Optical pumping magnetometer non-blind area data fusion method and system based on multiple probes

Abstract

The invention discloses an optical pumping magnetometer non-blind area data fusion method and system based on multiple probes, and relates to the technical field of magnetic field measurement data processing. The fusion method comprises the following steps: repairing an abnormal measurement value of a probe of a magnetometer by adopting a sliding window method; and carrying out weighted average on the repaired measurement values of the plurality of probes to obtain fused magnetic field measurement data. Through abnormal measurement value detection and restoration and dynamic weighted fusion, the problem of step errors caused by background magnetic field gradients in the probe switching process is effectively solved, non-blind area and high-precision magnetic field measurement data is realized, and the measurement precision, data continuity and reliability of the magnetometer in a complex real environment are remarkably improved. The method can be widely applied to the fields of aviation navigation, geological exploration, magnetic field anomaly detection and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic field measurement data processing, and particularly relates to a method and system for blind - area - free data fusion of an optically pumped magnetometer based on multiple probes. Background Art

[0002] A magnetometer is an important device in an airborne magnetic detection system for accurately measuring the spatial magnetic field intensity, and its measurement result should accurately reflect the true magnetic field intensity at a position. However, traditional single - probe magnetometers have a blind - area problem: when the angle between the probe and the geomagnetic field exceeds the normal working range, reliable readings cannot be provided. For this reason, multi - probe magnetometers are arranged with multiple probes in different directions to achieve full - angle coverage, ensuring that at least one probe can work properly regardless of attitude changes. However, due to the geomagnetic background gradient and probe position differences, step - like anomalies may occur during probe switching in multi - probe magnetometers, affecting measurement continuity and accuracy. Summary of the Invention

[0003] In view of the above problems, the present invention proposes a method and system for blind - area - free data fusion of an optically pumped magnetometer based on multiple probes to obtain blind - area - free and high - precision magnetic field measurement data.

[0004] According to one aspect of the present invention, a method for blind - area - free data fusion of an optically pumped magnetometer based on multiple probes is proposed. The method includes:

[0005] Repairing abnormal measurement values of the probes of the magnetometer by using a sliding window method;

[0006] Performing weighted averaging on the repaired measurement values of multiple probes to obtain fused magnetic field measurement data.

[0007] Further, the repairing of abnormal values of the probes of the optically pumped magnetometer by using a sliding window method includes:

[0008] The repairing of abnormal values of the probes of the optically pumped magnetometer by using a sliding window method includes: setting the measured magnetic field values within the sliding window of the i - th probe as Calculating the standard deviation of multiple data points within the sliding window. If the standard deviation is greater than a preset threshold, determining that the measured magnetic field value of the i - th probe within the sliding window is an abnormal measurement value;

[0009] Calculating the mean value of the measured magnetic field values within the sliding windows of other probes; calculating the difference between the mean value and the abnormal measurement value; obtaining the repaired value within the sliding window of the i - th probe by subtracting the difference from the mean value; for the obtained repaired values within multiple sliding windows, splicing them together to obtain the repaired measured magnetic field data of the i - th probe.

[0010] Further, the weighted averaging of the multiple repaired probes to obtain the fused magnetic field measurement data includes:

[0011] Calculating the cosine value of the angle between the direction vector of each probe and the total geomagnetic field vector at each moment;

[0012] Calculating the confidence level of each probe at each moment based on the cosine value of the angle;

[0013] Calculating the weight of each probe at each moment according to the confidence level;

[0014] Performing weighted averaging on the measured magnetic field data after repair of multiple probes based on the weight vectors of each probe at multiple moments to obtain the fused magnetic field measurement data.

[0015] Further, the calculation formula of the cosine value of the angle is as follows:

[0016]

[0017] In the formula, arccos represents the inverse cosine function; represents the direction vector of the i-th probe; represents the measured value of the fluxgate magnetometer at time t.

[0018] Further, the calculation formula of the confidence level of each probe is as follows:

[0019]

[0020] In the formula, c min , c max are respectively the minimum value and the maximum value of the normal working range of the probe.

