A method and apparatus for adaptive matching of ground power conditions for airborne transient electromagnetic launch

Abstract

This invention discloses an airborne transient electromagnetic transmission method and apparatus with adaptive matching to geoelectric conditions, belonging to the field of geophysical exploration technology. The method includes transmitting a transient electromagnetic pulse signal into the ground via a transmitter; a receiver acquiring the secondary field signal induced by the underground medium and extracting the late signal of its attenuation curve; calculating the measured time constant T; setting a target time constant; comparing the measured time constant and the target time constant to evaluate the geoelectric conditions; and adjusting the transmission duty cycle based on a PID control algorithm according to the evaluation results. This invention, by analyzing the late signal of the airborne transient electromagnetic secondary field attenuation curve in real time and using negative feedback to dynamically adjust the transmission duty cycle in real time to adapt to the geoelectric conditions of different survey areas, has significant technical advantages over traditional fixed duty cycle transmission, including strong adaptability, high detection efficiency, low system power consumption, high detection accuracy, and adaptability to complex geoelectric conditions.

Description

Technical Field

[0001] This invention belongs to the field of geophysical exploration technology, specifically relating to an airborne transient electromagnetic transmission method and device with adaptive matching of geoelectric conditions. Background Technology

[0002] The Airborne Transient Electromagnetic Method (ATEM) is a highly efficient geophysical exploration method widely used in mineral resource exploration, environmental geological surveys, and groundwater detection. Its basic principle involves transmitting a transient electromagnetic field into the subsurface, and a receiver receiving the secondary field signal induced by the subsurface medium. By analyzing the attenuation characteristics of the secondary field signal, the electrical distribution of the subsurface medium can be inferred. The attenuation characteristics of the secondary field signal are closely related to the resistivity of the subsurface medium; specifically, the electromagnetic signal attenuates more slowly in low-resistivity regions and more quickly in high-resistivity regions. In the electromagnetic signal attenuation curve, the early signal mainly carries shallow geological information, while the later signal mainly reflects deep geological information.

[0003] In practical applications, the subsurface resistivity of the detection area is often unpredictable, and the resistivity varies significantly across different regions. However, existing ATEM systems, both domestically and internationally, typically employ a fixed transmission duty cycle, failing to dynamically adapt to the resistivity variations in different areas. In low-resistivity regions, a smaller transmission duty cycle may not acquire sufficient late-stage signals, limiting deep exploration capabilities; in high-resistivity regions, an excessively large duty cycle implies a longer transmission time, but with less effective signal information, significantly increasing the system's ineffective power consumption. Furthermore, with a fixed transmission frequency, a larger duty cycle reduces the number of data points that can be collected per unit time, thereby lowering the spatial sampling rate. A reduced sampling rate directly impacts detection resolution, preventing the system from accurately identifying details of subsurface targets, thus affecting detection efficiency.

[0004] This fixed transmission duty cycle configuration makes it difficult to accommodate different geoelectric conditions, limiting the system's performance in both high and low resistivity regions. This not only results in high system power consumption, low detection efficiency (e.g., a high proportion of ineffective energy consumption in high-resistivity regions), and limited detection depth (e.g., insufficient late-stage signal acquisition in low-resistivity regions), but also leads to signal quality fluctuations (e.g., decreased signal-to-noise ratio in resistivity abrupt change areas), severely restricting the exploration accuracy and adaptability under complex geoelectric conditions.

[0005] While existing technologies have made some attempts to improve upon these issues, limitations remain. For example, segmented launch technology divides the detection area into several segments, each using different launch parameters. This method relies on prior geological information, cannot achieve real-time adaptive adjustment and dynamic adaptation, and suffers from low operational efficiency. Therefore, developing an airborne transient electromagnetic launch technology capable of adaptively and dynamically matching the launch duty cycle based on geoelectric conditions is of significant practical importance. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides an airborne transient electromagnetic transmission method and apparatus with adaptive matching of ground power conditions. By evaluating the late signal of the attenuation curve of the airborne transient electromagnetic secondary field in real time and dynamically adjusting the transmitter duty cycle using a negative feedback mechanism, adaptive matching of transmission parameters with ground power conditions is achieved, thereby improving detection efficiency, reducing system power consumption, and enhancing data quality.

