CN114186586A - Damage identification method and equipment based on two-dimensional convolutional neural network - Google Patents

Damage identification method and equipment based on two-dimensional convolutional neural network Download PDF

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CN114186586A
CN114186586A CN202111490405.4A CN202111490405A CN114186586A CN 114186586 A CN114186586 A CN 114186586A CN 202111490405 A CN202111490405 A CN 202111490405A CN 114186586 A CN114186586 A CN 114186586A
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damage
frequency band
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conductance
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艾德米
莫芳
程佳宝
朱宏平
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Huazhong University of Science and Technology
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    • G—PHYSICS
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    • G06F18/214—Generating training patterns; Bootstrap methods, e.g. bagging or boosting
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    • G06—COMPUTING; CALCULATING OR COUNTING
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    • G06F2218/00—Aspects of pattern recognition specially adapted for signal processing
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Abstract

The invention discloses a damage identification method and equipment based on a two-dimensional convolutional neural network, belonging to the field of structural health monitoring and comprising the following steps: sweeping frequency in a preset frequency band, and measuring a conductance signal of a structure at each frequency point; dividing a preset frequency band into a plurality of sub-frequency bands, calculating the deviation of the conductance signals in each sub-frequency band relative to the conductance signals in each sub-frequency band in a non-damage state, and taking n sub-frequency bands with the largest deviation as target frequency bands; extracting one-dimensional conductance signals under n target frequency bands, and constructing every two one-dimensional conductance signals into two-dimensional data to obtain a prediction sample; inputting the prediction sample into the trained damage recognition model to predict the current quality loss of the structure and obtain the damage state of the structure; the damage identification model is a two-dimensional convolutional neural network and is used for predicting the quality loss of the structure through two-dimensional data. The method can accurately classify and quantify the electrical impedance information with difference, and realize quantitative analysis and characterization of structural damage.

Description

Damage identification method and equipment based on two-dimensional convolutional neural network
Technical Field
The invention belongs to the field of structural health monitoring, and particularly relates to a damage identification method and equipment based on a two-dimensional convolutional neural network.
Background
With the rapid development of infrastructure construction, various large-scale civil and industrial buildings and the like emerge, and gradually become diversified, advanced, complicated and internationalized. While the building development in China is carried out, the requirement of people on the safety of the structure is improved along with the growth of the building. For various buildings at present, the loading action is gradually complicated, wherein the loading action comprises direct loading, indirect loading and accidental loading, and the series of loading actions are coupled together, so that the fatigue damage, the structural damage and the resistance decline of the structure are often caused. In addition, the building may be affected by various factors such as aging, corrosion, fatigue, environment and natural disasters of the building, which may damage the building structure to a certain extent, reduce its resistance, and further fail to ensure its safety. Once the key parts of the structure are damaged during the use, particularly large civil engineering structures, if the damage is allowed to develop and cannot be found and processed in time, the damage and the failure of the structure are likely to be caused, and the damage and the failure bring great influence to the country and people. Most of the damages belong to a gradual change process, no matter in the construction period or the service period, the micro damages of the structure are difficult to identify by naked eyes, the local damages and even the structural damages of the subsequent components caused by the small and large accumulation of the micro damages are fatal to a plurality of complex structures/precise structures, and how to accurately detect the micro damages as a big hotspot in the health detection field is also a big difficulty. The structural damage identification system based on the traditional piezoelectric impedance technology is characterized in that a piezoelectric ceramic (PZT) sensor is bonded on the surface of a structure or is implanted into the structure, the PZT self positive and negative piezoelectric effect is utilized through local high-frequency excitation vibration, meanwhile, the PZT self positive and negative piezoelectric effect is used as a driver and a sensor to obtain related information of the local performance (mass, rigidity, damping and the like) of the structure, the healthy (undamaged) state of the structure is generally used as a baseline reference state, impedance signals in different damage states are obtained according to the same method, and information of the local performance change of the structure is identified by comparing the impedance signals with the baseline state, so that the identification of the local micro damage of the structure is realized.
However, the piezoelectric impedance technology has its problems, and although this method can reflect the structural damage by using the change of the impedance spectrum measured by the piezoelectric patch to realize the damage identification of the complex structure, the judgment of the damage mostly stays in the qualitative level, and the quantitative analysis and characterization of the structural damage are difficult to realize.
