Aviation transient electromagnetic emission method and device with adaptive matching of geoelectric conditions

Abstract

The invention discloses an aviation transient electromagnetic emission method and device with adaptive matching of geoelectric conditions, and belongs to the technical field of geophysical exploration. The method comprises the following steps: transmitting a transient electromagnetic pulse signal to the underground through a transmitter; the receiver collects a secondary field signal induced by the underground medium and extracts a late signal of an attenuation curve of the secondary field signal; calculating an actual measurement time constant T; presetting a target time constant; and comparing the actually measured time constant with the target time constant, evaluating the geoelectric condition, and adjusting the emission duty ratio based on a PID control algorithm according to the evaluation result. According to the invention, by analyzing the late signal of the attenuation curve of the aviation transient electromagnetic secondary field in real time, the emission duty ratio is dynamically adjusted in real time through negative feedback so as to adapt to the geoelectric conditions of different measurement areas; the method has the remarkable technical advantages of high adaptability, high detection efficiency, low system power consumption, high detection precision, adaptability to complex geoelectric conditions and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of geophysical exploration, and particularly relates to an airborne transient electromagnetic emission method and device with self-adaptive matching of geoelectric conditions. Background Technique

[0002] The Airborne Transient Electromagnetic Method (ATEM) is an efficient geophysical exploration method, which is widely used in the fields of mineral resource exploration, environmental geological survey, groundwater detection, etc. Its basic principle is that the transmitter emits a transient electromagnetic field to the ground, and the receiver receives the secondary field signal induced by the underground medium. By analyzing the attenuation characteristics of the secondary field signal, the electrical property distribution of the underground medium is inferred. The attenuation characteristics of the secondary field signal are closely related to the resistivity of the underground medium. Specifically, the electromagnetic signal attenuates slowly in the low-resistivity area, while the electromagnetic signal attenuates quickly in the high-resistivity area. The early signals in the electromagnetic signal attenuation curve mainly carry shallow geological information, while the late signals mainly reflect deep geological information.

[0003] In practical applications, the underground resistivity of the detection area cannot be predicted in advance in most cases, and the resistivity varies greatly in different areas. However, the existing ATEM systems at home and abroad usually adopt a fixed emission duty cycle and cannot adaptively and dynamically match the resistivity changes in different survey areas. In the low-resistivity area, a small emission duty cycle may not be able to obtain enough late signals, restricting the deep exploration ability; in the high-resistivity area, an excessive duty cycle means a longer emission time, but the effective information of the signal is less, significantly increasing the ineffective power consumption of the system. At the same time, when the emission fundamental frequency is fixed, a larger duty cycle will reduce the number of data points that can be collected per unit time, thereby reducing the spatial sampling rate of the data. The reduction of the sampling rate will directly affect the detection resolution, making the system unable to accurately identify the details of underground targets, and then affecting the detection efficiency.

[0004] This fixed emission duty cycle parameter configuration is difficult to take into account different geoelectric conditions, and the performance of the system in high-resistivity areas and low-resistivity areas will be limited. It not only causes high system power consumption, low detection efficiency (such as a high proportion of ineffective energy consumption in high-resistivity areas), limited detection depth (such as insufficient late signal acquisition in low-resistivity areas), but also leads to signal quality fluctuations (such as a decrease in signal-to-noise ratio in resistivity mutation areas), seriously limiting the exploration accuracy and adaptability under complex geoelectric conditions.

[0005] In response to these problems, although some improvement attempts have been made in the prior art, there are still limitations. For example, the segmented emission technology: the detection area is divided into several segments, and different emission parameters are used for each segment. This method relies on prior geological information, cannot achieve real-time adaptive adjustment and dynamic adaptation, and has low operation efficiency. Therefore, it is of great practical significance to develop an airborne transient electromagnetic emission technology that can adaptively and dynamically match the emission duty cycle according to the geoelectric conditions. Summary of the Invention

