A cluster type sensor signal acquisition method based on matrix scanning

Abstract

The application relates to the technical field of sensor signal detection, and specifically discloses a cluster type sensor signal collection method based on matrix scanning. Under the architecture of global synchronous sampling and time-sharing conversion, the method separates the multi-source leakage components of the holding capacitor from the physical mechanism by using a hybrid leakage model, so that conventional devices can approach the theoretical voltage holding limit in long-time matrix scanning waiting. On this basis, the ground bypass switch of the unselected node is reconstructed into a common mode reference generator, and the parasitic capacitance crosstalk is converted into a controllable differential offset reference, so that the channel isolation degree is greatly improved. Further, through double-mode calibration, the charge injection error introduced by the anti-crosstalk action is accurately compensated, so that the leakage compensation and the common mode suppression are self-consistent and cooperative on the same hardware platform. The overall scheme realizes precise level measurement by using conventional devices, and can break through the fundamental restriction of the intrinsic physical effect of the cluster circuit on the matrix collection precision.

Description

Technical Field

[0001] This invention relates to the field of sensor signal detection technology, specifically to a cluster sensor signal acquisition method based on matrix scanning. Background Technology

[0002] Clustered sensor signal acquisition refers to arranging multiple similar sensors in an array or network on the object under test, and synchronously acquiring physical quantity information from multiple points through a unified and coordinated acquisition strategy. It is widely used in structural health monitoring, industrial non-destructive testing, geophysical exploration and other fields. In the scenario of magnetic leakage magnetic field detection based on magnetic sensors, clustered sensors are usually attached to the surface of ferromagnetic materials in an array form. By collecting the magnetic field strength at each point, the internal defects such as corrosion and cracks of the material are detected. However, in the engineering field, each matrix node in the magnetic sensor array will not only receive the leakage magnetic field generated by the defect being measured, but also the geomagnetic field, the stray magnetic field of the surrounding electrical equipment, and the remanent magnetism of the material being measured. These components and the leakage magnetic field generated by the defect being measured are superimposed in space to form a non-uniform background magnetic field that varies with position. This magnetic field is superimposed on the sensor output signal to form a non-uniform background voltage component.

[0003] Existing cluster-based sensor signal acquisition methods typically apply independent filtering to each channel when dealing with this background interference. For example, invention patent CN119355470B discloses a multi-sensor information fusion method for monitoring the insulation status of high-voltage cables. This method, which relates to the field of information technology, obtains magnetic flux distribution data at different spatial locations within a grounding box using a triaxial orthogonal magnetic flux sensor. It analyzes the magnetic flux distribution characteristics to obtain a spatial sensitivity distribution map. It also acquires the magnetic field signal generated by the cable fault discharge source, uses an inversion method based on the magnetic field gradient tensor to decompose and calculate the magnetic field gradient tensor, locates the defect location in the cable insulation, and obtains the three-dimensional spatial coordinate information of the defect location. Based on the spatial distribution evaluation results of the cable insulation status, it increases the density of fluxgate sensors in areas with high insulation fault incidence, optimizes the tetrahedral sensor array layout, and constructs a comprehensive evaluation index system.

[0004] However, the aforementioned technical approach focuses on sensor array layout optimization and fault location algorithms, without addressing the systematic separation of the non-uniform background magnetic field received by the sensor matrix nodes. When using a global synchronous sampling and holding architecture with matrix time-division conversion to freeze and separate the background field, the fundamental obstacle limiting accuracy is not the external magnetic field, but the inherent physical effects of the cluster circuit itself. On the one hand, during matrix scanning, the sampling of each matrix node suffers from complex voltage attenuation caused by multiple leakage mechanisms, and a single linear or exponential compensation model cannot cover the complete attenuation trajectory under long waiting times. On the other hand, hundreds or thousands of unselected matrix nodes in a large-scale matrix will couple to the common readout line through the off-state parasitic capacitance of their analog switches, forming a common-mode crosstalk charge accumulation. Traditional grounding bypass or simple compensation strategies cannot eliminate this effect, and any active measures that attempt to suppress this crosstalk will introduce new charge injection, causing secondary inaccuracies in the established leakage compensation model. Currently, there is no effective means to collaboratively solve the measurement limit problem caused by the aforementioned inherent circuit physical effects without introducing new errors. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a cluster-based sensor signal acquisition method based on matrix scanning, which can effectively solve the problems mentioned in the background technology.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a clustered sensor signal acquisition method based on matrix scanning, comprising: arranging clustered magnetic sensors according to a preset matrix topology on the surface of the ferromagnetic material to be measured, and applying an active bias magnetic field; during the steady-state maintenance of the bias magnetic field, using a global synchronization trigger signal to simultaneously activate the sample-and-hold circuits of each matrix node to enter a hold state, locking the current output voltage of each matrix node sensor to the bias state hold voltage; removing the active bias magnetic field until the magnetic field returns to the background state, and again using a global synchronization trigger signal to simultaneously activate the sample-and-hold circuits of each matrix node to enter a hold state, simulating the output of each matrix node sensor at the same time and locking it to the background state hold voltage; sequentially selecting each matrix node through row and column matrix switches, and using an analog-to-digital converter to sequentially convert the bias state hold voltage and the background state hold voltage to obtain the bias state hold voltage conversion result and the background state hold voltage conversion result; performing element-wise difference operations on the bias state hold voltage conversion result and the background state hold voltage conversion result of the same matrix node to obtain a leakage magnetic anomaly matrix.

