A method for obtaining transient electromagnetic step response

Abstract

The present invention provides a method for acquiring a transient electromagnetic step response, which samples and records the transient electromagnetic arbitrary emission waveform and response at all times to obtain a transient electromagnetic full waveform and a transient electromagnetic full waveform response; a pulse waveform is used to discretize the transient electromagnetic arbitrary emission waveform, and the discrete results are summarized and recursively obtained to obtain a relationship between the transient electromagnetic arbitrary waveform response and the transient electromagnetic step response; the relationship can be used to convert the transient electromagnetic arbitrary waveform response into a step waveform response. The method for acquiring the transient electromagnetic step response of the present invention can obtain the transient electromagnetic step response under ideal conditions, thereby improving the exploration accuracy.

Description

Technical Field

[0001] The invention belongs to the technical field of geophysical exploration, relates to transient electromagnetic, and specifically to a method for acquiring transient electromagnetic step response. Background Art

[0002] Transient electromagnetic method is an exploration method that observes transient electromagnetic secondary magnetic field signals during the period when the transmitting current is turned off by passing the transmitting current through the ground transmitting loop. Due to the advantages of high construction efficiency and good exploration effect, transient electromagnetic method is widely used by geophysicists at home and abroad in coal fields, metal mines, geological surveys and other fields. From a theoretical analysis, in the process of exploration using transient electromagnetic method, the faster the transmitting current is turned off, the more the measured response after the shutdown conforms to the basic theory of transient electromagnetic field, and the more its response characteristics can reflect the electrical laws of underground media. However, in actual applications, it is found that it is difficult for the transmitter to accurately control the transmitting current to turn it off in a step waveform, causing the early data of transient electromagnetic field to be affected by the transmitting waveform of transient electromagnetic wave, thereby affecting the exploration accuracy.

[0003] A Chinese invention patent with application publication number CN112731539A discloses a zero-flux multi-coil receiving transient electromagnetic detection device. The device uses a receiving coil of a special shape. By adjusting the positions of two or more transmitting coils, the total magnetic flux of the primary magnetic field generated by the transmitting coil inside the receiving coil is zero, thereby effectively eliminating the interference of the primary field on the receiving coil.

[0004] The Chinese utility model patent with authorization announcement number CN212808654U discloses a mining intrinsically safe coplanar equivalent reverse flux transient electromagnetic instrument. The patent uses a coplanar equivalent reverse flux structure of multiple groups of sub-transmitting coils to make the total magnetic flux generated by the multiple groups of sub-transmitting coils in the receiving coil zero, which can effectively reduce the influence of mutual inductance.

[0005] The Chinese utility model patent with authorization announcement number CN211406004U discloses a signal transmitting device that reduces the transient electromagnetic shutdown time. The patent uses a twisted pair and a dual electronic switch combination to effectively reduce the shutdown time of the transmitting current, making the measurement of the early channel signal of the transient electromagnetic field more accurate, thereby improving the exploration accuracy of transient electromagnetic.

[0006] The above-mentioned prior arts all start from the hardware perspective, using the combination of the position, size, and emission current intensity between multiple transmitting coils, and adjusting the magnetic flux of the primary field inside the receiving coil to zero at the moment of shutdown through the transmitting magnetic field in the opposite direction, so as to obtain the transient electromagnetic step response of the step emission waveform. However, these magnetic fields in the opposite direction also weaken the primary magnetic field near the underground exploration target, weakening the excitation energy, and the corresponding received secondary magnetic field also weakens, causing the exploration depth to become shallower, thereby affecting the exploration effect. Summary of the invention

[0007] In view of the defects and shortcomings of the prior art, the purpose of the present invention is to provide a method for obtaining a transient electromagnetic step response, so as to solve the technical problem in the prior art that the transient electromagnetic field is affected by the transient electromagnetic emission waveform, resulting in reduced exploration accuracy.

[0008] In order to solve the above technical problems, the present invention adopts the following technical solutions to achieve the above problems:

[0009] A method for acquiring a transient electromagnetic step response, the method samples and records a transient electromagnetic arbitrary emission waveform and response at all times to obtain a transient electromagnetic full waveform and a transient electromagnetic full waveform response; a pulse waveform is used to discretize the transient electromagnetic arbitrary emission waveform, and the discrete results are summarized and recursively obtained to obtain a relationship between a transient electromagnetic arbitrary waveform response and a transient electromagnetic step response; the relationship can be used to convert the transient electromagnetic arbitrary waveform response into a step waveform response.