Disclosure of Invention
Aiming at the defects and improvement requirements of the prior art, the invention provides a damage identification method and equipment based on a two-dimensional convolutional neural network, and aims to accurately classify and quantify differential electrical impedance information so as to realize quantitative analysis and characterization of structural damage.
To achieve the above object, according to an aspect of the present invention, there is provided a method for identifying an impairment based on a two-dimensional convolutional neural network, including:
sweeping frequency in a preset frequency band, and measuring a conductance signal of a structure at each frequency point;
dividing a preset frequency band into a plurality of sub-frequency bands, calculating the deviation of a conductance signal of the structure in each sub-frequency band relative to the conductance signal of the structure in each sub-frequency band in a non-damage state, and taking n sub-frequency bands with the maximum deviation as target frequency bands; each frequency band comprises N frequency points, N and N are positive integers, and N is more than or equal to 2;
the method comprises the steps of extracting conductance signals of a structure under N target frequency bands, constructing one-dimensional conductance signals in every two target frequency bands into N multiplied by N two-dimensional data, and forming a prediction sample by the constructed two-dimensional data;
inputting the prediction sample into the trained damage recognition model to predict the current quality loss of the structure and obtain the damage state of the structure;
the damage identification model is a two-dimensional convolutional neural network and is used for predicting the quality loss of the structure according to input two-dimensional data.
The method takes a two-dimensional convolutional neural network (2DCNN) as a damage identification model and is used for predicting the corresponding structural loss amount according to two-dimensional data constructed by conductance data of a structure under a plurality of different frequency bands, and the two-dimensional convolutional neural network has relatively small calculated amount, strong feature extraction capability and high accuracy, so that the quantitative analysis and characterization of structural damage can be realized; in addition, because the model input is constructed by the one-dimensional conductance data of different frequency bands, the model input requirement is ensured to be met, meanwhile, the characteristic enhancement can be effectively carried out, and the prediction precision of the trained model on the structure quality loss quantity is improved.
Further, the method for establishing the damage identification model comprises the following steps:
constructing an initial neural network model based on a two-dimensional convolutional neural network, and predicting the mass loss of the structure according to input two-dimensional data;
constructing a data set, wherein each sample comprises the mass loss of the structure and two-dimensional data constructed by one-dimensional conductance data of the structure under n target frequency bands in a corresponding damage state; the one-dimensional conductance data under each target frequency band consists of conductance data under N frequency points in the frequency band;
and dividing the data set into a training set and a testing set, taking the two-dimensional data in the sample as input, taking the corresponding quality loss amount as label information, respectively training and testing the initial neural network model by using the training set and the testing set, and taking the model meeting the testing requirement after training as a damage identification model.
According to the method, a two-dimensional convolutional neural network (2DCNN) is used as a damage identification model, two-dimensional data constructed by conductance data of a structure under a plurality of different frequency bands is used as model input, corresponding structure quality loss amount is used as a label, the model is trained, in the process, the network can be used for simulating the operation mechanism of a human neuron, the characteristics of impedance data are automatically learned and extracted, and the model obtained by training can be finally used for realizing quantitative identification of structural damage; in addition, the two-dimensional convolutional neural network has relatively small calculated amount, strong feature extraction capability and high accuracy, so that the damage identification model established by the invention can realize the quantitative analysis and characterization of structural damage.
Further, the n target frequency bands are n frequency sub-bands with the structure most sensitive to damage.
The sensitivity of the conductance data of the structure to damage under different frequency bands is different, the invention takes n sub-frequency bands with the most sensitive structure to damage as target frequency bands, and utilizes the conductance data under the frequency bands to construct the input of the damage identification model, thereby ensuring that the data of the input model more accurately reflects the damage condition of the structure and further improving the prediction precision of the structure damage.
