A method for inverting medium parameters and target location of a solid-solid layered medium
By combining measurement and imaging techniques with a multi-level refinement search method, the problem of inverting medium parameters and target position in solid-solid layered media was solved, achieving low-complexity and high-precision target positioning.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- DALIAN UNIV OF TECH
- Filing Date
- 2022-10-27
- Publication Date
- 2026-07-24
AI Technical Summary
Existing technologies struggle to effectively invert medium parameters and target locations in solid-solid layered media, especially when the interface shape is unknown, resulting in high computational complexity and insufficient accuracy.
By measuring the sound velocity of the upper solid medium using two rectangular piezoelectric transducers, and combining the interface shape and reflected wave pattern with a linearly arranged transducer array, the transverse wave velocity is estimated using full-focus imaging and multi-level refinement search methods. The longitudinal and transverse wave velocities of the lower medium are then inverted using the minimum variance of the target's possible point distribution group as the standard, and the target location is finally determined.
It achieves easy, low-computational-complexity, and high-inversion-accuracy positioning of targets in solid-solid layered media.
Smart Images
Figure CN115876886B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the technical field of ultrasonic testing, specifically to a method for inverting the medium parameters and target location of a solid-solid layered medium. Background Technology
[0002] For liquid-liquid layered media with a horizontal interface parallel to the surface, Li Jian et al. published a paper in Acta Physica Sinica, Vol. 37, No. 7, using the least squares method to invert the thickness and compression wave velocity of the upper liquid medium; and using the minimum dispersion of the target to invert the compression wave velocity of the lower liquid medium. Thus, the time reversal and reverse time migration (TR-RTM) method (Acta Physica Sinica, Vol. 36, No. 11) can be used to locate targets in such layered media. However, this method is only applicable to liquid-liquid layered media with a horizontal interface shape. In actual detection, the shape of the interface is unknown beforehand. Furthermore, for solid media, ultrasonic transducers can excite longitudinal and transverse waves in the solid. Therefore, to locate targets in such media, it is necessary to invert the longitudinal and transverse waves and the configuration of the interface in the solid-solid layered medium.
[0003] In summary, there is a need for a method that is easy to implement, has low computational complexity, and high inversion accuracy for inverting the medium parameters and target location of solid-solid layered media. Summary of the Invention
[0004] The main objective of this invention is to provide a method for inverting the medium parameters and target location of solid-solid layered media, so as to solve the problem of target location of solid-solid layered media in the prior art.
[0005] To achieve the above objectives, the present invention provides a method for inverting the medium parameters and target location of a solid-solid layered medium, comprising the following steps:
[0006] Step 1: Measure the sound velocity of the headwave of the upper solid medium by placing two rectangular piezoelectric transducers on the surface of the solid-solid layered medium;
[0007] Step 2: A linear array of transducers is placed on the surface of the solid-solid layered medium for detection. The acoustic image of the interface is obtained by processing the longitudinal wave reflection signal with the largest amplitude in the collected full matrix data signal. The position and shape of the interface are quantitatively characterized by the imaging image.
[0008] Step 3: Based on the measured longitudinal wave velocity of the upper medium and the configuration of the interface, compare the difference between the measured travel time and the predicted travel time of the reflected wave modes at each interface, and estimate the transverse wave velocity of the upper solid medium.
[0009] Step 4: Select the target scattered wave from the received multiple echoes. For the received target scattered echo signal group, use the minimum variance of the possible point distribution group of the target as the criterion to invert the longitudinal and transverse wave speeds of the lower medium.
[0010] Step 5: The center position of the target's possible point distribution group is the target's location result, thus realizing the target's location in the solid-solid layered medium.
[0011] Furthermore, one of the two rectangular piezoelectric transducers is used as a transmitting transducer and the other as a receiving transducer. Based on the measured travel time of the surface head wave, the sound velocity of the surface head wave, i.e. the sound velocity of the longitudinal wave of the upper solid medium, is calculated.
[0012] Furthermore, a linearly arranged transducer array is placed on the surface of a solid-solid layered medium. The number of array elements in the linearly arranged transducer array is n, and the center position of each element is (a... i The array consists of n elements (i = 1, 2, 3, ..., i, ..., n), with a center-to-center spacing of d between the elements. Each element of the piezoelectric transducer acts as both a transmitting and receiving transducer. A multi-transmitter / multi-receiver approach is used, where each element sequentially transmits signals as a transmitting element and receives signals as a receiving element. This allows the array to receive n signals. 2 A data stream, i.e., the full matrix data.