[0010] The present invention also has the following technical features:

[0011] Specifically, the method comprises the following steps:

[0012] Step 1: emission, recording and sampling;

[0013] Emitting and recording a transient electromagnetic emission waveform to obtain a transient electromagnetic arbitrary waveform Λ, wherein the transient electromagnetic arbitrary waveform Λ can be discretized into a superposition of multiple pulse waveforms; the transient electromagnetic arbitrary waveform Λ includes a continuous segment transient electromagnetic arbitrary waveform Λ1 and a descending segment transient electromagnetic arbitrary waveform Λ2;

[0014] Sampling the transient electromagnetic responses of the sustained section, the descending section, and the section after the shutdown to obtain a transient electromagnetic full waveform response P, wherein the transient electromagnetic full waveform response P can be discretized into a superposition of multiple pulse responses;

[0015] The recording and sampling are both performed in a linear and equally spaced manner, and the number of sampling points is m+n;

[0016] Step 2: Discretization, induction and recursion;

[0017] The transient electromagnetic full waveform response P obtained in step 1 is used to discretize the descending transient electromagnetic arbitrary waveform Λ2 described in step 1. The specific process of the discretization is as follows:

[0018] The mth pulse waveform is at t m The transient electromagnetic step response at time S m,m , as shown in Formula I:

[0019] S m,m =P m Formula I;

[0020] Where:

[0021] S m,m Indicates the mth pulse waveform at t m The transient electromagnetic step response at the moment;

[0022] P m Indicates t m The transient electromagnetic full waveform response actually recorded at all times;

[0023] The mth pulse waveform is at t j The transient electromagnetic step response S at time m,j , as shown in Formula II:

[0024] S m,j =S m,j-1 +P m Formula II;

[0025] Where:

[0026] S m,j Indicates the mth pulse waveform at t j The transient electromagnetic step response at time, in V;

[0027] S m,j-1 Indicates the mth pulse waveform at t j-1 The transient electromagnetic step response at time, in V;

[0028] P m Indicates t m The transient electromagnetic full waveform response actually recorded at the moment, in V;

[0029] j=m+1,m+2,...,m+n-1;

[0030] Substitute the above formula I into the above formula II to obtain the transient electromagnetic step response corresponding to the m-th pulse waveform;

[0031] The m-1th pulse waveform is at t m-1 The transient electromagnetic step response S at time m-1,m-1 , as shown in Formula III:

[0032] S m-1,m-1 =P m-1 Formula III;

[0033] Where:

[0034] S m-1,m-1 Indicates the m-1th pulse waveform at t m-1 The transient electromagnetic step response at time, in V;

[0035] P m-1 Indicates t m-1 The transient electromagnetic full waveform response actually recorded at the moment, in V;

[0036] The m-1th pulse waveform is at t j The transient electromagnetic step response S at time m-1,j , as shown in Formula IV:

[0037] S m-1,j =S m-1,j-1 +P j-1 Formula IV;

[0038] Where:

[0039] S m-1,j Indicates the m-1th pulse waveform at t j The transient electromagnetic step response at time, in V;

[0040] S m-1,j-1 Indicates the m-1th pulse waveform at t j-1 The transient electromagnetic step response at time, in V;

[0041] P j-1 Indicates t j-1 The transient electromagnetic full waveform response actually recorded at the moment, in V;

[0042] j=m+1,m+2,...,m+n-2;

[0043] Substitute the above formula III into the above formula IV to obtain the transient electromagnetic step response corresponding to the m-1th pulse waveform;

[0044] After summarizing and recursively analyzing the discretely obtained formulas Ⅰ, Ⅱ, Ⅲ and Ⅳ, we can obtain the relationship between the transient electromagnetic arbitrary waveform response and the transient electromagnetic step response, namely, formula V:

[0045]

[0046] Where:

[0047] S i,j Indicates the i-th pulse waveform at tj The transient electromagnetic step response at time, in V;

[0048] P j Indicates t j The transient electromagnetic full waveform response actually recorded at the moment, in V;

[0049] S i,j-1 Indicates the i-th pulse waveform at t j-1 The transient electromagnetic step response at time, in V;

[0050] P j-1 Indicates t j-1 The transient electromagnetic full waveform response actually recorded at the moment, in V;

[0051] Step 3: Convert;

[0052] The transient electromagnetic full waveform response P obtained in step 1 is iterated using formula V, so that the transient electromagnetic step response corresponding to the transient electromagnetic arbitrary waveform at any time can be obtained.

