, the master unit immediately sends a synchronization command to the slave unit through the data short transmission unit. After receiving the synchronization command from the master unit, the slave unit performs a handshake response through the data short transmission unit. After a successful handshake response, the master unit and the slave unit simultaneously send excitation signals to their respective ultrasonic probes upon receiving the next synchronization pulse, and record this moment as the ultrasonic signal transmission time T1 (i.e., the excitation signal transmission time).

[0067] The workflow of the dual-frequency adaptive ultrasonic time-of-flight open channel flow measurement system provided in this embodiment, implementing the dual-frequency adaptive ultrasonic time-of-flight open channel flow measurement method provided in Embodiment 1, is as follows: Figure 2 As shown, in engineering practice, the excitation voltage is often used as a direct and linear representation of the transmission power.

[0068] The dual-frequency adaptive ultrasonic time-of-flight method open channel flow measurement system provided in this embodiment also includes a water level sensing unit, which is built on one side of the main unit and connected to the main unit via a wire. The data acquisition unit calculates the water flow area based on the water level cross-sectional data, and then calculates the cross-sectional flow rate based on the velocity area method.

[0069] The dual-frequency adaptive ultrasonic time-difference method open channel flow measurement system provided in this embodiment also includes a power supply unit, which adopts a solar power supply system, with one set on each of the left and right banks, to supply power to the master unit, slave unit, and their respective clock synchronization unit, data short transmission unit, water level sensing unit, etc.

[0070] In one implementation, the data acquisition unit can determine which set of probes to activate based on the intensity of the received ultrasonic signal, in order to achieve a balance between high measurement accuracy and high flood flow stability. When the water is relatively clear and the flow velocity is low, the left bank H probe is activated. LF1 and right bank H RF1 Two high-frequency probes are used for measurement. Compared with low-frequency ultrasound, high-frequency ultrasound has advantages such as better directivity and higher time-difference resolution, which can obtain stable and high-precision flow data. When the high flood season arrives, the water body usually has a high sediment content and a high flow velocity. At this time, the attenuation problem of high-frequency ultrasound becomes more prominent, and the received signal strength weakens accordingly. When the signal strength weakens to a predetermined threshold, the data acquisition unit will automatically activate the left bank H... LF2 and right bank H RF2 Two low-frequency probes are used for measurement. Compared with high-frequency ultrasound, although low-frequency ultrasound has lower time-difference resolution and lower flow measurement accuracy, it has advantages such as better penetration and stronger resistance to sediment, and can obtain stable flow data in high-flood application scenarios. High-frequency ultrasound solves the problem of high-precision flow measurement, while low-frequency ultrasound solves the problem of flow measurement in complex scenarios with high sediment and high flow velocity. The flexible application of both can effectively solve the problem of insufficient applicability of traditional single-frequency ultrasonic time-difference flow measurement systems in all scenarios.

[0071] The dual-frequency adaptive ultrasonic time-difference method open channel flow measurement system provided in this embodiment operates the method provided in Embodiment 1.

[0072] When hardware failures, communication timeouts, clock synchronization issues, or insufficient power supply occur, the dual-frequency adaptive ultrasonic time-difference method for open channel flow measurement provided in this embodiment executes the S600 anomaly handling mechanism: (1) Hardware fault detection Before the start of each measurement cycle, the ultrasonic probe is subjected to impedance testing. If the probe impedance is found to be outside the normal range (e.g., short circuit or open circuit), the probe is determined to be faulty. At this time, while maintaining the current working mode, the system automatically switches to another set of probes with different frequencies and sends a fault alarm message to the cloud platform, including the faulty probe number, fault type, and timestamp.

[0073] (2) Communication timeout handling The master and slave units transmit data via the LoRa module. If the master unit sends synchronization commands three times consecutively without receiving a handshake response from the slave unit, a communication timeout is determined. In this case, the system pauses the initiation of a new measurement cycle, maintains the current operating mode, and attempts to re-establish the communication link. If communication is restored within 30 seconds, measurement automatically resumes; if it fails to restore within the timeout period, a communication fault log is recorded and an alarm message is sent.

