CN115113278A - Step frequency control method, system and equipment for marine controllable seismic source - Google Patents
Step frequency control method, system and equipment for marine controllable seismic source Download PDFInfo
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Abstract
The invention relates to the technical field of marine seismic exploration, in particular to a stepping frequency control method, a stepping frequency control system and stepping frequency control equipment for a marine controllable seismic source. The method comprises the steps of firstly, obtaining a linear sweep frequency signal, dividing the linear sweep frequency signal into a plurality of sub-band signals according to a preset stepping frequency, wherein the plurality of sub-band signals are used for exciting a plurality of controllable seismic sources, receiving echo signals of the sub-band signals, carrying out real-time phase correction on the echo signals, and synthesizing detection signals through the stepping frequency.
Description
Technical Field
The invention relates to the technical field of marine seismic exploration, in particular to a stepping frequency control method, a stepping frequency control system and stepping frequency control equipment for a marine controllable seismic source.
Background
In a marine controllable seismic source, in order to obtain seismic exploration data information with higher resolution, elastic waves generated by seismic source equipment are required to be wider in frequency and shorter in excitation time, but the elastic waves are a group of parameters which are contradictory to each other, the wider the excitation frequency is, the longer the excitation time is, and the longer the excitation time is, the exploration cost is multiplied, so that a controllable seismic source control method with shorter excitation time is needed, and meanwhile, a seismic exploration signal is ensured to have a relatively wider frequency range. There is a need for a method of vibroseis control.
In the actual exploration process, a seismic source excitation signal adopts a linear frequency sweeping signal, and elastic waves excited by a seismic source have signal distortions of different forms in a low-frequency band and a high-frequency band, so that the seismic source signal can be divided into a plurality of sub-band signals with stepping frequency, and the sub-band signals are synthesized at a receiving end to obtain a detection signal.
In a related technology, the phase error estimation value is continuously adjusted by using image contrast as a measuring criterion of synthetic aperture radar focusing, and the distance direction high-order phase error with the maximum contrast function is obtained. And (4) iterative solution is carried out by adopting a conjugate gradient algorithm to obtain a phase error which enables the contrast to be maximum.
The method needs to solve the contrast of the whole radar image in each iteration, the single iteration calculation amount is large, the iteration times are large, and the efficiency is low for the marine seismic exploration data volume.
In another related art, it is proposed to calculate a high resolution one-dimensional range profile (HRRP) based on an iterative process, using a quasi-newton method for HRRP calculation, and considering that a phase error is found when the HRRP entropy reaches a minimum.
The method reduces the single iteration calculation amount, improves the efficiency to a certain extent, but has more iteration times and low calculation efficiency, and is difficult to apply to engineering practice.
In conclusion, the conventional vibroseis cannot be directly applied to the marine vibroseis, the exploration time is long, the precision is low, and the calculation amount of the conventional algorithm is large and the efficiency is low.
Disclosure of Invention
In view of this, the present invention aims to provide a method, a system, and an apparatus for controlling a step frequency of a marine vibroseis, so as to solve the technical problem that the existing marine geophysical prospecting development efficiency and precision are contradictory, and random phase differences exist between subband signals, which results in inaccurate synthesized detection signals.
According to a first aspect of embodiments of the present invention, there is provided a step frequency control method for a marine vibrator, comprising:
acquiring a linear frequency sweeping signal, and dividing the linear frequency sweeping signal into a plurality of sub-band signals according to a preset stepping frequency, wherein the plurality of sub-band signals are used for exciting a plurality of controllable seismic sources;
receiving echo signals of the sub-band signals, wherein the echo signals carry stratum information of different depths;
and carrying out real-time phase correction on the echo signals, and synthesizing detection signals through stepping frequency.
Preferably, the dividing the linear frequency sweep signal into a plurality of subband signals according to a preset step frequency specifically includes:
the bandwidth B and the starting frequency f of the linear sweep frequency signal are measured 0 Dividing the signal into N sub-band signals;
and the overlap ratio of the sub-band signals is r, wherein r is more than 0;
then, sub-band signal bandwidth
Time width
Starting frequency of subband n is f n ＝f 0 +(n-1)(1-r)b。
Preferably, the calculating the phase error of the echo signal includes:
performing time shift and phase correction on a plurality of received echo signals;
and carrying out coherent superposition on the received echo signals on a time domain to obtain a spliced detection signal.