[0007] As a further method, the leakage current compensation coefficient is obtained as follows: in a zero magnetic field calibration environment, the signal path of a single matrix node composed of a sample-and-hold circuit, a ground bypass switch, and an analog switch in a row-column matrix switch is measured, and the holding capacitor voltage decay curve is measured under the highest impedance state when the analog switch is open and the ground bypass switch is closed; a hybrid leakage current model containing exponential decay components and linear decay components is established for the holding capacitor voltage decay curve, and the characteristic parameters of the hybrid leakage current model are used as the leakage current compensation coefficient of the matrix node.

[0008] As a further method, during the process of adjusting the selection sequence of the row and column matrix switches, the actual waiting time of the matrix nodes in the non-sensitive area is extended. During the long-term period, the matrix nodes in the non-sensitive area will increase the accumulation of common-mode crosstalk charge coupled to the column common output line through the parasitic capacitance of the simulated switch off state. To suppress the common-mode crosstalk caused by the increase in the accumulation of common-mode crosstalk charge, a common-mode reference construction strategy is implemented for the ground bypass switches of the unselected matrix nodes: the ground bypass switches of the matrix nodes in at least all unselected rows in the same column are configured to alternately turn on and off with a preset common-mode injection duty cycle, thereby converting the charge coupled to the column common output line through the parasitic capacitance of the simulated switch off state into a common-mode square wave current with controllable amplitude and frequency. The common-mode square wave current flows through the equivalent impedance to ground of the column common output line to establish a common-mode voltage reference. When the signal of the selected matrix node is read, it is differentially compared with the common-mode voltage reference to cancel the common-mode crosstalk component remaining in the actual signal.

[0009] As a further method, the alternating on and off states introduce an additional charge injection amount different from that in the normally closed state. This additional charge injection amount can cause inaccuracies in the characteristic parameters of the established hybrid leakage current model. To eliminate these inaccuracies, a dual-mode calibration is added to the leakage current calibration step: in a zero magnetic field calibration environment, the total leakage charge of each matrix node signal path is measured in both the normally closed mode and the common-mode injection mode of the ground bypass switch. Based on the degree of difference in the total leakage charge in the two modes, the additional charge injection amount introduced by the periodic operation of the ground bypass switch is separated, and this additional charge injection amount is incorporated as an independent compensation term into the characteristic parameters of the hybrid leakage current model to correct the actual voltage decay trajectory, including the periodic operation of the ground bypass switch.

[0010] Compared with the prior art, the embodiments of the present invention have at least the following advantages or beneficial effects: (1) This invention measures the voltage decay curve of the holding capacitor in the highest impedance state of a single-node signal path composed of a sample-and-hold circuit, a ground bypass switch and an analog switch, and establishes a hybrid leakage current model containing exponential decay components and linear decay components. The model characteristic parameters are used as leakage current compensation coefficients. This approach does not require additional compensation circuits or the selection of high-cost low-leakage devices. It only utilizes existing sample-and-hold and matrix switch hardware resources to separate leakage components from different sources, such as analog switch off-state leakage current and operational amplifier input bias current, from the physical mechanism. This allows ordinary analog switches and holding capacitors to approach their theoretical voltage holding limit, greatly reducing the selection threshold and hardware cost of core components for large-scale matrix acquisition systems.

[0011] (2) In this invention, the grounding bypass switches of all unselected matrix nodes in the same column are configured to alternately turn on and off with a preset common-mode injection duty cycle. By utilizing the grounding bypass switches that already exist in the matrix, without adding any additional wiring or isolation devices, the harmful charges that were originally randomly coupled by the parasitic capacitance of the analog switch off state are converted into common-mode square wave currents with controllable amplitude and frequency. A common-mode voltage reference that can be used for subsequent differential cancellation is established on the column common output line. This conversion turns the parasitic capacitance from a crosstalk noise source into a controllable common-mode reference generator, effectively suppressing the accumulated common-mode crosstalk under long-term waiting time, and improving the channel isolation under high-density matrix layout by orders of magnitude, thereby relaxing the stringent requirements on PCB layout wiring and the matching accuracy of analog switch off-state capacitance.