[0006] To solve the above technical problems, the present invention provides an airborne transient electromagnetic emission method and device with adaptive matching of geoelectric conditions. By real-time evaluating the late-stage signal of the attenuation curve of the airborne transient electromagnetic secondary field and combining a negative feedback mechanism to dynamically adjust the transmitter duty cycle, the adaptive matching of emission parameters and geoelectric conditions is achieved, thereby improving the detection efficiency, reducing the system power consumption, and enhancing the data quality.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] An airborne transient electromagnetic emission method with adaptive matching of geoelectric conditions, the method comprising:

[0009] Step 1: Transmit a transient electromagnetic pulse signal underground through a transmitter;

[0010] Step 2: A receiver collects the secondary field signal induced by the underground medium and extracts the late-stage signal of its attenuation curve;

[0011] Step 3: Based on the late-stage signal, calculate the measured time constant T;

[0012] Step 4: Preset a target time constant , the target time constant is a non-fixed value that is real-time optimized according to the geoelectric conditions of different regions and the measured electromagnetic signals;

[0013] Step 5: Compare the measured time constant T with the target time constant , evaluate the geoelectric conditions, and based on the evaluation result, adjust the emission duty cycle based on the PID control algorithm.

[0014] On the other hand, the present invention provides an airborne transient electromagnetic emission device with adaptive matching of geoelectric conditions, comprising: a transmitting module for transmitting a transient electromagnetic pulse signal underground through a transmitter;

[0015] a receiving module for collecting the secondary field signal induced by the underground medium through a receiver and extracting the late-stage signal of its attenuation curve;

[0016] a calculation module for calculating the measured time constant T based on the late-stage signal;

[0017] A preset module for presetting a target time constant wherein the target time constant is a non-fixed value that is optimized in real time according to the geoelectric conditions in different regions and the measured electromagnetic signals;

[0018] An adjustment module for comparing the measured time constant T with the target time constant evaluating the geoelectric conditions, and adjusting the emission duty cycle based on the PID control algorithm according to the evaluation result.

[0019] In a third aspect, the present invention provides an electronic device, including: one or more processors; a memory for storing one or more programs; wherein, when the one or more programs are executed by the one or more processors, the one or more processors implement the foregoing airborne transient electromagnetic emission method for adaptive matching of geoelectric conditions.

[0020] In a fourth aspect, the present invention provides a computer-readable storage medium, on which executable instructions are stored, and when the instructions are executed by a processor, the processor can implement the foregoing airborne transient electromagnetic emission method for adaptive matching of geoelectric conditions.

[0021] The beneficial effects of the present invention are as follows:

[0022] By evaluating the late-stage signals of the secondary field decay curve in real time and adaptively adjusting the emission duty cycle, the present invention can match different geoelectric conditions, significantly improving the adaptability of the system;

[0023] The introduction of an intelligent algorithm (such as the PID control algorithm) realizes the automatic adjustment of the emission duty cycle, ensuring that detection can be carried out with optimal emission parameters in different resistivity regions, improving the detection efficiency and data quality, automatically reducing the emission duty cycle in high-resistivity regions, avoiding unnecessary power consumption, and reducing the system operation cost; by optimizing the emission duty cycle, high-quality secondary field signals can be obtained under different geoelectric conditions, improving the detection accuracy and resolution.

[0024] The present invention can adapt to complex geoelectric conditions, ensuring stable detection effects in regions with large resistivity changes, reducing system power consumption, reducing energy consumption, meeting the requirements of energy conservation and environmental protection, and being applicable not only to airborne transient electromagnetic exploration, but also to fields such as ground transient electromagnetic exploration and marine electromagnetic exploration, having broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a flowchart of an airborne transient electromagnetic emission method for adaptive matching of geoelectric conditions according to the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0027] The present invention provides an airborne transient electromagnetic emission method with adaptive matching of geoelectric conditions. By real-time evaluating the late-stage signals of the decay curve of the airborne transient electromagnetic secondary field and combining a negative feedback mechanism to dynamically adjust the transmitter duty cycle in real time, the adaptive matching of the emission parameters with the geoelectric conditions is achieved, thereby improving the detection efficiency, reducing the system power consumption, and enhancing the data quality. Specifically:

[0028] The real-time evaluation of the late-stage signals of the secondary field decay curve extracts parameters such as the time constant T by fitting the late-stage signals of the secondary field decay curve, and reflects the geoelectric conditions of the detection area in real time, providing a basis for adaptively adjusting the emission duty cycle.

