Underwater acoustic emission data acquisition system

Abstract

The invention relates to the technical field of underwater acoustics, sensor technology and application thereof, solves the technical problems of insufficient monitoring precision, limited anti-interference capability and incomplete signal processing in a complex underwater environment in the prior art, and particularly relates to an underwater acoustic emission data acquisition system. The system is composed of a signal sound production unit, a signal preprocessing module, a signal analysis and calculation module, a real-time feedback unit and an evaluation module, all the modules are clear in structure and definite in function and work cooperatively, and a complete and efficient underwater acoustic emission signal collecting and processing system is formed. The internal and surface states of the LNG fuel low-temperature tank of the wharf can be efficiently and accurately monitored in a low-temperature complex underwater environment, underwater noise interference is effectively identified and inhibited, and the signal processing precision is improved, so that early warning of potential cracks, corrosion and other faults of the LNG low-temperature tank is realized, and safe operation of the LNG low-temperature tank is ensured.

Description

Technical Field

[0001] The present invention relates to the technical fields of underwater acoustics, sensor technology and their application technologies, and particularly relates to an underwater acoustic emission data acquisition system. Background Art

[0002] As a clean energy source, liquefied natural gas (LNG) is increasingly widely used globally, especially in the fields of maritime transportation and storage. Square pontoon LNG fuel cryogenic tanks are widely used in ships and offshore platforms. However, during the maritime transportation and storage of LNG cryogenic tanks, being exposed to complex marine environments for a long time, they may face various potential risks, such as tank corrosion, structural damage, leakage, etc., seriously threatening fuel safety and transportation stability. Therefore, it is of great significance to monitor the health and diagnose faults of LNG fuel cryogenic tanks.

[0003] In the prior art, common monitoring methods include traditional pressure, temperature, vibration sensors, and detection technologies such as X-rays and ultrasonic waves for detecting welding quality. Although these technologies can monitor the state of cryogenic tanks to a certain extent, they cannot monitor potential micro-cracks, corrosion and other abnormalities inside and on the surface of the tank in real time and comprehensively, and for complex noises and interferences in the underwater environment, the response sensitivity and stability of conventional sensors have limitations. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the present invention provides an underwater acoustic emission data acquisition system, which solves the technical problems of insufficient monitoring accuracy, limited anti-interference ability and incomplete signal processing in the complex underwater environment in the prior art.

[0005] To solve the above technical problems, the present invention provides the following technical solutions: An underwater acoustic emission data acquisition system, comprising:

[0006] A signal generating unit, which is used to collect or simulate acoustic emission signals generated during the operation of the LNG cryogenic tank, and perform preliminary amplification and filtering on the acoustic emission signals;

[0007] A signal preprocessing module, which is used to digitize the acoustic emission signals that have been preliminarily amplified and filtered, and further extract key characteristic parameters and then compress them;

[0008] A signal analysis and calculation module, which is used to perform signal spectrogram calculation according to the compressed key characteristic parameters to obtain a logarithmic mel spectrogram within different mel frequency ranges;

[0009] A real-time feedback unit, where the real-time feedback module analyzes the logarithmic Mel spectrogram to obtain an analysis result, and determines whether the signal quality and intensity of the acoustic emission signal have decreased or are abnormal. If so, a feedback signal is sent to the signal preprocessing module, and the signal preprocessing module performs dynamic adjustment of key feature parameters;

[0010] An evaluation module, which deeply mines the key feature parameters of the acoustic emission signal according to the analysis result, and conducts early prediction and comprehensive evaluation on microcracks, corrosion and other faults of the LNG cryogenic tank.

[0011] Further, the signal generating unit includes a signal generating module for capturing tiny acoustic emission signals, at least two preamplifier modules for preliminarily amplifying the tiny acoustic emission signals, and a filtering module for filtering the amplified acoustic emission signals.

[0012] Further, the filtering module includes a filter for performing band-selective filtering on the acoustic emission signal according to the characteristic frequency range of the acoustic emission signal to eliminate low-frequency noise and high-frequency interference, and an anti-modal aliasing filtering circuit for eliminating the modal aliasing effect in the acoustic emission signal.

