Acoustic tomography flow measurement system and acoustic signal double-frequency coding method applied by acoustic tomography flow measurement system

Abstract

The invention discloses an acoustic tomography flow measurement system and an acoustic signal double-frequency coding method applied by the acoustic tomography flow measurement system, and the method comprises the steps: (1) in the river acoustic tomography flow measurement system, editing and adjusting a single-frequency M code signal with a transmission modulation coefficient of 3, the transmission frequency of the single-frequency M code signal being f Hz, and the duration of one code bit being about 3 / f seconds; (2) modifying the front half section of one code bit in the single-frequency M-code signal into two sine waves, modifying the rear half section of one code bit into one sine wave, and modifying the single-frequency M-code signal into a double-frequency signal; according to the coding rule of the original single-frequency M-code signal, turning a code bit specified by a sequence for a dual-frequency signal to form a dual-frequency coded signal for transmission; and (3) receiving the dual-frequency coded signals, carrying out matched filtering, and identifying and separating different signals. The method can effectively reduce the peak width of a matched filtering result, reduces the mutual interference between signals, and improves the separation and recognition precision of different signals.

Description

Technical Field

[0001] The invention relates to the field of intelligent analysis of river flow measurement data, and in particular to an acoustic tomography flow measurement system and a dual-frequency encoding method of acoustic wave signals used in the system. Background Art

[0002] River acoustic tomography flow measurement technology is a new river measurement technology with the advantages of easy installation, little influence by river surface conditions, and high accuracy. Acoustic tomography technology calculates the river flow rate based on the characteristic that the propagation speed of sound waves in the downstream is faster than that in the upstream. Therefore, accurately calculating the propagation speed of sound waves in water is the key to acoustic tomography flow measurement. Since sound waves will reach the receiving device through different propagation paths (sound lines) in the water body, the received signal is the superposition of signals from multiple paths. At the same time, the received signal will also be interfered by water body noise and equipment noise, such as water plants on the river bottom sand and ships on the river surface. This will make it difficult to identify and distinguish the signals of different sound lines, causing large errors in the calculation of the propagation time of sound waves, and have a great impact on the subsequent calculation of the flow rate and flow of the river.

[0003] At present, unmodulated hydroacoustic signals are usually identified by the signal-to-noise ratio. In the prior art, the signal after coding modulation is calculated by the template matching filter algorithm to obtain the signal matching value, and then the signal position is found by finding the maximum value. Since the peak width of the result obtained by the template matching filter calculation of the single frequency coding signal is large, the sound waves arriving from different paths are superimposed together, and the wider peak will affect the separation and identification of different signals, resulting in errors in the arrival time of the sound waves, thereby affecting the subsequent flow velocity and flow calculation.

[0004] The existing patent technology is called a water flow detection system based on acoustic tomography cross-section detection, with application number CN202410695337.2. It receives the reflected signal through a data processing unit, pre-processes the reflected signal to obtain a pre-processed signal; evaluates the quality of the pre-processed signal to obtain an evaluation result, and dynamically adjusts the acoustic signal processing parameters according to the evaluation result to obtain the final pre-processed signal; extracts the pure signal and the noise signal from the pre-processed signal; calculates the variance of the noise signal, traverses all samples of the noise signal, calculates the difference between adjacent samples, and analyzes the final pre-processed signal according to the final pre-processed signal using the initial acoustic signal processing parameters and acoustic tomography technology to calculate the velocity distribution and flow rate. It is very difficult for this system and method to extract the pure signal and the noise signal. The system processing algorithm sample training is complex and slow to respond, and it is not the most effective method. Summary of the invention

[0005] In order to overcome the problems of the prior art, the present invention provides an acoustic tomography flow measurement system and a dual-frequency encoding method for acoustic wave signals used therein, which can effectively reduce the peak width of the matched filtering result, reduce mutual interference between signals, and improve the separation and recognition accuracy of different signals.