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

[0008] An airborne transient electromagnetic launch method with adaptive matching of ground power conditions, the method comprising:

[0009] Step 1: Transmit transient electromagnetic pulse signals into the ground via a transmitter;

[0010] Step 2: The receiver acquires the secondary field signal induced by the underground medium and extracts the late signal of its attenuation curve;

[0011] Step 3: Calculate the measured time constant T based on the late signal;

[0012] Step 4: Preset the target time constant The target time constant is a non-fixed value that is optimized in real time based on the geoelectric conditions and measured electromagnetic signals of different regions.

[0013] Step 5: Compare the measured time constant T with the target time constant The ground power conditions are evaluated, and the transmission duty cycle is adjusted based on the evaluation results using a PID control algorithm.

[0014] On the other hand, the present invention provides an airborne transient electromagnetic transmission device with adaptive matching of ground power conditions, comprising: a transmission module for transmitting transient electromagnetic pulse signals to the ground via a transmitter;

[0015] The receiving module is used to acquire the secondary field signal induced by the underground medium through the receiver and extract the late signal of its attenuation curve.

[0016] The calculation module is used to calculate the measured time constant T based on the late signal;

[0017] The preset module is used to preset the target time constant. The target time constant is a non-fixed value that is optimized in real time based on the geoelectric conditions and measured electromagnetic signals of different regions.

[0018] The adjustment module is used to compare the measured time constant T with the target time constant. The ground power conditions are evaluated, and the transmission duty cycle is adjusted based on the evaluation results using a PID control algorithm.

[0019] Thirdly, 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 cause the one or more processors to implement the aforementioned method for adaptive matching of ground power conditions for airborne transient electromagnetic transmission.

[0020] Fourthly, the present invention provides a computer-readable storage medium having executable instructions stored thereon, which, when executed by a processor, enable the processor to implement the aforementioned method for adaptive matching of ground power conditions for airborne transient electromagnetic launch.

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

[0022] This invention improves the system's adaptability by real-time evaluation of the late signal of the secondary field attenuation curve and adaptively adjusting the transmission duty cycle to match different ground power conditions.

[0023] By introducing intelligent algorithms (such as PID control algorithms) to achieve automatic adjustment of the transmission duty cycle, it is possible to detect with optimal transmission parameters in different resistivity regions, thereby improving detection efficiency and data quality. In high resistivity regions, the transmission duty cycle is automatically reduced to avoid unnecessary power consumption and reduce system operating costs. By optimizing the transmission duty cycle, high-quality secondary field signals can be obtained under different ground power conditions, thereby improving detection accuracy and resolution.

[0024] This invention can adapt to complex geoelectric conditions, ensuring stable detection results even in areas with large resistivity variations. It reduces system power consumption and energy consumption, meeting the requirements of energy conservation and environmental protection. It is not only suitable for airborne transient electromagnetic exploration, but also for terrestrial transient electromagnetic exploration, marine electromagnetic exploration and other fields, and has broad application prospects. Attached Figure Description

[0025] Figure 1 This is a flowchart of an airborne transient electromagnetic launch method based on adaptive matching of ground power conditions according to the present invention. Detailed Implementation

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

[0027] This invention provides an airborne transient electromagnetic transmission method with adaptive matching to ground power conditions. By real-time evaluation of the late-stage signal of the airborne transient electromagnetic secondary field attenuation curve and combining this with a negative feedback mechanism to dynamically adjust the transmitter duty cycle in real time, adaptive matching of transmission parameters with ground power conditions is achieved. This improves detection efficiency, reduces system power consumption, and enhances data quality. Specifically:

[0028] Real-time evaluation of the late signal of the secondary field attenuation curve: By fitting the late signal of the secondary field attenuation curve, parameters such as the time constant T are extracted to reflect the geoelectric conditions of the detection area in real time, providing a basis for adaptive adjustment of the transmission duty cycle.

