Transient electromagnetic emission system adaptive resistance network device and design method

Abstract

The invention relates to the field of electromagnetic detection, and discloses a transient electromagnetic transmitting system adaptive resistance network device and a design method, and the device comprises a transmitter transmitting coil, a Hall sensor, an AD conversion module, a controller, a relay and a resistance network. The Hall sensor is used for detecting emission current of an emission coil of the transmitter; the Hall sensor is electrically connected with the AD conversion module; the controller is electrically connected with the relay and the AD conversion module; the relay is electrically connected with the resistance network; according to the invention, the impedance matching of the transmitting coil is accurately optimized by automatically adjusting ten resistors with different resistance values (ranging from 1 ohm to 1024 ohm) which are connected in parallel and combining a greedy algorithm, linear regression analysis and an adaptive algorithm, so that the transmitting current is ensured to be stable and rapidly reduced to an ideal critical damping state.

Description

Technical Field

[0001] The invention relates to the field of electromagnetic detection, and in particular to an adaptive resistor network device of a transient electromagnetic emission system and a design method thereof. Background Art

[0002] Transient electromagnetic (TEM) is an efficient non-contact electromagnetic detection technology widely used in geological exploration. With its high resolution and deep detection capabilities, TEM is used in groundwater resource exploration, foundation assessment, military facility detection, and dam leakage detection. This method quickly reveals underground structures and resource distribution by emitting transient electromagnetic waves, especially in the non-destructive detection of shallow near-surface structures, ensuring infrastructure safety, guiding urban planning, and optimizing resource management. With technological advances, the application of TEM in complex geological conditions has become more and more common, becoming one of the key technologies in geological exploration.

[0003] Transient electromagnetic method is a detection technology based on the principle of electromagnetic induction. It transmits periodically changing pulse current into the ground through an ungrounded transmitting coil. The rapid change of current will generate a primary field signal in the surrounding area. When the signal propagates underground, the underground geological structure will generate induced eddy currents and form secondary field signals. The secondary field signal contains rich underground geological information. On the ground, the secondary field signal is extracted by the receiving coil, and analyzed and interpreted using relevant software and algorithms to obtain the basic physical properties of the underground geological body, such as the conductivity and burial depth.

[0004] In transient electromagnetic systems, the transmitter plays a key role, and the quality of its transmitted current waveform directly affects the effectiveness of the received secondary field signal. In particular, the non-zero off-time (or descent rate) has an important impact on the detection effect. The shorter the off-time, the more concentrated the energy distribution of the transmitted electromagnetic pulse, which helps to obtain clearer shallow underground information. Studies have shown that changes in the off-time can significantly affect the apparent resistivity in the intermediate stage of geological exploration.

[0005] In transient electromagnetic detection systems, the impedance matching of the transmitter coil is extremely important for the turn-off time and waveform characteristics of the transmitting current. Good matching can ensure that the transmitting current is quickly and stably turned off, avoiding delays and signal attenuation, thereby improving the sensitivity and accuracy of detection. At the same time, improper impedance matching may cause oscillations in the waveform of the transmitting current. This oscillation will reduce the clarity of the signal, may introduce measurement errors and interfere with data analysis, thereby generating additional noise and affecting the overall detection effect. Therefore, optimizing the impedance matching of the transmitting system can not only improve the stability and response speed of the current, but also ensure the integrity of the signal waveform, providing more reliable data support for detection.

[0006] At present, the main impedance matching method is to connect an adjustable resistor in parallel to the coil, and change the damping state of the transmitting system by manually adjusting the resistance of the resistor. However, due to the uncertainty of manual adjustment, the damping state finally obtained may not reach the ideal critical damping state, and there is a certain deviation. At the same time, due to the complex working environment of the transient electromagnetic detection system, the use of adjustable resistors may be affected by external factors, such as vibration or collision, which may cause the resistance value to change, thereby introducing uncertainty. Summary of the invention

[0007] The purpose of the present invention is to propose an adaptive resistor network device and a design method for a transient electromagnetic emission system, so as to solve the technical problem that the uncertainty caused by manual adjustment during impedance matching in the existing transient electromagnetic detection system leads to inaccurate final detection results.

[0008] Specifically, the present invention provides an adaptive resistor network device for a transient electromagnetic emission system, comprising the following:

[0009] Transmitter transmitting coil, Hall sensor, AD conversion module, controller, relay and resistor network;

[0010] The Hall sensor is used to detect the transmitting current of the transmitter transmitting coil;

[0011] The Hall sensor is electrically connected to the AD conversion module;

[0012] The controller is electrically connected to the relay and the AD conversion module;

[0013] The relay is electrically connected to the resistor network.