Further, sweeping frequency in a preset frequency band, and measuring conductance signals of the structure at each frequency point under different damage states;
dividing a preset frequency band into a plurality of sub-frequency bands, and respectively calculating the deviation of the conductance signals of the structure in each sub-frequency band in the damage state relative to the conductance signals of the structure in each sub-frequency band in the damage-free state for each damage state; each frequency band comprises N frequency points;
dividing different damage grades, wherein the quality loss ranges corresponding to the different damage grades are different; counting n sub-frequency bands with the maximum deviation average value under each damage level, and taking the n sub-frequency bands as target frequency bands corresponding to the corresponding damage levels;
for each damage state, determining a corresponding target frequency band according to the damage grade of the damage state, extracting conductance signals of the damage state in each target frequency band, multiplying one-dimensional conductance signals in every two target frequency bands by a matrix and then constructing N multiplied by N two-dimensional data in a normalization mode, and forming a sample by the constructed two-dimensional data and the mass loss of the damage state; a data set is formed from all samples.
Under the working conditions with similar damage degrees, the distribution of the deviation of the conductance signal of the structure relative to the conductance signal of the structure in a non-damage state in each sub-frequency band is similar.
Further, n is 2.
According to the method, only 2 frequency bands most sensitive to structural damage are selected as the target frequency bands, so that the calculated amount can be effectively reduced and the training efficiency of the model can be improved under the condition that the prediction accuracy of the model is ensured.
Further, dividing the preset frequency band into a plurality of sub-frequency bands, each frequency band including N frequency points, includes:
after removing the head and tail sections of the preset frequency band, dividing every N frequency points in the rest frequency band into a sub-frequency band.
According to the invention, before the sub-frequency bands are divided, the head and tail sections of the preset frequency band are removed, so that the influence caused by data fluctuation when the data acquisition starts and ends can be reduced.
Further, the preset frequency range is 40Hz-500 kHz.
According to another aspect of the present invention, there is provided an injury identifying apparatus based on a two-dimensional convolutional neural network, including: the system comprises a health monitoring module, a frequency band screening module, a data processing module and a damage identification module;
the health monitoring module is used for sweeping frequency in a preset frequency band and measuring a conductance signal of a structure at each frequency point;
the frequency band screening module is used for dividing a preset frequency band into a plurality of sub-frequency bands, calculating the deviation of the conductance signals of the structure in each sub-frequency band relative to the conductance signals of the structure in each sub-frequency band in a non-damage state, and taking the n sub-frequency bands with the maximum deviation as target frequency bands; each sub-frequency band comprises N frequency points, N and N are positive integers, and N is more than or equal to 2;
the data processing module is used for extracting conductance signals of the structure under N target frequency bands, constructing one-dimensional conductance signals in every two target frequency bands into N multiplied by N two-dimensional data, and forming a prediction sample by the constructed two-dimensional data;
the damage identification module is used for inputting the prediction sample into the trained damage identification model so as to predict and obtain the current quality loss of the structure and obtain the damage state of the structure;
the damage identification model is a two-dimensional convolutional neural network and is used for predicting the quality loss of the structure according to input two-dimensional data.
In general, according to the technical scheme, the two-dimensional convolutional neural network (2DCNN) is used as a damage identification model for predicting the corresponding structural loss according to the two-dimensional data constructed by the conductance data of the structure under a plurality of different frequency bands, and the two-dimensional convolutional neural network has relatively small calculated amount, strong feature extraction capability and high accuracy, so that the quantitative analysis and characterization of the structural damage can be realized; in addition, because the model input is constructed by the one-dimensional conductance data of different frequency bands, the model input requirement is ensured to be met, meanwhile, the characteristic enhancement can be effectively carried out, and the prediction precision of the trained model on the structure quality loss quantity is improved. On the basis, when a data set for model training and testing is constructed, the damage grades are divided, the target frequency bands corresponding to all working conditions in the same damage grade are determined in a statistical mode, and corresponding conductance data are extracted to construct model input, so that the influence of abnormal measurement results on target frequency band selection can be avoided, the training effect of the model is further ensured, and the prediction precision of damage prediction based on the model is ensured.
