Intelligent line patrol instrument based on multi-band electromagnetic induction and TDR fusion

Abstract

The invention belongs to the technical field of electric power and communication engineering, and particularly relates to an intelligent line patrol instrument based on multi-band electromagnetic induction and TDR fusion, and the intelligent line patrol instrument comprises a signal transmitting end which comprises a main control unit, a multi-band electromagnetic signal generator, a TDR pulse module and a self-adaptive coupling circuit. And the signal receiving end comprises a three-axis magnetic field sensor, an ADC module, an FPGA processing unit, a DSP processing unit and a touch display screen. The invention relates to an intelligent line patrol instrument combining multi-band electromagnetic induction and time domain reflection (TDR) technologies, which is used for path tracking, depth measurement and high-precision fault positioning of underground cables and optical cables, and is particularly suitable for underground pipeline maintenance and construction scenes under complex electromagnetic environments (such as transformer substations and dense pipeline areas).

Description

Technical Field

[0001] The present invention relates to an intelligent line patrol instrument based on the fusion of multi - band electromagnetic induction and TDR, belonging to the fields of electric power and communication engineering. Background Art

[0002] A line patrol instrument is an indispensable professional detection device in the fields of electric power, communication, and municipal engineering, mainly used for the positioning detection of underground cables and optical cables in a non - excavation state.

[0003] Traditional line patrol instruments mainly adopt two types of technical principles: one is carrier detection based on electromagnetic induction (10 kHz - 100 kHz), which locates pipelines by detecting the induced magnetic field around the wire, but is only applicable to non - metallic pipelines; the other is pulse detection based on time - domain reflectometry (TDR), which locates breakpoints by analyzing the reflected waveform, but waveform aliasing is prone to occur in complex branched lines. As described in the invention patent with the publication number CN114137620B, its single - band magnetic field detection scheme has obvious limitations: when the pipeline burial depth exceeds 1.5 meters, the signal attenuation reaches 60 dB, and it is impossible to distinguish the coupled signals of parallel multi - conductors. Industry research data shows that the average positioning error of existing equipment under complex working conditions exceeds 15%.

[0004] There are three major pain points in the current technology: 1) Functional singularity, unable to simultaneously achieve path tracking and precise fault location, unable to monitor and record the pipeline depth in real - time, only locating the fault point, resulting in an increase in positioning error; 2) Defects in dynamic interference suppression, power - frequency interference can deteriorate the signal - to - noise ratio of traditional receivers to below - 10 dB, and in a power - frequency interference (50 / 60 Hz) or strong electromagnetic environment, the signal attenuation is serious, further increasing the positioning error; 3) Lack of intelligent diagnosis, more than 90% of the equipment still relies on the operator's experience to judge the fault type, lacking the ability of digital twin modeling. As shown in the fault repair records of a certain provincial power grid in 2022, 38.6% of cable faults were caused by misjudgment of traditional equipment, leading to secondary excavation.

[0005] The industry's technological development shows three major trends: ① Multi - physical - field fusion detection, through electromagnetic - acoustic - optical multi - modal data complementarity; ② Adaptive anti - interference system, constructing a dynamic notch filter bank; ③ Intelligent diagnosis cloud collaboration, realizing fault mode recognition through deep learning. This requires that the new - generation line patrol instrument must have cross - band sensing, multi - source information fusion, and autonomous decision - making capabilities, and existing single - technology - route equipment has difficulty meeting the needs of new - type smart city construction. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide an intelligent line patrol instrument based on the fusion of multi - band electromagnetic induction and TDR to solve the above problems.