[0013] Further, the key feature parameters include signal envelope, ring count, arrival time, rise time, and amplitude.

[0014] Further, the specific process of obtaining the logarithmic Mel spectrogram includes:

[0015] Performing a short-time Fourier transform on the acoustic emission signal containing key feature parameters to obtain the amplitude spectrum of the acoustic emission signal at different times and frequencies;

[0016] Converting the acoustic emission signal located on the linear frequency axis to the Mel frequency axis, and the conversion formula is:

[0017]

[0018] In the formula, f is the original frequency of the acoustic emission signal; M is the converted Mel frequency;

[0019] Designing a group of band-pass filters on the Mel frequency axis, and the center frequencies of the band-pass filters are located at equally spaced points on the Mel scale to form a Mel filter bank;

[0020] Passing the spectral information in the amplitude spectrum through the Mel filter bank, and each Mel filter outputs the power information corresponding to the Mel frequency range;

[0021] Recording the change of the output of each Mel filter over time to form a power information spectrogram;

[0022] Perform logarithmic operation to convert the power spectrogram into decibel units to obtain the logarithmic Mel spectrogram.

[0023] Further, the real-time feedback unit includes a signal output module for transmitting the analysis result to an external display device, and a signal quality judgment module for evaluating the accuracy and reliability of the acoustic emission signal in real time according to the integrity, intensity, and stability of the acoustic emission signal.

[0024] Further, the expression of the short-time Fourier transform is:

[0025]

[0026] In the formula, x(t) is the input acoustic emission signal; ω(m - n) is the window function; ω is the angular frequency; n is the time index.

[0027] Further, the expression for converting the power spectrogram into decibel units is:

[0028] C(f) = log(1 + P(f))

[0029] In the formula, C(f) represents the value after logarithmic compression; P(f) is the power value in the power spectrogram.

[0030] By the above technical solution, the present invention provides an underwater acoustic emission data acquisition system, which has at least the following beneficial effects:

[0031] 1. The present invention can efficiently and accurately monitor the internal and surface states of the barge-mounted LNG fuel cryogenic tank in a low-temperature and complex underwater environment, and solve the problems of insufficient sensitivity and limited monitoring range of conventional sensors in the underwater environment in the prior art. At the same time, it can effectively identify and suppress underwater noise interference, improve the signal processing accuracy, so as to realize the early warning of potential cracks, corrosion and other faults of the LNG cryogenic tank, and ensure the safe operation of the LNG cryogenic tank.

[0032] 2. The present invention can adapt to the underwater low-temperature and complex environment, and at the same time has high sensitivity and high accuracy. It can not only monitor the health status of the cryogenic tank in real time, but also effectively identify and locate the noise interference generated in the underwater environment, improve the accuracy and reliability of the monitoring signal, so as to realize the early warning and fault diagnosis of potential risks of the LNG cryogenic tank, and ensure the safe operation of the barge-mounted LNG fuel cryogenic tank.

[0033] 3. The present invention can overcome the deficiencies of the prior art, utilize the propagation characteristics of acoustic emission signals, and can be widely applied to the health monitoring, environmental monitoring, underwater target detection and other fields of underwater facilities, and has important scientific research and engineering application values. It can further improve the accuracy, stability and safety of the underwater monitoring of the barge-mounted LNG fuel cryogenic tank, and has broad application prospects. Description of the Drawings

[0034] The drawings described herein are used to provide a further understanding of the present application and form a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not unduly limit the present application. In the drawings:

[0035] Figure 1 is a schematic block diagram of the underwater acoustic emission data acquisition system of the present invention;

[0036] Figure 2 is a flowchart of the underwater acoustic emission data acquisition system of the present invention. Detailed Description of the Invention

[0037] In order to make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the drawings and specific embodiments. Thereby, a full understanding of the implementation process of how the present application uses technical means to solve technical problems and achieve technical effects can be obtained and implemented accordingly.

