A load compensation method of a guided-wave damage monitoring signal

Abstract

The application belongs to the technical field of structural health monitoring, and particularly relates to a load compensation method for guided wave damage monitoring signals. The method comprises the following steps: step one, obtaining a baseline signal before monitoring starts and a current signal after monitoring starts; step two, calculating a time delay when a maximum absolute value of a cross-correlation function of the baseline signal and the current signal is obtained; step three, calculating instantaneous phases of the baseline signal and the current signal; step four, constructing a local distance matrix according to the time delay and the instantaneous phases; step five, constructing a global distance matrix according to the local distance matrix; step six, determining an optimal regular path in the global distance matrix through a backtracking algorithm; and step seven, completing phase load compensation of the current signal to the baseline signal according to the optimal regular path. The application overcomes the deficiency of the existing guided wave signal load compensation method that requires data samples to determine model parameters, can quickly determine load compensation parameters, and is suitable for practical engineering applications.

Description

Technical Field

[0001] This application belongs to the field of structural health monitoring technology, and specifically relates to a load compensation method for guided wave damage monitoring signals. Background Technology

[0002] Guided wave damage monitoring (CWDM) is considered one of the most effective structural health monitoring technologies and has received widespread attention from research institutions, universities, and industries. Currently, most damage identification methods in this field require comparison with a baseline signal. However, the external environment can affect guided wave propagation, thus influencing the comparison results and potentially leading to misjudgments of damage. Among these external environmental factors, besides temperature, structural load is one of the main factors affecting guided wave propagation. Changes in structural load can alter the amplitude and phase of the guided wave monitoring signal, thereby affecting the results of guided wave damage monitoring. Therefore, in guided wave monitoring of structural damage, the influence of structural load on the monitoring signal should be compensated for.

[0003] Current waveguide signal load compensation methods generally require data samples under known structural load conditions to determine model parameters. However, in engineering practice, structural forms and stress states are often highly variable, making it impossible to determine the model parameters for waveguide signal load compensation by obtaining data samples for all load conditions. Therefore, the effectiveness of existing waveguide signal load compensation methods in practical engineering applications is affected.

[0004] Therefore, it is desirable to have a technical solution to overcome or at least mitigate one of the aforementioned defects of the prior art. Summary of the Invention

[0005] The purpose of this application is to provide a load compensation method for guided wave damage monitoring signals, so as to solve the problem that existing guided wave signal load compensation methods require data samples to determine model parameters.

[0006] The technical solution of this application is:

[0007] A load compensation method for guided wave damage monitoring signals, comprising:

[0008] Step 1: Acquire the baseline signal before monitoring begins and the current signal after monitoring begins;

[0009] Step 2: Calculate the time delay when the cross-correlation function between the baseline signal and the current signal reaches its maximum absolute value;

[0010] Step 3: Calculate the instantaneous phase of the baseline signal and the current signal;

[0011] Step 4: Construct a local distance matrix based on the time delay and the instantaneous phase;

[0012] Step 5: Construct the global distance matrix based on the local distance matrix;

[0013] Step 6: Determine the optimal normalized path in the global distance matrix using a backtracking algorithm;

[0014] Step 7: Based on the optimal normalization path, complete the phase load compensation from the current signal to the baseline signal.

[0015] In at least one embodiment of this application, step one, acquiring the baseline signal before monitoring begins and the current signal after monitoring begins, includes:

[0016] Acquire the baseline signal b(t) before monitoring begins, where the baseline signal vector is b;

[0017] Obtain the current signal c(t) after monitoring begins, where the current signal vector is c.

[0018] In at least one embodiment of this application, step two, calculating the time delay when the cross-correlation function between the baseline signal and the current signal reaches its maximum absolute value, includes:

[0019] Calculate the cross-correlation function R between the baseline signal and the current signal. bc (τ):

[0020]

[0021] Cross-correlation function R bc (τ) Time delay τ when taking the maximum absolute value M :

[0022] τ M =argmax{|R bc (τ)|}

[0023] Where |·| represents taking the absolute value.