[0013] Furthermore, the receiving array element receives four types of interface reflected waves, namely P1-P1 wave, P1-S1 wave, S1-P1 wave and S1-S1 wave, where P represents longitudinal wave, S represents transverse wave (SV wave), subscript '1' represents upper medium and subscript '2' represents lower medium;
[0014] The first echo signal with the largest received signal amplitude in each receiving element of the full matrix data is processed using the full-focus imaging method, and then the position and shape of the solid-solid layered medium interface are quantitatively characterized using the -6dB method.
[0015] Furthermore, we set an unknown transverse wave sound velocity c. S1x The initial value is calculated based on Snell's law, and the acoustic signal is transmitted through the transmitting array element i(a) i ,0), passing through a certain point (x) on the interface s ,z s After reflection, it reaches the receiving array element j(a) j The travel time of ,0); compare this calculated travel time with the actual measured travel times of each echo. In the single-transmitter-multiple-receiver mode, the sum of squares of the measurement and predicted travel time errors of each transmit-receive pair is:
[0016]
[0017] Where m represents three different modes of reflected waves, When attempting to travel at the speed of sound, This represents the travel time of each measured echo.
[0018] Furthermore, a multi-level refinement search method is used to change the sound speed value c. S1x The speed of sound is estimated as the transverse wave speed of the upper solid medium until the sum of the squares of the measurement and prediction travel time errors of each transmitter-receiver pair is minimized.
[0019] Furthermore, in single-transmitter, multiple-receiver mode, the travel time t of a group of scattered wave signals from a specific target can be read. ij o =t i o +t j o (j=1,2,…i,…n), where the travel time of the incident portion of the scattered wave is t. i o The travel time consumed by the scattering portion of the scattered wave is t. j o .
[0020] Furthermore, for a selected group of scattered wave signals from each target, the path traversed by the scattered wave is divided into 4 segments, resulting in four possible modes: P1-XY-P1, P1-XY-S1, P1-XY-P1, and P1-XY-S1, where X and Y are unknown longitudinal and transverse wave speeds.
[0021] Initialize the P-wave and S-wave medium parameters, discretize the lower region into grid points, and calculate the sound wave emission from the transmitting array element i(a) according to four possible modes. i Starting from 0, passing through these points, and then passing through the interface again from these points, it reaches the receiving array element j(a). j When traveling (0):
[0022]
[0023] Where, d k It is the k-th segment of the four paths, c k M represents the speed of sound in the k-th segment of the path, which is one of the four possible modes.
[0024] Furthermore, by utilizing the center positions of the transmitting and receiving array elements and the travel time of the selected scattered waves, n arcs can be formed in the lower medium. The arc corresponding to the self-emitting and self-receiving array element intersects with other arcs, potentially at n-1 intersection points (x...). p ,z pThese points are called potential target points. The n-1 discrete potential target points form a distribution. The variance of this distribution group of potential target points is calculated as:
[0025]
[0026] in, The mean of the x-coordinates in the distribution group of possible target points. The mean value of the ordinate in the distribution group of possible target points;
[0027] Under the four possible modes, obtain the minimum value of the variance and its corresponding sound velocity. The corresponding sound velocity is the longitudinal and transverse wave sound velocity of the underlying medium.
[0028] Furthermore, the distance from a point (x,z) in the lower medium space to each possible target point (x) is calculated. p ,z p The distance and sum of )
[0029]
[0030] The search finds the point that minimizes the sum of the distances, thus reversing the location of the target in the solid-solid layered medium.
[0031] The technical solution of this invention can realize target positioning in solid-solid layered media, and has the advantages of being easy to implement, having low computational complexity, and high inversion accuracy. Attached Figure Description
[0032] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings:
[0033] Figure 1 This is a schematic flowchart of the method for retrieving the medium parameters and target location of a solid-solid layered medium according to the present invention;
[0034] Figure 2 This is a schematic diagram of the acoustic propagation path in a solid-solid layered medium, illustrating the method for inverting the medium parameters and target location of a solid-solid layered medium according to the present invention.
[0035] Figure 3 This is a schematic diagram of the measurement of the upper longitudinal wave velocity in a steel-copper layered medium according to a preferred embodiment of the present invention.