Preferably, the time shifting is performed on the received multiple echo signals, specifically:
time shifting a plurality of received echo signals, wherein the time shifting amount is the time width T of the sub-band signals sub 。
Preferably, the phase correcting the received echo signals includes:
the echo signal A or the echo signal B is phase shifted by c + pi so that the variance of the echo signal A and the echo signal B is minimized.
Preferably, the phase correction is performed on the received multiple echo signals, specifically:
and phase shifting the echo signal A or the echo signal B by c + pi, selecting a sampling point s between the echo signal A and the echo signal B, calculating the variance of the echo signal A and the echo signal B in a sampling window with a length of w from the sampling point s to the sampling point, and taking the inverse number of the maximum variance as the variance of the phase shift amount c.
Preferably, the phase correcting the received echo signals further includes:
calculating the coordinate error of a sampling point in the echo signal, specifically:
determining an initial position and selecting a direction phasor, adding the direction phasor and the initial position to obtain a vector of a detection point A, and adding a reverse direction vector of the direction phasor and the initial position to obtain a vector of a detection point B;
calculating the variance of the detection point A and the detection point B, taking the detection point with small variance as a first current position, calculating the variance of the first current position, storing the variance, selecting the minimum value in the iteration result as the current optimal position 1, and judging whether the current optimal position is converged;
if the convergence is reached, outputting a minimum value, and selecting an optimal position;
if not, the initial position is determined again and the direction phasor is selected.
Preferably, the phase correcting the received echo signals further includes:
solving n Levy solution coordinates according to a Levy flight algorithm, wherein n is far less than a solution quantity m existing in a vector space, and selecting a second current position;
calculating and storing the variance of the second current position;
judging whether the Levie solution is to be discarded or not according to the probability Pa, and calculating a random solution of the solution to be discarded between two Levie solution space connecting lines;
comparing the Levin solution with the random solution, if the Levin solution is smaller than the random solution, taking the Levin solution as a result of the current iteration, otherwise, taking the random solution as a result of the current iteration;
comparing the result of the current iteration with the minimum value in the results of the previous iterations, and judging whether the current optimal position is converged;
if the convergence is reached, outputting a minimum value, and selecting an optimal position;
if not, the Levin solution coordinates are determined again.
According to a second aspect of an embodiment of the invention, there is provided a stepped frequency control system for a marine vibrator, comprising:
the system comprises a dividing module, a processing module and a control module, wherein the dividing module is used for acquiring a linear sweep frequency signal and dividing the linear sweep frequency signal into a plurality of sub-band signals according to a preset stepping frequency, and the plurality of sub-band signals are used for exciting a plurality of controllable seismic sources;
the receiving module is used for receiving echo signals of the sub-band signals, and the echo signals carry stratum information of different depths;
and the correction module is used for carrying out real-time phase correction on the echo signals and synthesizing detection signals through stepping frequency.
According to a third aspect of embodiments of the present invention, there is provided a step frequency control apparatus for a marine vibrator, comprising: the method described above.
The technical scheme provided by the embodiment of the invention can have the following beneficial effects:
the method comprises the steps of firstly obtaining a linear sweep frequency signal, dividing the linear sweep frequency signal into a plurality of sub-band signals according to a preset stepping frequency, wherein the plurality of sub-band signals are used for exciting a plurality of controllable seismic sources, receiving echo signals of the sub-band signals, carrying out real-time phase correction on the echo signals, and synthesizing detection signals through the stepping frequency.
In addition, a longicorn algorithm or a cuckoo algorithm is adopted to search for the minimum phase error and obtain the optimal splicing position, so that the synthesized phase is more accurate, the calculation amount of the algorithm is greatly reduced, and the efficiency is improved.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and together with the description, serve to explain the principles of the invention.
