Space debris impact positioning and damage imaging method based on optical fiber sensing

Abstract

The invention discloses a space debris impact positioning and damage imaging method based on optical fiber sensing, and the method employs an optical fiber sensor pair structure for networking layout, and receives a sensor damage signal containing impact information and impact energy. Based on an adaptive threshold orthogonal wavelet transform denoising algorithm, filtering and denoising the sensor signals before and after the impact of the fragments; a center frequency sensitive to impact damage in each sensor signal is obtained based on a signal denoising and variable mode decomposition method, and a sensor narrowband signal under the center frequency is obtained based on a wavelet window function, so that the waveguide rate of the narrowband signal is obtained. On the basis of optical fiber sensor layout positions and waveguide rates, narrow-band signals before and after impact are analyzed on the basis of a sensor rhombus positioning and damage probability imaging algorithm to realize fragment impact structure positioning and damage envelope and degree imaging. According to the invention, real-time monitoring of in-orbit full-life-cycle fragment impact damage of a space structure can be realized.

Description

Technical Field

[0001] The present invention relates to a space debris positioning and damage imaging method based on optical fiber sensing, which realizes the positioning of debris impact sources and structural damage imaging at positions such as a space station cabin structure by using optical fiber grating sensor networking monitoring. Background Art

[0002] With the development of commercial spaceflight, low-orbit giant constellations represented by StarLink will dramatically increase the space load, and the waste and derivatives generated by the increase in space activities are also increasing, which will pose a serious threat to the safe operation of spacecraft in various countries. The instantaneous impact energy generated by space debris at high speeds will cause destructive damage to the structure of the spacecraft. Even the cumulative damage effect of centimeter-level, millimeter-level or even micron-level debris after high-speed collision will cause the spacecraft's structural bearing capacity to decrease, which will lead to a decrease in spacecraft performance at the least and even cause spacecraft function failure at the worst.

[0003] At present, the removal and protection of space debris is still a global problem. Among them, active removal mostly uses space robots to capture and drag debris to the graveyard orbit in a net-like manner; while the structural protection of spacecraft is achieved through a combination of passive and active protection. On the one hand, passive space protection technology is used to increase the structural strength through spacecraft structural design, ground tests, etc., but the above methods will increase the cost of spacecraft development; on the other hand, structural health monitoring technology is used to measure the parameters of the entire life cycle of the spacecraft structure during on-orbit operation in real time, and timely locate and image the impact damage of the spacecraft structure. In summary, in order to meet the long-life and high-reliability on-orbit work goals of the new generation of spacecraft with on-orbit maintenance needs represented by the space station, and to improve the efficiency and safety of spacecraft on-orbit operation, monitoring and imaging technology research is carried out around the structural damage caused by the impact load of space debris, and intelligent structural sensing technology is used to realize the on-orbit status monitoring of spacecraft.

[0004] Current research on monitoring space debris of spacecraft structures based on structural health monitoring technology mostly uses three monitoring technologies: acoustic emission, piezoelectric and fiber grating sensors.

[0005] Problems with acoustic emission monitoring methods in space station structure monitoring:

[0006] Acoustic emission technology is an active structural damage monitoring technology. Its impact source positioning is mostly analyzed by combining time difference positioning and regional positioning. However, in the detection of space structure impact damage, a signal source probe is required, and the signal-to-noise ratio of the received signal is high. The sensor is affected by space radiation and electromagnetic interference, which will cause loss of information in the transmission of electrical signals. In addition, the multi-layer structure will make the signal superposition complex, so it is more difficult to strip off the signal characteristic parameters that are sensitive to debris impact. Therefore, the requirements for signal denoising algorithms are more stringent in actual engineering applications.

