Structural health monitoring method and system based on electromechanical impedance technology
By combining segmented analysis with historical curves, the problem of electromechanical impedance technology being disturbed by environmental vibration in mechanical structures was solved, and accurate damage identification and monitoring in strong vibration environments was achieved.
Patent Information
- Application Number
- CN202510813473.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-18
- Publication Date
- 2025-09-16
AI Technical Summary
Electromechanical impedance technology is susceptible to interference from environmental vibrations in mechanical structure health monitoring, resulting in inaccurate monitoring results and the inability to monitor in real time.
By performing segmented analysis on the impedance curve of the piezoelectric element and calculating the root mean square deviation (RMSD), the persistence of local changes is judged by combining the historical impedance curve. The RMSD value of the abnormal sub-segment is corrected by applying the reward or penalty coefficient to suppress the environmental vibration interference.
The accuracy of damage identification is significantly improved in strong vibration environments, the false alarm rate is reduced by about 60%, and damage monitoring of carbon fiber plates and aluminum alloy cantilever beams is realized.
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Figure CN120651929A_ABST
Abstract
Description
Technical Field
[0001] The present application belongs to the field of electromechanical impedance technology, and specifically relates to a structural health monitoring method and system based on electromechanical impedance technology. Background Art
[0002] Electro-Mechanical Impedance (EMI) technology is a non-destructive structural health monitoring method. Its principle is to integrate a PZT (piezoelectric ceramic) with a structure through bonding, adsorption, or embedding. A swept frequency signal is applied to the PZT. Due to the piezoelectric properties of the PZT, the PZT vibrates and couples with local areas of the structure. This vibration coupling characteristic corresponds to the PZT's impedance curve. When damage occurs to the structure, the vibration coupling characteristic changes, and the PZT's impedance curve also changes synchronously. By measuring the PZT's impedance curve and using statistical indicators such as the root mean square deviation or correlation coefficient between the impedance curve and a reference curve, the damage is quantified and the health of the structure is determined. The reference curve refers to the impedance curve corresponding to the structure in its healthy state. Currently, EMI technology is widely used for health monitoring of civil and mechanical structures.
[0003] However, EMI technology has several drawbacks: it determines the health of a structure based on the vibration coupling relationship between the PZT and the structure. Therefore, factors that affect this coupling relationship directly impact the monitoring results, and environmental vibration is a significant source of interference. Consequently, EMI technology is primarily used for the health monitoring of civil structures. Application to the health monitoring of mechanical structures requires that the structure be inoperative to avoid interference from environmental vibration. Currently, EMI technology is primarily used for the health monitoring of static mechanical structures and cannot provide real-time monitoring.
[0004] Application Contents
[0005] The purpose of this application is to provide a structural health monitoring method and system based on electromechanical impedance technology. The structural health monitoring method and system of this application can suppress the interference of environmental vibration, thereby significantly improving the accuracy of monitoring, and the application field can also be expanded.
[0006] In one aspect, the present application provides a structural health monitoring method based on electromechanical impedance technology, comprising:
[0007] The impedance curve of each test is received and saved as a historical impedance curve. At the same time, starting from the impedance curve of the kth test, the following is performed on each received impedance curve:
[0008] S100: Divide the impedance curve into sub-segments according to the frequency band, calculate the RMSD value of each sub-segment, and construct an RMSD value sequence of the impedance curve based on the RMSD values of the sub-segments; the RMSD value of the sub-segment refers to the root mean square deviation value between the sub-segment and the corresponding sub-segment of the reference impedance curve;
[0009] S200: Determine whether the RMSD value of each sub-segment exceeds the first threshold T _RMSD If none of them exceed the limit, the structure is currently healthy; if any sub-segment exceeds the limit, the sub-segment that exceeds the limit is recorded as an abnormal sub-segment, and step S300 is executed for each abnormal sub-segment.
[0010] S300: Correcting the RMSD value of the abnormal sub-segment, including: starting from the impedance curve received this time, tracing back to the historical impedance curves of nearly W times, and counting the abnormal sub-segments in the historical impedance curves of nearly W times that exceed the first threshold T _RMSD The number of times S, if S exceeds the number threshold T _S , the RMSD value of the abnormal sub-segment is corrected to the RMSD value multiplied by the reward coefficient; otherwise, the RMSD value of the abnormal sub-segment is corrected to the RMSD value multiplied by the penalty coefficient;
[0011] in, n represents the number of sub-segments, RMSD Wi-averager-p Represents the average value of the RMSD values of the abnormal sub-segments in the historical impedance curves of the past W times, RMSD Wi-average-n The average value of the RMSD value of the abnormal sub-segment in the historical impedance curve where the abnormal sub-segment does not exceed the threshold;
[0012] S400: updating the RMSD value sequence of the impedance curve in step S100 using the correction value of the RMSD value of the abnormal sub-segment, and determining whether the structure is healthy based on the corrected RMSD value sequence;
[0013] The value of the above backtracking times W should not be less than 20, and the value of k should be greater than W.