[0012] (3) In the leakage current calibration step, the present invention also introduces dual-mode calibration, which measures the total leakage charge of each node signal path when the grounding bypass switch is in normally closed mode and common-mode injection mode respectively. The extra charge injection amount introduced by the periodic operation of the switch is separated from the difference between the two and added as an independent compensation term to the hybrid leakage model to correct the real voltage decay trajectory including this operation. Thus, the charge injection error introduced by the same group of grounding bypass switches can be accurately quantified and compensated, so that the common-mode injection anti-crosstalk mechanism and the high-precision leakage compensation mechanism can work together on the same hardware platform. It can achieve the measurement accuracy of precision instruments without relying on charge injection matching precision analog switches, and truly realize the self-consistent synergy of anti-interference and high-precision compensation under the same architecture. Attached Figure Description

[0013] The present invention will be further described with reference to the accompanying drawings, but the embodiments in the drawings do not constitute any limitation on the present invention. For those skilled in the art, other drawings can be obtained based on the following drawings without creative effort.

[0014] Figure 1 This is a schematic diagram of the method flow of the present invention. Detailed Implementation

[0015] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0016] Reference Figure 1 As shown, the present invention provides a cluster sensor signal acquisition method based on matrix scanning, comprising: attaching a cluster magnetic sensor to the surface of the ferromagnetic material to be measured according to a preset matrix topology, and applying an active bias magnetic field; during the steady-state maintenance of the bias magnetic field, using a global synchronization trigger signal to cause the sampling and holding circuits of each matrix node to simultaneously enter the holding state, thereby locking the current output voltage of each matrix node sensor to the bias state holding voltage.

[0017] It should be noted that the aforementioned clustered magnetic sensor refers to a sensor array integrated from multiple discrete magnetic sensing units according to a preset row and column topology. For example, in engineering tunnel scenarios, an M×N matrix structure can be set on a flexible circuit board to collect the spatial distribution parameters of the magnetic field intensity on the surface of the tested ferromagnetic material, such as the tunnel steel arch or gas transmission steel pipeline. At the same time, an active bias magnetic field is applied by an excitation coil or permanent magnet component wound around the outer periphery of the array. That is, a DC magnetic field that is much stronger than the Earth's magnetic field and sufficient to locally magnetize the tested material to near saturation is applied. During the period when the spatial distribution and intensity of the magnetic field reach the preset steady-state tolerance range, that is, during the steady-state maintenance period of the bias magnetic field, global synchronization is triggered, so that the sample-and-hold circuit of each matrix node, that is, the analog voltage freezing circuit composed of an analog switch, a holding capacitor, and a buffer amplifier, simultaneously enters the holding state, cuts off the electrical connection between the input terminal and the holding capacitor, and uses the physical mechanism of capacitor charge storage to freeze the transient voltage value and maintain the output.

[0018] The active bias magnetic field is removed until the magnetic field returns to the background state. Then, the global synchronization trigger signal is used again to make the sample-and-hold circuits of each matrix node enter the hold state simultaneously, so that the analog outputs of the sensors of each matrix node are locked at the same time as the background state hold voltage.

[0019] Further explanation is needed: when the active bias magnetic field is completely removed and sufficient magnetic field recovery time has elapsed, the magnetic field recovers to a non-uniform environmental magnetic field state consisting only of the geomagnetic field, surrounding electromagnetic interference, and the residual magnetic field of the measured material, which is the background state mentioned above. Then, the same signal acquisition process is followed to lock the background state holding voltage of each matrix node in the background state.

[0020] By acquiring the voltage response of the same physical location under two different magnetic field excitation states, the subsequent element-wise differential operation can cancel out the inherent non-uniform background magnetic field components at the location of each matrix node in a common-mode manner, thereby separating the pure leakage magnetic anomaly signal caused only by internal defects in the tested material. This achieves source separation of background interference from the system architecture level, rather than traditional back-end filtering processing.

[0021] Each matrix node is selected sequentially by row and column matrix switches, and the bias state holding voltage and background state holding voltage are converted sequentially by an analog-to-digital converter to obtain the bias state holding voltage conversion result and the background state holding voltage conversion result.

[0022] It should also be explained that the row and column matrix switches refer to a two-dimensional addressing circuit composed of a row selection switch array and a column selection switch array cascaded together. Selecting each matrix node means closing a specific row switch and a specific column switch simultaneously according to a preset scanning timing sequence, so as to connect the output terminal of the sample-and-hold circuit corresponding to that matrix node to the common column readout line. Then, at least one analog-to-digital converter can be selected to convert the above two holding voltages to obtain the digital bias state voltage value of the corresponding matrix node under active bias excitation, i.e., the bias state holding voltage conversion result, and the digital background state voltage value of the corresponding matrix node under passive background environment, i.e., the background state holding voltage conversion result. If there is also an online monitoring requirement with extremely high real-time detection requirements in the tunnel, at least two analog-to-digital converters can be selected to achieve multi-column parallel conversion, thereby compressing the full matrix scanning cycle by a factor of two, avoiding the introduction of significant errors due to excessive attenuation of the holding voltage of the early locked node caused by excessive scanning time.