[0029] The attenuation rate of the secondary field signal is directly related to the resistivity of the subsurface medium. In low resistivity regions, the secondary field signal attenuates more slowly, and the later signals can reflect deep geological information; in high resistivity regions, the secondary field signal attenuates more quickly, and the early signals characterize shallow features.

[0030] Late channel of secondary field voltage signal ( It follows the law of exponential decay:

[0031] ;

[0032] in, The initial voltage amplitude, for The magnitude of the secondary field voltage at time T, where T is the time constant. This is the noise term.

[0033] As shown in the above equation, the time constant T directly reflects the response characteristics of an underground conductor to a transient electromagnetic field. Specifically, the time constant describes the rate attenuation of the induced eddy current (secondary field) in the underground conductor. In low resistivity regions, the secondary field decays slowly, resulting in a larger time constant T. In high resistivity regions, the secondary field decays quickly, resulting in a smaller time constant T.

[0034] The negative feedback mechanism primarily employs a PID control algorithm, adjusting the transmission duty cycle in real time based on evaluation results to achieve adaptive matching between transmission parameters and ground power conditions. The current ground power conditions are determined by calculating the time constant T in real time.

[0035] Low-resistivity region: Increase the transmission duty cycle, extend the transmission pulse width, enhance late-stage signal acquisition capabilities, and improve detection depth.

[0036] High impedance region: Reduce the transmit duty cycle, shorten the transmit time, reduce ineffective power consumption, and maintain the signal spatial sampling rate at the same time.

[0037] Thus, by setting a reasonable duty cycle adjustment range based on actual ground power conditions, the system can operate stably in different resistivity regions. For example, in low resistivity regions, the transmission duty cycle is automatically increased to acquire later signals; in high resistivity regions, the transmission duty cycle is automatically decreased to reduce system power consumption and ensure detection accuracy. Simultaneously, a synchronous control system is used to synchronize the transmitter and receiver, and the received secondary field signals are preprocessed through amplification and filtering to improve signal quality.

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

[0039] Step 1: Transmit transient electromagnetic pulse signals into the ground via a transmitter;

[0040] The transmitter emits transient electromagnetic field signals into the ground. These transient electromagnetic field signals are periodic pulse signals with an adjustable duty cycle (adjustment range: 10%-75%). The pulse fundamental frequency is set according to the detection requirements (typical value: 25Hz-125Hz).

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

[0042] Step 2: The receiver acquires 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 preprocesses it through a low-noise amplifier, bandpass filter and noise reduction module (SNR≥20dB).

[0044] Step 2.2: Extract the late signal of the preprocessed secondary field signal attenuation curve (defined as the time interval after the amplitude of the preprocessed secondary field signal attenuates 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 conditions;

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

[0047] Step 3.1: Evaluate the signal-to-noise ratio (SNR) of the late signal to ensure that the SNR of the late signal is greater than or equal to 20 dB, and remove noise interference data.

[0048] Step 3.2: Calculate the measured time constant T;

[0049] The decay curve was fitted using the nonlinear least squares method, and the measured time constant T was solved.

[0050] ;

[0051] Among them, the fitting accuracy requirement .