[0053] Specifically, in step 1, the sampling time T of the sampling is as shown in the following formula, and the unit of the sampling time T is s:

[0054] T=(t1,t2,...,t m ,t m+1 ,...,t m+n );

[0055] The transient electromagnetic full waveform response P is shown in the following formula, and the unit of the transient electromagnetic waveform response P is V:

[0056] P=(P1,P2,...,P m ,P m+1 ,...,P m+n ).

[0057] Specifically, in step 1, the transient electromagnetic arbitrary waveform is specifically as follows: firstly, the emission is performed with a constant emission current I0, and then the emission current is reduced for emission, and the unit of the emission current is A; the moment when the emission current starts to decrease is the shutdown start time t1, and t1=0, and the moment when the emission current is reduced to zero is the shutdown end time t off .

[0058] Specifically, in step 1, the continuous-segment transient electromagnetic arbitrary waveform Λ1 is the waveform before the shutdown start time t1; the descending-segment transient electromagnetic arbitrary waveform Λ2 is the waveform after the shutdown start time t1.

[0059] Specifically, in step 1, m is the number of sampling points during the shutdown period, and the shutdown period is from the shutdown start time t1 to the shutdown end time t off The time period between the shutdown and the shutdown is the shutdown termination time t. off to m+n The time period between.

[0060] Specifically, in step 1, the recording interval is R, and the sampling interval is r; the sampling interval r is equal to the recording interval R.

[0061] Specifically, in step 1, the recording interval is R, and the sampling interval is r; if the sampling interval r is not equal to the recording interval R, an interpolation algorithm is used to resample the transient electromagnetic arbitrary emission waveform.

[0062] Specifically, the emission of the transient electromagnetic arbitrary waveform, the recording and sampling of the arbitrary waveform and the full waveform response are realized by using a transient electromagnetic processing device;

[0063] The transient electromagnetic processing device includes a transient electromagnetic ground transmitter, which is connected to a transmitting cable; and also includes a transient electromagnetic ground receiver, which is connected to an induced electromotive force receiving probe;

[0064] The transient electromagnetic ground transmitter is used to transmit and record the transient electromagnetic transmission waveform to obtain the transient electromagnetic arbitrary waveform Λ; the transient electromagnetic ground receiver is used to sample the transient electromagnetic response to obtain the transient electromagnetic full waveform response P.

[0065] Specifically, the transient electromagnetic ground transmitter and the transient electromagnetic ground receiver are synchronized using GPS or a quartz clock.

[0066] Compared with the prior art, the present invention has the following beneficial technical effects:

[0067] (I) The method for obtaining the transient electromagnetic step response of the present invention adopts the relationship between the transient electromagnetic arbitrary waveform response and the transient electromagnetic step response to iterate the transient electromagnetic full waveform response, that is, it is possible to obtain the transient electromagnetic step response under ideal conditions, thereby improving the exploration accuracy.

[0068] (II) The method for acquiring the transient electromagnetic step waveform of the present invention can obtain the transient electromagnetic step response without adding new hardware, and will not reduce the primary excitation field. The method is simple to operate and easy to implement.

[0069] (III) The transient electromagnetic processing device of the present invention can emit transient electromagnetic field waveforms, and can record and sample the emitted waveforms and responses over a full period of time, and is suitable for geological exploration operations in field environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 It is a schematic diagram of the transient electromagnetic full waveform and the transient electromagnetic full waveform response.

[0071] Figure 2 A discrete schematic diagram of the transient electromagnetic arbitrary emission waveform.

[0072] Figure 3 Schematic diagram of the transformation relationship between transient electromagnetic step response and transient electromagnetic pulse response

[0073] Figure 4 Schematic diagram of transient electromagnetic step waveform and transient electromagnetic step response, where the solid line represents the transient electromagnetic step waveform and the dotted line represents the transient electromagnetic step response.

[0074] Figure 5 It is a transient electromagnetic processing device.

[0075] The meanings of the numbers in the figure are: 1-transient electromagnetic ground transmitter, 2-transmitting cable, 3-transient electromagnetic ground receiver, 4-induced electromotive force receiving probe, 5-stratum to be explored, 6-low-resistance body, 7-primary magnetic field, 8-secondary magnetic field;

[0076] Λ-transient electromagnetic arbitrary waveform, P-transient electromagnetic full waveform response, S-transient electromagnetic step response;

[0077] Λ1-continuous transient electromagnetic arbitrary waveform, Λ2-decreasing transient electromagnetic arbitrary waveform.