[0029] The decay rate of the secondary field signal is directly related to the resistivity of the underground medium. The secondary field signal in the low-resistivity area decays slowly, and the late-stage signals can reflect the deep geological information; the secondary field signal in the high-resistivity area decays quickly, and the early-stage signals characterize the shallow features.

[0030] The late channels of the secondary field voltage signal ( ) follow the exponential decay law:

[0031] ;

[0032] where is the initial voltage amplitude, is the secondary field voltage amplitude at time, T is the time constant, which is positively correlated with the medium resistivity ( ), is the noise term.

[0033] As can be seen from the above formula, the time constant T directly reflects the response characteristics of the underground conductor to the transient electromagnetic field. Specifically, the time constant describes the speed of decay of the induced eddy current (secondary field) in the underground conductor. The secondary field in the low-resistivity area decays slowly, and the time constant T is larger. The secondary field in the high-resistivity area decays quickly, and the time constant T is smaller.

[0034] The negative feedback mechanism mainly uses the PID control algorithm to adjust the emission duty cycle in real time according to the evaluation results, and realizes the adaptive matching of the emission parameters with the geoelectric conditions. By calculating the time constant T in real time, the current geoelectric conditions are judged:

[0035] Low-resistance area: Increase the emission duty cycle, extend the emission pulse width, enhance the ability to collect late-stage signals, and improve the detection depth.

[0036] High-resistance area: Decrease the emission duty cycle, shorten the emission time, reduce the ineffective power consumption, and maintain the signal spatial sampling rate at the same time.

[0037] In this way, according to the actual geoelectric conditions, a reasonable duty cycle adjustment range is set to ensure that the system can work stably in different resistivity areas. For example, the transmission duty cycle is automatically increased in low resistivity areas to obtain later signals; the transmission duty cycle is automatically reduced in high resistivity areas to reduce system power consumption and ensure detection accuracy. At the same time, the time synchronization of the transmitter and the receiver is achieved through the synchronous control system, and the received secondary field signal is pre-processed by amplification, filtering, etc. to improve the signal quality.

[0038] The overall control implementation process is as follows Figure 1 As shown:

[0039] Step 1: Transmitting transient electromagnetic pulse signals underground through a transmitter;

[0040] The transmitter transmits a transient electromagnetic field signal underground. The transient electromagnetic field signal is a periodic pulse signal with an adjustable duty cycle (adjustment range: 10%-75%) and a pulse base frequency set according to detection requirements (typical value: 25Hz-125Hz).

[0041] The timing synchronization of transmission and reception is ensured by a synchronous control system, and the received signal is processed by a low-noise amplifier (gain ≥ 60dB), a bandpass filter (passband 10 Hz-60 kHz) and a denoising module (SNR ≥ 20dB).

[0042] Step 2: The receiver collects the secondary field signal induced by the underground medium and extracts the late signal of its attenuation curve;

[0043] Step 2.1: The receiver collects the secondary field signal induced by the underground medium and pre-processes it through a low-noise amplifier, a bandpass filter and a denoising module (SNR ≥ 20 dB).

[0044] Step 2.2, extract the late signal of the attenuation curve of the pre-processed secondary field signal (defined as the time interval after the amplitude of the pre-processed secondary field signal decays to 10% of the initial value).

[0045] Step 3: Based on the late signal, calculate the measured time constant T to characterize the current geoelectric condition;

[0046] The late signal of the pre-processed secondary field signal attenuation curve is quantitatively evaluated to extract parameters reflecting the geoelectric conditions. The present invention uses the measured time constant T as an evaluation parameter: the larger the T value, the higher the resistivity; the smaller the T value, the lower the resistivity.

[0047] Step 3.1, evaluating the signal-to-noise ratio of the late signal to ensure that the SNR of the late signal is ≥ 20 dB, and eliminating noise interference data;

[0048] Step 3.2, calculate the measured time constant T;

[0049] The attenuation curve is fitted by the nonlinear least squares method to solve the measured time constant T:

[0050] ;

[0051] where the fitting accuracy requirement .

