CN115792921A - Composite material structure collision source positioning method based on acoustic emission time difference approximation - Google Patents
Composite material structure collision source positioning method based on acoustic emission time difference approximation Download PDFInfo
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Abstract
The invention relates to a composite material structure collision source positioning method based on acoustic emission time difference approximation, which comprises the following steps of 1) obtaining the wave velocity-angle function relation of an acoustic signal on a composite material plate test piece; 2) Acquiring actual time difference vectors of the acoustic signals reaching the receiving sensors; 3) Grid division; 4) Calculating a theoretical time difference vector; 5) Coordinate location of the collision source. The invention compares the theoretical time difference of the receiving sensor with the actual time difference, can effectively solve the problem of positioning the collision source of the composite material plate test piece by approaching the collision source, can effectively position the collision source, and has high positioning precision.
Description
Technical Field
The invention belongs to the technical field of on-orbit safe operation monitoring of spacecrafts, and particularly relates to a composite material structure collision source positioning method based on acoustic emission time difference approximation.
Background
The composite material has the advantages of high specific strength, high specific stiffness, light weight and the like, and becomes a first-choice key manufacturing material in the aerospace industry. Meanwhile, frequent space missions gradually complicate the space environment, and the huge amount of space debris poses a great threat to the safe operation of the spacecraft. In order to ensure the completion of the space mission, an efficient, accurate and real-time collision source positioning system is researched, and it is particularly important to sense and position the collision position at the first time. Due to the fact that the composite material has opposite properties, compared with a metal material, the propagation process of lamb waves in the composite material structure is more complex, attenuation, reflection and other effects exist, the difficulty of analyzing and processing signals is increased, and monitoring efficiency and accuracy are further reduced.
Aiming at the problem of impact positioning, at present, there are several positioning methods based on different theories:
(1) An infrared imaging method: the infrared camera is used for shooting the spacecraft, so that the collision and leakage conditions of infrared radiation detection on the surface of the spacecraft can be monitored in real time.
(2) Resistance thin film method: because the resistance can change when the piezoresistive sensor deforms, a resistance film can be laid on the surface of the aerospace vehicle, and when the aerospace vehicle is deformed due to impact, the impact position can be determined by detecting the potential change.
(3) Fiber grating method: physical parameters of all positions of an object to be measured are collected through the distributed optical fiber sensor so as to determine the integrity of the structure.
(4) An acceleration method: the spacecraft can obtain certain acceleration after encountering space debris impact, and therefore, the collision information can be obtained by detecting the acceleration of the spacecraft.
However, the above method has the disadvantages of complex device, high cost, poor sensitivity, etc., and it is difficult to realize the rapid and accurate positioning of the collision position.
The acoustic emission method has the characteristics of high system integration level, high sensitivity, convenience and quickness in device and the like, and has the advantage of high detection speed. Furthermore, acoustic emission signals can be more complex as they propagate through the composite structure due to the anisotropic physical properties of the composite. Therefore, the patent provides a method for positioning a composite material structure collision source based on acoustic emission time difference approximation.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, provides a composite material structure collision source positioning method based on acoustic emission time difference approximation, can effectively solve the problem of collision source positioning in a composite material plate test-piece-shaped structure, and is high in positioning and measuring accuracy.