[0036] Figure 4This is a fully focused image of the first echo signal with the largest amplitude in the full matrix data stream, according to a preferred embodiment of the present invention.
[0037] Figure 5 The graph shows the error between the predicted and measured values of each transmit-receive pair as a function of the speed of sound, representing a preferred embodiment of the present invention.
[0038] Figure 6 This is a diagram showing the intersection points of arcs formed in the lower medium according to a preferred embodiment of the present invention.
[0039] Figure 7 For the present invention Figure 6 The possible target points and target location results. Detailed Implementation
[0040] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0041] like Figure 1 The method shown here for inverting the medium parameters and target location of a solid-solid layered medium includes the following steps:
[0042] Step 1: Measure the sound velocity of the headwave of the upper solid medium by placing two rectangular piezoelectric transducers on the surface of the solid-solid layered medium;
[0043] Step 2: A linear array of transducers is placed on the surface of the solid-solid layered medium for detection. The acoustic image of the interface is obtained by processing the longitudinal wave reflection signal with the largest amplitude in the collected full matrix data signal. The position and shape of the interface are quantitatively characterized by the imaging image.
[0044] Step 3: Based on the measured longitudinal wave velocity of the upper medium and the configuration of the interface, compare the difference between the measured and predicted values of the reflected wave modes of each interface to estimate the transverse wave velocity of the upper solid medium.
[0045] Step 4: Select the target scattered wave from the received multiple echoes. For the received target scattered echo signal group, use the minimum variance of the possible point distribution group of the target as the criterion to invert the longitudinal and transverse wave speeds of the lower medium.
[0046] Step 5: The center position of the target's possible point distribution group is the target's location result, thus realizing the target's location in the solid-solid layered medium.
[0047] Specifically, step 1: Two rectangular piezoelectric transducers are placed on the surface of the solid-solid layered medium to measure the head wave signal, thereby measuring the sound velocity of the longitudinal wave in the upper solid medium. One transducer acts as a transmitting transducer, and the other as a receiving transducer. The transmitting transducer will excite head waves, surface waves, various reflected waves, and target scattered waves. Among these, the head wave has the fastest velocity, and the surface head wave is exactly equal to the sound velocity of the longitudinal wave. Therefore, after measuring the travel time of the surface head wave, the sound velocity of the surface head wave can be calculated, which is also the sound velocity of the longitudinal wave in the upper solid medium.
[0048] Specifically, step 2: The surface of the solid-solid layered medium is placed using a linearly arranged transducer array for detection. The acoustic image of the interface is obtained by processing the longitudinal wave reflection signal with the largest amplitude in the collected full matrix data signal. The position and shape of the interface are quantitatively characterized using the imaging image.
[0049] A linearly arranged transducer array is placed on the surface of a solid-solid layered medium. This array has n elements, and the center position of each element is (a...). i The array consists of n piezoelectric transducers (i = 1, 2, 3, ..., i, ..., n), with a center-to-center spacing of d between the elements. Each element acts as both a transmitter and a receiver. A multi-transmitter / multi-receiver approach is used, where each element sequentially transmits signals as a transmitter and receives signals as a receiver. This allows for the reception of n signals. 2 A data stream, i.e., the full matrix data.
[0050] like Figure 2 As shown, the emitted sound waves generate both longitudinal and transverse waves upon passing through an interface or target. Therefore, each receiving element receives four types of interface reflected waves: P1-P1 wave, P1-S1 wave, S1-P1 wave, and S1-S1 wave. Here, P represents the longitudinal wave, and S represents the transverse wave (SV wave). The subscript '1' indicates the upper medium, and the subscript '2' indicates the lower medium.
[0051] The first echo signal with the largest received signal amplitude in each receiving element of the full matrix data is processed using the full-focus imaging method, and then the position and shape of the solid-solid layered medium interface are quantitatively characterized using the -6dB method.
[0052] Specifically, step 3: Based on the measured longitudinal wave velocity of the upper medium and the configuration of the interface, the transverse wave velocity of the upper solid medium is estimated by comparing the difference between the measured and predicted values of the reflected wave modes of each interface.