[0074] (3) Clock out-of-synchronization handling The clock synchronization unit uses GPS + BeiDou dual-mode timing. If a valid satellite synchronization pulse is not received for 10 consecutive seconds, the clock is considered out of sync. The system automatically records this out-of-sync event. If the out-of-sync state persists for more than 5 minutes, the measurement is paused and an alarm message is sent. Once the satellite signal is restored, the system automatically re-locks the synchronization pulse and resumes normal measurement.

[0075] (4) Handling insufficient power supply The power supply unit monitors the solar cell voltage and battery charge in real time. When the voltage is detected to be below a threshold (e.g., 11.5V), the measurement frequency is reduced (e.g., from once every 10 seconds to once every 30 seconds). Once the voltage returns to the normal range, the system automatically resumes full-function measurement.

[0076] (5) Adaptive reset after abnormal recovery Once the aforementioned anomalies are resolved, the system automatically resumes normal measurements and resets the adaptive learning parameters to their pre-fault state, or recovers based on valid historical data from the most recent 24 hours. If the fault lasts for more than 24 hours, system initialization (i.e., S100) is re-executed.

[0077] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "circumferential", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0078] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0079] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0080] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0081] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A dual-frequency adaptive ultrasonic time-of-flight method for open channel flow measurement, characterized in that, include: During flow measurement, the system should be initialized first: enable the left bank high-frequency ultrasonic probe and the right bank high-frequency ultrasonic probe; Then, in each measurement cycle, a comprehensive signal quality score is obtained; Determine the relationship between the overall signal quality score and the low-frequency handover threshold and high-frequency recovery threshold: If the left bank high-frequency ultrasound probe and the right bank high-frequency ultrasound probe are currently in operation, determine whether to turn off the left bank high-frequency ultrasound probe and the right bank high-frequency ultrasound probe and turn on the left bank low-frequency ultrasound probe and the right bank low-frequency ultrasound probe according to the size relationship. If the left bank low-frequency ultrasound probe and the right bank low-frequency ultrasound probe are currently in operation, determine whether to turn off the left bank low-frequency ultrasound probe and the right bank low-frequency ultrasound probe and turn on the left bank high-frequency ultrasound probe and the right bank high-frequency ultrasound probe based on the size relationship. Based on the information received by the high-frequency ultrasonic probe on the left bank and the high-frequency ultrasonic probe on the right bank, or the low-frequency ultrasonic probe on the left bank and the low-frequency ultrasonic probe on the right bank, the flow velocity of the water in the open channel is calculated according to the working principle of the ultrasonic time difference method. The high-frequency ultrasonic probe and the low-frequency ultrasonic probe on the left bank are set on the left bank of the open channel, and the high-frequency ultrasonic probe and the low-frequency ultrasonic probe on the right bank are set on the right bank of the open channel. The line connecting the high-frequency ultrasonic probe on the left bank and the high-frequency ultrasonic probe on the right bank is parallel to the line connecting the low-frequency ultrasonic probe on the left bank and the low-frequency ultrasonic probe on the right bank and forms an angle of 40 to 50 degrees with the direction of water flow in the open channel.

2. The dual-frequency adaptive ultrasonic time-difference method for open channel flow measurement according to claim 1, characterized in that, If the currently operating devices are a left-bank high-frequency ultrasound probe and a right-bank high-frequency ultrasound probe: When the overall signal quality score is determined to be greater than the low-frequency switching threshold and the high-frequency recovery threshold, and the overall signal quality score is greater than the low-frequency switching threshold, both the left-bank and right-bank high-frequency ultrasound probes continue to operate. To determine the relationship between the overall signal quality score and the low-frequency switching threshold and the high-frequency recovery threshold, when the overall signal quality score is less than the low-frequency switching threshold: first attempt to increase the ultrasonic excitation voltage. After the excitation voltage is increased, the system waits for one measurement cycle and then reacquires the current overall signal quality score. If the overall signal quality score is greater than or equal to the low-frequency switching threshold, the left bank high-frequency ultrasound probe and the right bank high-frequency ultrasound probe continue to work, and the current excitation voltage value is recorded as the new excitation voltage. If the overall signal quality score is still less than the low-frequency switching threshold, turn off the left bank high-frequency ultrasound probe and the right bank high-frequency ultrasound probe, and turn on the left bank low-frequency ultrasound probe and the right bank low-frequency ultrasound probe.