[0023] Specifically, during the process of sequentially selecting each matrix node for conversion via the row and column matrix switches, the system master control clock counter records the time period between the moment when the sample-and-hold circuit is locked and the moment when the analog-to-digital converter is selected for conversion, and marks it as the waiting time of each matrix node. The waiting time will have different durations depending on the selection order. The matrix node at the beginning of the scan sequence has a very short waiting time, while the matrix node at the end of the sequence has the longest waiting time.

[0024] A leakage current calibration step is also included before voltage lockout: In a zero-magnetic-field calibration environment, the entire sensor array is placed inside a multi-layer permalloy shielded cavity or an active magnetic compensation coil system, so that the ambient magnetic field strength is reduced to the nanoter level or below. The same reference voltage is applied to the sample-and-hold circuit of each matrix node, and full matrix sample-and-hold and time-division conversion are performed. The voltage decay slope of each matrix node during the actual waiting time is recorded to form the leakage current compensation coefficient of each matrix node.

[0025] It should be explained that the aforementioned reference voltage refers to a known constant DC voltage value provided by a high-precision, low-temperature drift reference voltage source. This voltage value is simultaneously connected to the sampling input terminals of all matrix nodes to simulate the initial voltage value at the moment the sample-and-hold circuit is locked in actual measurement. The voltage decay slope refers to the rate of change of the magnitude of the voltage across the holding capacitor due to leakage current per unit time in the holding state. Its physical essence is to characterize the total leakage rate of all leakage paths associated with the matrix node.

[0026] During the actual scanning and conversion of any matrix node, the voltage attenuation caused by leakage current during the actual waiting time is calculated based on the actual waiting time of the matrix node and the leakage current compensation coefficient corresponding to the matrix node. The voltage attenuation is then added to the conversion result to compensate and correct the conversion result.

[0027] It should also be explained that the above voltage attenuation calculation process is based on the characteristic parameters of the hybrid leakage current model corresponding to the matrix node. The actual waiting time is used as the independent variable input to the model, and the total voltage drop under the combined action of the exponential attenuation component and the linear attenuation component during the waiting period is calculated by integration, thereby obtaining the voltage attenuation.

[0028] Furthermore, the leakage current compensation coefficient is obtained as follows: In a zero-magnetic-field calibration environment, the voltage decay curve of the holding capacitor is measured in the highest impedance state when the analog switch is open and the ground bypass switch is closed, for each single matrix node signal path consisting of a sample-and-hold circuit, a ground bypass switch, and an analog switch in the row and column matrix switch.

[0029] It should be explained that the aforementioned single matrix node signal path specifically refers to the signal leakage path that starts from the upper plate of the holding capacitor in the sample-and-hold circuit of the matrix node, flows through the off-state parasitic impedance of the analog switch in the sample-and-hold circuit itself when it is in the off state, flows through the off-state parasitic impedance of the analog switch in the row and column matrix switches when it is in the off state, and finally converges to the common column readout line. This path physically defines the destination of all leakage of the holding capacitor charge. The ground bypass switch is a single-pole single-throw analog switch specifically connected in parallel between the output terminal of the matrix node and the reference ground. When it is turned off, it presents a high impedance to isolate the signal path from the ground plane. When the ground bypass switch is turned off, it means that the control logic level of the switch is in an invalid state, so that the channel of its internal MOS transistor is not formed, and there is only a very weak leakage current between the drain and source of the reverse bias PN junction. The horizontal axis of the holding capacitor voltage decay curve is the waiting time in seconds (s), and the vertical axis is the holding voltage value in volts (V). The curve starts from the initial reference voltage value and gradually decays over time under the action of the composite leakage mechanism.

[0030] A hybrid leakage current model containing exponential and linear decay components is established for the voltage decay curve of the holding capacitor, and the characteristic parameters of the hybrid leakage current model are used as the leakage current compensation coefficients of the matrix nodes.