[0053] The first echo received by the receiving element in the transducer array has been identified as the P1-P1 reflected wave. The travel time of the remaining interface reflected waves is then read. The unknown transverse wave velocity c is set. S1xThe initial values, for a certain transmit-receive pair {i,j}, the acoustic signal is generated by the transmit array element i(a i After the signal is emitted (0), the velocity of the longitudinal wave is known. The signal reaches a point on the interface at the longitudinal wave speed or the attempted transverse wave speed. After being reflected by the interface, the signal reaches the receiving element j(a) at the attempted transverse wave speed or longitudinal wave speed. j ,0). Therefore, under these three different propagation modes (P1-S1 wave, S1-P1 wave, or S1-S1 wave), based on Snell's law, the acoustic signal transmitted through the transmitting element i (a i ,0), passing through a certain point (x) on the interface s ,z s After reflection, it reaches the receiving array element j(a) j The travel time of (0, 0) is calculated. This calculated travel time is compared with the actual measured travel times of each echo. In a single-transmitter, multiple-receiver configuration, the sum of the squares of the errors between the measured and predicted travel times for each transmitter-receiver pair is:
[0054]
[0055] Where m represents three different modes of reflected waves, When attempting to travel at the speed of sound, This represents the travel time of each measured echo.
[0056] The sound speed value c is changed using a multi-level refinement search method. S1x The sound velocity is estimated as the transverse wave velocity of the upper solid medium until the sum of the squares of the measurement and prediction travel time errors of each transmitter-receiver pair in these three modes is minimized.
[0057] Thus, the interface reflection signal and the target scattering signal can be distinguished from the various received signals. After filtering out the interface reflection signal, the target scattering signal can be selected.
[0058] Specifically, step 4: Select the target scattered wave from the multiple received echoes. For the received target scattered echo signal group, use the minimum variance of the target possible point distribution group as the criterion to invert the longitudinal and transverse wave speeds of the lower medium.
[0059] In single-transmitter, multiple-receiver mode, for a group of scattered wave signals from a identified target, the path of the acoustic pulse signal emitted by the i-th element of the transducer linear array after refraction at the interface to reach the target is called the incident portion of the scattered wave. The travel time t taken to traverse this path is denoted as t. i o When a sound wave is scattered by the target, it passes through the interface again and is received by the receiving element j (j = 1, 2, ..., i, ..., n). This path is called the scattering part of the scattered wave, and the travel time consumed is t. jo For this target scattered wave signal group, the travel time t of the signal group can be read. ij o =t i o +t j o (j=1,2,…i,…n). For a given set of scattered wave signals from selected targets, the path traversed by the scattered wave is divided into 4 segments, such as... Figure 2 As shown, there are 16 possible modes, and these 16 target scattering waves are P1-P2-P2-P1, P1-P2-P2-S1, P1-P2-S2-P1, P1-P2-S2-S1, P1-S2-P2-P1, P1-S2-P2-S1, P1-S2-S2-P1, P1-S2-S2-S1, S1-P2-P2-P1, S1-P2-P2-S1, S1-P2-S2-P1, S1-S2-P2-S1, S1-S2-P2-S1, S1-S2-S2-P1, S1-S2-S2-P1, S1-S2-S2-S1 wave, etc. Currently, the longitudinal and transverse wave velocities of the upper medium have been obtained. Therefore, it can be considered as four possible modes, namely P1-XY-P1, P1-XY-S1, P1-XY-P1, and P1-XY-S1, where X and Y are unknown longitudinal and transverse wave velocities.
[0060] Initialize the P-wave and S-wave medium parameters. Discretize the lower region into grid points, and calculate the acoustic wave emission from the transmitting element i(a) according to four possible modes. i Starting from 0, passing through these points, and then passing through the interface again from these points, it reaches the receiving array element j(a). j When traveling (0):
[0061]
[0062] Where, d k It is the k-th segment of the four paths, c k M represents the speed of sound in the k-th segment of the path, which is one of the four possible modes.
[0063] Find the points that correspond to the travel times of the measured scattered echoes; these points form an arc in the underlying medium. In a single-transmitter, multiple-receiver configuration, there are n arcs, and these arcs have n-1 intersection points (x...). p ,z p These intersection points are called potential target points. These n-1 discrete potential target points form a distribution, and the variance of this distribution group is calculated as:
[0064]
[0065] in, The mean of the x-coordinates in the distribution group of possible target points. It represents the mean value of the ordinate in the distribution group of possible target points.
[0066] From the four possible modes, obtain the minimum value of the variance and its corresponding sound velocity. The corresponding sound velocity is the longitudinal and transverse wave sound velocity of the underlying medium.
[0067] Specifically, step 5: the center position of the target's possible point distribution group is the target's location result, thus realizing the target's location in the solid-solid layered medium.