FIG. 1 is a flow chart illustrating a method of step frequency control of a marine vibroseis according to an exemplary embodiment;
FIG. 2 is a flowchart illustrating a method for step frequency control of a marine vibroseis in general, in accordance with an exemplary embodiment;
fig. 3 is a diagram illustrating dividing the linear frequency sweep signal into a plurality of subband signals according to a preset step frequency according to an exemplary embodiment;
FIG. 4 is a flow diagram illustrating a step frequency synthesis of an echo signal in accordance with an exemplary embodiment;
FIG. 5 is a flow diagram illustrating error calculation of two subband signals according to an exemplary embodiment;
FIG. 6 is a phase shift-sample-error trend graph shown in accordance with an exemplary embodiment;
FIG. 7A is a flow diagram illustrating a Seircow whisker algorithm search error in accordance with an exemplary embodiment;
FIG. 7B is a graph illustrating a number of iterations for the longicorn whisker algorithm, according to an exemplary embodiment;
FIG. 8A is a flow chart illustrating a cuckoo algorithm search error according to an exemplary embodiment;
FIG. 8B is a schematic illustration of a Levy flight in accordance with an exemplary embodiment;
FIG. 8C is a graph illustrating a number of iterations of a cuckoo algorithm according to an exemplary embodiment;
FIG. 9 is a schematic diagram illustrating a step frequency control system for a marine vibroseis according to an exemplary embodiment.
Detailed Description
Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the invention, as detailed in the appended claims.
Example one
Referring to fig. 1, fig. 1 is a flow chart illustrating a method for step frequency control of a marine vibroseis, according to an exemplary embodiment, as shown in fig. 1, the method comprising:
step S11, acquiring a linear frequency sweeping signal, and dividing the linear frequency sweeping signal into a plurality of sub-band signals according to a preset stepping frequency, wherein the plurality of sub-band signals are used for exciting a plurality of controllable seismic sources;
step S12, receiving echo signals of the sub-band signals, wherein the echo signals carry stratum information of different depths;
and step S13, carrying out real-time phase correction on the echo signals, and synthesizing detection signals through stepping frequency.
It should be noted that, an application scenario to which the technical scheme provided by the embodiment is applicable is in the technical field of marine seismic exploration.
It can be understood that, in the technical scheme provided by this embodiment, the linear frequency sweep signal is obtained, and the linear frequency sweep signal is divided into a plurality of sub-band signals according to the preset step frequency, and the plurality of sub-band signals excite a plurality of controllable seismic sources, and the echo signals of the sub-band signals are received, and the echo signals carrying formation information of different depths are subjected to real-time phase correction, and the detection signal is synthesized through the step frequency.
In addition, a longicorn algorithm or a cuckoo algorithm is adopted to search for the minimum phase error and obtain the optimal splicing position, so that the synthesized phase is more accurate, the calculation amount of the algorithm is greatly reduced, and the efficiency is improved.
In a specific practice, in step S11, "divide the linear frequency sweep signal into a plurality of subband signals according to a preset step frequency", there may be a plurality of implementation manners, where one implementation manner may be:
specifically, referring to fig. 2, fig. 2 is a flowchart illustrating an overall method for controlling a step frequency of a marine vibroseis according to an exemplary embodiment, after a linear sweep signal is acquired, the linear sweep signal is divided into a plurality of subband signals according to a preset step frequency, where the unused subband signals are used for exciting different vibroseiss, for example, the linear sweep signal is divided into subband signal 1, subband signal 2, subband signal 3, and so on, as illustrated in fig. 2, only 3 subband signals are mentioned in this embodiment, but there may be a plurality of subband signals, and the subband signals are excited by the vibroseis.
It should be noted that, because there is only one formation channel, when the receiving device receives the echo signals, the echo signals are mixed together, and the mixed echo signals are classified and extracted through filtering, for example: by dividing the frequency into high, medium and low 3 segments, echo signals 1, echo signals 2, echo signals 3, etc. can be obtained, wherein the number of echo signals is the same as the number of subband signals. The echo signals contain stratum information of different depth stratums, however, because the underground structure is very different, the phase of the echo signals presents random characteristics, real-time phase correction needs to be carried out on the echo signals, and detection signals are obtained through step frequency synthesis until the detection is finished.
The preset step frequency is a step frequency segmentation algorithm, and the step frequency segmentation algorithm is divided into equal parts and redundant segmentation.