[0007] Problems with piezoelectric monitoring technology in space station structure monitoring:

[0008] (1) Lamb-based structural damage monitoring research is only applicable to thin plate structures, and the structural plates are in a plane stress state. The space station structural plates are non-single-layer metal thin walls, so the above method will not be suitable for Lamb's propagation principle during waveform propagation, and there will be problems of multiple waveforms being mixed. In the process of extracting the characteristic parameters of the impact load generated by the debris, the monitoring accuracy is affected due to the poor waveform signal-to-noise ratio;

[0009] (2) This method mostly uses piezoelectric excitation, but the piezoelectric demodulation system is easily affected by spatial electromagnetic interference, resulting in reduced monitoring efficiency. In addition, for composite sandwich structures, the integration of sensors and structures is poor, resulting in a decrease in structural strength caused by built-in sensors and the creation of structural weak areas.

[0010] There are still several problems in the engineering practice based on the above monitoring methods:

[0011] (1) The technology of locating the structural impact source through time difference analysis of sensor networking can only solve one impact position point. The linear layout uses two sensor points for elliptical positioning, and the sensor triangle layout will cause the coexistence of true and false impact points. Although the diamond layout will eliminate false impact points, it can only solve the impact position coordinates. In addition, in engineering applications, the damage to the space structure caused by the impact of space debris should be an irregular area, not a point position. The impact position obtained by previous research methods also has certain errors due to the signal processing process, and it is impossible to achieve damage imaging of the impact area.

[0012] (2) The black box model between the sensor signal and the impact source position established through ground tests ignores the inconsistency between the space structure and the ground structure, and the inconsistency between the ground test environment and the space environment. In addition, this method is highly dependent on structural information. If the size and material of the structure are changed, a new relationship model needs to be re-established, and the model has poor adaptability. Summary of the invention

[0013] The technical problem solved by the present invention is: to overcome the shortcomings of the prior art, to provide a space debris impact positioning and damage imaging method based on optical fiber sensors, and to adopt an impact damage probability reconstruction method to achieve the positioning reconstruction and damage imaging of the impact source of structural debris under the impact of space debris.

[0014] The technical solution of the present invention is: a method for space debris impact positioning and damage imaging based on optical fiber sensing, comprising:

[0015] Conduct fiber Bragg grating sensor configuration layout on the space target structure and collect sensor ultrasonic signals;

[0016] The central frequency of each sensor signal that is sensitive to impact damage is obtained based on the signal denoising and variable mode decomposition method, and the sensor narrowband signal at the central frequency is obtained based on the wavelet window function, and then the waveguide velocity of the narrowband signal is obtained;

[0017] The sensor diamond layout positioning and damage probability algorithm are used to process the sensor narrowband ultrasonic signal and waveguide velocity to complete the structural debris impact positioning and damage imaging.

[0018] The fiber grating sensor is selected to have a grating length of 3-5 mm.

[0019] The fiber grating sensor configuration layout adopts a surrounding monitoring layout configuration, and each monitoring position point adopts a 0°, 45°, and 90° strain gauge flower sensor layout.

[0020] The method of obtaining the center frequency of each sensor signal that is sensitive to impact damage based on the signal denoising and variable mode decomposition method, and obtaining the sensor narrowband signal at the center frequency based on the wavelet window function, and then obtaining the waveguide velocity of the narrowband signal, includes:

[0021] Based on the obtained sensor ultrasonic signal data, a denoising algorithm based on adaptive threshold orthogonal wavelet transform is used to filter and denoise the sensor ultrasonic signal;

[0022] The sensor ultrasonic signal after filtering and denoising is modally decomposed by a variable mode decomposition algorithm to obtain the center frequency of the sensor low-frequency ultrasonic signal that is highly sensitive to impact damage;

[0023] The wavelet window function is used to extract the narrow-band ultrasonic signal of the sensor in the central frequency range. Based on the line sensor array positioning method, the time difference of the narrow-band ultrasonic signal of the sensor at different positions on different sensor paths is obtained, and then the waveguide velocity of the narrow-band ultrasonic signal received by the sensor in the spatial structure plate is solved.

[0024] When the denoising algorithm based on adaptive threshold orthogonal wavelet transform is used to filter and denoise the sensor signal data, the wavelet soft threshold function used is specifically:

[0025]

[0026] sign() is the sign function, d i represents the ith sensor signal after the debris impact, T i is the noise threshold of the i-th sensor signal, d l Represents the calculated wavelet soft threshold.