[0078] The technical solution of the present invention is further described below in conjunction with embodiments. DETAILED DESCRIPTION

[0079] Based on the current status and analysis of the background technology, the present invention provides a method for acquiring a transient electromagnetic step response, which provides a new technical idea for the technical problem that the transmission waveform has an adverse effect on the transient electromagnetic field, thereby reducing the exploration accuracy, from the perspective of algorithm rather than hardware.

[0080] It should be noted that all the devices used in the present invention, unless otherwise specified, are devices known in the art.

[0081] In accordance with the above technical scheme, specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent changes made on the basis of the technical scheme of this application fall within the protection scope of the present invention.

[0082] Embodiment 1:

[0083] This embodiment provides a method for obtaining a transient electromagnetic step response, which specifically includes the following steps:

[0084] Step 1: emission, recording and sampling;

[0085] Emitting and recording a transient electromagnetic emission waveform to obtain a transient electromagnetic arbitrary waveform Λ, wherein the transient electromagnetic arbitrary waveform Λ can be discretized into a superposition of multiple pulse waveforms; the transient electromagnetic arbitrary waveform Λ includes a continuous segment transient electromagnetic arbitrary waveform Λ1 and a descending segment transient electromagnetic arbitrary waveform Λ2;

[0086] Sampling the transient electromagnetic responses of the sustained section, the descending section, and the section after the shutdown to obtain a transient electromagnetic full waveform response P, wherein the transient electromagnetic full waveform response P can be discretized into a superposition of multiple pulse responses;

[0087] The recording and sampling are both performed in a linear and equally spaced manner, and the number of sampling points is m+n;

[0088] Step 2: Discretization, induction and recursion;

[0089] The transient electromagnetic full waveform response P obtained in step 1 is used to discretize the descending transient electromagnetic arbitrary waveform Λ2 described in step 1. The specific process of the discretization is as follows:

[0090] The mth pulse waveform is at t m The transient electromagnetic step response at time S m,m , as shown in Formula I:

[0091] S m,m =P m Formula I;

[0092] Where:

[0093] S m,m Indicates the mth pulse waveform at t m The transient electromagnetic step response at the moment;

[0094] P m Indicates t m The transient electromagnetic full waveform response actually recorded at all times;

[0095] The mth pulse waveform is at t j The transient electromagnetic step response S at time m,j , as shown in Formula II:

[0096] S m,j =S m,j-1 +P m Formula II;

[0097] Where:

[0098] S m,j Indicates the mth pulse waveform at t j The transient electromagnetic step response at time, in V;

[0099] S m,j-1 Indicates the mth pulse waveform at t j-1 The transient electromagnetic step response at time, in V;

[0100] P m Indicates t m The transient electromagnetic full waveform response actually recorded at the moment, in V;

[0101] j=m+1,m+2,...,m+n-1;

[0102] Substitute the above formula I into the above formula II to obtain the transient electromagnetic step response corresponding to the m-th pulse waveform;

[0103] The m-1th pulse waveform is at t m-1 The transient electromagnetic step response S at time m-1,m-1 , as shown in Formula III:

[0104] S m-1,m-1 =P m-1 Formula III;

[0105] Where:

[0106] S m-1,m-1 Indicates the m-1th pulse waveform at t m-1 The transient electromagnetic step response at time, in V;

[0107] P m-1 Indicates t m-1 The transient electromagnetic full waveform response actually recorded at the moment, in V;

[0108] The m-1th pulse waveform is at t j The transient electromagnetic step response S at time m-1,j , as shown in Formula IV:

[0109] S m-1,j =S m-1,j-1 +P j-1 Formula IV;

[0110] Where:

[0111] S m-1,j Indicates the m-1th pulse waveform at t j The transient electromagnetic step response at time, in V;

[0112] Sm-1,j-1 Indicates the m-1th pulse waveform at t j-1 The transient electromagnetic step response at time, in V;

[0113] P j-1 Indicates t j-1 The transient electromagnetic full waveform response actually recorded at the moment, in V;

[0114] j=m+1,m+2,...,m+n-2;

[0115] Substitute the above formula III into the above formula IV to obtain the transient electromagnetic step response corresponding to the m-1th pulse waveform;