[0014] On the other hand, the present application provides a structural health monitoring system based on electromechanical impedance technology, comprising:
[0015] The first module is used to receive the impedance curve of each test and save it as a historical impedance curve;
[0016] At the same time, starting from the impedance curve of the kth test, the following is performed for each received impedance curve:
[0017] The second module is used to start from receiving the impedance curve of the kth test and perform the following on each received impedance curve: divide the impedance curve into sub-segments according to the frequency band, calculate the RMSD value of each sub-segment, and construct the RMSD value sequence of the impedance curve from the RMSD values of the sub-segments; the RMSD value of the sub-segment refers to the root mean square deviation value between the sub-segment and the corresponding sub-segment of the reference impedance curve;
[0018] The third module is used to determine whether the RMSD value of each sub-segment exceeds the first threshold T _RMSD , if none of them are exceeded, the structure is currently healthy; if any sub-segment exceeds, the exceeded sub-segment will be recorded as an abnormal sub-segment;
[0019] The fourth module is used to correct the RMSD value of the abnormal sub-segment, including: starting from the impedance curve received this time, looking back to the historical impedance curves of nearly W times, and counting the abnormal sub-segments in the historical impedance curves of nearly W times that exceed the first threshold T _RMSD The number of times S, if S exceeds the number threshold T _S , the RMSD value of the abnormal sub-segment is corrected to the RMSD value multiplied by the reward coefficient; otherwise, the RMSD value of the abnormal sub-segment is corrected to the RMSD value multiplied by the penalty coefficient;
[0020] in, n represents the number of sub-segments, RMSD Wi-averager-p Represents the average value of the RMSD values of the abnormal sub-segments in the historical impedance curves of the past W times, RMSD Wi-average-n The average value of the RMSD value of the abnormal sub-segment in the historical impedance curve where the abnormal sub-segment does not exceed the threshold;
[0021] The fifth module is used to update the RMSD value sequence of the impedance curve in step S100 using the correction value of the RMSD value of the abnormal sub-segment, and determine whether the structure is healthy based on the corrected RMSD value sequence.
[0022] Compared with the prior art, this application has the following advantages and beneficial effects:
[0023] This application extracts local variations in the impedance curve, referred to as "abnormal subsegments," by segmenting the piezoelectric element's impedance curve and calculating the RMSD of each segment. This process, combined with historical impedance curves, determines whether these local variations are persistent anomalies or transient fluctuations. Persistent anomalies indicate a high likelihood of structural damage, and a bonus factor is applied to the local variation to enhance the damage signature. Transient fluctuations indicate a high likelihood of environmental vibration, and a penalty factor is applied to the local variation to suppress that vibration. By iterating through multiple rounds of impedance curve testing, damage can be accurately identified even in strong vibration environments.
[0024] Traditional electromechanical impedance technology is susceptible to environmental vibration interference, resulting in abnormal impedance signal fluctuations and false alarms. However, experimental testing has shown that this application can accurately identify single-point and multi-point damage in carbon fiber plates even under continuous vibration interference. The false alarm rate can be reduced by approximately 60% in the 1-400kHz frequency band, demonstrating its adaptability to high-vibration environments. This application has been successfully applied to damage monitoring of carbon fiber plates and aluminum alloy cantilever beams. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.
[0026] Figure 1 is a flow chart of the structural health monitoring method provided by this application;
[0027] Figure 2 This is a photo of the test platform in the embodiment of this application;
[0028] Figure 3 is the corrected RMSD value between the impedance curve of each PZT sheet in the embodiment of the present application and the reference impedance curve;
[0029] Figure 4 It is a damage probability cloud map drawn according to the RMSD value of each PZT piece in the embodiment of the present application. DETAILED DESCRIPTION
[0030] In order to enable those skilled in the art to better understand the present application, the present application is further described in detail below in conjunction with the accompanying drawings and specific embodiments. Obviously, the embodiments described are only a part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making any creative efforts are within the scope of protection of the present application.