[0007] The intelligent line patrol instrument based on the fusion of multi - band electromagnetic induction and TDR according to the present invention includes: a signal transmitting end, which comprises a main control unit, a multi - band electromagnetic signal generator, a TDR pulse module and an adaptive coupling circuit; the multi - band electromagnetic signal generator is connected to the adaptive coupling circuit and is used to generate a continuous sine wave signal with a frequency range from 1 kHz to 100 kHz; the TDR pulse module is connected to the adaptive coupling circuit and is used to generate an encoded pulse signal with a pulse width from 2 ns to 10 ns; the adaptive coupling circuit selects to inject either the continuous sine wave signal or the encoded pulse signal into the target cable through a mode - switching switch; the main control unit is connected to the signal transmitting end and the receiving end and is used for mode - switching control and system collaborative scheduling; a signal receiving end, which comprises a three - axis magnetic field sensor, an ADC module, an FPGA processing unit, a DSP processing unit and a touch display screen; the three - axis magnetic field sensor is connected to the ADC module and is used to detect the magnetic field signal around the cable; the output end of the ADC module is connected to the FPGA processing unit and is used for signal digitization and real - time pre - processing; the FPGA processing unit communicates bidirectionally with the DSP processing unit and collaboratively executes adaptive filtering, path modeling and fault diagnosis; the output end of the DSP processing unit is connected to the touch display screen and is used to display the three - dimensional path and the fault location.

[0008] Among them, the multi - band electromagnetic signal generator includes a DDS chip and a Class - D power amplifier. The output end of the DDS chip is connected to the power amplifier through a low - pass filter, and the output end of the power amplifier is connected to the adaptive coupling circuit; the TDR pulse module includes an avalanche transistor and a high - voltage driving circuit. The output end of the avalanche transistor is connected to the adaptive coupling circuit through a pulse transformer.

[0009] Among them, the adaptive coupling circuit includes a mode - switching switch, an impedance - matching network and a signal detection unit. The mode - switching switch is a solid - state relay or a MOSFET array, and receives the instruction from the main control unit to switch to the electromagnetic induction mode or the TDR mode; the impedance - matching network is an adjustable LC circuit and dynamically adapts to the characteristic impedance of the cable; the signal detection unit monitors the reflected signal through a directional coupler and feeds it back to the main control unit to adjust the impedance - matching parameters.

[0010] The FPGA processing unit of the present invention: performs FFT spectrum analysis on the digital signal output by the ADC module to identify the power - frequency interference component; calculates the signal energy in real - time. When the energy attenuation in three consecutive time windows exceeds 30%, it triggers mode - switching; caches the TDR reflected - wave data and transmits it to the DSP processing unit.

[0011] The DSP processing unit of the present invention: runs the LMS adaptive filtering algorithm to dynamically update the filter coefficients to suppress noise; fuses the data of the three-axis magnetic field sensor and the IMU attitude information to generate a three-dimensional cable path model through a B-spline curve; analyzes the time delay, amplitude, and frequency characteristics of the TDR reflected wave, and matches the pre-stored fault library to determine the fault type.

[0012] The fault library of the present invention includes the following determination rules: If the positive mutation of the reflected wave amplitude exceeds 80% and the time delay is less than 0.1 μs, it is determined as a short-circuit fault; if the negative mutation of the reflected wave amplitude exceeds 50% and the reflection coefficient is greater than 0.8, it is determined as a break point fault; if the reflected wave shows multi-peak oscillation and the decay time exceeds 200 ns, it is determined as a water ingress fault.

[0013] The working logic of the present invention is: in the electromagnetic induction mode, it preferentially tracks the path through multi-band scanning and dynamically selects the optimal band;

[0014] When the receiving end detects that the signal attenuation exceeds the threshold or is manually triggered by the user, it switches to the TDR mode; in the TDR mode, after the fault is located, it automatically resumes the electromagnetic induction mode. Inject multi-band continuous wave signals into the cable through an adaptive coupling circuit, and the receiving end generates real-time path and burial depth data; when the signal attenuation exceeds the threshold, it switches to the TDR mode and injects coded pulses, and locates the fault through the analysis of the reflected wave; after the fault is located, it automatically switches back to the electromagnetic induction mode to continue path tracking.