[0052] Step 4: Preset the target time constant , and the target time constant is a non-fixed value that is optimized in real time according to the geoelectric conditions and measured electromagnetic signals in different regions;

[0053] Preset the target time constant , it should be noted that it is not a fixed value, but the optimal time constant set according to the exploration requirements, and it is optimized and corrected in real time according to the geoelectric conditions and measured electromagnetic signals in different regions during the flight operation. In the present invention, the target time constant is set and dynamically optimized by the following strategy:

[0054] Initialize the target time constant based on exploration requirements and prior conditions :

[0055] According to the target detection depth, regional geological background or historical exploration data, preset an empirical value of the target time constant: If mainly for deep exploration, it can be set to a larger value as appropriate (corresponding to the requirements of the low-resistivity area, giving priority to ensuring the late signal); if mainly for shallow high-resolution exploration, it can be set to a smaller value as appropriate (matching the fast attenuation characteristics of the high-resistivity area).

[0056] Or the system predicts the current area by using statistical methods (moving average, Kalman filter) based on the measured T values of a small number of measurement points (such as the first 50 - 100 points) at the initial stage of the operation .

[0057] Dynamic optimization mechanism:

[0058] Adopt the online learning and adaptive adjustment strategy to dynamically optimize the target time constant : During the formal flight operation, statistically calculate the mean or trend of the time constant T of continuous measurement points and adjust it in real time . At the same time, based on the signal quality, feedback calibration is performed on the target time constant to give priority to ensuring the signal quality. In the present invention, the signal-to-noise ratio (SNR) constraint method is adopted. If the SNR of the late signal of the measured signal is lower than the threshold of 20 dB, then automatically adjust and increase to extend the duty cycle and enhance the energy of the late signal.

[0059] Exception handling:

[0060] If the resistivity suddenly changes during the flight operation (such as in the case of geological structures like faults), temporarily store the current and resume after the area stabilizes.

[0061] Step 5: Use the PID control algorithm to achieve real-time dynamic adjustment of the transmission duty cycle ;

[0062] During the system flight operation, compare the measured time constant T of the observed data with the target time constant in real time, and dynamically adjust the duty cycle of the transmitter in real time through a negative feedback mechanism so that the measured time constant approaches the target time constant . In low resistivity areas (where T is larger), the duty cycle needs to be increased to obtain later signals. In high resistivity areas (where T is smaller), the duty cycle needs to be decreased to reduce ineffective power consumption.

[0063] Specifically, the present invention uses the PID control algorithm to achieve real-time dynamic adjustment of the transmission duty cycle :

[0064] ;

[0065] where the deviation , is the preset target time constant in step 4, T is the measured time constant calculated in real time from the observed secondary field signal during the flight operation of the airborne electromagnetic detection system, and t represents the time. is the proportional gain, which determines the adjustment speed. The larger the value, the faster the response, but it may cause oscillation; is the integral gain, which eliminates the steady-state error, but too large a value will cause integral saturation. is the derivative gain, which suppresses oscillation and enhances stability.

[0066] The above PID formula controls through the comprehensive proportional term , integral term and derivative term together, converts the error between the measured time constant T and the target time constant into a dynamic adjustment signal of the duty cycle, and realizes the adaptive matching of "large duty cycle in low resistance area - small duty cycle in high resistance area".

[0067] Proportional term : According to the error between the measured time constant T of the current measurement area or measurement point and the preset optimal target time constant , directly adjust the duty cycle.

[0068] When in the low resistivity region: , that is , the error is positive, and the proportional term output increases the emission duty cycle to obtain a later signal and improve the detection depth.

[0069] When in the high resistivity region: , that is , the proportional term output decreases the emission duty cycle to reduce the ineffective power consumption and ensure the detection accuracy at the same time.

[0070] Integral term : Accumulate the historical error and eliminate the steady-state error (such as long-term geoelectric condition fluctuations). If the system is in the low resistance region for a long time (continuous positive error), the integral term gradually increases the duty cycle to ensure that the measured time constant steadily approaches the target time constant , and vice versa, the integral term gradually decreases.

[0071] Differential term : Predict the change trend of the error and suppress overshoot. When the resistivity changes suddenly (such as entering the high resistance region from the low resistance region), the differential term quickly responds to the error change rate to avoid excessive adjustment of the duty cycle.