[0021] Further, the calculation formula of the weight of each probe is as follows:

[0022]

[0023] In the formula, N represents the total number of probes.

[0024] According to another aspect of the present invention, an optical pumping magnetometer blind area-free data fusion system based on multiple probes is proposed. The system includes:

[0025] An anomaly repair module configured to repair the abnormal measurement values of the probes of the magnetometer by using a sliding window method;

[0026] A data fusion module configured to perform weighted averaging on the measurement values of multiple repaired probes to obtain the fused magnetic field measurement data.

[0027] Further, the method for repairing the abnormal value of the probe of the optically pumped magnetometer by using the sliding window method in the abnormal repair module includes:

[0028] Let the measured magnetic field value within the sliding window of the i-th probe be Calculate the standard deviation of multiple data points within the sliding window. If the standard deviation is greater than the preset threshold, determine that the measured magnetic field value of the i-th probe within the sliding window is an abnormal measured value; calculate the mean value of the measured magnetic field values within the sliding windows of other probes; calculate the difference between the mean value and the abnormal measured value; obtain the repaired value within the sliding window of the i-th probe by subtracting the difference from the mean value; for the obtained repaired values within multiple sliding windows, splice them together to obtain the measured magnetic field data of the i-th probe after repair.

[0029] Further, the method for weighted averaging the multiple repaired probes in the data fusion module to obtain the fused magnetic field measurement data includes: calculating the cosine value of the angle between the direction vector of each probe and the total geomagnetic field vector at each moment; calculating the confidence of each probe at each moment based on the cosine value of the angle; calculating the weight of each probe at each moment according to the confidence; performing weighted averaging on the measured magnetic field data of the multiple repaired probes based on the weight vectors of each probe at multiple moments to obtain the fused magnetic field measurement data.

[0030] Further, the calculation formula for the cosine value of the angle in the data fusion module is as follows:

[0031]

[0032] In the formula, arccos represents the inverse cosine function; represents the direction vector of the i-th probe; represents the measured value of the fluxgate magnetometer at time t;

[0033] The calculation formula for the confidence of each probe is as follows:

[0034]

[0035] In the formula, c min , c max are respectively the minimum value and the maximum value of the normal working range of the probe;

[0036] The calculation formula for the weight of each probe is as follows:

[0037]

[0038] In the formula, N represents the total number of probes.

[0039] The beneficial technical effects of the present invention are:

[0040] The present invention provides a method and system for blind - area - free data fusion of an optically pumped magnetometer based on multiple probes. Through abnormal measurement value detection and repair, and dynamic weighted fusion, the problem of step error caused by background magnetic field gradient during the probe switching process is effectively solved, realizing blind - area - free and high - precision magnetic field measurement data, and significantly improving the measurement accuracy, data continuity and reliability of the magnetometer in complex real environments. The present invention can be widely applied to fields such as aviation navigation, geological exploration, and magnetic field anomaly detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] By reading the following detailed description with reference to the accompanying drawings, the above - mentioned and other objects, features and advantages of the exemplary embodiments of the present invention will become easily understandable. In the drawings, several embodiments of the present invention are shown in an exemplary but non - restrictive manner, where:

[0042] Figure 1 FIG. is a flowchart of a method for blind - area - free data fusion of an optically pumped magnetometer based on multiple probes according to an embodiment of the present invention.

[0043] Figure 2 FIG. is a schematic diagram of a multi - probe magnetometer in an embodiment of the present invention.

[0044] Figure 3 FIG. is a schematic diagram of the installation of a three - optical - system magnetometer and a fluxgate sensor in an embodiment of the present invention.

[0045] Figure 4 FIG. is an example diagram of the result after anomaly repair of a multi - probe magnetometer in an embodiment of the present invention.

[0046] Figure 5 FIG. is a schematic diagram of the probe direction calibration of a three - optical - system magnetometer in an embodiment of the present invention.

[0047] Figure 6 FIG. is an example diagram of the result of dynamic weighted fusion processing in an embodiment of the present invention.