[0031] See Figure 1 , which is a flow chart of a structural health monitoring method based on electromechanical impedance technology provided by an embodiment of the present application, will be combined with Figure 1 The specific real-time process of the structural health monitoring method of the present application is described in detail. It should be noted that, in this embodiment, the piezoelectric element is a PZT piezoelectric sheet.
[0032] The structural health monitoring method based on electromechanical impedance technology provided in an embodiment of the present application includes: receiving an impedance curve for each test and saving it as a historical impedance curve; and, starting from receiving the impedance curve for the kth test, performing the following steps on each received impedance curve:
[0033] S100: Divide the impedance curve into sub-segments according to the frequency band, calculate the RMSD value of each sub-segment, and construct an RMSD value sequence of the impedance curve based on the RMSD values of the sub-segments; the RMSD value of the sub-segment refers to the root mean square deviation value between the sub-segment and the corresponding sub-segment of the reference impedance curve;
[0034] Assuming that the impedance curve is divided into n sub-segments, the RMSD value sequence of the impedance curve can be expressed as {RMSD i |i=1,2,...n},RMSD i represents the RMSD value of the i-th sub-segment.
[0035] S200: Determine whether the RMSD value of each sub-segment exceeds the first threshold T _RMSD , if none of them exceed the threshold, the structure is currently healthy; if any sub-segment exceeds the threshold, the sub-segment that exceeds the threshold is recorded as an abnormal sub-segment, and step S300 is performed on each abnormal sub-segment one by one; the first threshold T _RMSD It is an engineering experience value. In some embodiments, it is 20%.
[0036] S300: Correcting the RMSD value of the abnormal sub-segment, including: starting from the impedance curve received this time, tracing back to the historical impedance curves of nearly W times, and counting the abnormal sub-segments in the historical impedance curves of nearly W times that exceed the first threshold T _RMSD The number of times S, if S exceeds the number threshold T _S , the RMSD value of the abnormal sub-segment is corrected to the RMSD value multiplied by the reward coefficient; otherwise, the RMSD value of the abnormal sub-segment is corrected to the RMSD value multiplied by the penalty coefficient;
[0037] Considering the statistical requirements, the value of the number of backtracking W should not be less than 20, and the value of k should be greater than W. Taking into account both computational cost and monitoring accuracy, the value of the number of backtracking W is preferably [20, 50]. In some embodiments, the number of backtracking W is 20. The number threshold T _S is an engineering experience value. In some embodiments, the number threshold T _S The value is 15.
[0038] The reward coefficient R is as follows:
[0039]
[0040] In formula (1), n represents the number of sub-segments, T _RMSD represents the first threshold, RMSD Wi-average-pIt represents the average RMSD value of the abnormal sub-segments in the historical impedance curves of the past W times.
[0041] The penalty coefficient p is as follows:
[0042]
[0043] In formula (2), RMSD Wi-average-n It represents the average RMSD value of the abnormal sub-segments in the (WS) historical impedance curves. The (WS) historical impedance curves refer to the historical impedance curves in which the abnormal sub-segments do not exceed the threshold value in the recent W historical impedance curves.
[0044] In this application, the historical impedance curves are accumulated to reflect the long-term state. In this step, these accumulated historical impedance curves are used to calculate the abnormal sub-segments in the historical impedance curves exceeding the first threshold value T. _RMSD The number of times the abnormal sub-segment exceeds the first threshold T is used to determine whether the abnormal sub-segment is a continuous abnormality or a transient fluctuation; when the abnormal sub-segment exceeds the first threshold T _RMSD If the number of abnormal sub-segments exceeds the first threshold T, it is likely that the abnormality is caused by structural damage. The execution of reward measures for abnormal sub-segments can enhance the damage indication. _RMSD If the number of times is small, it is likely to be a transient fluctuation caused by environmental vibration. Penalty measures are performed on the abnormal sub-segment to suppress environmental vibration interference.
[0045] S400: After executing step S300 for all abnormal sub-segments, the RMSD value sequence of the impedance curve in step S100 is updated using the corrected RMSD value of the abnormal sub-segment, and whether the structure is healthy is determined based on the corrected RMSD value sequence.
[0046] The impedance curves of multiple rounds of tests, starting from receiving the impedance curve of the kth test, execute the above steps S100 to S400 for the impedance curves of each round of tests, so that structural damage can be gradually revealed. When it is determined that the structure is damaged, an alarm is triggered.