[0116] After summarizing and recursively analyzing the discretely obtained formulas Ⅰ, Ⅱ, Ⅲ and Ⅳ, we can obtain the relationship between the transient electromagnetic arbitrary waveform response and the transient electromagnetic step response, namely, formula V:

[0117]

[0118] Where:

[0119] S i,j Indicates the i-th pulse waveform at t j The transient electromagnetic step response at time, in V;

[0120] P j Indicates t j The transient electromagnetic full waveform response actually recorded at the moment, in V;

[0121] S i,j-1 Indicates the i-th pulse waveform at t j-1 The transient electromagnetic step response at time, in V;

[0122] P j-1 Indicates t j-1 The transient electromagnetic full waveform response actually recorded at the moment, in V;

[0123] Step 3: Convert;

[0124] The transient electromagnetic full waveform response P obtained in step 1 is iterated using formula V, so that the transient electromagnetic step response corresponding to the transient electromagnetic arbitrary waveform at any time can be obtained.

[0125] As a specific solution of this embodiment, in step 1, the sampling time T of the sampling is as shown in the following formula, and the unit of the sampling time T is s:

[0126] T=(t1,t2,...,t m ,t m+1 ,...,t m+n );

[0127] The transient electromagnetic full waveform response P is shown in the following formula, and the unit of the transient electromagnetic full waveform response P is V:

[0128] P=(P1,P2,...,P m ,P m+1 ,...,P m+n ).

[0129] As a specific solution of this embodiment, in step 1, the transient electromagnetic arbitrary waveform is specifically as follows: first, the emission is performed with a constant emission current I0, and then the emission current is reduced for emission, and the unit of the emission current is A; the moment when the emission current begins to decrease is the shutdown start time t1, and t1=0, and the moment when the emission current is reduced to zero is the shutdown end time t off .

[0130] As a specific solution of this embodiment, in step 1, the continuous-segment transient electromagnetic arbitrary waveform Λ1 is the waveform before the shutdown start time t1; the descending-segment transient electromagnetic arbitrary waveform Λ2 is the waveform after the shutdown start time t1.

[0131] As a specific solution of this embodiment, in step 1, m is the number of sampling points during the shutdown period, and the shutdown period is from the shutdown start time t1 to the shutdown end time t off The time period between the shutdown and the shutdown is the shutdown termination time t. off to m+n The time period between.

[0132] As a specific solution of this embodiment, in step 1, the recording interval is R, and the sampling interval is r; the sampling interval r is equal to the recording interval R.

[0133] As a specific solution of this embodiment, in step 1, the recording interval is R, and the sampling interval is r; if the sampling interval r is not equal to the recording interval R, an interpolation algorithm is used to resample the transient electromagnetic arbitrary emission waveform.

[0134] In this embodiment, the sampling interval is reduced by an interpolation algorithm, so that the conversion accuracy can be improved.

[0135] In this embodiment, the transient electromagnetic ground transmitter periodically transmits positive and negative alternating trapezoidal waves. The full waveform response and transmission waveform of a single period of transient electromagnetic field are as follows: Figure 1 shown.

[0136] In this embodiment, the transient electromagnetic arbitrary emission waveform is discretized as follows: Figure 2As shown in the figure, point O is the starting moment of the transient electromagnetic field of a single emission cycle, the discrete number is m, and the discrete interval is R.

[0137] In this embodiment, there is a difference between the impulse response and the transient electromagnetic step response as follows: Figure 3 As shown in the conversion relationship, two transient electromagnetic step responses can be synthesized into a pulse response with a width of R through a delay of R.

[0138] In this embodiment, the transient electromagnetic full waveform response (P1, P2, ..., P m ,P m+1 ,...,P m+n ) corresponds to the transient electromagnetic step response time range of (t2, t3, ..., t n ), the converted transient electromagnetic step response is as follows Figure 4 shown.

[0139] Embodiment 2:

[0140] This embodiment provides a method for acquiring a transient electromagnetic step response. This method is based on the method for acquiring a transient electromagnetic step response given in Example 1. Further, the emission of the transient electromagnetic arbitrary waveform, the recording and sampling of the arbitrary waveform and the full waveform response are implemented using a transient electromagnetic processing device.