[0072] The PID algorithm realizes the smooth adjustment of the duty cycle through real-time error feedback, avoiding the interference of step mutations on the signal quality; the integral term compensates for the system nonlinearity, and the differential term suppresses the influence of environmental noise. The weight of the differential term is preferentially increased in the high resistance region, and the weight of the integral term is preferentially increased in the low resistance region to ensure stable control under complex geoelectric conditions.

[0073] Specifically, in the process of adjusting the emission duty cycle using the above PID control algorithm, the PID parameters need to be initialized first ( , , ). The present invention uses the Ziegler-Nichols method to realize the initial parameter setting. First, set , , and gradually increase until the system shows equal-amplitude oscillation (critical gain ), record the oscillation period , and then set the parameters according to the following rules:

[0074] , , ;

[0075] At the same time, fuzzy logic rules and anti-saturation processing are integrated into the above PID control algorithm to dynamically adjust the PID parameters (proportional coefficient , integral coefficient and differential coefficient ). According to the absolute value of the deviation and the deviation change rate (the superscript · represents the first-order time derivative), the PID parameters are dynamically adjusted: if is large and is large, then increase and decrease to suppress overshoot. If is small and is small, then increase to eliminate the steady-state error. At the same time, when occurs, the integral term is paused to avoid integral saturation, and the duty cycle adjustment range (10% - 75%) is restricted, and when the duty cycle update times are greater than the preset value N, the iteration is stopped to prevent hardware overload.

[0076] Without loss of generality, through multiple iterative adjustments and combining with the measured data, the PID parameters ( , , ) are optimized to achieve the adaptive matching of the emission duty cycle and the geoelectric conditions, ensuring the best detection effect in different resistivity regions. For example, in the low resistivity region, the system automatically increases the emission duty cycle to obtain later signals and improve the detection depth. In the high resistivity region, the system automatically reduces the emission duty cycle to avoid ineffective power consumption and ensure the detection accuracy.

[0077] On the other hand, the present invention provides an airborne transient electromagnetic emission device with adaptive matching of geoelectric conditions, and each module included therein can implement each step of the foregoing method. Specifically, it includes:

[0078] An emission module for transmitting a transient electromagnetic pulse signal to the ground through a transmitter;

[0079] A receiving module for collecting the secondary field signal induced by the underground medium through a receiver and extracting the later signal of its attenuation curve;

[0080] A calculation module for calculating the measured time constant T based on the later signal;

[0081] A preset module for presetting a target time constant , and the target time constant is a non-fixed value that is optimized in real time according to the geoelectric conditions of different regions and the measured electromagnetic signals;

[0082] An adjustment module for comparing the measured time constant T with the target time constant , evaluating the geoelectric conditions, and adjusting the emission duty cycle based on the evaluation result and the PID control algorithm.

[0083] In a third aspect, the present invention provides an electronic device, comprising: one or more processors; a memory for storing one or more programs; wherein, when the one or more programs are executed by the one or more processors, the one or more processors are caused to implement the foregoing airborne transient electromagnetic emission method with adaptive matching of geoelectric conditions.

[0084] In a fourth aspect, the present invention provides a computer-readable storage medium having executable instructions stored thereon, which when executed by a processor can cause the processor to implement the foregoing airborne transient electromagnetic emission method with adaptive matching of geoelectric conditions.

[0085] The specific embodiments described above further elaborate on the objectives, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. An airborne transient electromagnetic emission method for adaptively matching geoelectric conditions, characterized in that: The method comprises: Step 1: Transmitting transient electromagnetic pulse signals underground through a transmitter; Step 2: The receiver collects the secondary field signal induced by the underground medium and extracts the late signal of its attenuation curve; Step 3: Calculate the measured time constant T based on the late signal; Step 4: Preset target time constant , the target time constant is a non-fixed value that is optimized in real time according to the geoelectric conditions and measured electromagnetic signals in different regions; Step 5: Compare the measured time constants and the target time constant , evaluate the geoelectric conditions, and adjust the transmission duty cycle based on a PID control algorithm according to the evaluation results.