[0014] A method for designing an adaptive resistor network for a transient electromagnetic emission system, applied to the device, comprises the following steps:

[0015] S1: In the instantaneous electromagnetic transmission system, the Hall sensor is used to collect the real-time current of the transmitting coil;

[0016] S2: The real-time current is converted into a digital signal by the AD conversion module and then input into the controller;

[0017] S3: The controller analyzes the current change trend according to the linear regression method and identifies the damping state;

[0018] S4: According to the damping state, the controller calculates the resistance combination that meets the target impedance value based on the greedy algorithm, so that the system reaches the required damping state, and controls the resistance network through the relay to achieve the target impedance.

[0019] The beneficial effects provided by the present invention are:

[0020] The present invention designs a matching resistor network circuit. Compared with the traditional manual adjustment method, this design eliminates the error that may be generated when manually adjusting the resistance value of the parallel adjustable resistor, ensuring that the final damping state is closer to the ideal critical damping state. In addition, it also successfully solves the problem of uncertainty caused by changes in the adjustable resistor value due to equipment movement or vibration during the detection process. At the same time, the introduction of adaptive control allows the transient electromagnetic emission current to drop smoothly and quickly in any detection environment and when using detection coils of any size, number of turns and shape. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the structure of the device of the present invention;

[0022] Figure 2 It is a schematic diagram of the resistor network structure of the present invention;

[0023] Figure 3 Five groups of typical current data of the present invention during the self-adaptation process of wet grassland are shown. DETAILED DESCRIPTION

[0024] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0025] Before formally describing the present invention, the scheme of the present invention is first generally described for easy understanding.

[0026] Please refer to Figure 1-Figure 2 , Figure 1 It is a schematic diagram of the structure of the device of the present invention; Figure 2 It is a schematic diagram of the resistor network structure of the present invention;

[0027] The present invention provides an adaptive resistor network device for a transient electromagnetic emission system, comprising the following:

[0028] Transmitter transmitting coil, Hall sensor, AD conversion module, controller, relay and resistor network;

[0029] The Hall sensor is used to detect the transmitting current of the transmitter transmitting coil;

[0030] The Hall sensor is electrically connected to the AD conversion module;

[0031] The controller is electrically connected to the relay and the AD conversion module;

[0032] The relay is electrically connected to the resistor network.

[0033] It should be noted that the resistor network consists of ten standardized resistors R w2 -R w11 And a pull-up resistor Rw1 The resistance of each standardized resistor is arranged in binary increments.

[0034] The relay corresponds to a standardized resistor, which also includes ten, where the 3rd and 4th pins of the i-th relay are connected to the resistor R w(i+1) The two ends of the relay are connected, the 1st pin of the i-th relay is the control signal terminal, and the 2nd pin is grounded, where i = 1, 2, 3…, 10.

[0035] It should be noted that pin 3 of the (i+1)th relay is also electrically connected to pin 4 of the (i)th relay;

[0036] The resistors in the resistor network are connected as follows:

[0037] Resistor R w2 One end of the resistor R w1 One end of the resistor R w2 The other end of the resistor R w3 One end of the resistor R w3 The other end of the resistor R w4 One end of the resistor R w4 The other end of the resistor R w5 One end of the electrical connection; R w5 The other end of the resistor R w6 One end of the resistor R w6 The other end of the resistor R w7 One end of the resistor R w7 The other end of the resistor R w8 One end of the resistor R w8 The other end of the resistor R w9 One end of the electrical connection; R w9 The other end of the resistor R w10 One end of the resistor Rw is electrically connected; 10 The other end of the resistor R w11 One end of the electrical connection; R w1 The other end is used as the first output terminal, R w11 The other end of the resistor network serves as the second output end, and the first output end and the second output end together constitute the output of the resistor network.

[0038] As an example, the design of the relay-controlled resistor network is the core module of the adaptive impedance matching system. Its function is to achieve dynamic impedance adjustment through a series of fixed resistors in parallel to meet the impedance matching requirements under different load conditions. The entire network consists of ten resistors R w2 -R w11The resistors are arranged in binary increments, namely 1Ω, 2Ω, 4Ω, 8Ω, 16Ω, 32Ω, 64Ω, 128Ω, 256Ω and 512Ω. This design ensures that all possible resistance values ​​between 1Ω and 1024Ω can be accurately generated by combining these resistors.