[0024] In at least one embodiment of this application, step four, constructing a local distance matrix based on the time delay and the instantaneous phase, includes:

[0025] Construct a local distance matrix (DL), where the elements of the local distance matrix DL are:

[0026] DL mn =d(b m ,c n (m,n=1,…,N)

[0027] The distance d between the baseline signal and two data points in the current signal is:

[0028]

[0029] Among them, b m Let c be the m-th data point in the baseline signal. n This is the nth data point in the current signal.

[0030] In at least one embodiment of this application, step five, constructing a global distance matrix based on the local distance matrix, includes:

[0031] Construct a global distance matrix DG, wherein the elements of the global distance matrix DG are:

[0032] DG mn =DL mn +m g, i h n(DG m-g,n-h )(g={0,1},h={0,1},g+h>0,mg>0,nh>0)

[0033] In at least one embodiment of this application, step six, determining the optimal normalized path in the global distance matrix using a backtracking algorithm, includes:

[0034] The k-th element W in the optimal regularized path W k (1≤k≤L, N≤L<2N-1) is represented by W k =(i,j) k (1≤i≤N, 1≤j≤N), obtained using the following backtracking algorithm:

[0035] Initialization: Let the first element W1 of W be W1 = (N, N), i = j = N, and the loop pointer kc = 1;

[0036] Iterative search: When i+j≠2, first let g=i and h=j, then find the elements W of W. kc+1 for:

[0037] W kc+1 =(i,j) kc+1 =argmin(DG i,j (i = {g-1, g}, j = {h-1, h}, i + j) <g+h)

[0038] Then set the loop pointer kc = kc + 1 and continue iterating the above process until the condition i + j ≠ 2 is no longer met;

[0039] Determine the last element W of W. L For: W L = (1,1).

[0040] In at least one embodiment of this application, step seven, which involves performing phase load compensation from the current signal to the baseline signal based on the optimal warping path, includes:

[0041] According to the optimal regularization path W k =(i,j) k (1≤i≤N, 1≤j≤N), the j-th data point in the current signal c(t) is mapped to the i-th data point in the baseline signal b(t), thus completing the phase load compensation from the current signal to the baseline signal.

[0042] The invention has at least the following beneficial technical effects:

[0043] The load compensation method for guided wave damage monitoring signals in this application does not require the use of data samples under known load conditions to determine load compensation parameters, making it suitable for practical engineering applications. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the dimensions of a composite laminated plate and the location of a piezoelectric sensor according to one embodiment of this application;

[0045] Figure 2 This is a comparison diagram of the guided wave damage monitoring signal load before and after compensation according to one embodiment of this application. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are some, but not all, embodiments of this application. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application. The embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0047] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the scope of protection of this application.

[0048] The following is in conjunction with the appendix Figures 1 to 2 This application will be described in further detail.

[0049] This application provides a load compensation method for guided wave damage monitoring signals, comprising the following steps:

[0050] Step 1: Acquire the baseline signal before monitoring begins and the current signal after monitoring begins;

[0051] Step 2: Calculate the time delay when the cross-correlation function between the baseline signal and the current signal reaches its maximum absolute value;

[0052] Step 3: Calculate the instantaneous phase of the baseline signal and the current signal;

[0053] Step 4: Construct the local distance matrix based on the time delay and instantaneous phase;

[0054] Step 5: Construct the global distance matrix based on the local distance matrix;

[0055] Step 6: Determine the optimal normalized path in the global distance matrix using a backtracking algorithm;

[0056] Step 7: Based on the optimal normalization path, complete the phase load compensation from the current signal to the baseline signal.

