CN109781839A - A kind of object localization method in multilayer layered medium - Google Patents
A kind of object localization method in multilayer layered medium Download PDFInfo
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Abstract
The invention discloses the object localization methods in a kind of multilayer layered medium, transducer array is laid on n-layer medium uppermost surface, the reflection signal that one transmitting array element is fed back to acoustic beam, the reception of remaining array element by the scattered signal of object feedback and each interface before emitting into layered medium；The described method includes: each reception array element of step 1) does time reversal processing to the scattered signal received and n-1 reflection signal, simulation generates each reverse acoustic beam for receiving the corresponding n signal of array element；The forward direction acoustic beam received and the corresponding reverse acoustic beam of each array element are carried out process of convolution by step 2) respectively, the sum of each maximum value obtained after same point convolution using each array element thus generates the sound-filed simulation of n signal as the sound field value of the point in layered medium space；It is target scattering signal that the single corresponding signal of mountain peak shape sound field, which occurs, in step 3), then it is target position that sound field, which is worth the corresponding coordinate of highest point, in the sound-filed simulation of target scattering signal.
Description
Technical field
The present invention relates to acoustic detection technology fields, and in particular to the object localization method in a kind of multilayer layered medium.
Background technique
Acoustic detection and imaging are the important means of material and structure nondestructive inspection and diagnosis, it is also undersea detection and ground
The common method of Layer Detection.Target detection in multilayer dielectricity is always the problem of ultrasound detection.Due to the presence at interface, pass
The pulse echo methods of system are difficult to distinguish interface signals and echo signal.Lead to not realize multilayer dielectricity in target detection and
Positioning.For this problem, it is suggested with time reversal and reverse-time migration mixing method.Double-layer layered medium is had been carried out
Theoretical and experimental study.When so for three layers and the above layered medium, due to the presence at multilayer interface, detection to target and
Positioning is more difficult.
Summary of the invention
It is an object of the invention to overcome acoustic detection method in the prior art to cannot achieve in multilayer layered medium
The technical issues of target positions solves three layers and the above medium with the mixing method of time reversal (TR) and reverse-time migration (RTM)
The problem of middle target detection and positioning.
To achieve the above object, the present invention provides the object localization methods in a kind of multilayer layered medium, by energy converter
Array is laid on n-layer medium uppermost surface, any one array element in transducer array is selected to be situated between as transmitting array element to layering
To acoustic beam before transmitting in matter, and remaining array element is anti-by the scattered signal of object feedback and each interface as array element reception is received
The reflection signal of feedback；The described method includes:
The each reception array element of step 1) does time reversal processing to the scattered signal received and n-1 reflection signal,
Simulation generates each reverse acoustic beam for receiving the corresponding n signal of array element；
Step 2) each point in layered medium space, by the forward direction acoustic beam received and the corresponding reverse acoustic beam of each array element
Process of convolution is carried out respectively, and the sum of each maximum value obtained after same point convolution using each array element is as in layered medium space
The sound field value of the point, thus generates the sound-filed simulation of n signal；
It is target scattering signal that the single corresponding signal of mountain peak shape sound field occurs in n sound-filed simulation in step 3), then
It is target position that sound field, which is worth the corresponding coordinate of highest point, in the sound-filed simulation of target scattering signal.