The technical problem to be solved by the invention is realized by the following technical scheme:
a composite material structure collision source positioning method based on acoustic emission time difference approximation is characterized in that: the positioning system adopted by the positioning method comprises a composite plate test piece, an amplifier, receiving sensors, a power supply signal separator, an NI acquisition card and a computer, wherein four receiving sensors are symmetrically arranged on the composite plate test piece at equal intervals on two sides of a signal generating point, 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 with the NI acquisition card and the computer;
the method comprises the following steps:
1) Acquiring a wave velocity-angle function of an acoustic signal on a composite material plate test piece: with an original point (500 ) (unit is mm) as an excitation point, in the range of 0-90 degrees and with 10 degrees as increment, placing receiving sensors at two concentric circles of a signal generation point, transmitting a lead-breaking signal at the center of a composite plate test piece, receiving an acoustic signal by the receiving sensors, and determining the wave speed of a certain path as
Since the distance between the two receiving sensors is constant, the measurement A is carried out 0 The wave velocity of a certain path can be obtained by the time difference of the mode reaching two receiving sensors in the same path, the wave velocities of different paths are fitted to a cubic polynomial curve, and the fitted curve can be a function v(θ) represents;
2) Acquiring the actual time difference vector of the sound signal reaching each sensor: determination of A by adaptive thresholding 0 The time points at which the modal signals arrive at the different receiving sensors, the adaptive threshold T is expressed as:
wherein: n is a noise signal intercepted before the signal arrives;
n is the number of points of the truncated signal sequence;
k is the number of sequences used to calculate the threshold point;
determining the time of the sound signal reaching each sensor, and solving the theoretical time difference delta t 'of any two sensors i and j' ij ：
Δt′ ij ＝t i -t j (i≠j)
Calculating to obtain an actual arrival time difference vector T':
T′＝[Δt′ 12 Δt′ 13 … Δt′ ij ](i≠j)
3) Grid division: selecting a proper grid size according to the size of the composite plate test piece, and uniformly grid-dividing the composite plate test piece;
4) Calculating a theoretical time difference vector, and constructing an index matrix: assuming that each grid point is a collision source, since the coordinates of the grid point and the coordinates of the receiving sensors are known, the distance L from the grid point to each receiving sensor can be calculated by the formula:
wherein: lx is the abscissa of the sensor;
ly is the ordinate of the sensor;
x is the abscissa of the grid point;
y is the ordinate of the grid point;
the angle can be obtained by the following formula:
the distances and angles of the grid points to the receiving sensors are known, A 0 The propagation characteristic of the modal signal in the composite plate test piece can be calculated according to the following formula, and the theoretical time t from any grid point to the receiving sensor i can be calculated i ：
The theoretical time difference delta t of any two sensors i and j can be obtained according to the theoretical time from the grid point to the sensors ij ：
Δt ij ＝t i -t j (i≠j)
The time difference of the grid point of the m-th row and the n-th column position reaching any two sensors is constructed into a time difference vector T mn ，
T mn ＝[Δt 12 Δt 13 … Δt ij ](i≠j)
And constructing the time difference vectors of all grid points into a feature index matrix M:
5) Positioning: sequentially comparing the actual time difference vector T' with the theoretical time difference vector T mn Comparing the grid points and calculating the matching error e of the grid points at the m-th row and the n-th column positions mn ，
Generating an error matrix E according to the calculated matching error result:
according to the error matching result, the element coordinate position with the minimum matching error can be regarded as the position of the collision source.
The invention has the advantages and beneficial effects that:
compared with the prior art, the composite material structure collision source positioning method based on acoustic emission time difference approximation compares the theoretical time difference with the actual time difference of the sensor, can effectively solve the problem of collision source positioning of the composite material plate test piece in a collision source approximation mode, can effectively position the collision source, and has high positioning precision.
Drawings
FIG. 1 is a schematic diagram of a positioning system according to the present invention;
FIG. 2 is a diagram of receiving transducer position for obtaining acoustic signal wave velocity versus angle functions;
FIG. 3 is a schematic diagram of the present invention;
FIG. 4 is a flow chart of the present invention;
Detailed Description
The present invention is further illustrated by the following specific examples, which are intended to be illustrative, not limiting and are not intended to limit the scope of the invention.
A composite material structure collision source positioning method based on acoustic emission time difference approximation is innovative in that: the method comprises the following steps:
1) Building a positioning system: the TDOA-based collision sound source positioning system of the composite material plate test piece type structure comprises a carbon fiber composite material plate test piece-shaped structure model piece, an amplifier, a receiving sensor, a power supply signal separator, an NI acquisition card and a computer. Four receiving sensors are symmetrically arranged on the composite plate test piece at equal intervals on two sides of a signal generation point, the four receiving sensors are sequentially connected with an amplifier and a power supply signal separator, and the power supply signal separator is sequentially connected with the NI acquisition card and a computer.