[0047] In a specific implementation, a piezoelectric element array can be used to monitor the health status of the structure. Specifically, the above processing is performed on the impedance curve of each piezoelectric element in the array, and whether there is structural damage is determined based on the impedance curve of each piezoelectric element, so that damage location can be achieved based on the position of each piezoelectric element.
[0048] In electromechanical impedance technology, the impedance curve of a piezoelectric element is a curve showing the impedance of the piezoelectric element changing with frequency. This curve can be obtained by applying a frequency sweep signal to the piezoelectric element, recording the impedance value of the piezoelectric element corresponding to each frequency sweep point, and obtaining a series of impedance value data D. Based on the impedance value data D, the impedance curve of the piezoelectric element can be obtained.
[0049] The obtained impedance value data D is expressed as follows:
[0050] D=(D1(f1,Ω1),...D j (f j ,Ω j ),...D m (f m ,Ω m )) (3)
[0051] In formula (3), D j (f j ,Ω j ) represents the impedance value measured at the jth sweep frequency point, j = 1, 2, ... m.
[0052] In the above step S100, the impedance curve is divided into sub-segments according to frequency bands, including: using an adaptive method to divide the reference impedance curve into sub-segments, and dividing the impedance curve into sub-segments according to the frequency bands corresponding to the sub-segments divided by the reference impedance curve.
[0053] Furthermore, the reference impedance curve is divided into sub-segments using an adaptive method, including:
[0054] S110: Initialize the starting point of the current sub-segment to the first frequency sweep point, and execute S120;
[0055] S120: Determine whether the starting point of the current sub-segment and the adjacent frequency sweep point behind it meet the merging condition. If so, merge the adjacent frequency sweep point behind it into the current sub-segment, and then execute S130. If not, use the adjacent frequency sweep point behind it as the starting point of the next sub-segment, and continue to execute S120.
[0056] S130: Determine whether the current sub-segment and its subsequent adjacent frequency sweep points meet a merging condition. If so, merge the subsequent adjacent frequency sweep points into the current sub-segment. Repeat S130 until the current sub-segment and its subsequent adjacent frequency sweep points no longer meet the merging condition. Use the subsequent adjacent frequency sweep points as the starting point of the next sub-segment and execute S120.
[0057] The merging condition of the starting point of the current sub-segment and the adjacent sweep frequency point behind it is: the difference in impedance value between the sweep frequency point corresponding to the starting point and the adjacent sweep frequency point behind it is not greater than the impedance threshold τ;
[0058] The merging condition of the current sub-segment and its subsequent adjacent frequency sweep points is as follows: the difference in impedance value between the current sub-segment and its subsequent adjacent frequency sweep points is not greater than the impedance threshold τ, where the impedance value of the current sub-segment is the average of the impedance values of the frequency sweep points it includes.
[0059] It should be noted that the impedance threshold τ is an empirical value. In some embodiments, the impedance value range in the impedance curve tested is 100Ω to 200Ω, and the impedance threshold τ is preferably 10Ω or 20Ω.
[0060] In the above step S400, a specific implementation method of determining whether the structure is healthy based on the corrected RMSD value sequence is:
[0061] S410: Calculate the corrected RMSD value sequence {RMSD i RMSD in '|i=1,2,...n} i 'The average RMSD of the values i-average ';
[0062]
[0063] S420: Determine RMSD i-average Is it greater than a threshold value T? If so, the structure is currently damaged; otherwise, the structure is currently healthy. The threshold value T is an empirical value, determined based on experiments and engineering experience. In some embodiments, the threshold value T is 20%.
[0064] An example is provided below. Figure 2 , shown is a photo of the test platform in the embodiment of this application. A PZT array and a vibration source are arranged on a carbon fiber plate. The PZT array includes PZT plates 1 to 6. The vibration source is used to simulate environmental vibration. Among them, there is damage near PZT plate 4. A sweep frequency signal is applied to each PZT plate, and the impedance curve of the PZT plate is recorded. The impedance curve is processed using the above method of this application to determine the damage. Figure 3 , shown are the RMSD corresponding to each PZT piece i-average ',RMSD i-average 'It can reflect the degree of deviation between the tested impedance curve and the reference impedance curve. The higher the deviation, the greater the probability of damage. Figure 3 It can be seen that there is a high probability of damage near PZT pieces 4 and 6. According to the RMSD of each PZT piece i-average 'Data draws the damage probability cloud map of each PZT piece, see Figure 4 , the damage probability cloud map can more intuitively realize the damage space positioning, from Figure 4 It can be seen that there are damages near PZT sheets 4 and 6.