[0038] As a non-destructive testing technology, acoustic emission technology can efficiently and real-time monitor dynamic processes such as microcracks and crack propagation inside materials. Especially in the underwater environment, the propagation characteristics of acoustic emission signals give it unique advantages in the detection of liquefied gas storage tanks and transportation equipment. However, most current acoustic emission systems are optimized for monitoring in terrestrial environments and traditional structures, and do not fully consider the particularities of the underwater environment (such as water depth, temperature, noise interference, etc.). Especially in low-temperature situations, data acquisition will be greatly interfered.

[0039] First of all, the low-temperature environment has a significant impact on the performance and stability of underwater sensors. The decrease in water temperature may cause changes in the physical properties of sensor materials, such as an increase in resistance and a decrease in sensitivity, which will in turn affect the acquisition accuracy and quality of signals. Secondly, the sound wave propagation speed in water changes with temperature. Usually, the sound wave propagation speed in low-temperature waters is slower, which may lead to signal propagation delays and affect the timeliness and accuracy of data. In addition, low temperature may cause changes in the mechanical properties of some components in the system, such as the sealing performance, response speed, and battery performance of sensors. Especially, the battery may experience power attenuation at low temperatures, which will in turn affect the continuous working ability of the device. If these low-temperature factors are not considered, the data collected by the system may be distorted or the noise may increase, thus affecting the subsequent data processing and analysis results. Therefore, considering the influence of low temperature on the underwater acoustic emission system is a key factor in ensuring the accuracy of data acquisition and the stable operation of the system.

[0040] Considering the impact of low temperature on the underwater acoustic emission system is a key factor in ensuring the accuracy of data collection and the stable operation of the system. Therefore, there are still many deficiencies in the application of existing underwater acoustic emission systems in the square barge LNG fuel cryogenic tank, and high-precision real-time monitoring cannot be achieved.

[0041] This embodiment proposes an underwater acoustic emission data acquisition system, aiming to solve the problems of insufficient monitoring accuracy, limited anti-interference ability, and incomplete signal processing in the prior art in complex underwater environments. Through innovative modular structure design and optimized signal processing flow, the present invention can achieve high-sensitivity monitoring of the inside and surface of the square barge LNG fuel cryogenic tank, providing a scientific basis for the early detection and maintenance of potential faults. Please refer to Figure 1 - Figure 2 , this system consists of a signal generating unit, a signal preprocessing module, a signal analysis and calculation module, a real-time feedback unit, and an evaluation module. Each module has a clear structure and a definite function, and they work together to form a complete and efficient underwater acoustic emission signal acquisition and processing system.

[0042] Among them:

[0043] The signal generation module of the system is the basic module of the acoustic emission system, which is used to collect or simulate the acoustic emission signals generated during the operation of the LNG cryogenic tank. This module has been specially optimized for the complex underwater environment to ensure that it can capture tiny acoustic emission signals while ensuring the integrity of the signals, providing high-quality raw data for subsequent signal processing. The significance of this signal generation module is to provide a reliable data source for the entire system, and the quality of its performance directly affects the accuracy of the overall system monitoring.

[0044] The preamplifier module is responsible for initially amplifying the acoustic emission signals collected by the signal generation module. The main chip of the preamplifier module uses the AD825 of Analog Devices, Inc., which is a low-cost, general-purpose JFET-type high-speed amplifier. The preamplifier module supports a wide voltage supply of up to ±18V, a gain-bandwidth product of 41M, a slew rate of 140V / μs, and an output drive current of 50mA, and can be widely used in active filters, ADC / DAC input buffers, and large-signal amplification applications. At the same time, the preamplifier module reserves signal input and output interfaces for wiring terminals, which is convenient for terminal connection when used at low frequencies.

[0045] Since underwater acoustic emission signals are often weak and easily interfered by environmental noise, the preamplifier module can boost the weak signals to a processable level while minimizing the introduction of noise as much as possible. Through reasonable design, the preamplifier module ensures that the dynamic range of the signals can meet the requirements of subsequent processing and lays a foundation for subsequent signal filtering and feature extraction.