[0006] The present invention provides a dual-frequency encoding method for acoustic wave signals applied to an acoustic tomography flow measurement system, comprising the steps of:

[0007] (1) In a river acoustic tomography flow measurement system, a single-frequency M-code signal with a modulation coefficient of 3 is edited and adjusted. The frequency of the single-frequency M-code signal is f Hz, and the duration of one code position is 3 / f seconds;

[0008] (2) The first half of a code position in the single-frequency M code signal is modified into two sine waves, that is, the frequency is 4f / 3; the second half of a code position is modified into one sine wave, that is, the frequency is 2f / 3, so that the single-frequency M code signal is modified to become a dual-frequency signal; the dual-frequency signal is subjected to the code position specified by the sequence according to the original coding rule of the single-frequency M code signal, and the dual-frequency coded signal is formed and transmitted;

[0009] (3) Receive the dual-frequency coded signal and perform matched filtering to identify and separate different signals.

[0010] Furthermore, in step (1), the single-frequency M-code signal refers to an M-sequence code, which is a coded signal obtained by flipping a specified code position in a sine wave signal according to a specific sequence; one code position of the single-frequency M-code signal includes 3 sine waves.

[0011] Furthermore, in step (3), the dual-frequency coded signal is received and matched filtered, and the peak width of the filtering result is narrow, and different signals are identified and separated. The narrower peak width will reduce the signal identification error and reduce the coverage between different signals.

[0012] In the specific step (3), the processed signal after the dual-frequency coded signal is subjected to matched filtering weakens the matching degree of non-matching points without reducing the matching degree of matching points, thereby reducing mutual interference between signals and improving signal matching accuracy.

[0013] The present invention also provides an acoustic tomography flow measurement system with dual-frequency encoding of acoustic wave signals, comprising a host and a plurality of acoustic wave probes, wherein the host comprises:

[0014] A signal editing and adjustment module, used for editing and adjusting a single-frequency M-code signal with a modulation coefficient of 3, wherein the frequency of the single-frequency M-code signal is f Hz, and the duration of one code position is 3 / f seconds;

[0015] A dual-frequency signal processing module is used to modify the first half of a code position in the single-frequency M-code signal into two sine waves, that is, the frequency is 4f / 3; modify the second half of a code position into one sine wave, that is, the frequency is 2f / 3, so that the single-frequency M-code signal is modified to become a dual-frequency signal; and the dual-frequency signal is reversed according to the original coding rule of the single-frequency M-code signal, and the code position specified by the sequence is formed. A dual-frequency coded signal;

[0016] The dual-frequency signal filtering module is used to receive the dual-frequency coded signal, perform matched filtering, and identify and separate different signals.

[0017] Furthermore, the signal editing and adjustment module is also used for the single-frequency M-code signal, which refers to M-sequence coding, and is a coded signal obtained by flipping a specified code position in a sine wave signal according to a specific sequence; one code position of the single-frequency M-code signal contains 3 sine waves.

[0018] Furthermore, the dual-frequency signal filtering module is also used to perform matched filtering on the dual-frequency coded signal. The filtering result has a narrow peak width, which can identify and separate different signals. The narrower peak width can reduce the signal recognition error and reduce the coverage between different signals.

[0019] The technical advantages brought by the dual-frequency encoding method and system of the present invention are as follows:

[0020] (1) Compared with the existing single-frequency sound wave signal encoding method, the sound wave signal dual-frequency encoding processing method of the present invention weakens the matching degree of non-matching points without reducing the matching degree of the effective waveform signal matching point, reduces the mutual interference between signals, and especially eliminates the interference of clutter. By matching filtering the dual-frequency coded signal, the peak width of the filtering result is narrow, and the narrow peak will reduce the signal recognition error, and the coverage between different signals will be reduced, which is conducive to the identification and separation of different signals, and effectively improves the signal matching accuracy, so that different interference clutter signals in the water body can be effectively separated, and the accurate arrival time of each sound wave signal can be calculated, so as to analyze the sound line propagation in the water body and the river section, so as to improve the measurement accuracy of river flow rate and flow.

[0021] (2) To overcome the problem of insufficient recognition accuracy in processing single-frequency coded signals, the method and system of the present invention modify the single-frequency signal based on the M code into a dual-frequency signal. When performing the matched filter algorithm calculation, the matching value size of the incorrect matching position is greatly reduced without changing the matching value size of the correct matching position, thereby reducing the possibility of signal recognition errors. The calculation amount is small without the need for a large number of sample training, and the calculation accuracy of the arrival time of the sound wave in water is improved. The optimized and integrated measurement algorithm can obtain flow monitoring data that is more stable, accurate, and fast than the existing traditional measurement. The processing speed is 7-9% faster than the existing single-frequency sound wave signal processing speed, and the accuracy is improved by 11-13% compared with the existing single-frequency signal.