[0048] Figure 7 FIG. is another flowchart of a method for blind - area - free data fusion of an optically pumped magnetometer based on multiple probes according to an embodiment of the present invention.

[0049] Figure 8 FIG. is a structural diagram of a system for blind - area - free data fusion of an optically pumped magnetometer based on multiple probes according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0050] The principles and spirit of the present invention will be described below with reference to several exemplary embodiments. It should be understood that these embodiments are given only to enable those skilled in the art to better understand and then implement the present invention, rather than limiting the scope of the present invention in any way. On the contrary, these embodiments are provided to make the present disclosure more thorough and complete, and to be able to fully convey the scope of the present disclosure to those skilled in the art.

[0051] Those skilled in the art know that the embodiments of the present invention can be implemented as a system, a device, an equipment, a method, or a computer program product. Therefore, the present disclosure can be specifically implemented in the following forms, namely: entirely hardware, entirely software (including firmware, resident software, microcode, etc.), or a combination of hardware and software. In this article, it should be understood that any number of elements in the drawings is for illustration rather than limitation, and any naming is only for distinction and does not have any limiting meaning.

[0052] The present invention proposes a two-stage data fusion method for processing the data of a multi-probe magnetometer. In the first stage, the sliding window technique is used to detect and repair the abnormal values in the magnetic field data of each probe, eliminating the abnormal values in the data; in the second stage, a dynamic weight model is constructed based on the angle between the probe and the geomagnetic field to perform weighted fusion on the multi-channel probe data, smoothing the differences between the probes, and finally generating a magnetic field measurement data with no blind spots, high precision, and strong continuity.

[0053] An embodiment of the present invention proposes a blind-spot-free data fusion method for an optically pumped magnetometer based on multiple probes, as Figure 1 shown, the method includes:

[0054] S1. Repair the abnormal measurement values of the probes of the magnetometer by using the sliding window method; specifically, assume that the measured magnetic field value within the sliding window of the i-th probe is Calculate the standard deviation of multiple data points within the sliding window. If the standard deviation is greater than a preset threshold, determine that the measured magnetic field value of the i-th probe within the sliding window is an abnormal measurement value; calculate the mean value of the measured magnetic field values within the sliding windows of other probes; calculate the difference between the mean value and the abnormal measurement value; obtain the repaired value within the sliding window of the i-th probe by subtracting the difference from the mean value; for the obtained repaired values within multiple sliding windows, splice them together to obtain the measured magnetic field data of the i-th probe after repair;

[0055] S2. Perform weighted averaging on the measured values of multiple repaired probes to obtain the fused magnetic field measurement data. Specifically, calculate the cosine value of the angle between the direction vector of each probe and the total geomagnetic field vector at each moment; calculate the confidence level of each probe at each moment based on the cosine value of the angle; calculate the weight of each probe at each moment according to the confidence level; perform weighted averaging on the measured magnetic field data repaired by multiple probes at each moment based on the weight vectors of each probe at multiple moments to obtain the fused magnetic field measurement data.

[0056] The embodiments of the present invention will be described in detail below.

[0057] As Figures 2 - 3 shown, the multi-probe magnetometer consists of a magnetic field measurement module and a direction estimation module. The magnetic field measurement module synchronously measures the intensity of the geomagnetic field through three scalar probes, and the direction estimation module calculates the direction of the geomagnetic field in the magnetometer coordinate system using a fluxgate sensor. The probes and the fluxgate sensor are both fixed on the magnetic measurement platform.

[0058] The magnetometer synchronously acquires three-channel data. Since the angle between the probe and the geomagnetic field directly affects the accuracy of the reading, when the angle between the probe and the geomagnetic field is close to 0° or 90°, the probe may enter the "blind zone", and its reading will deviate from the true magnetic field intensity, resulting in the inability to correctly describe the magnetic field information at the current position. The multi-probe magnetometer ensures that at least one probe is within the normal working range at any time by reasonably arranging multiple probes, thereby achieving blind-zone-free measurement. However, during the working process, different probes will alternately enter the blind zone due to attitude changes, resulting in abnormal readings. Therefore, it is necessary to repair the abnormal data. The sliding window method is used to repair the abnormal measurement values of the probes of the magnetometer.