[0031] It should also be noted that the exponential decay component is mainly caused by the subthreshold leakage current of the reverse-biased PN junction when the sample-and-hold circuit simulates the switch off state and the dielectric absorption effect of the parasitic capacitance of the row and column matrix switch simulates the switch off state, which is a voltage drop component with a gradually decreasing rate of change over time. The linear decay component is mainly caused by the ion migration leakage current of the PCB substrate, the equivalent parallel resistance of the holding capacitor itself, and the constant leakage current path when the ground bypass switch is turned off, which is a voltage drop component with a constant rate. Therefore, in the constructed hybrid leakage current model, the input is the actual waiting time of the matrix node, and the output is the voltage decay corresponding to the actual waiting time. The characteristic parameters refer to the amplitude coefficient of the exponential decay component, the time constant of the exponential decay component, and the slope coefficient of the linear decay component in this model.

[0032] Preferably, when using the leakage current compensation coefficient of the hybrid leakage current model for compensation correction, the actual waiting time interval of any matrix node is divided into two consecutive compensation stages: When the actual waiting time is less than the preset time threshold, the voltage decay is dominated by the exponential decay component. The exponential decay component and the linear decay component of the hybrid leakage current model are used for compensation. Specifically, the actual waiting time is input into the hybrid leakage current model containing exponential and linear terms, the total voltage decay contributed by the exponential decay and linear decay is calculated, and the total voltage decay is added to the original conversion result output by the analog-to-digital converter to restore the initial voltage value at the lockout moment.

[0033] During the period when the actual waiting time is not less than the preset time threshold, the original state is maintained for compensation. That is, if the original state is that both the exponential decay component and the linear decay component are compensated, then the compensation strategy corresponding to this state is still followed. However, if the original state is that the exponential decay component is frozen and only the linear decay component is enabled for compensation, then the compensation strategy of only enabling the linear decay component is followed. The specific compensation process is to fix the output value of the exponential term to the exponential saturation decay amount that the component has reached at the time constant, subtract the preset time threshold (i.e. the start time of exponential decay saturation) from the current actual waiting time to obtain the timeout duration in the pure linear decay stage, and then multiply the timeout duration by the slope coefficient of the linear decay component. The resulting product is the linear decay increment. The sum of the exponential saturation decay amount and the linear decay increment is used as the total voltage decay amount, which is added to the original conversion result output by the analog-to-digital converter.

[0034] Specifically, the leakage current compensation coefficient also has usage limitations, as follows: When the voltage of a matrix node is locked twice, namely locked as the bias state holding voltage and the background state holding voltage respectively, the actual waiting time of each matrix node is recorded synchronously.

[0035] If the actual waiting time of a matrix node exceeds the sum of the preset time threshold and the preset tolerance value, then the exponential decay component corresponding to the matrix node is prohibited from being used for compensation, and only the linear decay component is enabled for compensation.

[0036] It should be explained that the aforementioned preset tolerance value is a time increment greater than zero, used to construct a buffer zone based on a preset time threshold; the sum of the preset tolerance value and the preset time threshold is set to be no less than three times the minimum time constant of the exponential decay component in all calibrated matrix nodes; by introducing this preset tolerance value, the exponential decay component is frozen only when the actual waiting time exceeds the sum of the two, thereby forming a buffer zone near the threshold, avoiding frequent switching of compensation modes due to individual differences in the exponential decay time constant of different matrix nodes, achieving an adaptive balance between accuracy and computational efficiency, and enhancing the system's robustness to batch differences in different devices.

[0037] Furthermore, the preset time threshold is determined as follows: In the zero magnetic field calibration environment, the voltage value of the sample-and-hold circuit of a certain matrix node is measured under different actual waiting times to obtain the voltage decay curve of the holding capacitor of the matrix node; the voltage decay curve of the holding capacitor is smoothed by low-pass filtering, and the first derivative is obtained after processing to obtain the decay rate curve.

[0038] It should be explained that the above low-pass filtering smoothing process means using a zero-phase-shift Butterworth digital filter to perform a convolution operation on the original attenuation curve to eliminate the differential amplification effect caused by quantization noise and thermal noise. In addition, calculating the first derivative means calculating the difference quotient of the smoothed holding capacitor voltage attenuation curve at adjacent sampling points. That is, for the smoothed curve, the rate of voltage change at each time point is calculated to obtain the voltage attenuation rate at each moment. Therefore, in the obtained attenuation rate curve, the horizontal axis is the waiting time in seconds (s), and the vertical axis is the voltage attenuation rate in volts per second (V / s).

[0039] The interval from the starting point to the inflection point of the rate drop in the decay rate curve is identified as the short-term region dominated by exponential decay, and the quasi-linear interval after the inflection point is identified as the long-term region dominated by linear decay; the preset time threshold is the time value corresponding to the inflection point.

[0040] Further explanation is needed: the rate drop inflection point indicates the turning point where the absolute value of the first derivative on the decay rate curve changes from a rapid decrease to a gradual flattening. Its mathematical characteristic is that the second derivative is a local maximum at this point. Quasi-linearity means that the change in decay rate over time within this interval is less than a preset percentage of its own average value, and visually it presents an approximately constant flat trajectory.