[0022] (3) The system and method of the present invention have wider applicability and overcome the influence of river beaches and riverbed aquatic plants. The dual-frequency signal after filtering the dual-frequency coded signal has low distortion and stronger anti-interference applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of single frequency coded signal.

[0024] Figure 2 It is a schematic diagram of the dual-frequency coded signal of the present invention.

[0025] Figure 3 It is a local schematic diagram of matched filtering of a single-frequency coded signal in the prior art.

[0026] Figure 4 The figure is a local schematic diagram of matching filtering a dual-frequency coded signal using the method of the present invention.

[0027] Figure 5 It is a schematic diagram of the results of matched filtering calculations on single-frequency coded signals in the prior art.

[0028] Figure 6 The figure is a schematic diagram of the calculation results of matched filtering of a dual-frequency coded signal using the method of the present invention. DETAILED DESCRIPTION

[0029] The technical solution in the embodiment of the invention will be clearly and completely described below in conjunction with the drawings in this embodiment.

[0030] The embodiment of the present invention provides a dual-frequency encoding method for acoustic wave signals applied to an acoustic tomography flow measurement system, comprising: step (1), in the river acoustic tomography flow measurement system, editing and adjusting a single-frequency M-code signal with a modulation coefficient of 3, wherein the frequency of the single-frequency M-code signal is f Hz, and the duration of one code position is approximately 3 / f seconds.

[0031] The dual-frequency coded signal is modified on the basis of the existing single-frequency M-code signal. M-code refers to M-sequence coding, which is a coded signal obtained by flipping a specified segment (code position) in a sine wave signal according to a specific sequence. M-code signals have the characteristics of high autocorrelation and low cross-correlation, and have good noise resistance for signal recognition tasks. The modulation coefficient refers to the number of sine waves contained in a code position in the signal. A single-frequency M-code signal with a modulation coefficient of 3 means that one code position of the signal contains 3 sine waves. Assuming that the signal transmission frequency is f Hz, the duration of one code position is approximately 3 / f seconds.

[0032] Step (2), modify the first half of a code position in the single-frequency M code signal into two sine waves, that is, the frequency is The second half of the code position is modified to a sine wave, that is, the frequency is Then the single-frequency M-code signal is modified to become a dual-frequency signal.

[0033] Assume that the M code sequence is {m1,m2,m3,...,m n}(m i =0,1), the dual-frequency signal is expressed in code bits as S = {s1,s2,s3,...,s n}, then the dual-frequency signal is flip-encoded according to the M code sequence, and finally the dual-frequency M code signal is obtained

[0034] The flipping position of the flip coding is determined by the M code sequence, and one sequence determines one flipping mode.

[0035] Step (3), receiving the dual-frequency coded signal for matched filtering, identifying and separating different signals. The filtered signal is used in the process of river acoustic tomography flow measurement, and the river flow velocity and flow are measured according to the arrival time of the filtered signal. This belongs to the prior art and is also disclosed in the previous patents of the applicant company, so it will not be introduced in detail here.

[0036] The method of the present invention performs matched filtering on the dual-frequency coded signal, and the peak width of the filtering result is narrow. The narrow peak width will reduce the signal recognition error, reduce the coverage between different signals, and facilitate the recognition and separation of different signals. The processed signal after the dual-frequency coded signal is matched filtered, weakens the matching degree of non-matching points without reducing the matching degree of matching points. Non-matching points are often interference clutter, which reduces the mutual interference between signals and improves the accuracy of signal matching.

[0037] The following is a detailed introduction to the effect of the dual-frequency coded signal in conjunction with the experimental waveform diagram.

[0038] Taking the acoustic wave measuring probe with a transmitting frequency of 25k as an example, the probe of the system transmits a single-frequency coded signal with a modulation coefficient of 3, such as Figure 1 As shown, it is a continuous 25k sine wave, in which a middle code position (i.e., segment) is flipped due to the M code encoding rule, see the solid line waveform part.

