Spacecraft Discontinuous Structure Debris Collision Location Method with Acoustic Wave Propagation Path Correction

Abstract

The present invention relates to a method for locating debris collisions of a spacecraft with a discontinuous structure by correcting the acoustic wave propagation path, which can achieve precise positioning of debris collisions of the spacecraft with a discontinuous structure, improve the positioning accuracy, and facilitate timely repair of spacecraft damage caused by space debris collisions.

Description

Technical Field

[0001] The present invention belongs to the technical field of spacecraft structural health detection, and particularly relates to a method for locating debris collisions of a non - continuous structure of a spacecraft with corrected acoustic wave propagation paths. Background Art

[0002] Space debris is one of the important factors affecting the long - term sustainable development of human space activities. Inevitable accidents in space, such as explosions or collisions caused by meteoroids and abandoned space facilities, will generate a large amount of space debris, which poses a safety hazard to the normal operation of spacecraft. To reduce the threat of space debris to spacecraft, it is an important means to quickly and accurately locate the position where the debris collides with the spacecraft, detect the degree of collision and repair it as appropriate.

[0003] In isotropic structures, locating acoustic emission sources based on the time difference of signals arriving at a given sensor (TDOA method) has been widely used. This method is based on the assumption of isotropic wave velocity and an uninterrupted propagation path. The structure of a spacecraft is complex, with non - continuous structures such as portholes, hatches, and penetrators. The propagation of acoustic waves is restricted in them, and the traditional TDOA method is no longer applicable. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a method for locating debris collisions of a non - continuous structure of a spacecraft with corrected acoustic wave propagation paths, which can achieve precise positioning of debris collisions in the non - continuous structure of the spacecraft.

[0005] The present invention solves its technical problems through the following technical solutions:

[0006] A method for locating debris collisions of a non - continuous structure of a spacecraft with corrected acoustic wave propagation paths, characterized in that the steps of the method are as follows:

[0007] 1) Set up a detection system: The detection system used in the positioning method includes piezoelectric sensors, signal amplifiers, signal acquisition cards and computers. The piezoelectric sensors and the metal part to be measured are installed together through brackets. With the penetration part of the metal part to be measured as the center of the circle, 4 piezoelectric sensors are evenly distributed in a circle at the same radius position of the center of the circle. The 4 piezoelectric sensors are jointly connected to the signal amplifier, the signal amplifier transmits the collected signal to the signal acquisition card, and the signal acquisition card transmits the signal to the computer;

[0008] 2) Assume that the penetration - shaped structure of a special part of the spacecraft is similar to a flat plate with holes, and divide this flat plate into multiple regions using a grid, establish a matrix matching the grid. Let each intersection point of the grid be a matrix node (i, j). Assume that the signal excitation source is a grid node, that is, the matrix node (i, j). The theoretical shortest distance from this node to the k - th sensor can be obtained through path analysis The propagation time from this node to the k-th sensor is:

[0009]

[0010] where: v is the wave velocity;

[0011] Since this array selects to use four piezoelectric sensors, the difference in propagation time from the node (i, j) to two different sensors l and m that can be obtained through path processing is:

[0012]

[0013] In addition, through actual signal analysis, the initial time when the four sensors receive the S0-mode Lamb wave can be obtained, and the time difference between the signals received by two different sensors l and m is calculated

[0014]

[0015] By calculating D xy the time deviation degree of each node (i, j), that is, the position point (x, y) can be obtained, and each grid node will obtain the corresponding D xy value. The closer the position point (x, y) is to the true signal generation point (x0, y0), the smaller the D xy value; for all position points (x, y), the position corresponding to the minimum D xy is the signal generation point, so the positioning of the collision can be achieved;

[0016] 3) If the time deviation degree D of the grid node xy does not meet the threshold requirement, secondary grid division can be performed on the basis of the initial positioning result to establish a denser grid, or interpolation can be used to estimate the time to calculate the part between grid nodes to improve the accuracy;

[0017] 4) Use COMSOL software to perform simulation analysis on the flat plate to be measured. The propagation of Lamb waves follows the Huygens-Fresnel theorem. When Lamb waves pass through an obstacle, they will bypass the obstacle and form a new wavefront. The signal generated by the signal source reaches the sensor through the shortest path, that is, make the tangents of the signal source and the sensor to the circular hole respectively. The sum of the tangent length and the arc length corresponding to the tangent point is the propagation path of the Lamb wave. If when the four sensors receive the Lamb wave signal, the signal reception path of at least one sensor does not follow a straight line, the route needs to be re-planned;

[0018] 5) Make the tangents of the signal source, the sensor and the circle and record their lengths. The sum of this length and the arc length corresponding to the tangent point is the signal propagation path If the propagation of the signal is unobstructed and the propagation path is a straight line, the collision point can be determined according to the algorithm flow of step 3) after determining the path.