[0027] The noise threshold value T of the i-th sensor signal i Specifically expressed as:

[0028]

[0029] Among them, E i represents the energy of the i-th sensor signal, j is the number of wavelet layers, N is the signal length, σ i is the standard deviation of the noise.

[0030] The standard deviation of the noise σ i The median c of the lowest wavelet coefficients in the sensor signal j It is estimated that:

[0031]

[0032] The method of using the sensor diamond layout positioning and damage probability algorithm to process the sensor narrowband ultrasonic signal and waveguide velocity to complete the structural debris impact positioning and damage imaging includes:

[0033] Based on the obtained narrow-band ultrasonic signals of the sensors and the waveguide velocity of the narrow-band ultrasonic signals in the space structure plate, the sensors are arranged in a diamond shape to calculate the time difference between the signals of the horizontal group and the vertical group of sensors caused by the impact energy generated by the structure plate when it is hit by space debris, and based on the obtained waveguide velocity, the preliminary positioning of the debris impact source is achieved;

[0034] Based on the preliminary positioning of damage after debris impacts the structural plate, combined with the damage probability imaging algorithm, the damage position and degree of damage in the irregular structural area formed after the debris impact can be imaged.

[0035] The characteristic value SDC in the damage probability imaging algorithm ij Specifically:

[0036]

[0037] Among them, B ijis the received signal of the i-th and j-th fiber Bragg grating sensors without impact, D ij is the received signal of the i-th and j-th fiber Bragg grating sensors after the debris impact, t k is the time of the narrowband ultrasonic signal in the kth path, N is the total number of sensor paths, and μ is the average value of the sensor signal amplitude;

[0038] According to the obtained eigenvalue SDC ij Value and the characteristic value SDC ij The damage imaging prior space probability distribution S ij (x,y), completing structural fragment impact positioning and damage imaging.

[0039] When structural line damage occurs, in order to extrapolate the uniqueness of the sensor path on the ultrasonic propagation path, the eigenvalue SDC ij The damage imaging prior space probability distribution S ij (x,y) is represented as:

[0040]

[0041] In the formula, (x i ,y i ) is the coordinate position of the i-th sensor, (x j ,y j ) is the coordinate position of the jth sensor, Q ij It is the ratio of the distance between any two fiber Bragg grating sensors and the space debris impact source to the distance between the two sensors; β is the shape parameter.

[0042] The advantages of the present invention compared with the prior art are:

[0043] 1) The instantaneous impact energy generated by space debris at ultra-high speed impact will cause destructive damage to the spacecraft structure. Compared with the previous technology that can only locate the coordinate position of the impact point, the present invention can achieve envelope positioning of the unexpected irregular structural damage area caused by space debris, and perform probabilistic imaging of the structural damage after the impact, and finally realize the visual interface confirmation of the damage degree and damage location.

[0044] 2) The present invention processes the sensor signal by combining variable mode decomposition with wavelet window function to extract the sensor narrowband signal. Compared with the traditional wavelet transform and empirical mode decomposition methods, the method of the present invention has advantages in dealing with mode mixing and mode aliasing problems, extracting periodic impulses and suppressing noise.

[0045] 3) The present invention improves the wavelet soft threshold function and comprehensively considers the characteristics of the sensor receiving signal, which can effectively strip off the noise-doped data to obtain sensor signal data with a high signal-to-noise ratio. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a flow chart of the space debris impact location and damage imaging method based on fiber Bragg grating sensors;

[0047] Figure 2 It is the layout of fiber Bragg grating strain rosette, the propagation of impact wave along the structural plate and the sensing mechanism diagram of fiber Bragg grating sensor;

[0048] Figure 3 It is the configuration layout of fiber Bragg grating sensor and the principle diagram of sensor data acquisition;

[0049] Figure 4 It is the waveform diagram of the impact signal received by the fiber grating sensor;

[0050] Figure 5 It is a schematic diagram of the location and visualization of damage to structures impacted by space debris;

[0051] Figure 6 This is the principle diagram of imaging irregular impact areas of space debris based on the damage probability imaging algorithm. DETAILED DESCRIPTION

[0052] The technical method of the present invention is described in detail below with reference to the accompanying drawings.