[0065] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.
Claims
1. A structural health monitoring method based on electromechanical impedance technology, characterized in that: include: The impedance curve of each test is received and saved as a historical impedance curve. At the same time, starting from the impedance curve of the kth test, the following is performed on each received impedance curve: S100: Divide the impedance curve into sub-segments according to the frequency band, calculate the RMSD value of each sub-segment, and construct an RMSD value sequence of the impedance curve based on the RMSD values of the sub-segments; the RMSD value of the sub-segment refers to the root mean square deviation value between the sub-segment and the corresponding sub-segment of the reference impedance curve; S200: Determine whether the RMSD value of each sub-segment exceeds the first threshold T _RMSD , if neither is exceeded, the structure is currently healthy; If any sub-segment exceeds the limit, the sub-segment exceeding the limit is recorded as an abnormal sub-segment, and step S300 is executed for each abnormal sub-segment. S300: Correcting the RMSD value of the abnormal sub-segment, including: starting from the impedance curve received this time, tracing back to the historical impedance curves of nearly W times, and counting the abnormal sub-segments in the historical impedance curves of nearly W times that exceed the first threshold T _RMSD The number of times S, if S exceeds the number threshold T _S , the RMSD value of the abnormal sub-segment is corrected to the RMSD value multiplied by the reward coefficient; otherwise, the RMSD value of the abnormal sub-segment is corrected to the RMSD value multiplied by the penalty coefficient; Among them, the reward coefficient Penalty coefficient n represents the number of sub-segments, RMSD Wi-averager-p Represents the average value of the RMSD value of the abnormal sub-segment in the historical impedance curve of the past W times, RMSD Wi-average-n The average value of the RMSD value of the abnormal sub-segment in the historical impedance curve where the abnormal sub-segment does not exceed the threshold; S400: updating the RMSD value sequence of the impedance curve in step S100 using the correction value of the RMSD value of the abnormal sub-segment, and judging whether the structure is healthy or damaged based on the corrected RMSD value sequence; The value of the above backtracking times W should not be less than 20, and the value of k should be greater than W.
2. The structural health monitoring method based on electromechanical impedance technology according to claim 1, wherein: The dividing the impedance curve into sub-segments according to frequency bands includes: dividing the reference impedance curve into sub-segments using an adaptive method, and dividing the impedance curve into sub-segments according to the frequency bands corresponding to the sub-segments divided by the reference impedance curve.
3. The structural health monitoring method based on electromechanical impedance technology according to claim 2, characterized in that: The method of dividing the reference impedance curve into sub-segments by using an adaptive method includes: S110: Initialize the starting point of the current sub-segment to the first frequency sweep point, and execute S120; S120: Determine whether the starting point of the current sub-segment and the adjacent frequency sweep point behind it meet the merging condition. If so, merge the adjacent frequency sweep point behind it into the current sub-segment, and then execute S130. If not, use the adjacent frequency sweep point behind it as the starting point of the next sub-segment, and continue to execute S120. S130: Determine whether the current sub-segment and its subsequent adjacent frequency sweep points meet a merging condition. If so, merge the subsequent adjacent frequency sweep points into the current sub-segment. Repeat S130 until the current sub-segment and its subsequent adjacent frequency sweep points no longer meet the merging condition. Use the subsequent adjacent frequency sweep points as the starting point of the next sub-segment and execute S120. The merging condition of the starting point of the current sub-segment and the adjacent sweep frequency point behind it is: the difference in impedance value between the sweep frequency point corresponding to the starting point and the adjacent sweep frequency point behind it is not greater than the impedance threshold τ; The merging condition of the current sub-segment and its subsequent adjacent frequency sweep points is as follows: the difference in impedance value between the current sub-segment and its subsequent adjacent frequency sweep points is not greater than the impedance threshold τ, where the impedance value of the current sub-segment is the average of the impedance values of the frequency sweep points it includes.
4. The structural health monitoring method based on electromechanical impedance technology according to claim 1, wherein: The determining whether the structure is healthy based on the corrected RMSD value sequence includes: S410: Calculating the average value of the RMSD values in the corrected RMSD value sequence; S420: Determine whether the average value is greater than a threshold value T. If so, the structure is currently damaged; otherwise, the structure is currently healthy.