As a kind of improvement of the above method, the step 1) is specifically included:
Step 1-1) using array element i as transmitting array element, transmitting signal is Ω (t), then receiving the signal that array element j is received is
Pij(t):
Pij(t)=m0ijΩ(t-t0)+m1ijΩ(t-t1)+…+mn-1ijΩ(t-tn-1) (1)
Wherein, m0ijFor target scattering coefficient, mkijFor the reflection coefficient at k-th of interface, 0≤k≤n-1；t0For array element i hair
It penetrates, when the travelling for the target scattering signal that j is received；t1,…tn-1Respectively array element i transmitting, the n-1 interface that j is received are anti-
When penetrating the travelling of signal；Wherein, n is the number of plies of medium, and t is the moment；
Step 1-2) each reverse acoustic beam for receiving the corresponding n signal of array element of simulation generation；
The reverse acoustic beam of target scattering signal are as follows: the ping that array element i emits is reflected by interface and target scattering, array element j
Shift to an earlier date Δ T after reception0The signal R of signal sending will be received0ij(t):
R0ij(t)=m0ij[Ω(t-t0+ΔT0)]TR+m1ij[Ω(t-t1+ΔT0)]TR+…+mn-1ij[Ω(t-tn-1+Δ
T0)]TR
Wherein, Δ T0Emit the time difference that array element j receives signal for array element i internal loopback signal and array element i；
The reverse acoustic beam of k-th of interface reflection signal are as follows: the ping that array element i emits is reflected by interface and target scattering,
Array element j shifts to an earlier date Δ T after receivingkThe signal R of signal sending will be receivedkij(t):
Rkij(t)=m0ij[Ω(t-t0+ΔTk)]TR+m1ij[Ω(t-t1+ΔTk)]TR+…+mn-1ij[Ω(t-tn-1+Δ
Tk)]TR
Wherein, Δ Tk=2Tk-Tkk, TkWhen receiving the travelling of interface reflection signal at k-th of interface to receive array element j,
TkkWhen transmitting signals to the travelling of k-th of interface internal loopback for array element i.
Present invention has an advantage that
1, interface reflection signal and target scattering signal can be successfully distinguished using method of the invention, inhibits interface letter
Number interference, make acoustic beam focal imaging at target (defect), to realize the detection and positioning of target in multilayer layered medium；
2, object localization method of the invention is analyzed by data, only can identify target and interface signals with primary experiment
Realize target (defect) positioning and detection.
Detailed description of the invention
Fig. 1 is the acoustic detection method flow chart of target or defect in a kind of layered medium provided by the invention；
Fig. 2 is that signal transmitting and received status diagram are executed using acoustic detection method of the invention；
Fig. 3 (a) is that signal sound field pattern is reflected at target first interface in second layer medium in present example；
Fig. 3 (b) is that signal sound field pattern is reflected at target second interface in second layer medium in present example；
Fig. 3 (c) is target target scattering signal sound field pattern in second layer medium in present example；
Fig. 3 (d) is target target position schematic diagram in second layer medium in present example；
Fig. 4 (a) is that signal sound field pattern is reflected at target first interface in first layer medium in present example；
Fig. 4 (b) is that signal sound field pattern is reflected at target second interface in first layer medium in present example；
Fig. 4 (c) is target target scattering signal sound field pattern in first layer medium in present example；
Fig. 4 (d) is target target position schematic diagram in first layer medium in present example；
Fig. 5 (a) is that signal sound field pattern is reflected at target first interface in third layer medium in present example；
Fig. 5 (b) is that signal sound field pattern is reflected at target second interface in third layer medium in present example；
Fig. 5 (c) is target target scattering signal sound field pattern in third layer medium in present example；
Fig. 5 (d) is target target position schematic diagram in third layer medium in present example.
Specific embodiment
Method of the invention is described in detail with reference to the accompanying drawings and examples.