[0141] Specifically, a transient electromagnetic processing device, such as Figure 5 As shown, it includes a transient electromagnetic ground transmitter 1, which is connected to a transmitting cable 2; it also includes a transient electromagnetic ground receiver 3, which is connected to an induced electromotive force receiving probe 4;

[0142] The transient electromagnetic ground transmitter 1 is used to transmit and record the transient electromagnetic arbitrary waveform to obtain the transient electromagnetic arbitrary waveform Λ; the transient electromagnetic ground receiver 3 is used to sample the transient electromagnetic response to obtain the transient electromagnetic full waveform response P.

[0143] As a specific solution of this embodiment, the transient electromagnetic ground transmitter 1 and the transient electromagnetic ground receiver 3 use GPS or a quartz clock for time synchronization.

[0144] In this embodiment, the transmitting cable 2 is a loop source or an electrical source.

[0145] The working principle of the transient electromagnetic processing device of the present invention is as follows:

[0146] The transient electromagnetic ground transmitter 1 transmits a transient electromagnetic primary field 7 under the formation 5 to be explored, and the transmitting cable 2 is used to transmit the transmitting current. When there is a low-resistance body 6 under the formation 5 to be explored, an induced eddy current is induced in the low-resistance body 6 during the power failure period, generating a secondary magnetic field 8. The transient electromagnetic ground receiver 3 receives the signal of the secondary magnetic field 8 through the induced electromotive force receiving probe 4 and records it. By observing and studying the changing law of the secondary magnetic field 8, the distribution of the low-resistance body 6 under the formation 5 to be explored can be inferred.

Claims

1. A method for obtaining a transient electromagnetic step response, characterized in that: The method samples and records the transient electromagnetic arbitrary emission waveform and response at all times to obtain the transient electromagnetic full waveform and transient electromagnetic full waveform response; the transient electromagnetic arbitrary emission waveform is discretized by using a pulse waveform, and the discrete results are summarized and recursively obtained to obtain the relationship between the transient electromagnetic arbitrary waveform response and the transient electromagnetic step response; the relationship can be used to convert the transient electromagnetic arbitrary waveform response into a step waveform response; The method specifically comprises the following steps: Step 1: emission, recording and sampling; Emitting and recording a transient electromagnetic emission waveform to obtain a transient electromagnetic arbitrary waveform Λ, wherein the transient electromagnetic arbitrary waveform Λ can be discretized into a superposition of multiple pulse waveforms; the transient electromagnetic arbitrary waveform Λ includes a continuous segment transient electromagnetic arbitrary waveform Λ1 and a descending segment transient electromagnetic arbitrary waveform Λ2; Sampling the transient electromagnetic responses of the sustained section, the descending section, and the section after the shutdown to obtain a transient electromagnetic full waveform response P, wherein the transient electromagnetic full waveform response P can be discretized into a superposition of multiple pulse responses; The recording and sampling are both performed in a linear and equally spaced manner, and the number of sampling points is m+n; m is the number of sampling points during the shutdown period, and the shutdown period is from the shutdown start time t1 to the shutdown end time t off The time period between the shutdown and the shutdown is the shutdown termination time t. off to m+n the time period between; Step 2: Discretization, induction and recursion; The transient electromagnetic full waveform response P obtained in step 1 is used to discretize the descending transient electromagnetic arbitrary waveform Λ2 described in step 1. The specific process of the discretization is as follows: The mth pulse waveform is at t m The transient electromagnetic step response at time S m,m , as shown in Formula I: S m,m =P m Formula I; Where: S m,m Indicates the mth pulse waveform at t m The transient electromagnetic step response at the moment; P m Indicates t m The transient electromagnetic full waveform response actually recorded at all times; The mth pulse waveform is at t j The transient electromagnetic step response S at time m,j , as shown in Formula II: S m,j =S m,j-1 +P m Formula II; Where: S m,j Indicates the mth pulse waveform at t j The transient electromagnetic step response at time, in V; S m,j-1 Indicates the mth pulse waveform at t j-1 The transient electromagnetic step response at time, in V; P m Indicates t m The transient electromagnetic full waveform response actually recorded at the moment, in V; j=m+1,m+2,...,m+n-1; Substitute the above formula I into the above formula II to obtain the transient electromagnetic step response corresponding to the m-th pulse waveform; The m-1th pulse waveform is at t m-1 The transient electromagnetic step response S at time m-1,m-1 , as shown in Formula III: S m-1,m-1 =P m-1 Formula III; Where: S m-1,m-1 Indicates the m-1th pulse waveform at t m-1 The transient electromagnetic step response at time, in V; P m-1 Indicates t m-1 The transient electromagnetic full waveform response actually recorded at the moment, in V; The m-1th pulse waveform is at t j The transient electromagnetic step response S at time m-1,j , as shown in Formula IV: S m-1,j =S m-1,j-1 +P j-1 Formula IV; Where: S m-1,j Indicates the m-1th pulse waveform at t j The transient electromagnetic step response at time, in V; S m-1,j-1 Indicates the m-1th pulse waveform at t j-1 The transient electromagnetic step response at time, in V; P j-1 Indicates t j-1 The transient electromagnetic full waveform response actually recorded at the moment, in V; j=m+1,m+2,...,m+n-2; Substitute the above formula III into the above formula IV to obtain the transient electromagnetic step response corresponding to the m-1th pulse waveform; After summarizing and recursively analyzing the discretely obtained formulas Ⅰ, Ⅱ, Ⅲ and Ⅳ, we can obtain the relationship between the transient electromagnetic arbitrary waveform response and the transient electromagnetic step response, namely, formula V: Where: S i,j Indicates the i-th pulse waveform at t j The transient electromagnetic step response at time, in V; P j Indicates t j The transient electromagnetic full waveform response actually recorded at the moment, in V; S i,j-1 Indicates the i-th pulse waveform at t j-1 The transient electromagnetic step response at time, in V; P j-1 Indicates t j-1 The transient electromagnetic full waveform response actually recorded at the moment, in V; Step 3: Convert; The transient electromagnetic full waveform response P obtained in step 1 is iterated using formula V, so that the transient electromagnetic step response corresponding to the transient electromagnetic arbitrary waveform at any time can be obtained.