[0015] Electromagnetic induction mode: The transmitting end injects a multi-frequency alternating current, and the receiving end captures the magnetic field intensity through a three-axis Hall sensor and calculates the path and depth (depth = K × (signal intensity / frequency), where K is the medium attenuation coefficient).

[0016] TDR mode: Transmit a nanosecond-level coded pulse, and locate the break point, short circuit, or water ingress fault through the time delay of the reflected wave (Δt = (2L) / (v), where L is the fault distance and v is the signal propagation speed) and the waveform characteristics (amplitude, phase).

[0017] Intelligent diagnosis: The fault type recognition library matches the characteristics of the reflected wave (such as a positive spike for a short circuit and a negative spike for a break point), and the fault location and type are displayed in real time through the touch screen.

[0018] Transmitting end design: The DDS chip outputs a sine wave of 1 kHz - 100 kHz, which is driven by a Class-D amplifier to a peak current of 5 A; the TDR pulse module uses a 2N5551 avalanche transistor to generate a 5 ns @ 200 V high-voltage pulse, supporting m-sequence coding.

[0019] Receiver design: The three-axis Hall sensor (MLX90393) collects magnetic field signals, which are sampled by a 24-bit ADC (ADS1256); the FPGA realizes real-time filtering and path fitting, and the DSP executes the fault diagnosis algorithm.

[0020] Dynamic path modeling: The Kalman filter fuses IMU attitude data and signal strength; the B-spline curve fitting generates a three-dimensional path, which is superimposed on the geographic information system (GIS).

[0021] The beneficial effects of the present invention compared with the prior art are as follows:

[0022] The intelligent pipeline patrol instrument based on the fusion of multi-band electromagnetic induction and TDR of the present invention is an intelligent pipeline patrol instrument that combines multi-band electromagnetic induction and time domain reflectometry (TDR) technology, and is used for path tracking, depth measurement and high-precision fault location of underground cables and optical cables, especially suitable for underground pipeline maintenance and construction scenarios in complex electromagnetic environments (such as substations, dense pipeline areas).

[0023] 1. Multi-modal collaborative detection: It simultaneously supports the detection of metal pipelines (electromagnetic induction mode) and non-metal pipelines (TDR mode), covering all types of pipelines such as power cables, communication optical cables, PVC / PE pipes, etc., filling the detection gap of traditional equipment for non-metal pipelines.

[0024] 2. Path-fault integrated detection: The path is tracked in real time and the burial depth is calculated in the electromagnetic induction mode, and the fault point is accurately located in the TDR mode. A single device completes the whole process of operation, reducing the equipment switching time by more than 60%.

[0025] 3. Significantly enhanced anti-interference performance: The multi-band electromagnetic signals (1 kHz - 100 kHz) are dynamically switched to avoid the power frequency interference band (such as 50 / 60 Hz), and the LMS algorithm is combined to suppress random noise in real time, and the signal-to-noise ratio is increased by ≥30 dB.

[0026] 4. Intelligent diagnosis and three-dimensional visualization: Based on the time delay, amplitude and frequency characteristics of the reflected wave (such as short circuit ΔV>80%, breakpoint ΔV<-50%, water ingress τ>200 ns), the fault type can be automatically identified with high accuracy.

[0027] 5. The positioning accuracy is improved, reducing the loss of mis-digging; the construction efficiency is improved, and the path tracking and fault location are completed in a single detection, shortening the working hours by 50%. It is especially suitable for the general survey and emergency repair of underground pipe networks in smart cities.