[0059] The core idea of single-probe data repair is to use the readings of one probe as the data to be repaired and the data of the other two probes as references to correct the abnormal values. Let the original magnetic field data of the three probes be H1, H2, and H3, and the data to be repaired and the reference data are defined as:

[0060]

[0061] Let the sliding window be win t =[t k , t k +L win -1], where the window length is L win , and the step size is The starting point t k of the window is expressed as:

[0062]

[0063] Within the window win t Let be the data to be repaired. The standard deviation of multiple data points within the window is used to judge data anomalies, and the threshold τ represents the criterion for judging anomalies. If the condition is satisfied, then it is necessary to perform repair and update.

[0064] Let the data of the reference probe be and The reference value within the window is calculated by the following formula:

[0065]

[0066] In the formula, mean represents taking the average value.

[0067] To eliminate the difference in probe readings caused by the background gradient, let the deviation be the difference between the first data point of the reference value and the first data point of the data to be repaired . Its calculation formula is:

[0068]

[0069] Subtract the deviation from the reference value to obtain the final repaired data

[0070]

[0071] For the multiple sets of data obtained within the windows, splice them together to obtain a single-channel magnetic field data. Through the above repair algorithm, the data of the three probes H1, H2, and H3 can be repaired in sequence to obtain three channels of magnetic field data without anomalies The repaired data can eliminate the influence of blind spots and accurately reflect the true magnetic field strength at the current position, providing high-quality input for subsequent data fusion. Figure 4 Shows the result graph after anomaly repair of the multi-probe magnetometer.

[0072] Next, perform weighted averaging on the measured values of the multiple repaired probes to obtain the fused magnetic field measurement data.

[0073] As Figure 5 shown, the coordinate system of the multi-probe magnetometer takes the focus of the extension lines of the three probes as the origin to establish an independent magnetometer coordinate system xyz. Among them, the x, y, and z axes respectively correspond to the three main axis directions of the carrier navigation coordinate system. In this coordinate system, the direction vectors of the three probes are respectively denoted as At the same time, the fluxgate sensor can measure the total geomagnetic field vector in real time The projection values on the x, y, and z coordinate axes. Denote the measured value of the fluxgate magnetometer at time t as Based on this information, the cosine value of the angle between the direction vector of each probe and the total geomagnetic field vector at each moment can be calculated using the cosine theorem. The formula is:

[0074]

[0075] In the formula, arccos represents the inverse cosine function.

[0076] The included angle of the probe is closely related to the accuracy of its reading. Let the normal working range of the probe be c = [-45°, 45°]. When is closer to the midpoint of the working range, the working state of the probe is more stable and the credibility of its reading is higher. The confidence level of probe i at time t is defined as:

[0077]

[0078] where c min , c max are the minimum and maximum values of the normal working range of the probe, respectively.

[0079] According to formula (7), the confidence levels of the three probes are calculated Furthermore, according to the confidence level function calculate the weight of the reading of each probe The formula is:

[0080]

[0081] In the formula, N represents the total number of probes.

[0082] According to the above formula, the weight vector w i , (i = 1, 2, 3) corresponding to probe i can be obtained over the entire data segment.

[0083] Combined with the repaired probe data The final output H of the magnetometer is obtained by weighted average out :

[0084]

[0085] Figure 6 The processing result diagram after dynamic weighted fusion is shown.