3. The dual-frequency adaptive ultrasonic time-difference method for open channel flow measurement according to claim 2, characterized in that, When the ultrasonic excitation voltage is increased, As the enhanced emission excitation voltage; Among them, U max U is the rated maximum excitation voltage of the ultrasonic probe; ΔU is the excitation voltage adjustment step, U current This represents the excitation voltage of the current ultrasonic probe.

4. The dual-frequency adaptive ultrasonic time-difference method for open channel flow measurement according to claim 1, characterized in that, If the currently operating devices are a left bank low-frequency ultrasound probe and a right bank low-frequency ultrasound probe: If the overall signal quality score is less than or equal to the high-frequency recovery threshold, the left-bank low-frequency ultrasound probe and the right-bank low-frequency ultrasound probe continue to work. If the overall signal quality score is greater than the high-frequency recovery threshold, turn off the left bank low-frequency ultrasound probe and the right bank low-frequency ultrasound probe, and turn on the left bank high-frequency ultrasound probe and the right bank high-frequency ultrasound probe.

5. The dual-frequency adaptive ultrasonic time-difference method for open channel flow measurement according to claim 1, characterized in that, The low-frequency handover threshold is less than the high-frequency recovery threshold. The difference between the high-frequency recovery threshold and the low-frequency handover threshold is the hysteresis interval. The initial value of the hysteresis interval is 0.15-0.25, and it is then dynamically adjusted based on historical data.

6. The dual-frequency adaptive ultrasonic time-difference method for open channel flow measurement according to claim 1, characterized in that, The overall signal quality score is obtained by simultaneously collecting the following data in each measurement cycle: The voltage amplitudes of the ultrasonic signals received by the right-bank and left-bank high-frequency ultrasonic probes are denoted as RSSI, respectively. H and RSSI R ; During the silent period of signal reception, the ambient noise baseline is collected, and the signal-to-noise ratio (SNR) within the first pulse cycle is calculated and denoted as SNR. The operating frequencies of the left bank high-frequency ultrasound probe and the left bank low-frequency ultrasound probe are F1 and F2, respectively; the operating frequencies of the right bank high-frequency ultrasound probe and the right bank low-frequency ultrasound probe are F1 and F2, respectively. A Fourier transform is performed on the received ultrasound pulse train, and the ratio of the F1 and F2 energies to the energies of each harmonic is extracted and denoted as the signal waveform distortion rate (THD). The formula for calculating the signal waveform distortion rate (THD) is as follows: ； Where V1 is the voltage amplitude of the fundamental frequency component, which is equal to the voltage amplitude of the current ultrasonic probe operating frequency F1 or F2, and the frequency of the fundamental frequency component is equal to the current operating frequency. n The voltage amplitude of the nth harmonic component is given, and its frequency is n times the fundamental frequency; N max The highest harmonic order; The current formula for calculating the overall signal quality score (Q) is: ； Among them, RSSI norm It is RSSI H and RSSI R The average value of the comprehensive processing results is taken: ； Then for RSSI avg Normalization yields RSSI norm ; Normalize the SNR to obtain the SNR norm ; Normalize the THD to obtain the THD. norm ; Among them, for RSSI H RSSI R SNR and THD are normalized, and the normalization adopts a linear mapping of the historical maximum and minimum values ​​to the [0,1] interval; α, β, and γ are weighting coefficients, with initial values ​​being preset empirical values, which are then dynamically optimized by the adaptive learning module.