[0057] The load compensation method for guided wave damage monitoring signals in this application firstly involves using a piezoelectric sensor network arranged on the structure to be monitored to acquire baseline signals and current signals before and after monitoring begins. Before monitoring begins, a baseline signal b(t) is acquired, and the baseline signal vector can be represented as b; after monitoring begins, a current signal c(t) is acquired, and the current signal vector can be represented as c.

[0058] Then, in step two, the time delay at which the cross-correlation function between the baseline signal and the current signal reaches its maximum absolute value is calculated, including:

[0059] Calculate the cross-correlation function R between the baseline signal and the current signal. bc (τ):

[0060]

[0061] Cross-correlation function R bc (τ) Time delay τ when taking the maximum absolute value M :

[0062] τ M =argmax{R bc (τ)}

[0063] Where |·| represents taking the absolute value.

[0064] In step three, the instantaneous phase of the baseline signal is calculated. and the instantaneous phase of the current signal

[0065] In step four, the local distance matrix between the two signals is established. Assuming that both the baseline signal and the current signal contain N data points, i.e., signal vectors b and c are both N-dimensional vectors, the local distance matrix DL between the two signals is an N×N matrix.

[0066] The elements of the local distance matrix DL are:

[0067] DL mn =d(b m ,c n (m,n=1,…,N)

[0068] The distance d between the baseline signal and two data points in the current signal is:

[0069]

[0070] Among them, b m Let c be the m-th data point in the baseline signal. n This is the nth data point in the current signal.

[0071] In step five, the global distance matrix is ​​constructed based on the local distance matrix, including:

[0072] Construct the global distance matrix DG, where each element is:

[0073]

[0074] Furthermore, in step six, the optimal regularization path W is determined, which involves obtaining the data point mapping for phase load compensation of the two signals.

[0075] The optimal normalized path in the global distance matrix is ​​determined using a backtracking algorithm, including:

[0076] The k-th element W in the optimal regularized path W k (1≤k≤L, N≤L<2N-1) is represented by W k =(i,j) k (1≤i≤N, 1≤j≤N), obtained using the following backtracking algorithm:

[0077] Initialization: Let the first element W1 of W be W1 = (N, N), i = j = N, and the loop pointer kc = 1;

[0078] Iterative search: When i+j≠2, first let g=i and h=j, then find the elements W of W. kc+1 for:

[0079] W kc+1 =(i,j) kc+1 =argmin(DG i,j (i = {g-1, g}, j = {h-1, h}, i + j) <g+h)

[0080] Then set the loop pointer kc = kc + 1 and continue iterating the above process until the condition i + j ≠ 2 is no longer met;

[0081] Determine the last element W of W. L For: W L = (1,1).

[0082] Finally, in step seven, the current signal phase is compensated to the baseline signal phase according to the optimal warping path W. This is done by mapping the two signal data points stored in the optimal warping path W to W. k =(i,j) k (1≤i≤N, 1≤j≤N), the j-th data point in the current signal c(t) is mapped to the i-th data point in the baseline signal b(t), thus completing the phase load compensation from the current signal to the baseline signal.

[0083] In one embodiment of this application, load compensation is performed on the guided wave monitoring signal of a carbon fiber composite laminate plate according to the steps described above. A total of two piezoelectric sensors are arranged on the composite plate. One acts as an exciter to generate the guided wave, and the other acts as a sensor to receive the guided wave. A schematic diagram of the dimensions of the composite laminate plate and the positions of the piezoelectric sensors is shown below. Figure 1 As shown. The composite material plate is mounted on a mechanical testing machine and subjected to a tensile load. The excitation signal of the guided wave is a sinusoidal modulated five-peak signal with a center frequency of 70 kHz. The signal sampling frequency is 10 MHz. Before monitoring begins, a baseline signal is acquired. Then, after applying a static tensile load to the composite material plate, the current signal is acquired. Using the baseline signal and the current signal, the phase of the current signal is compensated to the phase of the baseline signal according to the method provided in this application. A comparison of some signals before and after load compensation is shown below. Figure 2 As shown.