[0046] To eliminate the complex background noise and non-target signals in the underwater environment, the system is equipped with a filtering module consisting of a filter and an anti-modal aliasing filtering circuit. The anti-modal aliasing filtering circuit uses an LC passive low-pass filter, and the specific model is LPF-100. The filter can perform band-selective filtering on the signal according to the characteristic frequency range of the acoustic emission signal, removing low-frequency noise and high-frequency interference; the anti-modal aliasing filtering circuit further improves the purity of the signal by eliminating the modal aliasing effect. The significance of this part of the structure is to optimize the signal-to-noise ratio of the signal, provide more accurate input data for subsequent signal analysis, and at the same time improve the adaptability of the system in the complex underwater environment.

[0047] The signal preprocessing module is a key link in the signal processing chain. The filtered and amplified acoustic emission signal is input into a special software of the computer, where it is digitized and further key characteristic parameters are extracted. The acoustic emission signal has a large amount of waveform data and low information density. To facilitate analysis, typical characteristics usually need to be extracted. Commonly used waveform characteristic parameters of acoustic emission signals include envelope, ring count, arrival time, rise time, amplitude, etc. Among them, the signal envelope is the basis for extracting other characteristics. The short-time Fourier transform divides the signal into small time windows and performs Fourier transform on each window. This method is suitable for observing the changes of the signal in time and the distribution of frequency components. By adjusting the window size and overlap rate, the resolution can be balanced between the time domain and the frequency domain to capture important information in the signal. In the analysis of acoustic emission signals, the spectrogram analysis method based on the short-time Fourier transform can be used to detect the frequency components of acoustic emission events, identify abnormal signals, and track the changes of signals over time. This provides a powerful tool for acoustic emission monitoring and prediction. The preprocessing module extracts and compresses the effective information in the acoustic emission signal, providing rich and accurate feature vectors for subsequent spectrum analysis and pattern recognition. The design significance of this module is to reduce the computational complexity of subsequent data processing, while retaining the core information of the signal, and improving the analysis efficiency and accuracy.

[0048] The further analysis of the signal is completed by the signal analysis and calculation module. The signal analysis and calculation module performs signal spectrogram calculation on the preprocessed acoustic emission signal. The Mel spectrogram is another spectrogram analysis method used in signal processing. Different from traditional spectrogram analysis methods, the Mel spectrogram is more in line with the way the human auditory system perceives sound. This method has been widely used in the fields of speech recognition and audio processing and is gradually introduced into the analysis of acoustic emission signals. Applying Mel filters to the acoustic emission signal that has undergone short-time Fourier transform, a power information spectrogram in different Mel frequency ranges is obtained, and based on this, a logarithmic Mel spectrogram is obtained. Specifically, the specific process of obtaining the logarithmic Mel spectrogram includes:

[0049] The short-time Fourier transform (STFT) is used to transform the acoustic emission signal containing key characteristic parameters to obtain the amplitude spectrum of the acoustic emission signal at different times and frequencies;

[0050] The expression of the short-time Fourier transform (STFT) is:

[0051]

[0052] In the formula, x(t) is the input acoustic emission signal; ω(m - n) is the window function; ω is the angular frequency; n is the time index;

[0053] The acoustic emission signal located on the linear frequency axis is converted to the Mel frequency axis, and the conversion formula is:

[0054]

[0055] In the formula, f is the original frequency of the acoustic emission signal; M is the converted Mel frequency;

[0056] A group of band-pass filters are designed on the Mel frequency axis. The center frequencies of the band-pass filters are located at equally spaced points on the Mel scale to form a Mel filter bank;

[0057] The spectral information in the amplitude spectrum is passed through the Mel filter bank, and each Mel filter outputs the power information corresponding to the Mel frequency range;

[0058] Record the change of the output of each Mel filter over time to form a power information spectrogram. The power information spectrogram shows the change of the power of the acoustic emission signal in different Mel frequency ranges over time.

[0059] Based on obtaining the power information spectrogram, a logarithmic operation is performed to convert the power information spectrogram into decibel units to obtain a logarithmic Mel spectrogram. The expression is:

[0060] C(f) = log(1 + P(f))

[0061] In the formula, C(f) represents the value after logarithmic compression; P(f) is the power value in the power information spectrogram.

[0062] The role of this part in the underwater acoustic emission data acquisition system is to provide necessary basic data for damage assessment and ensure the scientificity and reliability of fault diagnosis.