The test piece of the composite material plate IS 1000mm multiplied by 3mm, the material IS T300 carbon fiber/IS 1301 epoxy resin type composite material, the layering IS 15 layers, and the layering direction IS [03/90/03/90/03/90/03]. The edge of the composite plate test piece is pasted with sound absorption daub so as to reduce the influence of echo caused by the reflection effect of the plate edge on measurement. Exciting a lead-breaking signal on a composite material plate test piece to simulate a signal generated by ultra-high-speed impact, wherein the positions of four receiving sensors are respectively arranged according to the wave speed-angle function of the obtained acoustic signal on the test piece or the obtained actual arrival time difference vector and are used for receiving the acoustic signal sent by an impact source, and each receiving sensor is connected with a 40dB amplifier to amplify the signal by 100 times; the amplified signals are transmitted to a computer for processing through an NI acquisition card.
2) Acquiring a wave velocity-angle function of an acoustic signal on a composite material plate test piece: the plane center of a composite plate test piece is used as an original point, two mutually perpendicular symmetrical axes are respectively used as an x axis and a y axis, the upward direction is the positive direction of the y axis, the rightward direction is the positive direction of the x axis, a rectangular coordinate system is established, an excitation point is used as the original point (500 ), a receiver uses 15mm and 45mm as radiuses to draw concentric circles, in the range of 0-90 degrees, 10 degrees are used as increments, sensors are placed at two concentric circles at the same angle, a lead-breaking signal is transmitted at the center of the composite plate test piece, the sensors receive acoustic signals, the wave speed of a certain path is equal to the wave speed of the certain path
Since the distance between the two sensors is constant, by measuring A 0 The wave velocity of a certain path can be obtained by the mode reaching the time difference of the sensor, and a 0-90-degree wave velocity is fitted to a cubic polynomial curve by using MATLAB.
3) Acquiring an actual time difference vector of the lead-breaking signal: uniformly arranging receiving sensors at four corners of a composite plate test piece, wherein coordinates are respectively No. 1 sensor (800 ), no. 2 sensor (0, 800), no. 3 sensor (0, 0) and No. 4 sensor (800, 0), the units of the data are mm, selecting a frequency band where an A0 modal signal is positioned as a filtering frequency band by adopting a self-adaptive threshold method, reasonably setting a threshold value, and measuring A 0 The adaptive threshold T may be expressed as:
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 used for calculating the sequence number of the threshold value point.
Determining the time of arrival of the acoustic signal at each sensor, and solving the theoretical time difference delta t 'between any two sensors i and j' ij ：
Δt′ ij ＝t i -t j (i≠j)
Calculating to obtain an actual arrival time difference vector T':
T′＝[Δt′ 12 Δt′ 13 … Δt′ ij ](i≠j)
4) Grid division: the composite material plate test piece is evenly divided into grids, the calculated amount is increased when the grids are too small, the positioning precision is not high when the grids are too small, the proper grid size is selected according to the size of the composite material structure test plate,
5) Calculating a theoretical time difference vector and an index matrix: assuming that each grid point is a collision source, since the coordinates of the grid point and the coordinates of the receiving sensor are known, the distance from the grid point to each sensor can be calculated by a formula
Wherein: l x Is the abscissa of the receiving sensor;
l y is the ordinate of the receiving sensor;
x is the abscissa of the receiving grid point;
y is the ordinate of the receiving grid point;
the angle can be obtained by the following formula:
knowing the distance and angle from the grid point to the sensor and the propagation characteristic of the A0 modal signal in the composite plate test piece, the theoretical time t from any grid point to the sensor i can be calculated according to the following formula i ：
The theoretical time difference delta t between any two sensors i and j can be obtained according to the theoretical time from the grid point to the sensors ij ：
Δt ij ＝t i -t j (i≠j)
The time difference of each grid point reaching any two sensors is constructed into a time difference vector T mn ，
T mn ＝[Δt 12 Δt 13 … Δt ij ](i≠j)
And constructing the time difference vectors of all grid points into a characteristic index matrix, wherein the index matrix of M is also established as follows:
wherein, T mn Representing the total time difference between the arrival of the grid point at the mth row, nth column position at any two sensors.