[0028] Through technology integration and intelligent innovation, the present invention realizes the leap from "single function, manual dependence" to "multi-modal collaboration, autonomous decision-making" in underground pipeline detection, significantly improving the detection accuracy and efficiency in complex environments, and providing reliable technical equipment support for the construction of new smart cities. Brief Description of the Drawings

[0029] Figure 1 is the overall system architecture diagram of the present invention;

[0030] Figure 2 is a schematic diagram of the multi - band signal generation principle;

[0031] Figure 3 is a schematic diagram of the principle of the TDR pulse module;

[0032] Figure 4 is a flowchart of the dual - mode collaborative working principle;

[0033] Figure 5 is a flowchart of the TDR pulse coding and reflection analysis;

[0034] Figure 6 is a flowchart of the adaptive filtering algorithm;

[0035] Figure 7 is a schematic diagram of the adaptive coupling circuit;

[0036] Figure 8 is a flowchart of the three - dimensional path modeling algorithm;

[0037] Figure 9 is a dual - mode switching working logic diagram. Detailed Embodiments

[0038] The present invention will be further described below in conjunction with specific embodiments.

[0039] The description of the present invention is only an embodiment of the structural and functional descriptions. The scope of the rights of the present invention is not limited by the embodiments described herein.

[0040] Such as Figures 1-9As shown in the figure, this embodiment is realized through the following technical solutions: The intelligent line patrol instrument based on the fusion of multi-band electromagnetic induction and TDR includes a signal transmitting end, which includes a main control unit, a multi-band electromagnetic signal generator, a TDR pulse module, and an adaptive coupling circuit; the multi-band electromagnetic signal generator is connected to the adaptive coupling circuit and is used to generate a continuous sine wave signal of 1 kHz to 100 kHz; the TDR pulse module is connected to the adaptive coupling circuit and is used to generate a coded pulse signal of 2 ns to 10 ns; the adaptive coupling circuit selects to inject the continuous sine wave signal or the coded pulse signal into the target cable through a mode switching switch; the main control unit is connected to the signal transmitting end and the receiving end and is used for mode switching control and system collaborative scheduling; a signal receiving end, which includes a three-axis magnetic field sensor, an ADC module, an FPGA processing unit, a DSP processing unit, and a touch display screen; the three-axis magnetic field sensor is connected to the ADC module and is used to detect the magnetic field signal around the cable; the output end of the ADC module is connected to the FPGA processing unit and is used for signal digitization and real-time preprocessing; the FPGA processing unit communicates bidirectionally with the DSP processing unit and collaborates to perform adaptive filtering, path modeling, and fault diagnosis; the output end of the DSP processing unit is connected to the touch display screen and is used to display the three-dimensional path and the fault location.

[0041] The multi-band electromagnetic signal generator includes a DDS chip and a Class-D power amplifier. The output end of the DDS chip is connected to the power amplifier through a low-pass filter, and the output end of the power amplifier is connected to the adaptive coupling circuit; the TDR pulse module includes an avalanche transistor and a high-voltage drive circuit, and the output end of the avalanche transistor is connected to the adaptive coupling circuit through a pulse transformer.

[0042] The adaptive coupling circuit includes a mode switching switch, an impedance matching network, and a signal detection unit. The mode switching switch is a solid-state relay or a MOSFET array, and receives the main control unit instruction to switch to the electromagnetic induction mode or the TDR mode; the impedance matching network is an adjustable LC circuit and dynamically adapts to the characteristic impedance of the cable; the signal detection unit monitors the reflected signal through a directional coupler and feeds it back to the main control unit to adjust the impedance matching parameters.