[0052] Step 4: Preset the target time constant The target time constant It is a non-fixed value that is optimized in real time based on the geoelectric conditions and measured electromagnetic signals of different regions;

[0053] Preset target time constant It is important to note that It is not a fixed value, but an optimal time constant set according to exploration needs, and is optimized and corrected in real time during flight operations based on geoelectric conditions and measured electromagnetic signals in different areas. The target time constant in this invention... The following strategies are adopted for setting and dynamic optimization:

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

[0055] Based on the target exploration depth, regional geological background, or historical exploration data, a target time constant empirical value is pre-set: if deep exploration is the primary focus... A larger value can be set as appropriate (to meet the needs of low-resistivity areas and prioritize late-stage signals); if the focus is on shallow, high-resolution exploration, It can be set to a smaller value as appropriate (to match the rapid attenuation characteristics in the high-resistivity region).

[0056] Alternatively, the system can predict the current area's T-values ​​at a small number of measurement points (e.g., the first 50-100 points) using statistical methods (moving average, Kalman filtering) during the initial stage of operation. .

[0057] Dynamic optimization mechanism:

[0058] The target time constant is adjusted using an online learning and adaptive adjustment strategy. Dynamic optimization: During formal flight operations, the mean or trend of the time constant T at continuous measurement points is statistically analyzed, and adjustments are made in real time. Meanwhile, based on the signal quality, the target time constant... Feedback calibration is performed to prioritize signal quality. This invention employs a signal-to-noise ratio (SNR) constraint method. If the SNR of the measured signal's late-stage signal is lower than a threshold of 20 dB, it is automatically adjusted to increase the SNR. This extends the duty cycle and enhances the energy of the late signal.

[0059] Exception handling:

[0060] If a sudden change in resistivity is encountered during flight operations (such as in geological structures like faults), the current situation will be temporarily saved. It will resume after the region stabilizes.

[0061] Step 5: Use a PID control algorithm to achieve the launch duty cycle. Real-time dynamic adjustment;

[0062] During system flight operations, the measured time constant T and the target time constant of the observed data are compared in real time. The transmitter's duty cycle is dynamically adjusted in real time through a negative feedback mechanism. This makes the measured time constant Approaching the target time constant In the low resistivity region (where T is relatively large), the duty cycle needs to be increased to obtain a later signal, while in the high resistivity region (where T is relatively small), the duty cycle needs to be decreased to reduce ineffective power consumption.

[0063] Specifically, this invention uses a PID control algorithm to achieve the transmission duty cycle. Real-time dynamic adjustment:

[0064] ;

[0065] Among them, deviation , The target time constant is preset for 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. The proportional gain determines the adjustment speed; a larger value results in a faster response, but may cause oscillations. This is used as the integral gain to eliminate steady-state error, but if it is too large, it will cause integral saturation. The differential gain suppresses oscillations and enhances stability.

[0066] The above PID formula incorporates the proportional term. Integral terms and differential terms Joint control, the measured time constant T is compared with the target time constant. The error is converted into a dynamic adjustment signal of the duty cycle, realizing adaptive matching of "large duty cycle in low resistance region - small duty cycle in high resistance region".

[0067] Proportional Term Based on the measured time constant T of the current measurement area or measurement point and the preset optimal target time constant To correct the error, directly adjust the duty cycle.

[0068] When in a low resistivity region: ,Right now The error is positive, and the proportional term output increases the transmission duty cycle. This is to obtain later signals and increase the detection depth.

[0069] When in a high resistivity region: ,Right now The proportional term output reduces the transmit duty cycle. This reduces unnecessary power consumption while ensuring detection accuracy.

[0070] Integral term Accumulate historical errors to eliminate steady-state errors (such as long-term fluctuations in geoelectric conditions). If the system remains in a low-resistance region for an extended period (continuous positive error), gradually increase the duty cycle of the integral term to ensure the measured time constant. Stable approach to target time constant Conversely, the integral term gradually decreases.

[0071] Differential term Predicts error trends and suppresses overshoot. When resistivity changes abruptly (e.g., from a low-resistivity region to a high-resistivity region), the differential term quickly responds to the rate of error change, avoiding excessive duty cycle adjustment.