Specifically, the number of the receiving devices and the frequency may be determined, for example, there are 4 receiving devices, and 100Hz may be equally divided into 0-20Hz, 20-40Hz, 40-80Hz, and 80-100 Hz. Besides, it can also be set as a redundant frequency division mode, if there are 9 receiving devices, 100Hz can be divided into 0-20Hz, 10-30Hz, 20-40Hz, 30-50Hz, 40-60Hz, 50-70Hz, 60-80Hz, 70-90 Hz, 80-100 Hz. The number of the receiving devices can be customized according to the actual situation, wherein the range of the stepping frequency can also be customized to be 2, 4, 8 or 10 frequency ranges, wherein the more frequency ranges, the more devices are required, the higher the complexity is, and the greater the difficulty is in performing stepping frequency synthesis. Different redundant frequencies have different influences on the synthesis effect of the stepping frequency, the more the split redundant frequencies are, the lower the efficiency is during the synthesis of the stepping frequency, but the better the obtained detection signal effect is, the closer the detection signal effect is to the actual condition of the stratum.
It should be noted that the step frequency listed in this embodiment is only an example, and does not limit the present invention, and the frequency division may be in other division manners, and the division method similar to the present application is within the protection scope of the present invention.
It should be noted that, in the technical scheme of the present invention, the linear sweep frequency signal is divided into a plurality of sub-band signals and transmitted, and in the prior art, 10 seconds are required from the transmission of the linear sweep frequency signal to the reception of the detection information.
Specifically, referring to fig. 3, fig. 3 is a schematic diagram illustrating dividing the linear frequency sweep signal into a plurality of subband signals according to a predetermined step frequency according to an exemplary embodiment, wherein a signal bandwidth B and a start frequency f of the linear frequency sweep signal are obtained 0 Dividing the signal into N sub-band signals;
and the overlap ratio of the sub-band signals is r, wherein r is more than 0;
then, sub-band signal bandwidth
Time width
Starting frequency of subband n is f n ＝f 0 +(n-1)(1-r)b。
In a specific practice, there may be multiple implementations of the "performing real-time phase correction on the echo signal" in step S13, where one implementation may be:
performing time shift and phase correction on a plurality of received echo signals;
and performing coherent superposition on the received multiple echo signals on a time domain to obtain a spliced detection signal.
Specifically, referring to fig. 4, fig. 4 illustrates a flow chart for step frequency synthesis of echo signals according to an exemplary embodiment. Firstly, the echo signals of different sub-band signals received by the receiving device need to be correspondingly time-shifted, and the time shift amount is the time width of the sub-band signal
And phase correction is carried out on different sub-band signals, and finally, coherent superposition is carried out on echo signals generated by different sub-band signals on a time domain to obtain spliced detection signals.
Wherein the phase correcting the received plurality of echo signals comprises:
the echo signal A or the echo signal B is phase shifted by c + pi so that the variance of the echo signal A and the echo signal B is minimized.
Specifically, referring to FIG. 5, FIG. 5 shows a flow chart for calculating the error of two subband signals, i.e., finding the phase difference between the echo signals of the two subband signals, according to an exemplary embodiment.
Two echo signals are selected from the echo signals 1, 2 and 3 … … and named as an echo signal A and an echo signal B, and when the phase shift c is carried out on the echo signal of one sub-band signal, the variance of the echo signal A and the echo signal B is minimum, namely the phase error of the echo signal A and the echo signal B is obtained.
It should be noted that the variance of the echo signal a and the echo signal B is the variance of the echo part, but not the variance of the noise part, and according to the signal coherence principle, when the phase difference of two coherent signals is pi, the two signals have destructive interference, at this time, the variance between the two signals is the largest, and when the phase difference is 0, the two signals have coherent superposition. Therefore, a complete signal time width should be used as a sampling window, and if it is required to ensure that echo signals exist in the sampling window and the error of the echo signals exists in the sampling window, a phase shift amount-pi with the largest superposition error in the sampling window should be found as a phase shift amount with the smallest error. The error in this window must be the error of the signal, not the error of the noise. And the phase shift amount-pi is the minimum variance phase shift amount.