Drawings
FIG. 1 is an admittance measuring system of a concrete structure specimen constructed according to an embodiment of the present invention;
fig. 2 is a flowchart of an injury identification method based on a two-dimensional convolutional neural network according to an embodiment of the present invention;
FIG. 3 is an admittance curve diagram of a concrete structure test piece provided by an embodiment of the present invention under a small mass loss (2.23% -8.46%) damage condition; wherein, (a), (b), (c) and (d) respectively represent admittance curve graphs under working conditions 1-4;
FIG. 4 is an admittance curve diagram of a concrete sample provided by an embodiment of the present invention under a large mass loss (47.06% -91.44%) damage condition; wherein, (a), (b), (c) and (d) respectively represent admittance curve graphs under working conditions 5-8;
FIG. 5 is an RMSD index diagram of the sub-band admittance of a concrete structure test piece under a smaller mass loss (2.23% -8.46%) damage condition, according to an embodiment of the present invention;
FIG. 6 is an RMSD index diagram of the sub-band admittance of a concrete sample under a large mass loss (47.06% -91.44%) damage condition, according to an embodiment of the present invention;
FIG. 7 is a schematic diagram of a loss identification model provided by an embodiment of the present invention;
fig. 8 is a training loss and accuracy curve of a two-dimensional convolutional neural network under a small mass loss for a concrete sample provided by the embodiment of the present invention; wherein, (a) is the training loss, and (b) is the correct rate curve;
FIG. 9 is a training loss and accuracy curve of a two-dimensional convolutional neural network under a large mass loss for a concrete specimen provided by an embodiment of the present invention; wherein, (a) is a training loss, and (b) is a correct rate curve.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
In the present application, the terms "first," "second," and the like (if any) in the description and the drawings are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order.
In order to solve the problem of establishing a mapping relation from data to a damage state in the traditional piezoelectric impedance technology, the invention provides a damage identification method and equipment based on a two-dimensional convolutional neural network, and the overall thought of the method is as follows: the method comprises the steps of utilizing a characteristic that a conductance signal of a structure can reflect the damage condition of the structure, taking a trained two-dimensional convolutional neural network as a damage identification model, predicting corresponding structure loss according to two-dimensional data constructed by the conductance data of the structure under a plurality of different frequency bands, and accurately classifying and quantifying electrical impedance information with differences based on the model to realize quantitative analysis and characterization of the damage of the structure.
The admittance signal comprises a conductance signal and a susceptance signal at the same time, specifically, the real part of the admittance signal is the conductance signal, and the imaginary part of the admittance signal is the susceptance signal, so that the conductance signal of the structure can be obtained by collecting the admittance signal of the structure; based on this, in order to collect conductance data of a structure, the present invention establishes an admittance measuring system based on a piezoelectric admittance technology, as shown in fig. 1, which includes: personal computer, impedance meter, PZT sensor connected to the main structure. The impedance meter outputs voltage to control the PZT sheet to vibrate; then receiving an electric signal generated by the PZT sheet due to the vibration transmitted by the sensing structure, converting the electric signal into a conductive signal and transmitting the conductive signal to a computer; and finally, collecting and sorting data by a computer.
Based on the admittance testing system shown in fig. 1, the specific way of carrying out admittance testing on the structure in the invention is as follows: the PZT sensor connected with the main structure is electrically excited by an impedance meter, an original admittance signal is generated by frequency sweeping, and the admittance signal is collected and a conductance signal is extracted from the admittance signal.
It should be noted that the measurement system shown in fig. 1 is only an alternative measurement system of the present invention, and should not be construed as the only limitation of the present invention, and other measurement systems that can be used to measure a structural conductance signal may also be suitable for use in the present invention.
The following are examples.
Example 1:
a method for identifying an injury based on a two-dimensional convolutional neural network, as shown in fig. 2, includes:
sweeping frequency in a preset frequency band, and measuring a conductance signal of a structure at each frequency point;
dividing a preset frequency band into a plurality of sub-frequency bands, calculating the deviation of a conductance signal of the structure in each sub-frequency band relative to the conductance signal of the structure in each sub-frequency band in a non-damage state, and taking n sub-frequency bands with the maximum deviation as target frequency bands; each frequency band comprises N frequency points, N and N are positive integers, and N is more than or equal to 2;
the method comprises the steps of extracting conductance signals of a structure under N target frequency bands, constructing one-dimensional conductance signals in every two target frequency bands into N multiplied by N two-dimensional data, and forming a prediction sample by the constructed two-dimensional data; in this embodiment, the two-dimensional data is constructed in a manner that two one-dimensional conductance signals are subjected to matrix multiplication and then normalized;
inputting the prediction sample into the trained damage recognition model to predict the current quality loss of the structure and obtain the damage state of the structure;
the damage identification model is used for predicting the quality loss amount of the structure according to the input two-dimensional data.