The present invention proposes the object detection method in a kind of multilayer layered medium, and the detection method is based on time reversal
The mixed method combined with reverse-time migration technology not only can be identified target using this method from the interference of interface signals
Come, and the location information of target (defect) can be obtained, that is, realizes the positioning of target (defect).As shown in Figure 1, the detection
Method specifically includes the following steps:
Transducer array is laid on layered medium surface by step 1), selects in transducer array any one array element to more
To acoustic beam before transmitting in layer layered medium, and is received by remaining array element in transducer array and dissipated by what target or defect were fed back
Penetrate the reflection signal of signal and interface feedback；
The each array element of step 2) does time reversal processing according to the scattered signal and reflection signal that receive, and simulation generates
The corresponding reverse acoustic beam of each array element；
Using array element i as transmitting array element, transmitting signal is Ω (t), then receiving the signal that array element j is received is Pij(t):
Pij(t)=m0ijΩ(t-t0)+m1ijΩ(t-t1)+…+mn-1ijΩ(t-tn-1) (1)
Wherein, m0ijFor target scattering coefficient, mkijFor the reflection coefficient at k-th of interface, 0≤k≤n-1；t0For array element i hair
It penetrates, when the travelling for the target scattering signal that j is received；t1,…tn-1Respectively array element i transmitting, the n-1 interface that j is received are anti-
When penetrating the travelling of signal；Wherein, n is the number of plies of medium, and t is the moment；
Simulation generates each reverse acoustic beam for receiving the corresponding n signal of array element；
The reverse acoustic beam of target scattering signal are as follows: the ping that array element i emits is reflected by interface and target scattering, array element j
Shift to an earlier date Δ T after reception0The signal R of signal sending will be received0ij(t):
R0ij(t)=m0ij[Ω(t-t0+ΔT0)]TR+m1ij[Ω(t-t1+ΔT0)]TR+…+mn-1ij[Ω(t-tn-1+Δ
T0)]TR
Wherein, Δ T0Emit the time difference that array element j receives signal for array element i internal loopback signal and array element i；
The reverse acoustic beam of k-th of interface reflection signal are as follows: the ping that array element i emits is reflected by interface and target scattering,
Array element j shifts to an earlier date Δ T after receivingkThe signal R of signal sending will be receivedkij(t):
Rkij(t)=m0ij[Ω(t-t0+ΔTk)]TR+m1ij[Ω(t-t1+ΔTk)]TR+…+mn-1ij[Ω(t-tn-1+Δ
Tk)]TR
Wherein, Δ Tk=2Tk-Tkk, TkWhen receiving the travelling of interface reflection signal at k-th of interface to receive array element j,
TkkWhen transmitting signals to the travelling of k-th of interface internal loopback for array element i.
Step 3) each point in layered medium space, by the forward direction acoustic beam received and the corresponding reverse acoustic beam of each array element
Process of convolution is carried out respectively, and the sum of each maximum value obtained after same point convolution using each array element is as in layered medium space
The sound field value of the point then judges this signal for target scattering if forming single mountain peak shape sound-filed simulation after this signal convolution
Signal, as if it is not, if select next signal to carry out convolution, compare and obtain the corresponding coordinate of the highest point of sound field value as mesh
Mark (defect) position.
Below by taking the defect detection of three layer multi-layer media as an example, illustrate the specific implementation of acoustic detection method described above
Process.As shown in Fig. 2, layered medium is by velocity of sound c1Medium 1, velocity of sound c2Medium 2 and the velocity of sound be C3Medium 3 form, defect
There may be target O in medium 2 in three kinds of media with defect, in coordinate points (x0, z0) at, at 1 surface z=0 of medium,
A transducer array is disposed, array number there are n, and array element spacing is d.