[0043] The working principle of the entire system is as follows: First, connect the adaptive coupler at the signal transmitting end to the target cable. The transmitting end selects the output signal according to the current working mode. In the electromagnetic induction mode, the multi-band signal generator generates a continuous sine wave from 1 kHz to 100 kHz, which is amplified by the Class-D power amplifier and then injected into the cable. An alternating magnetic field is generated around the cable. The three-axis Hall sensor at the receiving end detects the magnetic field intensity in real time. Combining the signal frequency and the preset medium attenuation coefficient, it calculates the burial depth of the cable (formula: h = k·S / f, where S is the magnetic field intensity, f is the frequency, and k is the calibration constant). At the same time, it draws the running path of the cable through continuous scanning, with an accuracy of within 5 centimeters. When the receiving end detects that the magnetic field signal suddenly decays by more than 30% (for example, the magnetic field is interrupted due to cable breakage), or the user manually triggers a fault detection, the system automatically switches to the TDR mode: The transmitting end immediately stops the continuous wave output and instead generates a high-voltage short pulse (such as 5 ns @ 200 V) by the TDR pulse module. The pulse is superimposed with a 127-bit pseudo-random code (m sequence) to improve the anti-interference ability and is injected into the cable through the coupler. The high-speed ADC at the receiving end samples the reflected wave signal at 1 GSPS, demodulates the code using the cross-correlation algorithm, calculates the delay Δt of the reflected wave (formula: L = v·Δt / 2, where v is the propagation speed of the signal in the cable), and matches the fault library in combination with the waveform characteristics (positive spikes indicate short circuits, negative spikes indicate breakpoints, and multi-peak oscillations indicate water ingress). Finally, the fault location is displayed on the touch screen (error ≤ 0.5%). Once the fault location is completed or the user manually switches, the system immediately resumes the electromagnetic induction mode and continues the path tracking, forming a closed-loop detection process of "path - fault - path". The adaptive filtering algorithm runs throughout this process. By analyzing the environmental noise spectrum through FFT, it dynamically selects the optimal frequency band and filters out the power frequency interference in real time through the LMS algorithm (updating the filter coefficient through the least mean square error, formula: w(n + 1) = w(n) + μ·e(n)·x(n), where μ is the step size, e is the error, and x is the input signal), ensuring the signal purity in both modes, so as to maintain high-precision detection in a complex electromagnetic environment.

[0044] w(n): The filter weight vector at the current moment (the nth iteration). The weights determine how the input signals are weighted and combined to generate the output of the filter. μ: The step size parameter (learning rate), usually with a value range of 0 < μ < 1 / input signal power. Controls the amplitude of the weight update.

[0045] Too large: May cause oscillation or non-convergence.

[0046] Too small: The convergence speed is slow and more iteration times are required.

[0047] e(n): The error signal, which is the difference between the desired output d(n) and the actual output y(n):

[0048] e(n) = d(n) - y(n) = d(n) - w(n)^T·x(n), which reflects the gap between the current filtering effect and the ideal target and is the driving force for weight adjustment.

[0049] x(n): Input signal vector, including the input values at the current and past moments. It provides the direction information for weight adjustment and jointly determines the update direction with the error.

[0050] By adjusting the weights w, the output y(n) of the filter is made to approach the desired signal d(n) as closely as possible, thereby minimizing the mean square error E[e^2(n)]. If the current error e(n) is large, or the input signal x(n) is highly correlated with the error, the weight adjustment amplitude is greater. The adjustment direction of the weights is along the negative gradient direction of the error and the input signal, gradually approaching the optimal solution.

[0051] Three-dimensional path modeling algorithm process: The IMU provides attitude angles and acceleration data, the Kalman filter fuses the electromagnetic signal strength and position information, uses B-spline curves to generate a smooth three-dimensional path model, supports real-time update, superimposes the path model on the GIS map (integrated GPS module), the prediction error ≤ 10 cm, and the touch screen displays the historical path and fault marks.

[0052] IMU (Inertial Measurement Unit): Such as MPU6050, provides attitude angles (θ, φ) and acceleration data, DSP + GPU: Such as NVIDIA Jetson Nano, performs Kalman filtering and B-spline curve fitting. IMU and Kalman filtering are prior arts, and this patent achieves innovation through multi-sensor fusion weight optimization and real-time B-spline control point update.