In consideration of the fact that the two-dimensional convolutional neural network is relatively small in calculated amount, strong in feature extraction capability and high in accuracy, in order to obtain better damage identification prediction precision, in the embodiment, a two-dimensional convolutional neural network is adopted to establish a damage identification model, and the damage identification model is used for predicting the mass loss of the structure according to input two-dimensional data; the establishment method of the damage identification model comprises the following steps:
constructing an initial neural network model based on a two-dimensional convolutional neural network, and predicting the mass loss of the structure according to input two-dimensional data;
constructing a data set, wherein each sample comprises the mass loss of the structure and two-dimensional data constructed by one-dimensional conductance data of the structure under n target frequency bands in a corresponding damage state; the one-dimensional conductance data under each target frequency band consists of conductance data under N frequency points in the frequency band;
dividing a data set into a training set and a testing set, taking two-dimensional data in a sample as input, taking corresponding quality loss as label information, respectively training and testing an initial neural network model by using the training set and the testing set, and taking a model meeting testing requirements after training as a damage identification model;
considering that the sensitivity of the conductance data of the structure to damage under different frequency sub-bands is different, in order to input the data of the model to more accurately reflect the damage condition of the structure, in this embodiment, when the data set is constructed, the selected n target frequency bands are the n frequency sub-bands of which the structure is most sensitive to damage; experiments show that only 2 sub-frequency bands which are most sensitive to structural damage are selected as target frequency bands, so that the calculated amount can be effectively reduced and the training efficiency of the model can be improved under the condition of ensuring the prediction accuracy of the model, and therefore n is set to be 2;
as an optional implementation manner, in this embodiment, the structure is damaged by a cutting machine, so that the structure is damaged by a specified mass loss amount, and each mass loss amount corresponds to one damage working condition; for each working condition, measuring admittance curves respectively, and measuring 100 groups for each working condition;
based on the admittance testing system shown in fig. 1, in this embodiment, when a data set is constructed, 1V voltage excitation is specifically set by an impedance meter in the admittance testing system, frequency is swept in a wide frequency band (40Hz-500kHz) range, and original admittance signals of structures at various frequency points under different damage states are measured, and 100 sets of admittance data are measured under each damage state; the original admittance signals have 801 dimensions, and each dimension corresponds to a measurement result under a frequency point;
in order to ensure the data accuracy and improve the identification degree among the working condition data, the first 81 data and the last 80 data of the 801-dimensional data are removed and reduced to 640-dimensional data, so that the influence caused by data fluctuation when the data acquisition starts and ends is reduced;
dividing 640-dimensional data into 20 sections in sequence, wherein each section is 32-dimensional data and each section is used as a sub-frequency band;
in this embodiment, the deviation of the conductance signal of the structure in each frequency sub-band in the current damage state relative to the conductance signal of the structure in each frequency sub-band in the damage-free state is used as the sensitivity of the structure to damage; as an optional implementation manner, in this embodiment, the sensitivity of the structure to damage is measured specifically by Root Mean Square Deviation (RMSD); correspondingly, the calculation formula of the sensitivity of the structure to damage under each sub-frequency band is as follows:
Figure BDA0003399070390000101
in the formula, N represents the data dimension in the sub-band, i.e. the number of frequency points; i is 1,2 … …, and N represents the serial number of the frequency point in the sub-band; x is the number ofi、yiRespectively representing the nondestructive state of the structure and the electrical admittance signal value after damage; since 100 sets of admittance data are measured for each damage condition in this embodiment, xiThe mean of 100 groups of data.