[0053] The present invention is a method for locating space debris impact and imaging damage based on optical fiber sensing. The overall process of the method is as follows: Figure 1 shown.

[0054] The specific implementation steps of the present invention are as follows:

[0055] 1) Layout the fiber grating sensor configuration on the space target structure and collect the sensor ultrasonic signal

[0056] Step 1: Choose a fiber Bragg grating sensor with the appropriate grating length

[0057] The monitoring of the upper frequency limit of the ultrasonic wave generated by the impact of space debris is limited by the length of the fiber Bragg grating sensor. The fiber Bragg grating sensor should be less than half of the wavelength of the ultrasonic signal. At this time, the fiber Bragg grating sensor can effectively receive the sensor ultrasonic damage signal generated by the impact of debris. The wavelength of the ultrasonic signal is inversely proportional to the frequency and proportional to the wave speed. Therefore, the fundamental frequency response of the structural plate can be used as the input for selecting the sensor grating length.

[0058] At present, the common grating lengths of fiber Bragg grating sensors are 3mm, 5mm, and 10mm. If the grating length of the selected fiber Bragg grating sensor is smaller, the limit on the ultrasonic wavelength and frequency will be lower. However, the reflectivity of the fiber Bragg grating sensor is proportional to the grating length. If the grating length is too low, the reflectivity is too low and the sensor sensitivity decreases. Therefore, a fiber Bragg grating sensor with a grating length of 3-5mm is used. The fiber Bragg grating sensor with this grating length can not only sense the multi-physical field of structural temperature and strain coupling, but also be sensitive to space debris impact signals.

[0059] Step 2: Bulkhead structure fiber Bragg grating sensor configuration layout

[0060] Based on the principle that fiber Bragg grating sensors are more sensitive to strain waves in the axial direction of the grating, a 0°, 45°, and 90° sensor strain rosette layout is used. By comparing the sensor signal strength at three angles at the same wall panel position point, the direction of the impact source can be predicted. The fiber optic sensor with the largest spectral deformation and the smallest correlation coefficient before and after the impact of space debris is selected, and the equivalent extension along the grating axial direction is used. The impact source is located on the extension line. Figure 2 shown.

[0061] In addition, in order to achieve full coverage of the target monitoring wall panel area and effectively capture the impact source waveform data, fiber grating sensor strain rosette layout is used at the four corners and boundaries of the monitoring area. By collecting sensor data at different time points, a three-dimensional data matrix model based on sensor signals, sensor positions and time is established. Figure 3 shown.

[0062] 2) Based on the signal denoising and variable mode decomposition method, the center frequency of each sensor signal that is sensitive to impact damage is obtained, and the sensor narrowband signal at the center frequency is obtained based on the wavelet window function, and then the waveguide velocity of the narrowband signal is obtained.

[0063] When the space structure wall is hit by ultra-high-speed debris, the fiber grating sensors at different positions will receive the flat ultrasonic waves generated by the impact strain energy, such as Figure 4 shown.

[0064] Step 1: Use a denoising algorithm based on adaptive threshold orthogonal wavelet transform to filter and denoise the sensor ultrasonic signal data

[0065] In order to locate the impact source, it is necessary to select the waveform data that is most sensitive to the impact position as the input of the subsequent debris impact location and imaging algorithm. Due to the influence of the superimposed waves generated by ultrasonic refraction and reflection, the collected sensor signal needs to be filtered and denoised. Through the signal denoising method of adaptive threshold orthogonal wavelet transform, a wavelet packet with high similarity to the ultrasonic waveform signal received by the optical fiber sensor is selected. The wavelet function is sym5, and the number of decomposition layers is 5. On this basis, the noise data doped with the signal is stripped off, and then a sensor signal with a high signal-to-noise ratio is obtained.