7. A dual-frequency adaptive ultrasonic time-of-flight method open channel flow measurement system, characterized in that, include: A high-frequency ultrasonic probe and a low-frequency ultrasonic probe are provided on the left bank of the open channel, and a high-frequency ultrasonic probe and a low-frequency ultrasonic probe are provided on the right bank of the open channel. The line connecting the high-frequency ultrasonic probe on the left bank and the low-frequency ultrasonic probe on the right bank is parallel to the line connecting the low-frequency ultrasonic probe on the left bank and the low-frequency ultrasonic probe on the right bank and forms an angle of 40 to 50 degrees with the direction of water flow in the open channel. The data acquisition unit is used for system initialization during flow measurement: activating the left bank high-frequency ultrasonic probe and the right bank high-frequency ultrasonic probe; then, in each measurement cycle, acquiring a comprehensive signal quality score; determining the relationship between the comprehensive signal quality score and the low-frequency switching threshold and the high-frequency recovery threshold: if the left bank high-frequency ultrasonic probe and the right bank high-frequency ultrasonic probe are currently operating, determining whether to close the left bank high-frequency ultrasonic probe and the right bank low-frequency ultrasonic probe and activate the left bank low-frequency ultrasonic probe and the right bank low-frequency ultrasonic probe based on the relationship; if the left bank low-frequency ultrasonic probe and the right bank low-frequency ultrasonic probe are currently operating, determining whether to close the left bank low-frequency ultrasonic probe and the right bank low-frequency ultrasonic probe and activate the left bank high-frequency ultrasonic probe and the right bank high-frequency ultrasonic probe based on the relationship; calculating the flow velocity of the water in the open channel based on the information received by the currently operating left bank high-frequency ultrasonic probe and the right bank high-frequency ultrasonic probe or the left bank low-frequency ultrasonic probe and the right bank low-frequency ultrasonic probe, according to the principle of ultrasonic time difference method.

8. The dual-frequency adaptive ultrasonic time-difference method open channel flow measurement system according to claim 7, characterized in that, It also includes a water level sensing unit, which is connected to the data acquisition unit. The data acquisition unit calculates the water flow area based on the water level cross-sectional data and then calculates the cross-sectional flow rate based on the velocity-area method.

9. The dual-frequency adaptive ultrasonic time-difference method open channel flow measurement system according to claim 7, characterized in that, When the data acquisition unit determines the relationship between the overall signal quality score and the low-frequency switching threshold and the high-frequency recovery threshold: If the currently operating devices are a left-bank high-frequency ultrasound probe and a right-bank high-frequency ultrasound probe: When the overall signal quality score is determined to be greater than the low-frequency switching threshold and the high-frequency recovery threshold, and the overall signal quality score is greater than the low-frequency switching threshold, both the left-bank and right-bank high-frequency ultrasound probes continue to operate. To determine the relationship between the overall signal quality score and the low-frequency switching threshold and the high-frequency recovery threshold, when the overall signal quality score is less than the low-frequency switching threshold: first attempt to increase the ultrasonic excitation voltage. After the excitation voltage is increased, the system waits for one measurement cycle and then reacquires the current overall signal quality score. If the overall signal quality score is greater than or equal to the low-frequency switching threshold, the left bank high-frequency ultrasound probe and the right bank high-frequency ultrasound probe continue to work, and the current excitation voltage value is recorded as the new excitation voltage. If the overall signal quality score is still less than the low-frequency switching threshold, turn off the left bank high-frequency ultrasound probe and the right bank high-frequency ultrasound probe, and turn on the left bank low-frequency ultrasound probe and the right bank low-frequency ultrasound probe.

10. The dual-frequency adaptive ultrasonic time-difference method open channel flow measurement system according to claim 9, characterized in that, When the data acquisition unit performs ultrasonic excitation voltage boosting... As the enhanced emission excitation voltage; Among them, U max U is the rated maximum excitation voltage of the ultrasonic probe; ΔU is the excitation voltage adjustment step, U current This represents the excitation voltage of the current ultrasonic probe.

Images