[0068] Calculate the distance from a point (x, z) in the lower medium space to each possible target point (x). p ,z p The distance and sum of )
[0069]
[0070] The search finds the point that minimizes the sum of the distances, thus reversing the location of the target in the solid-solid layered medium.
[0071] Preferred embodiment:
[0072] The solid-solid layered medium consists of an upper layer of steel and a lower layer of copper. The steel layer has a longitudinal wave velocity of 5941 m / s and a transverse wave velocity of 3251 m / s, with a thickness of 23.7 mm. The copper layer has a longitudinal wave velocity of 4700 m / s and a transverse wave velocity of 2260 m / s. A 1 mm radius hole was drilled in the lower layer as the target. Using the center of the first element of the transducer array as the origin, the center coordinates of the target are (18.0 mm, 39.3 mm).
[0073] Two strip-shaped PZT piezoelectric ceramic wafers with a center frequency of 2MHz are placed on the upper surface of a steel-copper layered dielectric at a horizontal interface. The distance between the two strip-shaped PZT piezoelectric ceramic wafers is d. h =32.4mm. One is used as a transmitting transducer, and the other as a receiving transducer. The received signal is as follows: Figure 3 As shown in the figure, a small-amplitude headwave can be clearly seen being received by the receiving array element. The measured headwave velocity is 5978 m / s, which is close to the longitudinal wave velocity of steel, 5941 m / s.
[0074] A transducer array consisting of 20 elements with a center frequency of 5MHz was placed on the surface of a solid-solid layered medium. The full matrix data was captured using a multi-transmitter, multi-receiver method, and a total of 400 signal streams were received.
[0075] The first echo signal with the largest amplitude in the full matrix data stream is processed using a full-focus imaging method, and the resulting imaging is as follows: Figure 4 As shown, the location and shape of the solid-solid layered medium interface are quantitatively characterized by the -6dB method.
[0076] Based on the obtained longitudinal wave velocity of the upper medium and the interface configuration, an initial value for the transverse wave velocity of the upper medium is first set. The travel time of the three interface reflection wave modes under this initial velocity value can then be calculated. A multi-level refinement search method is employed to adjust parameters and find the velocity that minimizes the sum of squared residuals between the model output and the measured values. Figure 5 As shown, the transverse wave velocity of the upper medium obtained by inversion is 3314 m / s.
[0077] After retrieving the transverse wave velocity of the upper medium, the target scattered wave is selected from the received echoes. For the received target scattered echo signal group, the longitudinal and transverse wave velocities of the lower medium are retrieved using the minimum variance of the possible target point distribution group as a metric. Taking the first received target scattered echo as an example, a multi-level refinement search method is used to search for the minimum variance in four possible modes. Then, optimization is performed among the individual extrema of these four modes, i.e., the minimum value is found among the four individual extrema, resulting in the target scattered wave mode being P1-XY-P1, where the sound velocities of X and Y are 4450 m / s and 4900 m / s, respectively, both close to the longitudinal wave velocity of copper. Figure 6 The arc formed by the propagation of sound waves into the underlying medium. Figure 7 The intersection points of these arcs and the center of the intersection point distribution group, i.e., the target location result, are (18.7mm, 38.1mm).
[0078] Therefore, the inversion yielded medium parameters such as the sound velocity and interface configuration of the upper and lower layers of the solid-solid layered medium, and also enabled the localization of the target.
[0079] The method for inverting the medium parameters and target location of solid-solid layered media proposed in this invention is also applicable to other isotropic solid media.
[0080] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.