[0063] The signal output module and the signal quality judgment module constitute the real-time feedback mechanism of the system. The area enclosed under the signal envelope detection line can reflect both the intensity (amplitude) of the signal and the width (duration) of the signal. Therefore, it is a very important characterization parameter in acoustic emission detection. Adding the energy counts of individual signals gives the total energy E of the acoustic emission signal, that is:

[0064]

[0065] Wherein, R is the time interval experienced by the time signal when it first crosses the threshold and reaches the maximum amplitude; V represents the amplitude of the acoustic emission signal.

[0066] The amplitude refers to the peak amplitude of the acoustic emission signal waveform, and the amplitude is often used for the identification of acoustic emission source types, intensity or attenuation measurement. In an acoustic emission system, the amplitude is often converted into the form of decibel value (DB), such as the formula:

[0067] Amp = 20lgV b

[0068] Wherein, Amp is the peak amplitude value of the acoustic emission signal; V b is the peak value of the waveform output after the signal received by the sensor is amplified by the preamplifier and the gain and adjusted through the threshold.

[0069] The signal output module transmits the analysis result to the external display device; meanwhile, the signal quality judgment module evaluates the accuracy and reliability of the signal in real time according to the integrity, intensity and stability of the signal. If a decrease or abnormality in signal quality is detected, this module can automatically trigger a feedback mechanism to dynamically adjust the system parameters to ensure the credibility of the monitoring result. This design greatly improves the automation degree of the system and the real-time performance of the monitoring, providing guarantee for the long-term stable operation under complex working environments.

[0070] In addition, the core advantage of the present invention is also reflected in the implementation of its software functions. The damage assessment software embedded in the system deeply excavates the characteristics of the acoustic emission signal through parameter analysis and correlation analysis. Combining with artificial intelligence algorithms, this software can conduct early prediction and comprehensive evaluation on the microcracks, corrosion and other faults of the cryogenic tank. By generating a detailed analysis report, the system provides a scientific decision-making basis for engineers, significantly improving the efficiency and accuracy of maintenance work.

[0071] Compared with the prior art, the underwater acoustic emission data acquisition system proposed in this embodiment has the following remarkable advantages and positive effects:

[0072] Low-temperature high sensitivity and high-precision monitoring: Through a set of self-designed acoustic emission detection system, the present invention optimizes the acquisition and processing technology of underwater acoustic emission signals, and can achieve high-sensitivity and accurate real-time monitoring in a low-temperature complex underwater environment, effectively identifying the tiny cracks, corrosion and other abnormalities inside and on the surface of the cryogenic tank, making up for the deficiencies of traditional sensors in monitoring accuracy and response speed in a low-temperature underwater environment.

[0073] Excellent noise suppression ability: The present invention adopts an algorithm with noise suppression and signal enhancement, which can effectively filter out background noise and interference signals in the underwater environment, ensuring the accuracy and reliability of acoustic emission signals, improving the adaptability of the system under complex underwater conditions, and ensuring high-quality monitoring results.

[0074] Improve safety and reliability: By realizing efficient early warning of early faults in cryogenic tanks, the present invention can detect and locate in time before potential risks occur, providing a scientific basis for the maintenance and management of LNG fuel cryogenic tanks, thus greatly improving the safety and reliability of the system and effectively reducing potential safety hazards and economic losses caused by equipment failures.

[0075] The present invention has significant technical advantages, can overcome the deficiencies of the prior art, improve the accuracy, stability and safety of underwater monitoring of LNG fuel cryogenic tanks on square pontoons, and has broad application prospects.

[0076] In summary, the underwater acoustic emission system of the LNG fuel cryogenic tank on the square pontoon of the present invention realizes high-sensitivity and high-reliability monitoring in a complex underwater environment through an innovative modular design and a real-time feedback mechanism. Each module has a clear function and cooperates with each other to form a complete process of signal acquisition, processing, analysis and evaluation. The system has significant advantages in improving underwater noise suppression ability, signal analysis accuracy and automation degree, can provide an important guarantee for the operation safety of the LNG fuel cryogenic tank on the square pontoon, and has broad application potential in other similar underwater acoustic monitoring fields.