Therefore, the error process after the phase shift c between the two signals is:
1. phase shift of c, sampling window of w, samples of s
2. Performing c + pi phase shift on one echo signal of the echo signal A or the echo signal B
3. All sampling points between two signals of a retrieval wave signal A and an echo signal B
4. Calculating the variance of two signals of an echo signal A and an echo signal B for a window with the length of w from each sampling point to the rear of the sampling point
5. The inverse of the largest variance in the results is taken as the variance of the phase shift amount c.
The relation between phase shift, sampling and error is simulated in MATLAB software, and it can be seen that, in one period, the stronger the echo signal is at different sampling positions, the larger the error fluctuation in the phase shift direction is. The global error has a highest point, and the phase shift amount-pi of the highest point is the lowest point of the signal error, specifically, referring to fig. 6, fig. 6 is a phase shift-sampling-error trend diagram according to an exemplary embodiment.
In a specific practice, the "performing real-time phase correction on the echo signal" in step S13 may be implemented in various ways, where another way may be:
calculating the coordinate error of a sampling point in the echo signal, specifically:
determining an initial position and selecting a direction phasor, adding the direction phasor and the initial position to obtain a vector of a detection point A, and adding a reverse direction vector of the direction phasor and the initial position to obtain a vector of a detection point B;
calculating the variance of the detection point A and the detection point B, taking the detection point with small variance as a first current position, calculating the variance of the first current position, storing the variance, selecting the minimum value in the iteration result as the current optimal position 1, and judging whether the current optimal position is converged;
if the convergence is reached, outputting a minimum value, and selecting an optimal position;
if not, the initial position is determined again and the direction phasor is selected.
Referring specifically to fig. 7A, fig. 7A is a flow chart illustrating searching for errors using the longicorn whisker algorithm according to an exemplary embodiment,
1. firstly, randomly determining an initial position, namely a random phase shift and a random sampling point;
2. calculating the variance of the current position and storing the variance;
3. randomly selecting a direction vector, and adding the direction vector with a certain length to the initial position to be used as a vector of the detection point A;
4. adding the opposite direction of the direction vector to the initial position according to the same length to be used as the vector of the detection point B;
5. calculating the variance of the position of the probe point A, B;
6. if the variance of the detection point A is smaller than that of the detection point B, taking the position of the detection point A as a new current position;
7. if the variance of the detection point B is smaller than that of the detection point A, taking the position of the detection point B as a new current position;
8. calculating the variance of the current position, storing the variance, and taking the minimum value in the example iteration result as the current optimal position;
9. and judging whether the optimal position result is converged, namely whether the optimal position is unchanged in iteration of a certain number of times.
10. If the convergence is reached, the process is ended. If not, the initial position and the selected direction phasor are determined again.
The results obtained, please refer to fig. 7B, where fig. 7B is a graph illustrating the number of iterations of the longicorn whisker algorithm according to an exemplary embodiment.
In a specific practice, the "performing real-time phase correction on the echo signal" in step S13 may be implemented in various ways, where another way may be:
solving n Levy solution coordinates according to a Levy flight algorithm, wherein n is far less than a solution quantity m existing in a vector space, and selecting a second current position;
calculating and storing the variance of the second current position;
judging whether the Levie solution is to be discarded or not by using probability Pa, and calculating a random solution of the solution to be discarded between two Levie solution space connecting lines;
comparing the Levin solution with the random solution, if the Levin solution is smaller than the random solution, taking the Levin solution as a result of the current iteration, otherwise, taking the random solution as a result of the current iteration;
comparing the result of the current iteration with the minimum value in the results of the previous iterations, and judging whether the current optimal position is converged;
if the convergence is reached, outputting a minimum value, and selecting an optimal position;
if not, the Levin solution coordinates are determined again.
Referring specifically to fig. 8A, fig. 8A is a flow chart illustrating searching for errors using the cuckoo algorithm according to an exemplary embodiment,
1. initializing;
2. selecting n lavi solutions using lavi flight, n < m (m is the number of solutions that may exist in the vector space), specifically referring to fig. 8B, fig. 8B is a lavi flight diagram according to an exemplary embodiment;
3. calculating the variance of the current position and storing the variance;
4. to discard each solution with a probability P;
5. solving a new random solution given to each abandoned solution in a way that a new space position is randomly selected between space connecting lines of the other two random Levin solutions to serve as a random solution;
6. comparing each solution, if the Levy solution is smaller than the random solution, taking the Levy solution as the current iteration result, and if not, taking the random solution as the current iteration result;
7. selecting the minimum value as the iteration result in the iteration solution;
8. selecting a minimum value from the iteration results of the previous times as a currently found minimum value;
9. if the minimum value found at present is converged, namely in the iteration of a certain number of times, the optimal position is not changed;
10. if the convergence is reached, the process is ended. If not, the Lave flight is reused to select n Lave solutions.
