Composite structure impact source location method based on acoustic emission time difference approximation

Abstract

The present application relates to a kind of composite structure collision source positioning method based on acoustic emission time difference approximation, comprising 1) obtaining the wave velocity-angle function relationship of acoustic signal in composite plate test piece;2) obtaining the actual time difference vector of acoustic signal to each receiving sensor;3) grid division;4) calculate theoretical time difference vector;5) coordinate positioning of collision source.The present application compares the theoretical time difference of receiving sensor with actual time difference, and by the way of approximating collision source, can effectively solve the collision source positioning problem of composite plate test piece, can effectively carry out the positioning of collision source, and positioning precision is high.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of on-orbit safe operation monitoring of spacecraft, and particularly relates to a composite material structure collision source positioning method based on acoustic emission time difference approximation. BACKGROUND

[0002] Composite materials have the advantages of large specific strength, large specific stiffness and light weight, and have become the preferred key manufacturing material in the aerospace industry. At the same time, frequent space missions have gradually complicated the space environment, and a large number of space debris have posed a great threat to the safe operation of spacecraft. In order to ensure the completion of space missions, it is particularly important to perceive and locate the collision position in the first time by using an efficient, accurate and real-time collision source positioning system. Due to the anisotropy of composite materials, the propagation process of Lamb waves in composite material structures is more complex than that in metal materials, and there are attenuation, reflection and other effects, which increase the difficulty of signal analysis and processing, and further reduce the monitoring efficiency and accuracy.

[0003] For the problem of impact positioning, there are currently the following positioning methods based on different theories:

[0004] (1) Infrared imaging method: an infrared camera is used to take pictures of the spacecraft, which can monitor the infrared radiation of the spacecraft surface in real time to detect the collision and leakage conditions.

[0005] (2) Resistance film method: the resistance of a piezoresistive sensor changes when it is deformed, so a resistance film can be laid on the surface of a spacecraft. When the spacecraft is subjected to impact deformation, the impact position can be determined by detecting the change in electric potential.

[0006] (3) Fiber grating method: the physical parameters of the object to be measured at each position are collected by a distributed optical fiber sensor to determine the integrity of the structure.

[0007] (4) Acceleration method: the spacecraft will obtain a certain acceleration after being hit by space debris, so the collision information can be obtained by detecting the acceleration of the spacecraft.

[0008] However, the above methods have the disadvantages of complex device, high cost, poor sensitivity, etc., and it is difficult to quickly and accurately locate the impact position.

[0009] The acoustic emission method has the advantages of high system integration, high sensitivity, convenient device, fast detection speed, etc. In addition, due to the anisotropic physical properties of composite materials, the acoustic emission signal propagates more complexly in the composite material structure. Therefore, the present application proposes a composite material structure collision source positioning method based on acoustic emission time difference approximation. SUMMARY

[0010] The present application aims at overcoming the deficiencies of the prior art, and provides a composite material structure collision source positioning method based on acoustic emission time difference approximation, which can effectively solve the collision source positioning problem in a composite material plate test specimen structure and has high positioning measurement accuracy.

[0011] The present application solves its technical problems by the following technical solutions:

[0012] A composite material structure collision source positioning method based on acoustic emission time difference approximation, characterized by comprising a positioning system, wherein the positioning system comprises a composite material plate test specimen, an amplifier, a receiving sensor, a power supply signal separator, an NI acquisition card and a computer, four receiving sensors are symmetrically arranged at equal intervals on both sides of a signal generation point on the composite material plate test specimen, the four receiving sensors are sequentially connected with the amplifier and the power supply signal separator, and the power supply signal separator is sequentially connected to the NI acquisition card and the computer.