[0077] Those of ordinary skill in the art can understand that all or part of the steps in implementing the method of the above embodiments can be completed by instructing relevant hardware through a program. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk memories, CD-ROMs, optical memories, etc.) containing computer-usable program codes.

[0078] The above embodiments have introduced the present invention in detail. Specific examples are used in this article to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. An underwater acoustic emission data acquisition system, characterized in that: include: A signal sound generating unit, which is used to collect or simulate the acoustic emission signal generated by the LNG cryogenic tank during operation, and to preliminarily amplify and filter the acoustic emission signal; A signal preprocessing module, which is used to digitize the acoustic emission signal after preliminary amplification and filtering, and further extract key characteristic parameters and then compress it; A signal analysis and calculation module, wherein the signal analysis and calculation module is used to perform signal spectrum calculation according to the compressed key characteristic parameters to obtain a logarithmic Mel frequency spectrum within different Mel frequency ranges; A real-time feedback unit, wherein the real-time feedback module parses the logarithmic Mel spectrum to obtain analysis results, and determines whether the signal quality and intensity of the acoustic emission signal are reduced or abnormal. If so, a feedback signal is sent to the signal preprocessing module, and the signal preprocessing module dynamically adjusts key characteristic parameters; An evaluation module, wherein the evaluation module conducts in-depth mining of key characteristic parameters of the acoustic emission signal based on the analysis results, and performs early prediction and comprehensive evaluation of microcracks, corrosion and other failures of the LNG cryogenic tank.

2. The underwater acoustic emission data acquisition system according to claim 1, characterized in that: The signal sound generating unit comprises a signal generating module for capturing a tiny acoustic emission signal, at least two preamplifier modules for preliminarily amplifying the tiny acoustic emission signal, and a filtering module for filtering the amplified acoustic emission signal.

3. The underwater acoustic emission data acquisition system according to claim 2, characterized in that: The filtering module includes a filter for performing frequency band selective filtering on the acoustic emission signal according to the characteristic frequency range of the acoustic emission signal to remove low-frequency noise and high-frequency interference, and an anti-modal aliasing filtering circuit for eliminating the modal aliasing effect in the acoustic emission signal.

4. The underwater acoustic emission data acquisition system according to claim 1, characterized in that: The key characteristic parameters include signal envelope, ring count, arrival time, rise time, and amplitude.

5. The underwater acoustic emission data acquisition system according to claim 1, characterized in that: The specific process of obtaining the logarithmic Mel-spectrogram includes: The acoustic emission signal containing key characteristic parameters is transformed by short-time Fourier transform to obtain the amplitude spectrum of the acoustic emission signal at different times and frequencies; The acoustic emission signal on the linear frequency axis is converted to the Mel frequency axis. The conversion formula is: Where, f is the original frequency of the acoustic emission signal; M is the converted Mel frequency; A set of bandpass filters are designed on the Mel frequency axis, and the center frequencies of the bandpass filters are located at equally spaced points on the Mel scale to form a Mel filter bank; The spectrum information in the amplitude spectrum is passed through a Mel filter bank, and each Mel filter outputs power information within the corresponding Mel frequency range; Record the changes of each Mel filter output over time to form a power information spectrum; A logarithmic operation is performed to convert the power information spectrogram into a decibel value unit to obtain a logarithmic Mel-spectrogram.

6. The underwater acoustic emission data acquisition system according to claim 1, characterized in that: The real-time feedback unit includes a signal output module for transmitting the analysis result to an external display device, and a signal quality judgment module for performing real-time evaluation on the accuracy and reliability of the acoustic emission signal according to the integrity, strength and stability of the acoustic emission signal.

7. The underwater acoustic emission data acquisition system according to claim 6, characterized in that: The expression of the short-time Fourier transform is: Where x(t) is the input acoustic emission signal; ω(mn) is the window function; ω is the angular frequency; and n is the time index.

8. The underwater acoustic emission data acquisition system according to claim 6, characterized in that: The expression for converting the power information spectrum into decibel units is: C(f)=log(1+P(f)) Where C(f) represents the value after logarithmic compression; P(f) is the power value in the power information spectrum.

Images