Claims
1. A method for inverting the medium parameters and target location of a solid-solid layered medium, characterized in that, Includes the following steps: Step 1: Measure the sound velocity of the headwave of the upper solid medium by placing two rectangular piezoelectric transducers on the surface of the solid-solid layered medium; Step 2: A linear array of transducers is placed on the surface of the solid-solid layered medium for detection. The acoustic image of the interface is obtained by processing the longitudinal wave reflection signal with the largest amplitude in the collected full matrix data signal. The position and shape of the interface are quantitatively characterized by the imaging image. Step 3: Based on the measured longitudinal wave velocity of the upper medium and the configuration of the interface, compare the difference between the measured travel time and the predicted travel time of the reflected wave modes at each interface, and estimate the transverse wave velocity of the upper solid medium. Step 4: Select the target scattered wave from the received multiple echoes. For the received target scattered echo signal group, use the minimum variance of the possible point distribution group of the target as the criterion to invert the longitudinal and transverse wave speeds of the lower medium. Step 5: The center of the distribution group of possible target points is the target location result; One of the two rectangular piezoelectric transducers is used as a transmitting transducer and the other as a receiving transducer. The sound velocity of the surface head wave, i.e. the sound velocity of the longitudinal wave of the upper solid medium, is calculated based on the travel time of the measured surface head wave. Set an unknown transverse wave speed. The initial value is calculated based on Snell's law, and the acoustic signal is transmitted through the transmitting array element i(a) i ,0), passing through a certain point (x) on the interface s , z s After reflection, it reaches the receiving array element j(a) j The travel time of each echo is calculated as 0. This calculated travel time is compared with the actual measured travel times of each echo. In the single-transmitter-multiple-receiver configuration, the sum of the squares of the measurement and predicted travel time errors for each transmitter-receiver pair is: Where m represents three different modes of reflected waves, When attempting to travel at the speed of sound, Represents the travel time of each measured echo; The sound speed value is changed using a multi-level refinement search method. The sound velocity is estimated as the transverse wave speed of the upper solid medium until the sum of the squares of the measurement and prediction travel time errors of each transmitter-receiver pair is minimized. For a selected group of scattered wave signals from each target, the path traversed by the scattered wave is divided into 4 segments, resulting in four possible modes: P1-XY-P1, P1-XY-S1, P1-XY-P1, and P1-XY-S1, where X and Y are unknown longitudinal and transverse wave speeds. Initialize the P-wave and S-wave medium parameters, discretize the lower region into grid points, and calculate the sound wave emission from the transmitting array element i(a) according to four possible modes. i Starting from 0), passing through these points, and then passing through the interface again from these points, it reaches the receiving array element j(a). j When traveling (0): Where, d k It is the k-th segment of the four paths, c k M represents the speed of sound in the k-th segment of the path among the four possible modes. By utilizing the center positions of the transmitting and receiving array elements and the travel time of the selected scattered waves, n arcs can be formed in the lower medium. The arc corresponding to the self-emitting and self-receiving array element intersects with the other arcs, potentially at n-1 intersection points (x...). p , z p These points are called potential target points. The n-1 discrete potential target points form a distribution. The variance of this distribution group of potential target points is calculated as: in, The mean of the x-coordinates in the distribution group of possible target points. The mean value of the ordinate in the distribution group of possible target points; Under the four possible modes, obtain the minimum value of the variance and its corresponding sound velocity. The corresponding sound velocity is the longitudinal and transverse wave sound velocity of the underlying medium. Calculate the distance from a point (x, z) in the lower medium space to each possible target point (x). p , z p The distance and sum of ) The search finds the point that minimizes the sum of the distances, thus reversing the location of the target in the solid-solid layered medium.
2. The method for inverting the medium parameters and target location of a solid-solid layered medium according to claim 1, characterized in that, A linearly arranged transducer array is placed on the surface of a solid-solid layered medium. The number of array elements is n, and the center position of each element is (a...). i In a piezoelectric transducer array (i=1, 2, 3, …, i, … n), the center-to-center spacing between the elements is d. Each element acts as both a transmitter and a receiver, employing a linear transducer array with multiple transmit and receive modes. Each element sequentially transmits signals as a transmitter and receives signals as a receiver. Therefore, it can receive n signals. 2 A data stream, i.e., the full matrix data.
3. The method for inverting the medium parameters and target location of a solid-solid layered medium according to claim 2, characterized in that, The receiving array element receives four types of interface reflected waves: P1-P1 wave, P1-S1 wave, S1-P1 wave, and S1-S1 wave. Here, P represents longitudinal wave, S represents transverse wave, and the subscript '1' represents the upper medium. The first echo signal with the largest received signal amplitude in each receiving element of the full matrix data is processed using the full-focus imaging method, and then the position and shape of the solid-solid layered medium interface are quantitatively characterized using the -6 dB method.
4. The method for inverting the medium parameters and target location of a solid-solid layered medium according to claim 1, characterized in that, In single-transmitter, multiple-receiver mode, the travel time t of a group of scattered wave signals from a specific target can be read. ij o =t i o +t j o (j=1, 2, …i, …n), where the travel time of the incident portion of the scattered wave is t. i o The travel time consumed by the scattering portion of the scattered wave is t. j o .