[0013] The method comprises the following steps:

[0014] 1) Obtaining the wave speed-angle function of the acoustic signal in the composite material plate test specimen: taking the origin (500, 500) (unit: mm) as the excitation point, placing the receiving sensors at two concentric circles of the signal generation point in the range of 0° to 90° with an increment of 10°, emitting a lead breaking signal at the center of the composite material plate test specimen, and receiving the acoustic signal by the receiving sensors, so that the wave speed of a certain path is

[0015]

[0016] Since the distance between the two receiving sensors is certain, the time difference of the A0 mode reaching the two receiving sensors of a certain path can be obtained, the wave speeds of different paths are fitted with a cubic polynomial curve, and the fitting curve can be represented by the function v(θ);

[0017] 2) Obtaining the actual time difference vector of the acoustic signal reaching each sensor: the time points of the A0 mode signal reaching different receiving sensors are determined by using the adaptive threshold value method, and the adaptive threshold value T is represented as:

[0018]

[0019] Wherein: N is the noise signal intercepted before the signal arrives;

[0020] n is the number of points of the intercepted signal sequence;

[0021] k is the sequence number for calculating the threshold point;

[0022] The time of the acoustic signal reaching each sensor is determined, and the theoretical time difference Δt' of any two sensors i and j is obtained ij :

[0023] Δt′ ij =t i -t j (i≠j)

[0024] The actual arrival time difference vector T' is calculated:

[0025] T' = [Δt' 12 Δt' 13 Δt' ij Δt' ](i≠j)

[0026] 3) Meshing: according to the size of the composite plate specimen, select the appropriate mesh size, and uniformly mesh the composite plate specimen;

[0027] 4) Calculate the theoretical time difference vector and construct the index matrix: assume that each grid point is a collision source, since the grid point coordinates and the receiving sensor coordinates are known, the distance L of the grid point to each receiving sensor can be calculated by the formula:

[0028]

[0029] Wherein: lx is the horizontal coordinate of the sensor;

[0030] ly is the vertical coordinate of the sensor;

[0031] x is the horizontal coordinate of the grid point;

[0032] y is the vertical coordinate of the grid point;

[0033] The angle can be obtained by the following formula:

[0034]

[0035] Given the distance and angle of the grid point to the receiving sensor, and the propagation characteristics of the A0 mode signal in the composite plate specimen, the theoretical time t of any grid point to receiving sensor i can be calculated according to the following formula: i :

[0036]

[0037] According to the theoretical time of the grid point to the sensor, the theoretical time difference Δt of any two sensors i and j can be obtained: ij :

[0038] Δt ij =t i -t j (i≠j)

[0039] The time difference of the grid point at the mth row and the nth column position to any two sensors is constructed as a time difference vector T mn ,

[0040] T mn =[Δt 12 Δt 13 … Δt ij ](i≠j)

[0041] The time difference vectors of all grid points are constructed as a feature index matrix M:

[0042]

[0043] 5) positioning: the actual time difference vector T' is compared with the theoretical time difference vector T mn in turn, and the matching error e mn ,

[0044]

[0045] According to the calculated matching error result, an error matrix E is generated:

[0046]

[0047] According to the matching error result, the element coordinate position with the minimum matching error can be considered as the position of the collision source.

[0048] The advantages and beneficial effects of the present application are:

[0049] Compared with the prior art, the composite material structure collision source positioning method based on acoustic emission time difference approximation of the present application compares the theoretical time difference of the sensor with the actual time difference, and through the approximation of the collision source, the collision source positioning problem of the composite material plate specimen can be effectively solved, the collision source can be effectively positioned, and the positioning precision is high. BRIEF DESCRIPTION OF DRAWINGS

[0050] Figure 1 It is a structural schematic diagram of the positioning system of the present application;

[0051] Figure 2 It is a receiving sensor position diagram for obtaining the sound signal wave speed-angle function;

[0052] Figure 3 It is a schematic diagram of the present application;

[0053] Figure 4 It is a flowchart of the present application; DETAILED DESCRIPTION

[0054] The application will be further described in detail below by specific examples, the following examples are only descriptive, not limiting, and cannot limit the protection scope of the application.

[0055] A composite material structure collision source positioning method based on acoustic emission time difference approximation, the innovation of which is that the steps of the method are:

[0056] 1) Build a positioning system: the collision sound source positioning system of the composite material plate test piece structure based on TDOA is composed of a carbon fiber composite material plate test piece structure model, an amplifier, a receiving sensor, a power signal separator, an NI acquisition card and a computer. Four receiving sensors are symmetrically arranged at equal intervals on both sides of the signal generation point on the composite material plate test piece, and the four receiving sensors are sequentially connected with an amplifier and a power signal separator, and the power signal separator is sequentially connected to the NI acquisition card and the computer.