2. The method for obtaining a transient electromagnetic step response according to claim 1, characterized in that: In step 1, the sampling time T of the sampling is as shown in the following formula, and the unit of the sampling time T is s: T=(t1,t2,...,t m ,t m+1 ,...,t m+n ); The transient electromagnetic full waveform response P is shown in the following formula, and the unit of the transient electromagnetic waveform response P is V: P=(P1,P2,...,P m ,P m+1 ,...,P m+n )。 3. The method for obtaining transient electromagnetic step response according to claim 1, characterized in that: In step 1, the transient electromagnetic arbitrary waveform is specifically as follows: first, the emission is performed with a constant emission current I0, and then the emission current is reduced for emission, the unit of the emission current is A; the moment when the emission current begins to decrease is the shutdown start time t1, t1=0, and the moment when the emission current is reduced to zero is the shutdown end time t off .

4. The method for obtaining a transient electromagnetic step response according to claim 1, characterized in that: In step 1, the continuous-segment transient electromagnetic arbitrary waveform Λ1 is the waveform before the shutdown start time t1; the descending-segment transient electromagnetic arbitrary waveform Λ2 is the waveform after the shutdown start time t1.

5. The method for obtaining transient electromagnetic step response according to claim 1, characterized in that: In step 1, the recording interval is R, and the sampling interval is r; the sampling interval r is equal to the recording interval R.

6. The method for obtaining transient electromagnetic step response according to claim 1, characterized in that: In step 1, the recording interval is R, and the sampling interval is r; if the sampling interval r is not equal to the recording interval R, an interpolation algorithm is used to resample the transient electromagnetic arbitrary emission waveform.

7. The method for acquiring transient electromagnetic step response according to claim 1, characterized in that: The emission of the transient electromagnetic arbitrary waveform, the recording and sampling of the arbitrary waveform and the full waveform response are realized by using a transient electromagnetic processing device; The transient electromagnetic processing device comprises a transient electromagnetic ground transmitter (1), wherein the transient electromagnetic ground transmitter (1) is connected to a transmitting cable (2); and also comprises a transient electromagnetic ground receiver (3), wherein the transient electromagnetic ground receiver (3) is connected to an induced electromotive force receiving probe (4); The transient electromagnetic ground transmitter (1) is used to transmit and record the transient electromagnetic transmission waveform to obtain the transient electromagnetic arbitrary waveform Λ; the transient electromagnetic ground receiver (3) is used to sample the transient electromagnetic response to obtain the transient electromagnetic full waveform response P.

8. The method for acquiring transient electromagnetic step response according to claim 7, characterized in that: The transient electromagnetic ground transmitter (1) and the transient electromagnetic ground receiver (3) use GPS or a quartz clock for time synchronization.

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