The result obtained, please refer to fig. 8C, and fig. 8C is a graph illustrating the number of iterations corresponding to the cuckoo algorithm according to an exemplary embodiment.
Example two
Referring to fig. 9, fig. 9 is a schematic diagram illustrating a step frequency control system for a marine vibrator according to an exemplary embodiment, where the step frequency control system 900 for a marine vibrator, as shown in fig. 9, includes:
the dividing module 901 is configured to acquire a linear frequency sweep signal and divide the linear frequency sweep signal into a plurality of subband signals according to a preset step frequency, where the plurality of subband signals are used to excite a plurality of controllable seismic sources;
a receiving module 902, configured to receive an echo signal of the subband signal, where the echo signal carries formation information of different depths;
and a correcting module 903, configured to perform real-time phase correction on the echo signal, and synthesize a detection signal by using a step frequency.
It should be noted that, an application scenario to which the technical scheme provided by the embodiment is applicable is in the technical field of marine seismic exploration.
It can be understood that, in the technical solution provided in this embodiment, the dividing module 901 is configured to acquire a linear frequency sweep signal, divide the linear frequency sweep signal into a plurality of subband signals according to a preset step frequency, wherein, the plurality of subband signals are used for exciting a plurality of vibroseis, the receiving module 902 is used for receiving echo signals of the subband signals, and the echo signals carry formation information of different depths, the correcting module 903, the method and the device are used for performing real-time phase correction on the echo signals and synthesizing the detection signals through the stepping frequency.
In addition, a longicorn algorithm or a cuckoo algorithm is adopted to search for the minimum phase error and obtain the optimal splicing position, so that the synthesized phase is more accurate, the calculation amount of the algorithm is greatly reduced, and the efficiency is improved.
EXAMPLE III
A step frequency control apparatus for a marine vibrator according to an exemplary embodiment is shown, comprising: the method described above.
It can be understood that, in the technical scheme provided in this embodiment, a linear frequency sweep signal is obtained first, and the linear frequency sweep signal is divided into a plurality of sub-band signals according to a preset step frequency, where the plurality of sub-band signals are used to excite a plurality of controllable seismic sources, receive echo signals of the sub-band signals, and the echo signals carry formation information of different depths, and perform real-time phase correction on the echo signals, and synthesize a detection signal through the step frequency.
In addition, a longicorn algorithm or a cuckoo algorithm is adopted to search for the minimum phase error and obtain the optimal splicing position, so that the synthesized phase is more accurate, the calculation amount of the algorithm is greatly reduced, and the efficiency is improved.
It is understood that the same or similar parts in the above embodiments may be mutually referred to, and the same or similar parts in other embodiments may be referred to for the content which is not described in detail in some embodiments.
Any process or method descriptions in flow charts or otherwise described herein may be understood as representing modules, segments, or portions of code which include one or more executable instructions for implementing specific logical functions or steps in the process, and alternate implementations are included within the scope of the preferred embodiment of the present invention in which functions may be executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved, as would be understood by those reasonably skilled in the art of the present invention.
It should be understood that portions of the present invention may be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, the various steps or methods may be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, any one or combination of the following techniques, which are known in the art, may be used: a discrete logic circuit having a logic gate circuit for implementing a logic function on a data signal, an application specific integrated circuit having an appropriate combinational logic gate circuit, a Programmable Gate Array (PGA), a Field Programmable Gate Array (FPGA), or the like.
It will be understood by those skilled in the art that all or part of the steps carried by the method for implementing the above embodiments may be implemented by hardware related to instructions of a program, which may be stored in a computer readable storage medium, and when the program is executed, the program includes one or a combination of the steps of the method embodiments.
In addition, functional units in the embodiments of the present invention may be integrated into one processing module, or each unit may exist alone physically, or two or more units are integrated into one module. The integrated module can be realized in a hardware mode, and can also be realized in a software functional module mode. The integrated module, if implemented in the form of a software functional module and sold or used as a stand-alone product, may also be stored in a computer readable storage medium.