[0057] The composite material plate test piece is 1000mm*1000mm*3mm, the material is T300 carbon fiber / IS1301 epoxy resin type composite material, the layer is 15 layers, and the layer direction is [03 / 90 / 03 / 90 / 03 / 90 / 03 / 90 / 03]. The edge of the composite material plate test piece is pasted with sound-absorbing cement to reduce the echo effect of the edge of the plate. A broken lead signal is excited on the composite material plate test piece to simulate the signal generated by the super-high-speed impact, and four receiving sensors are arranged according to the wave speed-angle function of the acquired acoustic signal on the test piece or the actual arrival time difference vector to receive the acoustic signal emitted by the collision source. Each receiving sensor is connected with a 40dB amplifier to amplify the signal by 100 times; the amplified signal is transmitted to the computer for processing through the NI acquisition card.

[0058] 2) Obtain the wave speed-angle function of the acoustic signal on the composite material plate test piece: take the center of the plane of the composite material plate test piece as the origin, take two mutually perpendicular symmetric axes as the x-axis and y-axis, take the upward direction as the positive direction of the y-axis and the right direction as the positive direction of the x-axis, establish a rectangular coordinate system, and the excitation point is the origin (500, 500). Draw concentric circles with 15mm and 45mm as radii, place sensors at the same angle in the two concentric circles within the range of 0° to 90° with an increment of 10°, and transmit a broken lead signal at the center of the composite material plate test piece. The wave speed of a certain path is

[0059]

[0060] Since the distance between the two sensors is fixed, the time difference of A0 mode reaching the sensor can be determined to obtain the wave speed of a certain path. A cubic polynomial curve is fitted from 0° to 90° using MATLAB.

[0061] 3) Obtain the actual time difference vector of the lead break signal: evenly arrange the receiving sensors on the four corners of the composite material plate test piece, and the coordinates are 1st sensor (800, 800), 2nd sensor (0, 800), 3rd sensor (0, 0), and 4th sensor (800, 0), the units of the above data are mm, the adaptive threshold method is used, the frequency band of A0 modal signal is selected as the filtering frequency band, the threshold is reasonably set, the time points of A0 modal signal reaching different sensors are determined, and the adaptive threshold T can be represented as:

[0062]

[0063] Wherein, N is the noise signal intercepted after the signal does not arrive, n is the point number of the intercepted signal sequence, and k is the sequence number of the threshold point for calculating.

[0064] Determine the time of the sound signal reaching each sensor, and calculate the theoretical time difference Δt' of any two sensors i and j ij :

[0065] Δt′ ij =t i -t j (i≠j)

[0066] The actual arrival time difference vector T' is calculated as:

[0067] T′=[Δt′ 12 Δt′ 13 … Δt′ ij ](i≠j)

[0068] 4) Grid division: evenly divide the composite material plate test piece into grids, too small grid will increase the calculation amount, and too small grid will not be high in positioning accuracy, according to the size of the composite material structure test plate, select appropriate grid size,

[0069] 5) Calculate the theoretical time difference vector and index matrix: assume that each grid point is a collision source, since the grid point coordinates and receiving sensor coordinates are known, the distance of the grid point reaching each sensor can be calculated by the formula

[0070]

[0071] Wherein: l x is the horizontal coordinate of the receiving sensor;

[0072] l y is the vertical coordinate of the receiving sensor;

[0073] x is the horizontal coordinate of the receiving grid point;

[0074] y is the vertical coordinate of the receiving grid point;

[0075] The angle can be obtained by the following formula:

[0076]

[0077] Given the distance and angle of the grid point to the sensor, and the propagation characteristics of the A0 modal signal in the composite plate specimen, the theoretical time t of any grid point to sensor i can be calculated according to the following formula: i

[0078]

[0079] According to the theoretical time of the grid point to the sensor, the theoretical time difference Δt of any two sensors i and j can be obtained ij

[0080] Δt ij = t i - t j (i≠j)

[0081] The time difference of each grid point to any two sensors is constructed into a time difference vector T mn

[0082] T mn = [Δt 12 Δt 13 … Δt ij ](i≠j)

[0083] The time difference vectors of all grid points are constructed into a feature index matrix M, and the index matrix of M is also established as follows:

[0084]

[0085] Where T mn represents the total time difference of the grid point at the mth row and nth column position to any two sensors.