Specific operation process are as follows:
(1) in an array, it is assumed that emit array element i as signal emitting-source, coordinate is (xi,0)；Transmitting signal is Ω
(t), it reaches and receives array element j, coordinate is (xj,0)；Receiving signal form indicates are as follows:
Pij(t)=aijΩ(t-t0)+bijΩ(t-t1)+cijΩ(t-t2) (1)
Wherein t0,t1,t2Signal emitting-source transmitting is corresponded to, the two interfaces reflection signal and a target that j is received dissipate
When penetrating the travelling of signal.Target is likely to be at first layer, in the second layer and third layer medium.It is in second layer medium with target
Example, is analyzed:
Fi(t)=Ω (t) (2)
And reverse acoustic beam Rij(t) it is transmitting array element transmitting ping by interface reflection and target scattering, reaches j-th gust
The signal that member receives carries out time reversal, and Δ T in advance0It is issued by j array element, Δ T0It is spontaneous to emit array element in first signal
From number time difference for receiving signal with other array elements of collecting mail, i.e.,Referring to fig. 2,
Reverse acoustic beam is after time reversal in Δ T in advance at this time0It issues, and Δ T0It is to be obtained by measurement.Receive
Array element (array element i) by interface, reaches the time that array element j is returned to after target scattering to emission source is received.And transmitting array element i
It is emitted through after the target scattering of interface in the time for returning to array element iIt is then available:
Then reverse acoustic beam Rij(t) are as follows:
Rij(t)=aij[Ω(t-t0+ΔT0)]TR+bij[Ω(t-t1+ΔT0)]TR+cij[Ω(t-t2+ΔT0)]TR
(3)
Then for any point (x, z) in space, two signals are subjected to process of convolution in this o'clock:
It can be obtained by a carinate distribution, the position that crestal culmination line passes through target.For different array element, obtain different
Carinate distribution.But all by forming common intersection point, i.e. focus at target.Therefore these carinate distributions are stacked up:
It is formed the sound-filed simulation of mountain peak shape, so that it is determined that the position of target out.
Signal (referring to fig. 2) is reflected to the interface of first interface s1, also uses identical processing mode.But it is reverse
The delay of acoustic beamHere T1=r1/c1AndIt is the travelling for emitting array element and transmitting signals to interface internal loopback
When
And for second contact surface s2, similarly, accordinglyHereAnd
Therefore it is when being delayedOrWhen, it is also formed and is orientated different carinate distributions one by one, but these carinate distributions are without altogether
Same intersection point, after further stacking up, cannot form single shape sound-filed simulation in mountain peak outstanding, and maximum value is smaller.
Pass through the method for above description, so that it may distinguish interface and target, while determine target position.
In the following, carrying out sound field simulation analysis to above-mentioned method.Array is made of 20 array elements, and array element spacing is 2mm,
Array total length is 41mm, and the 1st element position is at 1mm.Top dielectric 1 is silicon rubber, and velocity of longitudinal wave is
1020m/s, density 985kg/m3, thickness 20mm.Middle layer medium 2 is gelatin, and velocity of longitudinal wave 1400m/s, density is
1400kg/m3, thickness 20mm.Underlying dielectric 3 is water, velocity of longitudinal wave 1500m/s, density 1000kg/m3.
Target is placed in second layer medium first, aiming spot is (10mm, 30mm).At this moment by first battle array
Member transmitting ping, then three signals will be will receive receiving array element, according to the sequencing of time wherein first signal
It is the signal of target scattering for the reflection signal of interface s1, second, third signal is the reflection signal of interface s2.For certainly
For the array element 1 of receipts, three signals are also received.
It for interface s1 and s2, handles, is obtained shown in sound-filed simulation figure such as Fig. 3 (a) and Fig. 3 (b) by TR-RTM.
As we can see from the figure there is no the sound-filed simulation of prominent single mountain peak shape, but one defocus it is lesser uneven
Distribution.TR-RTM processing further is carried out to target scattering signal, shown in obtained result figure such as Fig. 3 (d), it can be seen that obtain
The sound-filed simulation of mountain peak shape outstanding and its focus is exactly target position (x, z)=(10,30) mm.And the sound after focusing
Field mountain peak is prominent, and maximum value is 8 times of the maximum value of the sound field of out-focus or so, i.e. 18dB or so.It can sentence in this way
Which signal that breaks is target scattering signal, while realizing the detection and positioning to target.
As shown in Fig. 4 (a)-Fig. 4 (d), the situation that target is located in first layer medium, target position are further discussed
(10mm, 10mm) first signal is target scattering signal, and the 2nd, 3 signal is respectively the reflection letter of interface s1 and interface s2
Number.Equally there is similar result as follows.