[0039] In addition, R w1 The resistance is 10Ω. This resistor mainly plays the role of limiting the current. No matter how the relay changes, this resistor is always connected to the coil, thereby increasing the resistance value. When the connected resistance is selected to be 0 ohms, the current will not be too large.

[0040] Specifically, one end of the ten resistors is connected to the loop of the load coil through an independent relay, while the other end is directly connected to the common ground wire. The contacts of each relay control the on and off of a resistor. When the coil of the relay is energized, its contacts are closed, and the corresponding resistor is connected to the loop in parallel with the load coil. By controlling the opening and closing state of the relay, any combination of resistance values ​​can be achieved. The main control unit is responsible for calculating the target resistance value and sending the corresponding control signal to switch the state of the relay, thereby selecting the corresponding resistance combination.

[0041] The core advantages of this design are flexibility and reliability. Using fixed resistors instead of adjustable resistors avoids the problem of resistance drift caused by mechanical structure aging or environmental factors (such as vibration). The switching of resistor combinations through relays also greatly improves the response speed and adjustment accuracy of the system. In addition, the binary arrangement of resistance combinations makes the process of calculating resistance values ​​both efficient and intuitive.

[0042] A method for designing an adaptive resistor network for a transient electromagnetic emission system, applied to the device, comprises the following steps:

[0043] S1: In the instantaneous electromagnetic transmission system, the Hall sensor is used to collect the real-time current of the transmitting coil;

[0044] S2: The real-time current is converted into a digital signal by the AD conversion module and then input into the controller;

[0045] S3: The controller analyzes the current change trend according to the linear regression method and identifies the damping state;

[0046] S4: According to the damping state, the controller calculates the resistance combination that meets the target impedance value based on the greedy algorithm, so that the system reaches the required damping state, and controls the resistance network through the relay to achieve the target impedance.

[0047] In general, the present invention collects the emission current data in real time through the Hall sensor, inputs it into the controller after AD conversion, and uses the linear regression algorithm to analyze the current change trend and identify the damping state. The controller calculates the resistance combination that meets the target impedance value based on the greedy algorithm, and connects the corresponding resistor in parallel to the transmitting coil through the relay control network. The matching process uses segmented PID adjustment to optimize the resistance value, so that the system reaches the critical damping state and realizes the smooth and rapid attenuation of the emission current, thereby improving the performance and detection accuracy of the transient electromagnetic system.

[0048] In order to ensure that any target resistance value between 1Ω and 1024Ω is achieved, the system adopts a greedy algorithm based on binary representation. Specifically, the process of calculating the resistor combination in step S4 is as follows:

[0049] S41, input target impedance value T;

[0050] S42, select the largest resistor R from the resistor network that does not exceed the target impedance value max , where R max ∈[R w2 ,R w11 ];

[0051] S43, update target impedance value T = TR max , determine whether Tˋ is 0, if not, repeat steps S42 to S43 until Tˋ is 0;

[0052] S44, output the selected resistance combination.

[0053] As an embodiment, the basic idea of ​​the algorithm is to select the largest available resistance value in the current target value each time, and gradually reduce the highest binary bit of the target value until the target value is completely decomposed into the sum of a group of resistance values.

[0054] For example, assuming the target resistance is 522Ω, the algorithm first selects the maximum resistance value of 512Ω that does not exceed 522Ω and updates the target value to 10Ω; then selects the maximum resistance value of 8Ω that does not exceed 10Ω and updates the target value to 2Ω; finally selects 2Ω and reduces the target value to 0. In this way, the target resistance of 522Ω is finally generated through the combination of 512Ω, 8Ω and 2Ω.

[0055] The greedy algorithm ensures that any target value can be accurately decomposed through a finite number of calculations, which is due to the binary arrangement characteristics of the resistor value. Each target value can be uniquely represented as the sum of several binary bits, and the value of each binary bit corresponds to the resistance value of an available resistor. For example, the binary representation of 522 is 1000001010, where the decimal resistance values ​​corresponding to the bits with a value of 1 in the binary representation are 512Ω, 8Ω, and 2Ω, respectively. These resistance value combinations just meet the target resistance value of 522Ω. Due to the uniqueness of the binary representation, the greedy algorithm can always find the global optimal solution through the local optimal selection.