[0072] The PID algorithm achieves smooth adjustment of the duty cycle through real-time error feedback, avoiding interference with signal quality caused by step changes; the integral term compensates for system nonlinearity, and the derivative term suppresses the influence of environmental noise. In the high-resistivity region, the weight of the derivative term is increased first, and in the low-resistivity region, the weight of the integral term is increased first, ensuring stable control under complex ground power conditions.

[0073] Specifically, in the process of adjusting the transmit duty cycle using the above PID control algorithm, the PID parameters must first be initialized ( , , This invention uses the Ziegler-Nichols method to set the initial parameters. First, the initial parameters are set... , and gradually increase Until the system exhibits constant-amplitude oscillations (critical gain) Record the oscillation period Then set the parameters according to the following rules:

[0074] , , ;

[0075] Meanwhile, 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 coefficients Based on the absolute value of the deviation. and rate of change of deviation (The superscript · indicates the first-order time derivative) Dynamically adjust PID parameters: If large and If it is large, then it will increase. , reduce Suppress overshoot, if Small and If it is small, then increase. This eliminates steady-state error. Simultaneously, when… At that time, the points item was suspended. To avoid integral saturation, the duty cycle adjustment range is limited (10%~75%), and iteration is stopped when the number of duty cycle updates exceeds the preset value N to prevent hardware overload.

[0076] Without loss of generality, the PID parameters are optimized through multiple iterative adjustments, combined with measured data. , , This system achieves adaptive matching between the transmission duty cycle and ground electrical conditions, ensuring optimal detection performance across different resistivity regions. For example, in low resistivity regions, the system automatically increases the transmission duty cycle to acquire later signals and improve detection depth. In high resistivity regions, the system automatically decreases the transmission duty cycle to avoid unnecessary power consumption while maintaining detection accuracy.

[0077] On the other hand, the present invention provides an airborne transient electromagnetic launch device with adaptive matching of ground power conditions, the various modules of which can implement the various steps of the aforementioned method, specifically including:

[0078] The transmitting module is used to transmit transient electromagnetic pulse signals into the ground via a transmitter.

[0079] The receiving module is used to acquire the secondary field signal induced by the underground medium through the receiver and extract the late signal of its attenuation curve.

[0080] The calculation module is used to calculate the measured time constant T based on the late signal;

[0081] The preset module is used to preset the target time constant. The target time constant is a non-fixed value that is optimized in real time based on the geoelectric conditions and measured electromagnetic signals of different regions.

[0082] The adjustment module is used to compare the measured time constant T with the target time constant. The ground power conditions are evaluated, and the transmission duty cycle is adjusted based on the evaluation results using a PID control algorithm.

[0083] Thirdly, 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 cause the one or more processors to implement the aforementioned method for adaptive matching of ground power conditions for airborne transient electromagnetic transmission.

[0084] Fourthly, the present invention provides a computer-readable storage medium having executable instructions stored thereon, which, when executed by a processor, enable the processor to implement the aforementioned method for adaptive matching of ground power conditions for airborne transient electromagnetic launch.

[0085] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An airborne transient electromagnetic transmission method with self-adaptive matching of geoelectric conditions, characterized in that, The method comprises: Step 1: transmitting a transient electromagnetic pulse signal to the underground through a transmitter; Step 2: collecting a secondary field signal induced by the underground medium by a receiver, and extracting a late signal of the attenuation curve, wherein the late signal is defined as a signal in a time interval after the amplitude of the preprocessed secondary field signal is attenuated to 10% of the initial value; Step 3: based on the late signal, the nonlinear least squares method is used to fit the attenuation curve, and the measured time constant T is calculated; Step 4: preset target time constant The target time constant is a non-fixed value dynamically optimized by real-time online learning strategy according to the geoelectric conditions of different areas and the measured electromagnetic signals. Step 5: Comparing the measured time constant with the target time constant evaluating the geoelectric conditions, based on the evaluation result, adjusting the transmission duty cycle based on a PID control algorithm : ； wherein the deviation t represents time, is a proportional gain, which determines the adjustment speed; is an integral gain, is a differential gain, is a proportional term, is an integral term, is a differential term; when hour, In the low resistivity region, the proportional and integral terms increase the transmit duty cycle. ; When , , in the high resistivity region, the proportional term output, the integral term output decrease the emission duty cycle ; derivative term For predicting error change tendency, suppressing overshoot.