[0053] Kalman filtering: Fuses IMU attitude data and electromagnetic signal strength to eliminate noise, formula: x^k = x^k|k - 1 + Kk(zk - Hx^k|k - 1)

[0054] B-spline fitting: Generates a smooth path model, the control point spacing ≤ 10 cm, formula:

[0055]

[0056] where Ni,p(t) is the basis function and Pi is the control point.

[0057] Reflection wave characteristics Fault type Judgment threshold Positive spike (ΔV>80%) Short circuit Time delay Δt < 0.1 μs Negative spike (ΔV < -50%) Breakpoint Reflection coefficient Γ>0.8 Multi-peak oscillation Water ingress into the cable Attenuation time constant τ>200ns

[0058] Of course, the above content is only the preferred embodiment of the present invention and cannot be considered as limiting the scope of the embodiments of the present invention. The present invention is not limited to the above examples either. Equal changes and improvements made by those of ordinary skill in the art within the essence of the present invention shall fall within the scope covered by the patent of the present invention.

Claims

1. An intelligent line patrol instrument based on the fusion of multi-band electromagnetic induction and TDR, characterized in that Comprising: A signal transmitting end, including a main control unit, a multi-band electromagnetic signal generator, a TDR pulse module, and an adaptive coupling circuit; the multi-band electromagnetic signal generator is connected to the adaptive coupling circuit and is used to generate a continuous sine wave signal from 1 kHz to 100 kHz; the TDR pulse module is connected to the adaptive coupling circuit and is used to generate a coded pulse signal from 2 ns to 10 ns. The adaptive coupling circuit selects to inject a continuous sine wave signal or a coded pulse signal into the target cable through a mode switching switch; the main control unit is connected to the signal transmitting end and the receiving end and is used for mode switching control and system collaborative scheduling. A signal receiving end, including a three-axis magnetic field sensor, an ADC module, an FPGA processing unit, a DSP processing unit, and a touch display screen; the three-axis magnetic field sensor is connected to the ADC module and is used to detect the magnetic field signal around the cable; the output end of the ADC module is connected to the FPGA processing unit and is used for signal digitization and real-time preprocessing; the FPGA processing unit communicates bidirectionally with the DSP processing unit and collaboratively performs adaptive filtering, path modeling, and fault diagnosis; the output end of the DSP processing unit is connected to the touch display screen and is used to display the three-dimensional path and the fault location.

2. The intelligent line patrol instrument based on the fusion of multi-band electromagnetic induction and TDR according to claim 1, wherein The multi-band electromagnetic signal generator includes a DDS chip and a Class-D power amplifier. The output end of the DDS chip is connected to the power amplifier through a low-pass filter, and the output end of the power amplifier is connected to the adaptive coupling circuit.

3. The intelligent line patrol instrument based on the fusion of multi-band electromagnetic induction and TDR according to claim 2, characterized in that The TDR pulse module includes an avalanche transistor and a high-voltage drive circuit. The output end of the avalanche transistor is connected to the adaptive coupling circuit through a pulse transformer.

4. The intelligent line patrol instrument based on the fusion of multi-band electromagnetic induction and TDR according to claim 2 or 3, characterized in that, The adaptive coupling circuit includes a mode switching switch, an impedance matching network, and a signal detection unit.

5. The intelligent line patrol instrument based on the fusion of multi-band electromagnetic induction and TDR according to claim 4, characterized in that, The mode switching switch is a solid-state relay or a MOSFET array and receives the main control unit instruction to switch to the electromagnetic induction mode or the TDR mode.

6. The intelligent line patrol instrument based on the fusion of multi-band electromagnetic induction and TDR according to claim 5, characterized in that, The impedance matching network is an adjustable LC circuit and dynamically adapts to the characteristic impedance of the cable.

7. The intelligent line patrol instrument based on the fusion of multi-band electromagnetic induction and TDR according to claim 6, characterized in that The signal detection unit monitors the reflected signal through a directional coupler and feeds it back to the main control unit to adjust the impedance matching parameters.

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