Considering that under the working conditions with similar damage degrees, the distribution of the deviation of the conductance signal of the structure relative to the conductance signal of the structure under the non-damage state is similar in each sub-frequency band, so the structural damage working conditions are divided into different damage grades according to the mass loss range; in the actual measurement, aiming at a measurement result which may be abnormal under a specific working condition, in order to avoid interference caused by the abnormal measurement result, as a preferred embodiment, in this embodiment, after the RMSD under each working condition and in each sub-band is obtained by calculation, 2 sub-bands with the largest average deviation under each damage level are counted and taken as the target frequency band corresponding to the corresponding damage level; the following further explains the process of determining the target frequency band by taking two impairment levels, i.e. a smaller quality impairment and a larger quality impairment as an example:
the loss amount range corresponding to the smaller mass damage is (2.23% -8.46%), and the loss amounts corresponding to four working conditions are as follows: 2.23%, 4.41%, 6.49%, 8.46%, respectively labeled 1,2, 3, 4;
the loss amount range corresponding to the larger mass damage is (47.06% -91.44%), and the loss amounts corresponding to four working conditions are as follows: 47.06%, 69.95%, 83.26%, 91.44%, labels 5, 6, 7, 8, respectively;
admittance curve graphs under various damage working conditions in the smaller mass damage, namely working conditions 1-4, are respectively shown as (a), (b), (c) and (d) in fig. 3, and in fig. 3, the numerical values corresponding to the working conditions are residual masses; as can be seen from fig. 3, for the small-mass damage condition, the data of each working condition is nearly the same, the resonance peak value change of the conductance data is relatively irregular, only the peak value fluctuates along with the increase of the damage amount, and the damage size is difficult to judge through observation;
admittance curve graphs under working conditions of large mass damage, namely working conditions 5-8, are respectively shown as (a), (b), (c) and (d) in fig. 4, and numerical values corresponding to the working conditions in fig. 4 are residual masses; as can be seen from fig. 4, the conductance curve gradually shifts to the left with increasing damage, indicating that the peak of the conductance resonance exhibits a regular change due to the decrease in structural stiffness caused by the addition of mass damage. The increase in the degree of damage can be qualitatively judged by this change;
the RMSD index map of each sub-band admittance under each damage condition in a smaller mass damage is shown in fig. 5, and it can be seen from fig. 5 that the RMSD values of 4 and 8 sub-bands are larger, which means that there is a larger difference between conductance data of each condition in the interval, i.e. it is more sensitive to damage, and therefore, for each condition in a smaller mass damage, the 4 th and 8 th sub-bands are selected as target bands;
the RMSD index map of each sub-band admittance under each damage condition in the larger mass damage is shown in fig. 6, and it can be seen from fig. 6 that the RMSD values of the 8 and 12 sub-bands are larger, which means that there is a larger difference between conductance data of each condition in the interval, i.e. it is more sensitive to damage, and therefore, for each condition in the larger mass damage, the 8 th and 12 th sub-bands are selected as target bands;
for other damage levels, the determination method of the target frequency band is similar, and will not be described herein; it should be noted that the specific division manner of the damage level can be determined according to the actual application requirement, and is only an exemplary description here, and should not be construed as the only limitation to the present invention.
After the target frequency band corresponding to each damage level is determined, for each damage state, the corresponding target frequency band is determined according to the damage level to which the damage state belongs, the conductance signals of the damage state in each target frequency band are extracted, one-dimensional conductance signals in every two target frequency bands are multiplied through a matrix and then normalized to construct 32 x 32 two-dimensional data, the constructed two-dimensional data and the structural mass loss amount under the damage state form a sample, the two-dimensional data in the sample is used as the input of a two-dimensional convolutional neural network, and the structural mass loss amount in the sample is used as label information;
a data set is formed from all samples.
According to the embodiment, different damage levels are firstly divided for the damage degree, the target frequency bands corresponding to all working conditions in the same damage level are determined in a statistical mode, corresponding conductance data are extracted to construct model input, therefore, the influence of abnormal measurement results on target frequency band selection can be avoided, and the training effect of the model is further ensured. It should also be noted that, after the RMSD value of each frequency band is obtained through calculation, in some other embodiments of the present invention, under the condition that measurement abnormality is not considered, two sub-frequency bands with the largest RMSD may also be directly selected as target frequency bands, 32-dimensional vectors corresponding to the two frequency bands are subjected to matrix multiplication, so that 32 × 32 two-dimensional data is obtained, and the two-dimensional data is normalized to obtain final two-dimensional data, where the two-dimensional data is used as an input of the established two-dimensional convolutional neural network, and a quality loss amount corresponding to the two-dimensional data is used as tag information in a model training stage.