[0041] Preferably, the preset time threshold is determined by the minimum time constant of the exponential decay component of each matrix node in the leakage current calibration step. Specifically, the minimum value of the exponential decay time constant in the hybrid leakage current model of all calibrated matrix nodes is selected, multiplied by a preset safety factor, and then used as a globally unified preset time threshold.

[0042] During the matrix scan conversion process of the bias state holding voltage and the background state holding voltage, by adjusting the selection order of the row and column matrix switches, firstly, the leakage magnetic anomaly matrix (an M×N numerical matrix) obtained in the previous round is used to calculate the gradient value of each node in both row and column directions using a two-dimensional spatial gradient operator (such as the Sobel operator). Then, the square root of the sum of the squares of the gradient components in these two directions is taken, and the resulting magnitude is the abnormal gradient magnitude of that node. The selection order of the current scan cycle is dynamically remapped according to the abnormal gradient magnitude, so that matrix nodes in sensitive areas where the estimated leakage magnetic anomaly change gradient is higher than the gradient threshold are selected and converted first, ensuring that the actual waiting time of the matrix nodes that are converted first is less than the preset time threshold. In addition, the estimated leakage magnetic anomaly change gradient can be obtained by performing a two-dimensional spatial gradient operator operation on the leakage magnetic anomaly matrix obtained in the previous detection cycle, that is, calculating the ratio of the leakage magnetic anomaly difference between adjacent matrix nodes to their physical distance. However, for matrix nodes in non-sensitive areas, if their actual waiting time exceeds the sum of the preset time threshold and the preset tolerance value, then compensation is performed using only the linear decay component in the manner described above.

[0043] Specifically, during the process of adjusting the selection sequence of the row and column matrix switches, nodes far from the expected defect location in the matrix are arranged at the end of the scan queue to extend the actual waiting time of matrix nodes in non-sensitive areas. During the long-term period, the matrix nodes in non-sensitive areas will increase the accumulation of common-mode crosstalk charge coupled to the column common output line through the parasitic capacitance of the analog switch in the off state. The accumulation of common-mode crosstalk charge means that when a matrix node in the same column is selected and read out, the locked holding voltage on all other unselected matrix nodes in that column will inject charge into the commonly connected column common output line in the form of displacement current through the drain-source parasitic capacitance of the analog switch in the off state of their respective row and column matrix switches. These charges accumulate on the equivalent impedance to ground of the column line to form an offset voltage, and the more unselected nodes there are and the longer the waiting time, the greater the total amount of accumulated charge.

[0044] To suppress the common-mode crosstalk caused by the increase in common-mode crosstalk charge accumulation, a common-mode reference construction strategy is implemented for the grounding bypass switch of the unselected matrix node: At least all the unselected rows in the same column are configured to have their ground bypass switches turned on and off alternately with a preset common-mode injection duty cycle, thereby converting the charge coupled to the column common output line through the simulated switch off-state parasitic capacitance into a common-mode square wave current with controllable amplitude and frequency.

[0045] It should be explained that the aforementioned common-mode injection duty cycle refers to the proportion of the ground bypass switch's on-time to the total duration of a switching cycle. The process of alternating on and off using this value involves periodically shorting the output of the unselected node to ground and then releasing it at a rate much higher than the matrix scan row switching frequency. This prevents the leakage current coupled from parasitic capacitance from accumulating irregularly, instead modulating it into a pulse current with a fixed frequency. In the process of converting the charge into a common-mode square wave current with controllable amplitude and frequency, the specific conversion method is to use the rapid switching of the ground bypass switch to forcibly neutralize and rebuild the charge slowly leaking from the parasitic capacitance of the simulated switch off state in each switching cycle, thereby shaping the irregular DC leakage into an AC square wave current determined by the switching frequency.

[0046] The common-mode square wave current flows through the equivalent impedance to ground of the column common output line to establish a common-mode voltage reference. Specifically, the square wave current generates a square wave voltage drop of the same frequency on the equivalent impedance formed by the parallel connection of the column line parasitic resistance and parasitic capacitance to ground. The average voltage value of this square wave voltage drop is the stable and controllable common-mode voltage reference.

[0047] When the signal of the selected matrix node is read, it is differentially compared with the common-mode voltage reference to cancel the common-mode crosstalk component remaining in the actual signal. Specifically, the column line voltage of the selected matrix node is differentially compared with the common-mode voltage reference extracted by the low-pass filter by the instrumentation amplifier in the analog domain to cancel the common-mode crosstalk component remaining in the actual signal.