[0066] For sensor signal denoising in debris impact monitoring, wavelet soft threshold denoising should be selected. Considering the different energies of different spectral signals, the improved wavelet soft threshold function of the present invention is shown in formula (1):

[0067]

[0068] sign() is the sign function, d i represents the ith sensor signal after the debris impact, T i is the noise threshold of the ith sensor signal, d l represents the calculated wavelet soft threshold. The noise component in the sensor signal collected before and after the debris impact is not a standard quantity, and its energy distribution is different. Therefore, different thresholds T should be defined in the i-th sensor signal. i See formula (2):

[0069]

[0070] Among them, E i It represents the energy of the i-th sensor signal, j is the number of wavelet layers. As j increases, lg(j+1) increases, and the threshold T i The gradual decrease is in line with the noise law. The standard deviation of the noise σ i The median c of the lowest wavelet coefficients in the sensor signal j Make an estimate, N is the sensor signal length, see formula (3).

[0071]

[0072] Step 2: The sensor ultrasonic signal data after filtering and denoising is used to obtain the signal center frequency with high sensitivity to impact damage through the variable mode decomposition algorithm, and the sensor narrowband signal at the center frequency is extracted based on the wavelet window function, and the narrowband signal waveguide velocity is calculated.

[0073] Since the complex signal is formed by the superposition of multiple amplitude-modulated and frequency-modulated sub-signals, in order to extract waveform data that is sensitive to the position of the impact source, it is necessary to use the variational mode decomposition (VMD) method to perform modal decomposition on the denoised optical fiber sensor signal, and perform signal decomposition by finding the minimum modal bandwidth of the sensor signal. The variable mode decomposition algorithm should predefine the number of decomposition layers K of the algorithm. Too many decomposition layers will cause computational redundancy of the algorithm, and too few decomposition layers will lead to incomplete signal decomposition. The present invention defines the number of decomposition layers K as 6 layers and the balance parameter α as 200. Among them, the low-frequency mode retains the low-frequency spectrum characteristics of the initial signal of the sensor, and its vibration signal characteristics and amplitude are similar to the initial signal of the sensor; while the modal signal similarity between the high-frequency modal signal and the initial signal of the sensor is high.

[0074] The location of space debris impact is based on the principle of waveform propagation. The distance between the impact source and the sensor is calculated as the product of the wave velocity and the time when the optical fiber sensor receives the signal. The wave velocity is solved by the ratio of the sensor distance difference to the sensor receiving signal time difference. The denoised sensor signal can be decomposed at different center frequencies by the VMD algorithm, and the center frequency close to the intrinsic mode component 1 (IMF1) is selected as the center frequency of the original signal extraction. This method is based on the principle that the low-frequency mode maintains the low-frequency characteristics of the original signal and has similar amplitudes. In addition, the impact energy represented by the signal amplitude is the most important information for monitoring the impact source.

[0075] The narrowband signal of the sensor with a center frequency close to the center frequency of IMF1 is extracted by the wavelet window function method. The narrowband signal processing of different sensors can obtain the signal time difference of the ultrasonic signal caused by the debris impact to different sensors. Through the ground lead break simulation impact test, based on the line sensor array positioning method, the optical fiber sensor signal time difference at different positions on different propagation paths is obtained to solve the propagation rate of the narrowband ultrasonic signal of the fiber Bragg grating sensor on the space structure plate. The waveguide velocity can provide support for the subsequent solution of the distance information between the debris impact source and the sensor, and realize the positioning of the debris impact source.

[0076] 3) Use the sensor diamond layout positioning and damage probability algorithm to process the sensor narrowband ultrasonic signal and waveguide velocity to complete the structural debris impact positioning and damage imaging

[0077] Based on the research on the propagation rate of ultrasonic impact waves in space structural plates, combined with the configuration layout of fiber grating sensors, the location of the impact source of space debris can be realized. Among them, based on the sensor diamond layout method to solve the impact source and realize the preliminary location of damage, combined with the damage probability imaging algorithm, the damage imaging of irregular areas caused by debris impact can be realized, such as Figure 5 shown.