[0019] The advantages and beneficial effects of the present invention are as follows:

[0020] A method for positioning the collision of non - continuous structure debris of a spacecraft with corrected acoustic wave propagation path proposed by the present invention can achieve precise positioning of the collision of debris of the non - continuous structure of the spacecraft, improve the positioning accuracy, and facilitate the timely repair of the damage to the spacecraft caused by the collision of space debris. Brief Description of the Drawings

[0021] Figure 1 It is a schematic diagram of the system structure of the present invention:

[0022] Figure 2 It is a schematic diagram of the Lamb wave dispersion curve of the present invention:

[0023] Figure 3 It is a schematic diagram for obtaining the starting time of the Lamb wave S0 wave of the present invention;

[0024] Figure 4 It is a schematic diagram of the grid division of the positioning algorithm structure of the present invention;

[0025] Figure 5 It is a schematic diagram of the algorithm flow of the present invention;

[0026] Figure 6 It is a schematic diagram of the wave surface simulation of the present invention;

[0027] Figure 7 It is a schematic diagram of the area division of the present invention. Detailed Embodiment

[0028] The present invention will be further described in detail below through specific embodiments. The following embodiments are only descriptive and not restrictive, and the protection scope of the present invention cannot be limited thereby.

[0029] A method for positioning the collision of non - continuous structure debris of a spacecraft with corrected acoustic wave propagation path, the innovation of which lies in: the steps of the method are as follows:

[0030] 1) Set up a detection system: The detection system used in the positioning method includes a piezoelectric sensor, a signal amplifier, a signal acquisition card and a computer. The piezoelectric sensor and the metal part to be measured are installed together through a bracket. With the penetration part of the metal part to be measured as the center of the circle, 4 piezoelectric sensors are evenly distributed in a circle at the same radius position of the center of the circle. The 4 piezoelectric sensors are jointly connected to the signal amplifier, the signal amplifier transmits the collected signal to the signal acquisition card, and the signal acquisition card transmits the signal to the computer;

[0031] 2) When space debris collides with the detection system, elastic waves will be generated. When these elastic waves propagate to the sensor, electrical signals will be produced. When the amplitude of the electrical signal of any one sensor is greater than the preset threshold, it can be considered that a debris collision has occurred.

[0032] According to the vibration displacement direction of the particle, Lamb waves are divided into symmetric modes and antisymmetric modes, which are represented as S i and A i (i = 1, 2,...), the propagation characteristics of Lamb waves change with the incident angle, frequency, and structural geometry. Therefore, there are infinite S i and A i wave modes in a finite object, as shown in Figure 1 .

[0033] Since the Lamb wave signal will undergo dispersion during propagation, the collected signal will undergo mode separation. The mode with the fastest propagation speed is the S0 mode. Therefore, the moment of the mode in the collected Lamb wave signal is used as the calculation reference for S0, as shown in Figure 3 .

[0034] Many structures can be simplified to plate-like structures because the one-dimensional dimension of most actual structures is much smaller than the other two-dimensional dimensions. For the convenience of analysis, it can be considered that the through-shaped structure of the special part of the spacecraft is similar to a flat plate with a hole. And the flat plate is divided into multiple regions by using a grid, as shown in Figure 4 .

[0035] Establish a matrix that matches the grid. Let each intersection of the grid be a matrix node (i, j). Assume that the excitation source of the signal is a grid node, that is, the matrix node (i, j). The theoretical shortest distance from this node to the kth sensor can be obtained through path analysis The propagation time from this node to the kth sensor is:

[0036]

[0037] where v is the wave speed. Since four piezoelectric sensors are selected for this array, the propagation time difference from the node (i, j) to two different sensors l and m obtained through path processing is:

[0038]

[0039] In addition, through actual signal analysis, the initial time when the four sensors receive the S0 mode Lamb wave can be obtained Calculate the time difference between the signals received by two different sensors l and m

[0040]

[0041] By calculating D xy the time deviation degree of each node (i, j), that is, the position point (x, y) can be obtained, and each grid node will get the corresponding D xy value. The closer the position point (x, y) is to the true signal generation point (x0, y0), the smaller the D xy value. Therefore, for all position points (x, y), the position corresponding to the minimum D xy is the signal generation point, so the positioning of the collision can be realized.

[0042] The density of the grid nodes determines the positioning accuracy. Therefore, theoretically, the denser the grid nodes are divided, the higher the positioning accuracy. However, an overly dense grid will bring a large increase in the amount of computation and the computation time will become longer, so the grid should not be overly dense. In addition, if the time deviation degree D xy of the grid nodes does not meet the threshold requirements, a secondary grid division can be performed on the basis of the initial positioning result to establish a denser grid. Or interpolation can be used to estimate the time and calculate the part between the grid nodes to improve the accuracy. The specific operation flow chart is shown in Figure 5 .