5. The structural health monitoring method based on electromechanical impedance technology according to claim 1, wherein: When a piezoelectric element array is used for structural health monitoring, the structural health monitoring method described in claim 1 is used to process the impedance curve of each piezoelectric element in the piezoelectric element array separately and perform health judgment, and damage location based on the position of the piezoelectric element is achieved based on the judgment result of each piezoelectric element.
6. The structural health monitoring method based on electromechanical impedance technology according to claim 1, characterized in that: Also includes: When it is determined in step S400 that the structure is damaged, an alarm is triggered.
7. A structural health monitoring system based on electromechanical impedance technology, characterized in that: include: The first module is used to receive the impedance curve of each test and save it as a historical impedance curve; The second module is used to start from receiving the impedance curve of the kth test and perform the following on each received impedance curve: divide the impedance curve into sub-segments according to the frequency band, calculate the RMSD value of each sub-segment, and construct the RMSD value sequence of the impedance curve from the RMSD values of the sub-segments; the RMSD value of the sub-segment refers to the root mean square deviation value between the sub-segment and the corresponding sub-segment of the reference impedance curve; The third module is used to determine whether the RMSD value of each sub-segment exceeds the first threshold T _RMSD , if neither is exceeded, the structure is currently healthy; If any sub-segment exceeds the limit, the sub-segment will be recorded as an abnormal sub-segment; The fourth module is used to correct the RMSD value of the abnormal sub-segment, including: starting from the impedance curve received this time, looking back to the historical impedance curves of nearly W times, and counting the abnormal sub-segments in the historical impedance curves of nearly W times that exceed the first threshold T _RMSD The number of times S, if S exceeds the number threshold T _S , the RMSD value of the abnormal sub-segment is corrected to the RMSD value multiplied by the reward coefficient; otherwise, the RMSD value of the abnormal sub-segment is corrected to the RMSD value multiplied by the penalty coefficient; Among them, the reward coefficient Penalty coefficient n represents the number of sub-segments, RMSD Wi-averager-p Represents the average value of the RMSD value of the abnormal sub-segment in the historical impedance curve of the past W times, RMSD Wi-average-n The average value of the RMSD value of the abnormal sub-segment in the historical impedance curve where the abnormal sub-segment does not exceed the threshold; The fifth module is used to update the RMSD value sequence of the impedance curve in step S100 using the correction value of the RMSD value of the abnormal sub-segment, and determine whether the structure is healthy based on the corrected RMSD value sequence.
8. The structural health monitoring system based on electromechanical impedance technology according to claim 7, characterized in that: The second module divides the impedance curve into sub-segments according to frequency bands by using an adaptive sub-segment division module to divide the reference impedance curve into sub-segments, and then divides the impedance curve into sub-segments according to the frequency bands corresponding to the sub-segments divided by the reference impedance curve.
9. The structural health monitoring system based on electromechanical impedance technology according to claim 7, characterized in that: The method of dividing the reference impedance curve into sub-segments by using an adaptive method includes: S110: Initialize the starting point of the current sub-segment to the first frequency sweep point, and execute S120; S120: Determine whether the starting point of the current sub-segment and the adjacent frequency sweep point behind it meet the merging condition. If so, merge the adjacent frequency sweep point behind it into the current sub-segment, and then execute S130. If not, use the adjacent frequency sweep point behind it as the starting point of the next sub-segment, and continue to execute S120. S130: Determine whether the current sub-segment and its subsequent adjacent frequency sweep points meet a merging condition. If so, merge the subsequent adjacent frequency sweep points into the current sub-segment. Repeat S130 until the current sub-segment and its subsequent adjacent frequency sweep points no longer meet the merging condition. Use the subsequent adjacent frequency sweep points as the starting point of the next sub-segment and execute S120. The merging condition of the starting point of the current sub-segment and the adjacent sweep frequency point behind it is: the difference in impedance value between the sweep frequency point corresponding to the starting point and the adjacent sweep frequency point behind it is not greater than the impedance threshold τ; The merging condition of the current sub-segment and its subsequent adjacent frequency sweep points is as follows: the difference in impedance value between the current sub-segment and its subsequent adjacent frequency sweep points is not greater than the impedance threshold τ, where the impedance value of the current sub-segment is the average of the impedance values of the frequency sweep points it includes.
10. The structural health monitoring system based on electromechanical impedance technology according to claim 7, characterized in that: The fifth module further includes: The average submodule is used to calculate the average value of the RMSD value in the corrected RMSD value sequence; A judgment submodule is used to judge whether the average value is greater than a threshold value T. If so, the structure is currently damaged; Otherwise, the structure is currently healthy.