[0039] After being processed and modified by the method of the present invention, it is transformed into a dual-frequency coded signal such as Figure 2 As shown, it is a dual-frequency sine wave with a high frequency band of 33k and a low frequency band of 17k. Figure 2 The dotted line wave in the middle represents the high frequency band, and the solid line represents the low frequency band waveform. It can be seen that the middle code position is due to the reversal of the encoding rules of the M code.

[0040] right Figure 1 The single frequency coded signal is matched filtered to obtain the waveform result as follows Figure 3 As shown. Figure 2 The dual-frequency coded signal is matched filtered to obtain the waveform result as follows Figure 4 As shown in Figure 2, it can be seen that the peak width of the waveform of the matched filtering result of the single-frequency coded signal is about 100 sampling points, while Figure 4 The peak width of the waveform of the matched filtering result of the dual-frequency coded signal is significantly narrower than that of the single-frequency coded signal, with only about 25 sampling points. The narrower peak will make the signal recognition error smaller and the coverage between different signals will be greatly reduced. The different signals include actual detection signals, ships on the river surface, river bottom water plants and other interference clutter signals, which is conducive to identifying and separating interference signals and retaining real and useful detection signals.

[0041] The comparative test results are as follows.

[0042] For a single-frequency signal, assume that the signal strength is 1. Under a background of five times the intensity of white noise, five single-frequency signals are superimposed at the 1000th, 1010th, 1015th, 1030th, and 1050th time points to form a simulated received signal. The received signal data is processed using conventional techniques using single-frequency coded signals, and then matched filtering is performed to obtain the following results: Figure 5 .

[0043] Under the same noise background as above, dual-frequency signals of the same intensity are superimposed at the same time point, and then processed using the dual-frequency encoding method of the present invention, and then matched filtering calculation is performed to obtain the following result: Figure 6 .

[0044] Through the comparison of the experimental waveform data, it can be seen that the single-frequency coded signal matching filtering result has only three obvious peak points, which are located at the 1001st, 1029th and 1052nd time points respectively, and two sound wave signals are submerged by other signals; while the dual-frequency coded signal matching filtering result processed by the method of the present invention has five obvious peak points, which are located at the 1000th, 1009th, 1016th, 1030th and 1050th time points respectively, which are almost consistent with the positions of the original signals. It can be proved that the dual-frequency coded signal processed by the method of the present invention has a better effect on the separation and identification of different sound wave signals, and can effectively improve the signal matching accuracy, so as to effectively separate different interference clutter signals in the water body, calculate the accurate arrival time of each sound wave signal, thereby analyzing the sound line propagation in the water body and the river section, and realizing the improvement of the measurement accuracy of river flow rate and flow.

[0045] The present invention also provides an acoustic chromatography flow measurement system with dual-frequency encoding of acoustic wave signals, which adopts the method of the present invention, and includes a host and a plurality of acoustic wave probes, wherein the host includes: a signal editing and adjustment module, which is used to edit and adjust a single-frequency M-code signal with a modulation coefficient of 3, wherein the frequency of the single-frequency M-code signal is f Hz, and the duration of one code position is 3 / f seconds;

[0046] The dual-frequency signal processing module is used to modify the first half of a code position in the single-frequency M-code signal into two sine waves, that is, the frequency is 4f / 3; the second half of a code position is modified into one sine wave, that is, the frequency is 2f / 3, so that the single-frequency M-code signal is modified into a dual-frequency signal; the dual-frequency signal is used to flip the code positions specified by the sequence according to the original coding rules of the single-frequency M-code signal to form a dual-frequency coded signal to the probe transmitting end.

[0047] The dual-frequency signal filtering module is used to receive the dual-frequency coded signal transmitted from the probe receiving end, perform matched filtering, and identify and separate different signals. The filtered signal is used in the river acoustic tomography flow measurement process.

[0048] The signal editing and adjustment module is also used to edit the single-frequency M-code signal, which is a coded signal obtained by flipping a specified code position in a sine wave signal according to a specific sequence; one code position of the single-frequency M-code signal contains 3 sine waves.