2. The method for adaptively matching geoelectric conditions with airborne transient electromagnetic emission according to claim 1, characterized in that: In step 1, the transient electromagnetic pulse signal is a periodic pulse signal with an adjustable duty cycle, and the transmitter and the receiver are time synchronized through a synchronous control system.

3. The method for adaptively matching geoelectric conditions with airborne transient electromagnetic emission according to claim 1, characterized in that: The step 2 comprises: Step 2.1, the receiver collects the secondary field signal induced by the underground medium and pre-processes it through a low noise amplifier, a band pass filter and a denoising module; Step 2.2, extracting the late signal of the attenuation curve of the pre-processed secondary field signal, wherein the late signal is defined as the signal in the time interval after the amplitude of the pre-processed secondary field signal decays to 10% of the initial value.

4. The method for adaptively matching geoelectric conditions with airborne transient electromagnetic emission according to claim 1, characterized in that: The step 3 comprises: Step 3.1, evaluating the signal-to-noise ratio of the late signal to eliminate noise interference data; Step 3.2: Use the nonlinear least squares method to fit the decay curve and solve the measured time constant T: ； In the formula, is the initial voltage amplitude, for The secondary field voltage amplitude at time , is the noise term.

5. The method for adaptively matching geoelectric conditions with airborne transient electromagnetic emission according to claim 1, characterized in that: The step 4 comprises: Initialize target time constant based on exploration requirements and prior conditions ; The target time constant is adjusted by online learning and adaptive adjustment strategy. Perform dynamic optimization, including: continuously obtain the average value of the measured time constant T, and adjust in real time ; At the same time, based on the signal quality, the target time constant Perform feedback calibration.

6. The method for adaptively matching geoelectric conditions with airborne transient electromagnetic emission according to claim 1, characterized in that: The step 5 includes comparing the measured time constant T of the observed data with the target time constant in real time during the flight operation of the system. , using PID control algorithm to increase or decrease the duty cycle : ； In the formula, deviation , t represents the time, is the proportional gain, which determines the adjustment speed; is the integral gain, is the differential gain, is the proportional term, is the integral term, is the differential term; when hour, , in the low resistivity area, the proportional output increases, the integral output increases the emission duty cycle ; when hour, , in the high resistivity area, the proportional output decreases, the integral output decreases, and the emission duty cycle ; Differential term Used to predict error change trends and suppress overshoot.

7. The method for adaptively matching geoelectric conditions with airborne transient electromagnetic emission according to claim 6, characterized in that: The process of increasing or decreasing the duty cycle by using the PID control algorithm includes: Initialize PID parameters , , ,set up , , and gradually increase When the system oscillates with equal amplitude, record the critical gain , oscillation period , and then set the parameters according to the following rules: ， ， ； According to the deviation and the rate of change of deviation Dynamically adjust PID parameters; When the duty cycle adjustment range exceeds [10%~75%] or the duty cycle update times are greater than the preset value N, the update iteration is stopped.

8. An aviation transient electromagnetic transmitting device with adaptive matching of geoelectric conditions, characterized in that: include: A transmitting module, used for transmitting a transient electromagnetic pulse signal underground through a transmitter; A receiving module, used for collecting secondary field signals induced by underground media through a receiver and extracting late signals of its attenuation curve; A calculation module, used for calculating the measured time constant T based on the late signal; Preset module for presetting target time constants , the target time constant is a non-fixed value that is optimized in real time according to the geoelectric conditions and measured electromagnetic signals in different regions; Adjustment module, used to compare the measured time constant T with the target time constant , evaluate the geoelectric conditions, and adjust the transmission duty cycle based on a PID control algorithm according to the evaluation results.

9. An electronic device, characterized in that: include: one or more processors; A memory for storing one or more programs; Wherein, when one or more programs are executed by the one or more processors, the one or more processors implement the aviation transient electromagnetic emission method with adaptive matching of geoelectric conditions as described in any one of claims 1-7.

10. A computer-readable storage medium, characterized in that: Executable instructions are stored thereon, and when the instructions are executed by the processor, the processor can implement the aviation transient electromagnetic emission method for adaptively matching geoelectric conditions as described in any one of claims 1-7.

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