After a data set is constructed, dividing the data set into a training set and a testing set according to a certain proportion, training the established two-dimensional convolutional neural network by using the training set, testing the trained model by using the testing set, and outputting an accurate identification result of the damage size by automatically learning the conductance characteristics through a network model; in practical application, the division ratio of the training set and the test set, and the test requirement may be set according to practical application requirements, optionally, in this embodiment, the ratio of the training set to the test set is 7:3, and the test requirement includes: the accuracy is higher than 99%, and the loss of single data is less than 0.1; in the model training and testing process, the used loss function is a cross entropy loss function.
In this embodiment, after the model training is finished, the structural parameters of the obtained model are shown in table 1, and the corresponding model structure is specifically shown in fig. 7.
Fig. 8 (a) and (b) show curves of the two-dimensional convolutional neural network training loss and accuracy for measuring the smaller mass damage of the concrete specimen, respectively; fig. 9 (a) and (b) show the two-dimensional convolutional neural network training loss and accuracy curves for measuring the large mass damage of the concrete specimen, respectively. It can be seen that the recognition rate can reach 100% for the two types of mass damage conditions, and the accuracy rate of 100% for the small mass damage is reached after about 400 iterations; and for the condition of large-mass damage, the damage is achieved about 100 times, which fully proves the feasibility and the effectiveness of the embodiment on the accurate identification of the micro-structural damage.
TABLE 1 two-dimensional convolutional neural network architecture parameter settings
Figure BDA0003399070390000131
In general, the damage identification model established based on the two-dimensional convolutional neural network can realize quantitative identification of damage, has high identification precision, can effectively solve the problem of establishing a mapping relation from data to a damage state by a piezoelectric impedance technology, can perform quantitative identification on structural damages of different types, and can accurately identify micro-damages; therefore, the damage identification method based on the two-dimensional convolutional neural network provided by the embodiment can accurately classify and quantify the electrical impedance information with differences, realize quantitative analysis and characterization of structural damage, and can replace manpower to automatically analyze a large number of monitored impedance signals and realize automatic identification of damage size in long-term structural health monitoring practice.
Example 2:
an injury recognition device based on a two-dimensional convolutional neural network, comprising: the system comprises a health monitoring module, a frequency band screening module, a data processing module and a damage identification module;
the health monitoring module is used for sweeping frequency in a preset frequency band and measuring a conductance signal of a structure at each frequency point;
the frequency band screening module is used for dividing a preset frequency band into a plurality of sub-frequency bands, calculating the deviation of the conductance signals of the structure in each sub-frequency band relative to the conductance signals of the structure in each sub-frequency band in a non-damage state, and taking the n sub-frequency bands with the maximum deviation as target frequency bands; each sub-frequency band comprises N frequency points, N and N are positive integers, and N is more than or equal to 2;
the data processing module is used for extracting conductance signals of the structure under N target frequency bands, constructing one-dimensional conductance signals in every two target frequency bands into N multiplied by N two-dimensional data, and forming a prediction sample by the constructed two-dimensional data;
the damage identification module is used for inputting the prediction sample into the trained damage identification model so as to predict and obtain the current quality loss of the structure and obtain the damage state of the structure;
the damage identification model is a two-dimensional convolutional neural network and is used for predicting the mass loss of the structure according to input two-dimensional data;
in this embodiment, the specific implementation of each module can refer to the description in embodiment 1, and will not be repeated here.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (8)

1. A damage identification method based on a two-dimensional convolutional neural network is characterized by comprising the following steps:
sweeping frequency in a preset frequency band, and measuring a conductance signal of a structure at each frequency point;
dividing the preset frequency band into a plurality of sub-frequency bands, calculating the deviation of the conductance signal of the structure in each sub-frequency band relative to the conductance signal of the structure in each sub-frequency band in a non-damage state, and taking the n sub-frequency bands with the maximum deviation as target frequency bands; each frequency band comprises N frequency points, N and N are positive integers, and N is more than or equal to 2;
the method comprises the steps of extracting conductance signals of a structure under N target frequency bands, constructing one-dimensional conductance signals in every two target frequency bands into N multiplied by N two-dimensional data, and forming a prediction sample by the constructed two-dimensional data;
inputting the prediction sample into a trained damage recognition model to predict the current quality loss of the structure and obtain the damage state of the structure;
the damage identification model is a two-dimensional convolutional neural network and is used for predicting the quality loss of the structure according to input two-dimensional data.