As shown in Fig. 5 (a)-Fig. 5 (d), when target is located in third layer medium, target position (10mm, 60mm) also has class
As result.
It should be noted last that the above examples are only used to illustrate the technical scheme of the present invention and are not limiting.Although ginseng
It is described the invention in detail according to embodiment, those skilled in the art should understand that, to technical side of the invention
Case is modified or replaced equivalently, and without departure from the spirit and scope of technical solution of the present invention, should all be covered in the present invention
Scope of the claims in.
Claims (2)
1. transducer array is laid on n-layer medium uppermost surface by the object localization method in a kind of multilayer layered medium, choosing
Any one array element in transducer array is selected to make before emitting as transmitting array element into layered medium to acoustic beam, and by remaining array element
The reflection signal fed back by the scattered signal of object feedback and each interface is received to receive array element；The described method includes:
The each reception array element of step 1) does time reversal processing to the scattered signal received and n-1 reflection signal, simulation
Generate the reverse acoustic beam of the corresponding n signal of each reception array element；
Step 2) each point in layered medium space distinguishes the corresponding reverse acoustic beam of the forward direction acoustic beam received and each array element
Process of convolution is carried out, the sum of each maximum value obtained after same point convolution using each array element is as the point in layered medium space
Sound field value, thus generate the sound-filed simulation of n signal；
It is target scattering signal that the single corresponding signal of mountain peak shape sound field occurs in n sound-filed simulation in step 3), then target
It is target position that sound field, which is worth the corresponding coordinate of highest point, in the sound-filed simulation of scattered signal.
2. the object localization method in multilayer layered medium according to claim 1, which is characterized in that the step 1) tool
Body includes:
Step 1-1) using array element i as transmitting array element, transmitting signal is Ω (t), then receiving the signal that array element j is received is Pij
(t):
Pij(t)=m0ijΩ(t-t0)+m1ijΩ(t-t1)+…+mn-1ijΩ(t-tn-1) (1)
Wherein, m0ijFor target scattering coefficient, mkijFor the reflection coefficient at k-th of interface, 0≤k≤n-1；t0For array element i transmitting, j
When the travelling of the target scattering signal received；t1,…tn-1Letter is reflected at respectively array element i transmitting, the n-1 interface that j is received
Number travelling when；Wherein, n is the number of plies of medium, and t is the moment；
Step 1-2) each reverse acoustic beam for receiving the corresponding n signal of array element of simulation generation；
The reverse acoustic beam of target scattering signal are as follows: the ping that array element i emits is reflected by interface and target scattering, and array element j is received
Shift to an earlier date Δ T afterwards0The signal R of signal sending will be received0ij(t):
R0ij(t)=m0ij[Ω(t-t0+ΔT0)]TR+m1ij[Ω(t-t1+ΔT0)]TR+…+mn-1ij[Ω(t-tn-1+ΔT0)]TR
Wherein, Δ T0Emit the time difference that array element j receives signal for array element i internal loopback signal and array element i；
The reverse acoustic beam of k-th of interface reflection signal are as follows: the ping that array element i emits is reflected by interface and target scattering, array element j
Shift to an earlier date Δ T after receptionkThe signal R of signal sending will be receivedkij(t):
Rkij(t)=m0ij[Ω(t-t0+ΔTk)]TR+m1ij[Ω(t-t1+ΔTk)]TR+…+mn-1ij[Ω(t-tn-1+ΔTk)]TR
Wherein, Δ Tk=2Tk-Tkk, TkWhen receiving the travelling of interface reflection signal at k-th of interface to receive array element j, TkkFor
When array element i transmits signals to the travelling of k-th of interface internal loopback.
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| CN110455931A (en) * | 2019-09-05 | 2019-11-15 | 中国科学院声学研究所 | Target detection and localization method in a kind of layered medium |
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