[0056] In actual implementation, the greedy algorithm is combined with the main control unit (controller). First, the main control unit analyzes the damping state of the coil and determines the required impedance matching value based on the collected emission current data. By connecting different resistance values ​​in parallel to the coil, its damping coefficient can be effectively changed, so that the current flowing through the coil can be stable and can drop quickly, thereby optimizing the dynamic performance of the system. Subsequently, the greedy algorithm accurately calculates the resistance combination that needs to be connected based on the target resistance value. Finally, the main control unit controls the opening and closing of the relay according to the calculation results, and dynamically connects the corresponding resistance to the coil in parallel. The whole process is efficient and reliable, and can complete the adjustment within milliseconds, ensuring the real-time responsiveness of the system in complex environments, while improving signal quality and detection accuracy.

[0057] On the other hand, the present invention also realizes adaptive automatic impedance matching. It should be noted that step S3 is specifically as follows:

[0058] S31. Calculate the lowest current point k min The trend slope α to the last sampling point k;

[0059] S32. The damping state of the transient electromagnetic emission system is determined according to the trend slope α. If the system has not reached the critical damping state, a segmented PID controller is introduced to adjust the target impedance value, thereby adjusting the trend slope. If the system has reached the critical damping state, it means that the resistance combination in the current resistance network meets the requirements.

[0060] As an embodiment, the Hall sensor is used as a key acquisition element of the system to capture the real-time dynamic changes of transient current. When the current of the transmitting coil passes through the Hall sensor, the sensor outputs a voltage signal proportional to the current.

[0061] The signal is sent to the analog-to-digital converter (ADC) and converted into discrete sampling points in digital form for subsequent calculations. In this paper, the sampling frequency is 10MHz, and a total of 170 sampling points are obtained with a time interval of 0.1 microseconds.

[0062] In order to evaluate the characteristics of the emission current under different damping conditions, it is first necessary to perform a trend analysis on the current data.

[0063] Specifically, first calculate the current from the lowest point and set it as k min . Use k=k min The linear regression analysis was performed on the data from k = 170, and the trend slope from the lowest current point to the last sampling point was calculated by the following formula:

[0064]

[0065] in:

[0066] and They are respectively the sampling index mean and current value mean of the selected data segment.

[0067] The trend slope α is the core parameter to distinguish different damping states. If α>0.04, the system is in an underdamped state; if 0<α<0.04, the system is close to a critical damping state.

[0068] According to the error between the trend slope α and the target slope, the system introduces a segmented PID controller to adjust the resistance value. The output of the PID controller is calculated as follows:

[0069] output n =K p ·e n +K d ·Δe n (2)

[0070] where e n =Slope target -slope n That is, the target α minus the current α, Δe n =e n -e n-1 That is, the difference obtained this time minus the difference obtained last time. p The initial value of K is set to 20. d The initial value is set to 10, and according to e n The system performs adaptive adjustment according to the difference in resistance, as shown in Table 1. The output value in Table 1 is used as the basis for resistance adjustment. The system completes hardware adjustment through the relay network according to the new resistance value.

[0071] Table 1 PID control adaptive adjustment

[0072] Error <![CDATA[Adjustment(K p )]]> <![CDATA[Adjustment(K d )]]> <![CDATA[|e n |>0.5]]> <![CDATA[K p =K p +10]]> <![CDATA[K d =K d +3]]> <![CDATA[0.07>|and n |>0.1]]> <![CDATA[K p =K p -5]]> <![CDATA[K d =K d -2]]> <![CDATA[0.1≥|e n |>0.07]]> <![CDATA[K p =K p -10]]> <![CDATA[K d =K d -2]]> <![CDATA[0.07≥|e n |>0.04]]> <![CDATA[K p =K p -3]]> <![CDATA[K d =K d -1]]>

[0073] Example:

[0074] Please refer to Figure 3 , Figure 3 Five sets of typical current data of the present invention in the process of wet grassland adaptation are shown. Figure 3 (a) in the figure illustrates the adaptive adjustment process of the emission current. The blue curve is the initial adaptive stage (current oscillation), the green curve is the fine adjustment stage (strong damping effect), and the red curve is the critical damping state. Figure 3 (b) shows the change in the slope of the feedback quantity during the resistance adaptation process. The green dotted line represents the ideal slope value. At the 10th iteration, the current reaches the critical damping state and the resistance value is 55Ω.

[0075] In general, the adaptive impedance resistor network in the present invention has a novel structure and low production cost, and can automatically perform impedance matching on the transmitting coil in the transient electromagnetic detection transmitter system, so that the transmitting current can drop quickly and smoothly, thereby enhancing the stability and functionality of the detection system, and is suitable for the field of transient electromagnetic detection.