2. The method for identifying the damage based on the two-dimensional convolutional neural network as claimed in claim 1, wherein the damage identification model is established in a manner comprising:
constructing an initial neural network model based on a two-dimensional convolutional neural network, and predicting the mass loss of the structure according to input two-dimensional data;
constructing a data set, wherein each sample comprises the mass loss of the structure and two-dimensional data constructed by one-dimensional conductance data of the structure under n target frequency bands in a corresponding damage state; the one-dimensional conductance data under each target frequency band consists of conductance data under N frequency points in the frequency band;
and dividing the data set into a training set and a testing set, taking two-dimensional data in a sample as input, taking corresponding quality loss amount as label information, respectively training and testing the initial neural network model by using the training set and the testing set, and taking a model meeting testing requirements after training as the damage identification model.
3. The damage identification method based on the two-dimensional convolutional neural network as claimed in claim 1 or 2, wherein the n target frequency bands are n sub-frequency bands in which the structure is most sensitive to damage in the frequency sweep range.
4. The two-dimensional convolutional neural network-based lesion identification method of claim 3, wherein constructing a data set comprises:
sweeping frequency in a preset frequency band, and measuring conductance signals of the structure at each frequency point under different damage states;
dividing the preset frequency band into a plurality of sub-frequency bands, and respectively calculating the deviation of the conductance signals of the structure in each sub-frequency band in the damage state relative to the conductance signals of the structure in each sub-frequency band in the damage-free state for each damage state; each frequency band comprises N frequency points;
dividing different damage grades, wherein the quality loss ranges corresponding to the different damage grades are different; counting n sub-frequency bands with the maximum deviation average value under each damage level, and taking the n sub-frequency bands as target frequency bands corresponding to the corresponding damage levels;
for each damage state, determining a corresponding target frequency band according to the damage grade of the damage state, extracting conductance signals of the damage state in each target frequency band, multiplying one-dimensional conductance signals in every two target frequency bands by a matrix and then constructing N multiplied by N two-dimensional data in a normalization mode, and forming a sample by the constructed two-dimensional data and the mass loss of the damage state; the data set is composed of all samples.
5. The two-dimensional convolutional neural network-based impairment recognition method of claim 4, wherein n-2.
6. The method for identifying the damage based on the two-dimensional convolutional neural network as claimed in claim 4 or 5, wherein dividing the preset frequency band into a plurality of sub-frequency bands, each frequency band containing N frequency points comprises:
and after removing the head section and the tail section of the preset frequency band, dividing every N frequency points in the rest frequency bands into a sub-frequency band.
7. The two-dimensional convolutional neural network-based impairment recognition method of claim 6, wherein the preset frequency band is 40Hz-500 kHz.
8. An injury recognition device based on a two-dimensional convolutional neural network, comprising: the system comprises a health monitoring module, a frequency band screening module, a data processing module and a damage identification module;
the health monitoring module is used for sweeping frequency in a preset frequency band and measuring a conductance signal of a structure at each frequency point;
the frequency band screening module is used for dividing the preset frequency band into a plurality of sub-frequency bands, calculating the deviation of the conductance signal of the structure in each sub-frequency band relative to the conductance signal of the structure in each sub-frequency band in a non-damage state, and taking the n sub-frequency bands with the maximum deviation as target frequency bands; each sub-frequency band comprises N frequency points, N and N are positive integers, and N is more than or equal to 2;
the data processing module is used for extracting conductance signals of the structure under N target frequency bands, constructing one-dimensional conductance signals in every two target frequency bands into N multiplied by N two-dimensional data, and forming a prediction sample by the constructed two-dimensional data;
the damage identification module is used for inputting the prediction sample into a trained damage identification model so as to predict and obtain the current quality loss of the structure and obtain the damage state of the structure;
the damage identification model is a two-dimensional convolutional neural network and is used for predicting the quality loss of the structure according to input two-dimensional data.
CN202111490405.4A 2021-12-08 2021-12-08 Damage identification method and equipment based on two-dimensional convolutional neural network Pending CN114186586A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117520983A (en) * 2023-11-07 2024-02-06 浙江大学 Structural damage identification robust method based on electromechanical impedance and CNN

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117520983A (en) * 2023-11-07 2024-02-06 浙江大学 Structural damage identification robust method based on electromechanical impedance and CNN

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