The storage medium mentioned above may be a read-only memory, a magnetic or optical disk, etc.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
Claims (10)
1. A method of step frequency control of a marine vibroseis, comprising:
acquiring a linear frequency sweeping signal, and dividing the linear frequency sweeping signal into a plurality of sub-band signals according to a preset stepping frequency, wherein the plurality of sub-band signals are used for exciting a plurality of controllable seismic sources;
receiving echo signals of the sub-band signals, wherein the echo signals carry stratum information of different depths;
and carrying out real-time phase correction on the echo signals, and synthesizing detection signals through stepping frequency.
2. The method according to claim 1, wherein the dividing the linear frequency sweep signal into a plurality of subband signals according to a preset step frequency specifically comprises:
the bandwidth B and the starting frequency f of the linear sweep frequency signal are measured 0 Dividing the signal into N sub-band signals;
and the overlap ratio of the sub-band signals is r, wherein r is more than 0;
then, sub-band signal bandwidth
Time width
Starting frequency of subband n is f n ＝f 0 +(n-1)(1-r)b。
3. The method of claim 2, wherein the real-time phase correcting the echo signals comprises:
performing time shift and phase correction on a plurality of received echo signals;
and carrying out coherent superposition on the received echo signals on a time domain to obtain a spliced detection signal.
4. The method according to claim 3, wherein said time shifting a plurality of said received echo signals is performed by:
time shifting a plurality of received echo signals, wherein the time shifting amount is the time width T of the sub-band signal sub 。
5. The method of claim 3, wherein the phase correcting the received plurality of echo signals comprises:
the echo signal A or the echo signal B is phase shifted by c + pi so that the variance of the echo signal A and the echo signal B is minimized.
6. The method according to claim 5, wherein said phase correcting a plurality of said received echo signals is performed by:
and phase shifting the echo signal A or the echo signal B by c + pi, selecting a sampling point s between the echo signal A and the echo signal B, calculating the variance of the echo signal A and the echo signal B in a sampling window with a length of w from the sampling point s to the sampling point, and taking the inverse number of the maximum variance as the variance of the phase shift amount c.
7. The method of claim 5, wherein the phase correcting the received plurality of echo signals further comprises:
calculating the coordinate error of a sampling point in the echo signal, specifically:
determining an initial position and selecting a direction phasor, adding the direction phasor and the initial position to obtain a vector of a detection point A, and adding a reverse direction vector of the direction phasor and the initial position to obtain a vector of a detection point B;
calculating the variance of the detection point A and the detection point B, taking the detection point with small variance as a first current position, calculating the variance of the first current position, storing the variance, selecting the minimum value in the iteration result as the current optimal position 1, and judging whether the current optimal position is converged;
if convergence occurs, outputting a minimum value, and selecting an optimal position;
if not, the initial position is determined again and the direction phasor is selected.
8. The method of claim 5, wherein the phase correcting the received plurality of echo signals further comprises:
solving n Levy solution coordinates according to a Levy flight algorithm, wherein n is far less than a solution quantity m existing in a vector space, and selecting a second current position;
calculating and storing the variance of the second current position;
judging whether the Levie solution is to be discarded or not by using probability Pa, and calculating a random solution of the solution to be discarded between two Levie solution space connecting lines;
comparing the Levin solution with the random solution, if the Levin solution is smaller than the random solution, taking the Levin solution as a result of the current iteration, otherwise, taking the random solution as a result of the current iteration;
comparing the result of the current iteration with the minimum value in the results of the previous iterations, and judging whether the current optimal position is converged;
if the convergence is reached, outputting a minimum value, and selecting an optimal position;
if not, the Levin solution coordinates are determined again.
9. A step frequency control system for a marine vibroseis, comprising:
the system comprises a dividing module, a processing module and a control module, wherein the dividing module is used for acquiring a linear sweep frequency signal and dividing the linear sweep frequency signal into a plurality of sub-band signals according to a preset stepping frequency, and the plurality of sub-band signals are used for exciting a plurality of controllable seismic sources;
the receiving module is used for receiving echo signals of the sub-band signals, and the echo signals carry stratum information of different depths;
and the correction module is used for carrying out real-time phase correction on the echo signals and synthesizing detection signals through stepping frequency.
10. A step frequency control apparatus for a marine vibroseis, comprising: a process as claimed in any one of claims 1 to 8.
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