[0048] Furthermore, the alternating on and off states introduce an additional charge injection amount different from that in the normally closed state. This additional charge injection amount refers to the amount of charge that was originally present in the channel of the MOS transistor of the ground bypass switch when it switches from on to off. This charge is released outward through the source and drain. The amount of charge injected into the drain side connected to the column line is a particular charge injection amount. This additional charge injection amount can cause the characteristic parameters of the established hybrid leakage current model to become inaccurate.

[0049] To eliminate the aforementioned misalignment, a dual-mode calibration is added to the leakage current calibration step: In a zero magnetic field calibration environment, the total leakage charge of the signal path of each matrix node was measured in both the normally closed mode of the grounding bypass switch and the common-mode injection mode. Specifically, during calibration, the same matrix node was configured in a normal continuous off state and an alternating switching state with a common-mode injection duty cycle applied, and the total attenuation of the holding capacitor voltage was recorded for the same waiting time.

[0050] Based on the difference in total leakage charge between the two modes, the additional charge injection introduced by the periodic operation of the grounding bypass switch is separated. By subtracting the voltage decay in the normally closed mode from the voltage decay in the common-mode injection mode, the additional charge injection introduced by the periodic operation of the grounding bypass switch is separated. This additional charge injection is then incorporated as an independent compensation term into the characteristic parameters of the hybrid leakage current model to correct the actual voltage decay trajectory, including the periodic operation of the grounding bypass switch. The final corrected voltage decay trajectory can eliminate the charge injection side effects caused by the introduction of anti-common-mode crosstalk measures, ensuring that the voltage decay compensation remains accurate even when the common-mode reference construction strategy is implemented. This collaboratively solves the fundamental obstacle of intrinsic circuit physical effects restricting measurement accuracy without introducing new errors.

[0051] The leakage magnetic anomaly matrix is ​​obtained by performing element-wise difference operations on the bias state holding voltage conversion result and the background state holding voltage conversion result of the same matrix node.

[0052] It should be explained that the element-by-element differential operation refers to subtracting the digitized bias-state holding voltage of the matrix nodes belonging to the same row and column address after compensation and correction from the digitized background-state holding voltage, resulting in an M×N leakage magnetic anomaly amplitude matrix that completely corresponds to the physical layout of the sensor. Specifically, the compensation and correction are performed on the bias-state holding voltage conversion result and the background-state holding voltage conversion result according to the leakage current compensation coefficient corresponding to each matrix node. In the tunnel scenario, this leakage magnetic anomaly matrix directly reflects the location and severity of defects such as thinning of the steel arch or gas pipeline wall and cracks.

[0053] The above description is merely an example and illustration of the structure of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A cluster-based sensor signal acquisition method based on matrix scanning, characterized in that, include: Clustered magnetic sensors are attached to the surface of the ferromagnetic material to be measured according to a preset matrix topology, and an active bias magnetic field is applied. During the steady-state maintenance of the bias magnetic field, the sampling and holding circuits of each matrix node are simultaneously put into the holding state by a global synchronization trigger signal, and the current output voltage of each matrix node sensor is locked to the bias state holding voltage. The active bias magnetic field is removed until the magnetic field returns to the background state. Then, the global synchronization trigger signal is used again to make the sample-and-hold circuits of each matrix node enter the hold state simultaneously, so that the analog output of each matrix node sensor is locked at the same time as the background state hold voltage. Each matrix node is selected sequentially by row and column matrix switches, and the bias state hold voltage and background state hold voltage are converted sequentially by an analog-to-digital converter to obtain the bias state hold voltage conversion result and the background state hold voltage conversion result; The leakage magnetic anomaly matrix is ​​obtained by performing element-wise difference operations on the bias state holding voltage conversion result and the background state holding voltage conversion result of the same matrix node.

2. The cluster sensor signal acquisition method based on matrix scanning according to claim 1, characterized in that: During the process of sequentially selecting each matrix node through the row and column matrix switches for conversion, the time period between the time when the sample-and-hold circuit is locked and the time when the analog-to-digital converter is selected for conversion is obtained for the holding voltage of each matrix node, and marked as the waiting time of each matrix node; A leakage current calibration step is also included before voltage lockout: In a zero magnetic field calibration environment, the same reference voltage is applied to the sample-and-hold circuit of each matrix node and full matrix sample-and-hold and time-division conversion are performed. The voltage decay slope of each matrix node during the actual waiting time is recorded to form the leakage current compensation coefficient of each matrix node. During the actual scanning and conversion of any matrix node, the voltage attenuation caused by leakage current during the actual waiting time is calculated based on the actual waiting time of the matrix node and the leakage current compensation coefficient corresponding to the matrix node. The voltage attenuation is then added to the conversion result to compensate and correct the conversion result.