[0078] Step 1: Preliminary location of debris impact source using diamond sensor layout based on sensor narrowband ultrasonic signal

[0079] According to the configuration layout of the fiber grating sensor on the structural plate, the sensor signals at the diagonal positions of the diamond are used to predict the location of the impact source. For example, the horizontal sensors 7 and 15 are grouped together with a horizontal length of a; the vertical sensors 3 and 11 are grouped together with a vertical length of b. Figure 3 When the structural plane is hit by space debris, the time when sensors 3, 7, 11, and 15 receive the impact energy generated by the debris impact is t3, t7, and t 11 and t 15 , where the time difference generated for the horizontal group sensors (7, 15) is Δt X , which generates a time difference of Δt for the vertical group sensors (3, 11) Y , then:

[0080] Δt X =t7-t 15

[0081] Δt Y =t3-t 11 (4)

[0082] According to the spatial structure surface wave velocity V calculated in step 2, the sign function sgn() is given, and the location of the impact source (X, Y) can be realized:

[0083]

[0084] Through the diamond layout of multiple groups of sensors, the first group (2,8,10,16), the second group (2,7,10,15), the third group (2,6,10,14), the fourth group (3,8,11,16), the fifth group (3,7,11,15), the sixth group (3,6,11,14), the seventh group (4,8,12,16), the eighth group (4,7,12,15), and the ninth group (4,6,12,14), nine impact source positions are calculated according to formula (5). The above positioning points can be used to preliminarily determine the two-dimensional coordinate position of the debris impact source.

[0085] Step 2: Based on the sensor diamond layout method to solve the impact source and achieve preliminary damage positioning, combined with the damage probability imaging algorithm, the damage position and degree of the irregular structural area formed after the fragment impact are imaged.

[0086] Based on the preliminary determination of the impact source location based on the diamond sensor layout, the damage probability imaging algorithm can be combined to realize the imaging of the impact area, such as Figure 6The waveform signal of the diagonally arranged fiber Bragg grating sensor is analyzed, and the sensor signal amplitude data representing the impact strain energy is used as input to calculate the correlation coefficient and characteristic value SDC of the sensor narrow-band ultrasonic signal before and after the impact. ij , see formula (6).

[0087]

[0088] SDC ij =1-ρ ij

[0089] In the formula, B ij is the received signal of the i-th and j-th fiber Bragg grating sensors without impact, D ij is the received signal of the i-th and j-th fiber Bragg grating sensors under the impact state, ρ ij is the correlation coefficient, t k is the time of the narrowband ultrasonic signal in the kth path, N is the total number of sensor paths, and μ is the average value of the sensor signal amplitude.

[0090] When structural line damage occurs, in order to further extrapolate the debris impact source position and receive the SDC of the fiber Bragg grating sensor along the straight line propagation direction ij Unique value, defining the prior spatial probability distribution S ij (x,y) is as follows:

[0091]

[0092] β=1.005

[0093]

[0094] In the formula, (x i ,y i ) is the coordinate position of the i-th sensor, (x j ,y j ) is the coordinate position of the jth sensor, Q ij It is the ratio of the distance between any two fiber Bragg grating sensors and the space debris impact source to the distance between the two sensors. β is the shape parameter, which has a significant impact on the damage area in the damage imaging image and is set to 1.005.

[0095] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solution of the present invention by using the technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for space debris impact positioning and damage imaging based on optical fiber sensing, It is characterized in that include: Conduct fiber Bragg grating sensor configuration layout on the space target structure and collect sensor ultrasonic signals; Obtaining the center frequency of each sensor signal that is sensitive to impact damage, and obtaining the sensor narrowband signal at the center frequency based on the wavelet window function, and then obtaining the waveguide velocity of the narrowband signal; The sensor narrowband ultrasonic signal and waveguide velocity are processed to complete the structural debris impact location and damage imaging.

2. According to the method of claim 1, a method for space debris impact positioning and damage imaging based on optical fiber sensing, It is characterized in that The fiber grating sensor is selected to have a grating length of 3-5 mm.

3. The method for space debris impact positioning and damage imaging based on optical fiber sensing according to claim 1, It is characterized in that The fiber grating sensor configuration layout adopts a surrounding monitoring layout configuration, and each monitoring position point adopts a 0°, 45°, and 90° strain gauge flower sensor layout.