[0049] The dual-frequency signal filtering module is also used to match filter the dual-frequency coded signal. The peak width of the filtering result is narrow, and different signals can be identified and separated. The narrow peak width will reduce the signal identification error and reduce the coverage between different signals. The filtering eliminates clutter interference signals and improves measurement accuracy. The system equipment of the present invention has a high degree of intelligence, can be remotely and centrally controlled, has high data processing efficiency, and its accuracy is 11-13% higher than that of the existing single-frequency signal system. The software system architecture model is simple, easy to maintain, and has high reliability.

Claims

1. A dual-frequency encoding method for acoustic wave signals applied to an acoustic tomography flow measurement system, characterized in that: Includes steps: (1) In a river acoustic tomography flow measurement system, a single-frequency M-code signal with a modulation coefficient of 3 is edited and adjusted. The frequency of the single-frequency M-code signal is f Hz, and the duration of one code position is 3 / f seconds; (2) The first half of a code position in the single-frequency M code signal is modified into two sine waves, that is, the frequency is 4f / 3; the second half of a code position is modified into one sine wave, that is, the frequency is 2f / 3, so that the single-frequency M code signal is modified to become a dual-frequency signal; the dual-frequency signal is subjected to the code position specified by the sequence according to the original coding rule of the single-frequency M code signal, and the dual-frequency coded signal is formed and transmitted; (3) Receive the dual-frequency coded signal and perform matched filtering to identify and separate different signals.

2. According to claim 1, a dual-frequency encoding method for acoustic wave signals applied to an acoustic tomography flow measurement system is characterized in that: In step (1), The single-frequency M-code signal refers to an M-sequence code, which is a coded signal obtained by flipping a specified code position in a sine wave signal according to a specific sequence; one code position of the single-frequency M-code signal includes 3 sine waves.

3. According to claim 1, a dual-frequency encoding method for acoustic wave signals applied to an acoustic tomography flow measurement system is characterized in that: In step (3), The dual-frequency coded signal is received and matched filtered. The peak width of the filtering result is narrow, and different signals are identified and separated. The narrow peak width will reduce the signal identification error and reduce the coverage between different signals.

4. A dual-frequency encoding method for acoustic wave signals applied to an acoustic tomography flow measurement system according to any one of claims 1 to 3, characterized in that: In step (3), The processed signal after the dual-frequency coded signal is subjected to matched filtering weakens the matching degree of non-matching points without reducing the matching degree of matching points, thereby reducing mutual interference between signals.

5. An acoustic tomography flow measurement system with dual-frequency encoding of acoustic wave signals, comprising a host and a plurality of acoustic wave probes, characterized in that: The host includes A signal editing and adjustment module, used for editing and adjusting a single-frequency M-code signal with a modulation coefficient of 3, wherein the frequency of the single-frequency M-code signal is f Hz, and the duration of one code position is 3 / f seconds; A dual-frequency signal processing module is used to modify the first half of a code position in the single-frequency M-code signal into two sine waves, that is, the frequency is 4f / 3; modify the second half of a code position into one sine wave, that is, the frequency is 2f / 3, so that the single-frequency M-code signal is modified to become a dual-frequency signal; and the dual-frequency signal is reversed according to the original coding rule of the single-frequency M-code signal, and the code position specified by the sequence is formed. A dual-frequency coded signal; The dual-frequency signal filtering module is used to receive the dual-frequency coded signal, perform matched filtering, and identify and separate different signals.

6. The acoustic tomography flow measurement system with dual-frequency encoding of acoustic wave signals according to claim 5, characterized in that: The signal editing and adjustment module is also used for the single-frequency M code signal, which refers to the M sequence encoding, which is a coded signal obtained by flipping the specified code position in a sine wave signal according to a specific sequence; one code position of the single-frequency M code signal contains 3 sine waves.

7. The acoustic tomography flow measurement system with dual-frequency encoding of acoustic wave signals according to claim 5, characterized in that: The dual-frequency signal filtering module is also used to match filter the dual-frequency coded signal. The filtering result has a narrow peak width, which can identify and separate different signals. The narrower peak width can reduce the signal recognition error and reduce the coverage between different signals.

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