3. The cluster sensor signal acquisition method based on matrix scanning according to claim 2, characterized in that: The leakage current compensation coefficient is obtained as follows: In a zero magnetic field calibration environment, the signal path of a single matrix node, which consists of a sample-and-hold circuit, a ground bypass switch, and an analog switch in a row and column matrix switch, is measured. The holding capacitor voltage decay curve is measured under the highest impedance state when the analog switch is open and the ground bypass switch is closed. A hybrid leakage current model containing exponential and linear decay components is established for the voltage decay curve of the holding capacitor, and the characteristic parameters of the hybrid leakage current model are used as the leakage current compensation coefficients of the matrix nodes.

4. The cluster sensor signal acquisition method based on matrix scanning according to claim 3, characterized in that: When using the leakage current compensation coefficient of the hybrid leakage current model for compensation correction, the actual waiting time interval of any matrix node is divided into two consecutive compensation stages: During the period when the actual waiting time is less than the preset time threshold, the voltage decay is dominated by the exponential decay component, and the exponential decay component and the linear decay component of the hybrid leakage current model are used together for compensation. During the period when the actual waiting time is not less than the preset time threshold, the original state is maintained and compensation is performed.

5. The cluster sensor signal acquisition method based on matrix scanning according to claim 4, characterized in that: The leakage current compensation coefficient also has usage limitations, as follows: When the voltage of a matrix node is locked twice, the actual waiting time of each matrix node is recorded synchronously. If the actual waiting time of a matrix node exceeds the sum of the preset time threshold and the preset tolerance value, then the exponential decay component corresponding to the matrix node is prohibited from being used for compensation, and only the linear decay component is enabled for compensation.

6. The cluster sensor signal acquisition method based on matrix scanning according to claim 5, characterized in that: The preset time threshold is determined as follows: In the zero magnetic field calibration environment, the voltage value of the sample-and-hold circuit of a certain matrix node is measured under different actual waiting times, and the voltage decay curve of the holding capacitor of the matrix node is obtained. The decay curve of the holding capacitor voltage is smoothed by low-pass filtering, and the first derivative is obtained after processing to obtain the decay rate curve. The interval from the starting point to the inflection point of the rate drop in the decay rate curve is identified as the short-term region dominated by exponential decay, and the quasi-linear interval after the inflection point is identified as the long-term region dominated by linear decay. The preset time threshold is the time value corresponding to the inflection point.

7. The cluster sensor signal acquisition method based on matrix scanning according to claim 6, characterized in that: The preset time threshold is determined by the minimum time constant of the exponential decay component of each matrix node in the leakage current calibration step. During the matrix scan conversion of the bias state holding voltage and the background state holding voltage, by adjusting the selection order of the row and column matrix switches, the matrix nodes in sensitive areas where the estimated leakage magnetic flux abnormality change gradient is higher than the gradient threshold are selected and converted first, so as to ensure that the actual waiting time of the matrix nodes that are converted first is less than the preset time threshold.

8. The cluster sensor signal acquisition method based on matrix scanning according to claim 7, characterized in that: During the process of adjusting the selection sequence of the row and column matrix switches, the actual waiting time of the matrix nodes in the non-sensitive region is extended, and the matrix nodes in the non-sensitive region will increase the accumulation of common-mode crosstalk charge coupled to the common output line of the simulated switch off-state parasitic capacitance during the long-term period. To suppress the common-mode crosstalk caused by the increase in common-mode crosstalk charge accumulation, a common-mode reference construction strategy is implemented for the grounding bypass switch of the unselected matrix node: At least all the grounding bypass switches of the matrix nodes on the unselected rows in the same column are configured to alternately turn on and off with a preset common-mode injection duty cycle, thereby converting the charge coupled to the column common output line through the simulated switch off-state parasitic capacitance into a common-mode square wave current with controllable amplitude and frequency. The common-mode square wave current flows through the equivalent impedance to ground of the column common output line to establish a common-mode voltage reference; When the signal of the selected matrix node is read, it is differentially compared with the common-mode voltage reference to cancel out the common-mode crosstalk component remaining in the actual signal.

9. The cluster sensor signal acquisition method based on matrix scanning according to claim 8, characterized in that: The alternating on and off states also introduce an additional charge injection amount that differs from the normally closed state. This additional charge injection amount can cause inaccuracies in the characteristic parameters of the established hybrid leakage current model. To eliminate the aforementioned misalignment, a dual-mode calibration is added to the leakage current calibration step: In a zero magnetic field calibration environment, the total leakage charge of each matrix node signal path was measured in both the normally closed mode of the grounding bypass switch and the common mode injection mode. Based on the difference in total leakage charge between the two modes, the additional charge injection caused by the periodic operation of the grounding bypass switch is separated, and the additional charge injection is incorporated as an independent compensation term into the characteristic parameters of the hybrid leakage current model to correct the actual voltage decay trajectory including the periodic operation of the grounding bypass switch.

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