[0084] The load compensation method for guided wave damage monitoring signals proposed in this application overcomes the shortcomings of existing guided wave signal load compensation methods that require data samples to determine model parameters. It can quickly determine load compensation parameters and is suitable for practical engineering applications.

[0085] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A load compensation method for guided wave damage monitoring signals, characterized in that, include: Step 1: Acquire the baseline signal before monitoring begins and the current signal after monitoring begins; Step 2: Calculate the time delay when the cross-correlation function between the baseline signal and the current signal reaches its maximum absolute value; Step 3: Calculate the instantaneous phase of the baseline signal and the current signal; Step 4: Construct a local distance matrix based on the time delay and the instantaneous phase; Step 5: Construct the global distance matrix based on the local distance matrix; Step 6: Determine the optimal normalized path in the global distance matrix using a backtracking algorithm; Step 7: Based on the optimal normalization path, complete the phase load compensation from the current signal to the baseline signal.

2. The load compensation method for guided wave damage monitoring signals according to claim 1, characterized in that, In step one, the baseline signal before monitoring begins and the current signal after monitoring begins are acquired, including: Acquire the baseline signal b(t) before monitoring begins, where the baseline signal vector is b; Obtain the current signal c(t) after monitoring begins, where the current signal vector is c.

3. The load compensation method for guided wave damage monitoring signals according to claim 2, characterized in that, Step two involves calculating the time delay when the cross-correlation function between the baseline signal and the current signal reaches its maximum absolute value, including: Calculate the cross-correlation function R between the baseline signal and the current signal. bc (τ): Cross-correlation function R bc (τ) Time delay τ when taking the maximum absolute value M : t M =argmax{|R bc (t)|} Where |·| represents taking the absolute value.

4. The load compensation method for guided wave damage monitoring signals according to claim 3, characterized in that, In step four, a local distance matrix is ​​constructed based on the time delay and the instantaneous phase, including: Construct a local distance matrix (DL), where the elements of the local distance matrix DL are: DL mn =d(b m ,c n ),m,n=1,…,N The distance d between the baseline signal and two data points in the current signal is: Among them, b m Let c be the m-th data point in the baseline signal. n This is the nth data point in the current signal.

5. The load compensation method for guided wave damage monitoring signals according to claim 4, characterized in that, In step five, a global distance matrix is ​​constructed based on the local distance matrix, including: Construct a global distance matrix DG, wherein the elements of the global distance matrix DG are:

6. The load compensation method for guided wave damage monitoring signals according to claim 5, characterized in that, In step six, the optimal normalized path in the global distance matrix is ​​determined using a backtracking algorithm, including: The k-th element W in the optimal regularized path W k Represented as W k =(i,j) k Where 1≤k≤L, N≤L≤2N-1, 1≤i≤N, 1≤j≤N, is obtained using the following backtracking algorithm: Initialization: Let the first element W1 of W be W1 = (N, N), i = j = N, and the loop pointer kc = 1; Iterative search: When i+j≠2, first let g=i and h=j, then find the elements W of W. kc+1 for: W kx+1 =(i,j)j) kx+1 =arg min(DG i，j ),={g-1,g},={h-1,h},i+j<g+h Then set the loop pointer kc = kc + 1 and continue iterating the above process until the condition i + j ≠ 2 is no longer met; Determine the last element W of W. L For: W L = (1,1).

7. The load compensation method for guided wave damage monitoring signals according to claim 6, characterized in that, In step seven, phase load compensation from the current signal to the baseline signal is performed according to the optimal warping path, including: According to the optimal regularization path W k =(i,j) k 1≤i≤N, 1≤j≤N, map the j-th data point in the current signal c(t) to the i-th data point in the baseline signal b(t), and complete the phase load compensation from the current signal to the baseline signal.

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