[0043] The COMSOL software is used to perform a simulation analysis on the flat plate to be measured. The wavefront diagram of its Lamb wave when passing through the cavity is shown in Figure 6 , and it can be seen from the figure that the propagation of the Lamb wave follows the Huygens-Fresnel theorem. When the Lamb wave passes through an obstacle, it will bypass the obstacle and form a new wavefront. From Figure 6 (d), it can be clearly seen that the wavefront after the Lamb wave passes through the hole is composed of a series of small wave sources superimposed, and there is a time delay. Therefore, it can be considered that the signal generated by the signal source reaches the sensor through the shortest path, that is, the tangents of the signal source and the sensor to the circular hole are made respectively, and the sum of the tangent length and the arc length corresponding to the tangent point is the propagation path of the Lamb wave.

[0044] Assume that the positions of the four sensor arrays are (-40, 40), (-40, -40), (40, 40), and (40, -40), and the tangents of the four sensors to the circular hole are obtained, as shown in Figure 7 . If the signal source is within the illustrated area, when the four sensors receive the Lamb wave signal, at least one sensor's signal reception path will not be along a straight line and needs to be re-planned. Make the tangents of the signal source, the sensor and the circle and record their lengths. The sum of this length and the arc length corresponding to the tangent point is the signal propagation path If the signal source is outside the divided area, the propagation of the signal is not hindered and the propagation path is a straight line. After determining the path, the collision point can be determined according to the above algorithm flow.

[0045] Although embodiments and drawings of the present invention are disclosed for illustrative purposes, those skilled in the art will understand that various substitutions, changes, and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the content disclosed in the embodiments and drawings.

Claims

1. A method for locating debris collisions in a discontinuous structure of a spacecraft with corrected acoustic wave propagation paths, characterized by: The steps of the method are as follows: 1) Set up a detection system: The detection system used in the positioning method includes a piezoelectric sensor, a signal amplifier, a signal acquisition card and a computer. The piezoelectric sensor and the metal part to be measured are installed together through a bracket. With the penetration part of the metal part to be measured as the center of the circle, 4 piezoelectric sensors are evenly distributed in a circle at the same radius position of the center of the circle. The 4 piezoelectric sensors are jointly connected to the signal amplifier, and the signal amplifier transmits the collected signal to the signal acquisition card, and the signal acquisition card transmits the signal to the computer; 2) Set the through-shaped structure of the special part of the spacecraft to be similar to a flat plate with holes, divide the flat plate into multiple regions using a grid, establish a matrix matching the grid, set each intersection of the grid as a matrix node (i, j), assume that the excitation source of the signal is a grid node, that is, the matrix node (i, j), and the theoretical shortest distance from this node to the k-th sensor can be obtained through path analysis. The propagation time from this node to the k-th sensor is: where: v is the wave velocity; Since four piezoelectric sensors are selected, the difference in propagation time from a node (i, j) that can be obtained through path processing to two different sensors l and m is as follows: In addition, through actual signal analysis, the initial times when the four sensors receive the S0 mode Lamb wave can be obtained, and the time difference between the signals received by two different sensors l and m is calculated By calculating D xy the time deviation degree of each node (i, j), that is, the position point (x, y) can be obtained, and each grid node will get the corresponding D xy value. The closer the position point (x, y) is to the true signal generation point (x0, y0), the smaller the D xy value; for all position points (x, y), the position corresponding to the minimum D xy is the signal generation point, so the positioning of the collision can be realized; 3) If the time deviation degree D of the grid node xy does not meet the threshold requirement, secondary grid division can be performed on the basis of the initial positioning result to establish a denser grid, or interpolation can be used to calculate the part between grid nodes for time estimation to improve the accuracy; 4) Use COMSOL software to perform simulation analysis on the flat plate to be measured. The propagation of Lamb waves follows the Huygens-Fresnel theorem. When Lamb waves encounter an obstacle, they will bypass the obstacle and form a new wavefront. The signal generated by the signal source reaches the sensor through the shortest path, that is, the tangents of the signal source and the sensor to the circular hole are made respectively. The sum of the tangent length and the arc length corresponding to the tangent point is the propagation path of the Lamb wave. If at least one of the signal reception paths of the four sensors does not follow a straight line when receiving the Lamb wave signal, the route needs to be re-planned; 5) Make tangents from the signal source and the sensor to the circle and record their lengths. The sum of this length and the arc length corresponding to the tangent point is the signal propagation path. If the signal propagation is unobstructed, the propagation path is a straight line. After determining the path, the collision point can be determined according to the algorithm flow in step 3).

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