[0076] 1) The relay-controlled resistor network consists of 10 fixed resistors with resistance values ​​of 1Ω, 2Ω, 4Ω, 8Ω, 16Ω, 32Ω, 64Ω, 128Ω, 256Ω and 512Ω. Through the control of the greedy algorithm, the combination of these 10 resistors can achieve precise adjustment of any resistance value in the range of 1Ω to 1024Ω, effectively meeting the requirements of adaptive impedance matching.

[0077] 2) By analyzing the change trend of the current data between the lowest point and the last point, the slope is calculated using linear regression, and the slope is input into the segmented PID algorithm as the feedback value. The PID algorithm adjusts the output resistance value according to the feedback value, and the system controls the resistor network through relays, dynamically adjusts the resistance, and completes the matching adjustment of the hardware conditions.

[0078] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An adaptive impedance resistor network device for a transient electromagnetic emission system, characterized in that: include: Transmitter transmitting coil, Hall sensor, AD conversion module, controller, relay and resistor network; The Hall sensor is used to detect the transmitting current of the transmitter transmitting coil; The Hall sensor is electrically connected to the AD conversion module; The controller is electrically connected to the relay and the AD conversion module; The relay is electrically connected to the resistor network.

2. The adaptive impedance resistor network device of a transient battery transmitter system according to claim 1, characterized in that: The resistor network consists of ten standardized resistors R w2 -R w11 And a pull-up resistor R w1 The resistance of each standardized resistor is arranged in binary increments.

3. The adaptive impedance resistor network device of a transient battery transmitter system according to claim 2, characterized in that: The relay corresponds to a standardized resistor, which also includes ten, where the 3rd and 4th pins of the i-th relay are connected to the resistor R w(i+1) The two ends of the relay are connected, the 1st pin of the i-th relay is the control signal terminal, and the 2nd pin is grounded, where i = 1, 2, 3…, 10.

4. The adaptive impedance resistor network device of a transient battery transmitter system as claimed in claim 3, characterized in that: Pin 3 of the (i+1)th relay is also electrically connected to pin 4 of the (i)th relay.

5. The adaptive impedance resistor network device of a transient battery transmitter system as claimed in claim 4, characterized in that: Resistor R w2 One end of the resistor R w1 One end of the resistor R w2 The other end of the resistor R w3 One end of the resistor R w3 The other end of the resistor R w4 One end of the resistor R w4 The other end of the resistor R w5 One end of the electrical connection; R w5 The other end of the resistor R w6 One end of the resistor R w6 The other end of the resistor R w7 One end of the resistor R w7 The other end of the resistor R w8 One end of the resistor R w8 The other end of the resistor R w9 One end of the electrical connection; R w9 The other end of the resistor R w10 One end of the resistor Rw is electrically connected; 10 The other end of the resistor R w11 One end of the electrical connection; R w1 The other end is used as the first output terminal, R w11 The other end of the resistor network serves as the second output end, and the first output end and the second output end together constitute the output of the resistor network.

6. A method for designing an adaptive resistor network for a transient electromagnetic emission system, applied to the device according to any one of claims 1 to 5, characterized in that: The method comprises the following steps: S1: In the instantaneous electromagnetic transmission system, the Hall sensor is used to collect the real-time current of the transmitting coil; S2: The real-time current is converted into a digital signal by the AD conversion module and then input into the controller; S3: The controller analyzes the current change trend according to the linear regression method and identifies the damping state; S4: According to the damping state, the controller calculates the resistance combination that meets the target impedance value based on the greedy algorithm, so that the system reaches the required damping state, and controls the resistance network through the relay to achieve the target impedance.

7. A method for designing an adaptive resistor network for a transient electromagnetic emission system as claimed in claim 6, characterized in that: The process of calculating the resistance combination in step S4 is as follows: S41, input target impedance value T; S42, select the largest resistor R from the resistor network that does not exceed the target impedance value max , where R max ∈[R w2 ,R w11 ]; S43, update target impedance value T = TR max , determine whether Tˋ is 0, if not, repeat steps S42 to S43 until Tˋ is 0; S44, output the selected resistance combination.

8. A method for designing an adaptive resistor network for a transient electromagnetic emission system as claimed in claim 6, characterized in that: Step S3 is as follows: S31. Calculate the lowest current point k min The trend slope α to the last sampling point k; S32. The damping state of the transient electromagnetic emission system is determined according to the trend slope α. If the system has not reached the critical damping state, a segmented PID controller is introduced to adjust the target impedance value, thereby adjusting the trend slope. If the system has reached the critical damping state, it means that the resistance combination in the current resistance network meets the requirements.

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