4. The method for space debris impact positioning and damage imaging based on optical fiber sensing according to claim 1, It is characterized in that The method of obtaining a center frequency sensitive to impact damage in each sensor signal, and obtaining a sensor narrowband signal at the center frequency based on a wavelet window function, and then obtaining a waveguide velocity of the narrowband signal, includes: Filtering and denoising the obtained ultrasonic signal of the sensor; The sensor ultrasonic signal after filtering and denoising is modally decomposed by a variable mode decomposition algorithm to obtain the center frequency of the sensor low-frequency ultrasonic signal that is highly sensitive to impact damage; The wavelet window function is used to extract the narrow-band ultrasonic signal of the sensor in the central frequency range. Based on the line sensor array positioning method, the time difference of the narrow-band ultrasonic signal of the sensor at different positions on different sensor paths is obtained, and then the waveguide velocity of the narrow-band ultrasonic signal received by the sensor in the spatial structure plate is solved.

5. The method for space debris impact positioning and damage imaging based on optical fiber sensing according to claim 4, It is characterized in that The sensor signal data is filtered and denoised using a denoising algorithm based on adaptive threshold orthogonal wavelet transform. The wavelet soft threshold function used is: sign() is the sign function, d i represents the ith sensor signal after the debris impact, T i is the noise threshold of the i-th sensor signal, d l Represents the calculated wavelet soft threshold.

6. The method for space debris impact positioning and damage imaging based on optical fiber sensing according to claim 5, It is characterized in that The noise threshold value T of the i-th sensor signal i Specifically expressed as: Among them, E i represents the energy of the i-th sensor signal, j is the number of wavelet layers, N is the signal length, σ i is the standard deviation of the noise.

7. The method for space debris impact positioning and damage imaging based on optical fiber sensing according to claim 6, It is characterized in that The standard deviation of the noise σ i The median c of the lowest wavelet coefficients in the sensor signal j It is estimated that:

8. The method for space debris impact positioning and damage imaging based on optical fiber sensing according to claim 1, It is characterized in that The processing of the narrowband ultrasonic signal of the sensor and the waveguide velocity to complete the structural debris impact positioning and damage imaging includes: Based on the obtained narrow-band ultrasonic signals of the sensors and the waveguide velocity of the narrow-band ultrasonic signals in the space structure plate, the sensors are arranged in a diamond shape to calculate the time difference between the signals of the horizontal group and the vertical group of sensors caused by the impact energy generated by the structure plate when it is hit by space debris, and based on the obtained waveguide velocity, the preliminary positioning of the debris impact source is achieved; Based on the preliminary positioning of damage after debris impacts the structural plate, combined with the damage probability imaging algorithm, the damage position and degree of damage in the irregular structural area formed after the debris impact can be imaged.

9. The method for space debris impact positioning and damage imaging based on optical fiber sensing according to claim 8, It is characterized in that The characteristic value SDC in the damage probability imaging algorithm ij Specifically: Among them, B ij is the received signal of the i-th and j-th fiber Bragg grating sensors without impact, D ij is the received signal of the i-th and j-th fiber Bragg grating sensors after the debris impact, t k is the time of the narrowband ultrasonic signal in the kth path, N is the total number of sensor paths, and μ is the average value of the sensor signal amplitude; According to the obtained eigenvalue SDC ij Value and the characteristic value SDC ij The damage imaging prior space probability distribution S ij (x,y), completing structural fragment impact positioning and damage imaging.

10. The method for space debris impact positioning and damage imaging based on optical fiber sensing according to claim 9, It is characterized in that When structural line damage occurs, in order to extrapolate the uniqueness of the sensor path on the ultrasonic propagation path, the eigenvalue SDC ij The damage imaging prior space probability distribution S ij (x,y) is represented as: In the formula, (x i ,y i ) is the coordinate position of the i-th sensor, (x j ,y j ) is the coordinate position of the jth sensor, Q ij It is the ratio of the distance between any two fiber Bragg grating sensors and the space debris impact source to the distance between the two sensors; β is the shape parameter.

Images