2. The airborne transient electromagnetic method of claim 1, wherein, In step 1, the transient electromagnetic pulse signal is a periodic pulse signal, and the duty cycle is adjustable. The transmitter and the receiver are time-synchronized through a synchronous control system.

3. The airborne transient electromagnetic method of claim 1, wherein, 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 preprocessed secondary field signal.

4. The airborne transient electromagnetic method of claim 1, wherein, The step 3 comprises: Step 3.1, the signal-to-noise ratio of the late signal is evaluated, and the noise interference data is removed; Step 3.2, the nonlinear least squares method is used to fit the attenuation curve, and the measured time constant T is solved: ； wherein is the initial voltage amplitude, is is the secondary field voltage amplitude at the moment of time, is the noise term.

5. The airborne transient electromagnetic method of claim 1, wherein, The step 4 comprises: Initializing a target time constant based on exploration needs and prior conditions ; Adopting online learning and self-adaptive adjustment strategy to target time constant Dynamic optimization is performed, including: statistically obtaining the mean value of continuously obtained measured time constant T, adjusting in real time ; at the same time, feedback calibration is performed on target time constant based on signal quality.

6. The airborne transient electromagnetic method of claim 1, wherein, The process of increasing or decreasing the duty cycle by using the PID control algorithm comprises: Initialize PID parameters , , , set , , and gradually increase to the system appears to be the critical gain , oscillation period , then set the parameters according to the following rules: ， ， ； According to the deviation And the deviation change rate Dynamic adjustment of PID parameters; When the duty cycle adjustment range exceeds [10%~75%] or when the number of duty cycle updates is greater than the preset value N, stop updating iteration.

7. An airborne transient electromagnetic transmitter arrangement with self-adapting matching to the geoelectric conditions, characterized in that, Comprise: A transmitting module for transmitting a transient electromagnetic pulse signal to the underground through a transmitter; A receiving module for collecting a secondary field signal induced by the underground medium by a receiver, and extracting a late signal of the attenuation curve, wherein the late signal is defined as a signal in a time interval after the amplitude of the preprocessed secondary field signal is attenuated to 10% of the initial value; A calculation module for fitting the attenuation curve by using the nonlinear least squares method based on the late signal, and calculating the measured time constant T; A preset module is configured to preset a target time constant The target time constant is a non-fixed value dynamically optimized according to real-time online learning strategies based on geoelectric conditions of different regions and measured electromagnetic signals. a regulation module for comparing the measured time constant T with a target time constant evaluating the geoelectric condition and, based on the evaluation result, adjusting the transmission duty cycle on the basis of a PID control algorithm : ； wherein the deviation t represents time, is a proportional gain, which determines the adjustment speed; is an integral gain, is a differential gain, is a proportional term, is an integral term, is a differential term; when hour, In the low resistivity region, the proportional and integral terms increase the transmit duty cycle. ; when hour, In the high resistivity region, the proportional and integral terms reduce the transmit duty cycle. ; derivative term For predicting error change tendency, suppressing overshoot.

8. An electronic device, comprising: Comprise: One or more processors; A memory for storing one or more programs; When one or more programs are executed by the one or more processors, the one or more processors implement the airborne transient electromagnetic transmission method of adaptive matching of geoelectric conditions according to any one of claims 1-6.

9. A computer-readable storage medium, characterized in that, Executable instructions are stored thereon, which instructions are executed by a processor to enable the processor to implement the airborne transient electromagnetic transmission method of adaptive matching of geoelectric conditions according to any one of claims 1-6.

Images