6) Error matching, determining an anchor point: sequentially comparing the actual time difference vector T' with the theoretical time difference vector T mn Comparing and calculating the matching error e of the grid points at the m-th row and n-th column positions mn ，
And generating an error matrix E according to the calculated matching error result:
according to the error matching result, the element coordinate position with the minimum matching error can be regarded as the position of the collision source.
Although the embodiments of the present invention and the accompanying drawings are disclosed for illustrative purposes, those skilled in the art will appreciate that: various substitutions, changes and modifications are possible without departing from the spirit and scope of the invention and the appended claims, and therefore the scope of the invention is not limited to the disclosure of the embodiments and the accompanying drawings.
Claims (1)
1. A composite material structure collision source positioning method based on acoustic emission time difference approximation is characterized in that: the positioning system adopted by the positioning method comprises a composite plate test piece, an amplifier, receiving sensors, a power supply signal separator, an NI acquisition card and a computer, wherein four receiving sensors are symmetrically arranged on the composite plate test piece at equal intervals on two sides of a signal generating point, 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 with the NI acquisition card and the computer;
the method comprises the following steps:
1) Acquiring a wave velocity-angle function of an acoustic signal on a composite material plate test piece: using an original point (500 ) (unit is mm) as an excitation point, within the range of 0-90 degrees, using 10 degrees as increments, placing receiving sensors at two concentric circles of a signal generation point, transmitting a lead-breaking signal at the center of a composite plate test piece, receiving an acoustic signal by the receiving sensors, and determining the wave speed of a certain path as
Since the distance between the two receiving sensors is constant, the measurement A is carried out 0 The time difference of the mode reaching two receiving sensors in the same path can be obtainedFitting the wave velocities of different paths to a cubic polynomial curve at the wave velocity of a certain path, wherein the fitted curve can be represented by a function v (theta);
2) Acquiring the actual time difference vector of the sound signal reaching each sensor: determination of A by adaptive thresholding 0 The adaptive threshold T is expressed as:
wherein: n is a noise signal intercepted before the signal arrives;
n is the number of points of the truncated signal sequence;
k is the number of sequences used to calculate the threshold point;
determining the time of the sound signal reaching each sensor, and solving the theoretical time difference delta t 'of any two sensors i and j' ij ：
Δt' ij ＝t i -t j (i≠j)
Calculating to obtain an actual arrival time difference vector T':
T'＝[Δt’ 12 Δt’ 13 …Δt’ ij ] (i≠j)
3) Grid division: selecting a proper grid size according to the size of the composite plate test piece, and uniformly grid-dividing the composite plate test piece;
4) Calculating a theoretical time difference vector, and constructing an index matrix: assuming that each grid point is a collision source, since the coordinates of the grid point and the coordinates of the receiving sensors are known, the distance L from the grid point to each receiving sensor can be calculated by the formula:
wherein: l. the x Is the abscissa of the sensor;
l y is the ordinate of the sensor;
x is the abscissa of the grid point;
y is the ordinate of the grid point;
the angle can be obtained by the following formula:
the distances and angles of the grid points to the receiving sensors are known, A 0 The propagation characteristic of the modal signal in the composite plate test piece can be calculated according to the following formula, and the theoretical time t from any grid point to the receiving sensor i can be calculated i ：
The theoretical time difference delta t of any two sensors i and j can be obtained according to the theoretical time from the grid point to the sensors ij ：
Δt ij ＝t i -t j (i≠j)
The time difference of the grid point of the m-th row and the n-th column position reaching any two sensors is constructed into a time difference vector T mn ，
T mn ＝[Δt 12 Δt 13 …Δt ij ](i≠j)
And constructing the time difference vectors of all grid points into a characteristic index matrix M:
5) Positioning: sequentially comparing the actual time difference vector T' with the theoretical time difference vector T mn Comparing the grid points and calculating the matching error e of the grid points at the m-th row and the n-th column positions mn ，
Generating an error matrix E according to the calculated matching error result:
according to the error matching result, the element coordinate position with the minimum matching error can be regarded as the position of the collision source.
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