[0086] 6) Error matching, determine the positioning point: compare the actual time difference vector T' with the theoretical time difference vector T mn in turn, calculate the matching error e mn of the grid point at the mth row and nth column position.

[0087]

[0088] According to the calculated matching error result, an error matrix E is generated:

[0089]

[0090] According to the result of error matching, the element coordinate position with the minimum matching error can be considered as the position of the impact source.​​​

[0091] While embodiments of the present application and the foregoing description have been set forth in the context of a particular implementation, it will be apparent to those skilled in the art that variations, changes, and modifications can be made to the present application and that the scope of the application should not be limited to what has been presented in a foregone description or a drawing.

Claims

1. A method for locating a source of impact on a composite structure based on acoustic emission time-difference-of-arrival approximation, the method comprising: The positioning system of the positioning method comprises a composite material plate test piece, an amplifier, a receiving sensor, a power supply signal separator, an NI acquisition card and a computer, four receiving sensors are symmetrically arranged at equal intervals on both sides of a signal generation point on the composite material plate test piece, the four receiving sensors are sequentially connected with the amplifier and the power supply signal separator, and the power supply signal separator is sequentially connected to the NI acquisition card and the computer; ​ The steps of the method are: 1) obtaining the wave velocity-angle function of the acoustic signal on the composite material plate test piece: taking the origin (500, 500) as the excitation point, taking the unit as mm, taking 10° as the increment in the range of 0° to 90°, placing the receiving sensors at two concentric circles of the signal generation point, transmitting the lead-breaking signal at the center of the composite material plate test piece, and receiving the acoustic signal by the receiving sensor, then the wave velocity of a certain path is Since the distance of the two receiving sensors is certain, the time difference of the A0 mode reaching the two receiving sensors of a certain path can be obtained, the wave velocities of different paths are fitted into a cubic polynomial curve, and the fitting curve can be represented by the function v(θ); 2) obtaining the actual time difference vector of the acoustic signal reaching each sensor: the time points of the A0 mode signal reaching different receiving sensors are measured by using the adaptive threshold method, and the adaptive threshold T is represented as: Wherein: N is the noise signal intercepted before the signal arrives; N is the number of points of the intercepted signal sequence; K is the sequence number used to calculate the threshold point; determining the time of arrival of the acoustic signal at each sensor, obtaining the theoretical time difference Δt' of any two sensors i and j ij : Δt' ij = t i - t j , i≠j; The actual arrival time difference vector T' is calculated as: T' = [Δt' 12 Δt' 13 …Δt' ij ], i≠j 3) grid division: according to the size of the composite material plate test piece, a suitable grid size is selected, and the composite material plate test piece is uniformly divided into grids; 4) calculating the theoretical time difference vector and constructing the index matrix: assuming that each grid point is a collision source, since the grid point coordinates and the receiving sensor coordinates are known, the distance L of the grid point reaching each receiving sensor can be calculated by the formula: wherein: l x is the abscissa of the sensor; l y is the longitudinal coordinate of the sensor; X is the horizontal coordinate of the grid point; Y is the vertical coordinate of the grid point; The angle can be obtained by the following formula: Knowing the distance and angle of the grid point to the receiving sensor, and knowing the propagation characteristics of the A0 mode signal in the composite plate specimen, the theoretical time t of any grid point to the receiving sensor i can be calculated according to the following formula i : The theoretical time difference At between any two sensors i and j can be obtained from the theoretical times of the grid points to the sensors ij : Δt ij = t i - t j , i≠j The time difference of the grid point at the mth row and the nth column position to any two sensors is constructed as a time difference vector T mn , T mn = [Δt 12 Δt 13 …Δt ij ], i≠j The time difference vectors of all grid points are constructed into a characteristic index matrix M: 5) Positioning: the actual time difference vector T' is compared with the theoretical time difference vector T mn The matching error e of the grid point at the mth row and nth column position is calculated by comparison mn , According to the calculated matching error result, an error matrix E is generated: According to the matching result of the error, the coordinate position of the matching error minimum element can be considered as the position of the collision source.

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