[0086] In summary, as Figure 7 shown, the specific implementation steps for repairing the data of the three-light system probe are:

[0087] Step 1: Initialize the magnetic field data H to be repaired according to Equation (1) r and the reference magnetic field data and

[0088] Step 2: Based on the sliding window win t , for each probe to be repaired within each window segment perform anomaly detection and calculate its standard deviation

[0089] Step 3: If the data within the window segment is abnormal (i.e., satisfies ), calculate the reference value within the window segment according to Equation (3) and replace it with the reference value

[0090] Step 4: Calculate the repaired magnetic field deviation according to Equation (4) to eliminate the influence of the background gradient;

[0091] Step 5: Calculate the repaired window data according to Equation (5)

[0092] Through the above steps, repair the data of the three probes H1, H2, and H3 one by one, and finally obtain the repaired magnetic field data without anomalies

[0093] Step 6: Calculate the angles between the three probes and the geomagnetic field according to Equation (6)

[0094] Step 7: Calculate the confidence levels corresponding to the three probes according to Equation (7) to reflect the reliability of the probe readings;

[0095] Step 8: Calculate the weights w of each magnetic field component according to Equation (8) i , and allocate weights based on the confidence levels;

[0096] Step 9: Calculate the integrated magnetometer output H according to Equation (9) output , and fuse the repaired three-channel data

[0097] Another embodiment of the present invention proposes a blind - area - free data fusion system for an optically pumped magnetometer based on multiple probes, as Figure 8 shown. The system includes:

[0098] Anomaly repair module 810, configured to repair the abnormal measurement values of the probes of the magnetometer by using the sliding window method;

[0099] A data fusion module 820, which is configured to perform weighted averaging on multiple probe measurement values after repair to obtain fused magnetic field measurement data.

[0100] In this embodiment, preferably, the abnormal repair module 810 uses a sliding window method to repair the abnormal values of the probes of the optically pumped magnetometer, including:

[0101] Let the measured magnetic field value within the sliding window of the i-th probe be Calculate the standard deviation of multiple data points within the sliding window. If the standard deviation is greater than a preset threshold, determine that the measured magnetic field value of the i-th probe within the sliding window is an abnormal measurement value; calculate the mean value of the measured magnetic field values within the sliding windows of other probes; calculate the difference between the mean value and the abnormal measurement value; subtract the difference from the mean value to obtain the repaired value within the sliding window of the i-th probe; for the obtained repaired values within multiple sliding windows, splice them together to obtain the measured magnetic field data of the i-th probe after repair.

[0102] In this embodiment, preferably, the weighted averaging of multiple probes after repair in the data fusion module 820 to obtain fused magnetic field measurement data includes: calculating the cosine value of the angle between the direction vector of each probe and the total geomagnetic field vector at each moment; calculating the confidence of each probe at each moment based on the cosine value of the angle; calculating the weight of each probe at each moment according to the confidence; performing weighted averaging on the measured magnetic field data of multiple probes after repair based on the weight vectors of each probe at multiple moments to obtain fused magnetic field measurement data.

[0103] In this embodiment, preferably, the calculation formula of the cosine value of the angle in the data fusion module 820 is as follows:

[0104]

[0105] In the formula, arccos represents the inverse cosine function; represents the direction vector of the i-th probe; represents the measured value of the fluxgate magnetometer at time t;

[0106] The calculation formula of the confidence of each probe is as follows:

[0107]

[0108] In the formula, c min , c max are respectively the minimum and maximum values of the normal working range of the probe;

[0109] The calculation formula of the weight of each probe is as follows:

[0110]

[0111] In the formula, N represents the total number of probes.

[0112] It should be noted that the function of the blind - area - free data fusion system of an optically pumped magnetometer based on multiple probes described in the embodiments of the present invention can be illustrated by the aforementioned blind - area - free data fusion method of an optically pumped magnetometer based on multiple probes. For the parts not detailed in this embodiment, please refer to the above method embodiments.

[0113] It should be noted that although several units, modules or sub - modules are mentioned in the above - detailed description, this division is merely exemplary and not mandatory. In fact, according to the embodiments of the present invention, the features and functions of two or more modules described above can be embodied in one module. Conversely, the features and functions of one module described above can be further divided and embodied by multiple modules.

[0114] In addition, although the operations of the method of the present invention are described in a specific order in the drawings, this does not require or imply that these operations must be performed in that specific order, or that all the shown operations must be performed to achieve the desired result. Additionally or alternatively, some steps may be omitted, multiple steps may be combined into one step for execution, and / or one step may be decomposed into multiple steps for execution.

[0115] Although the spirit and principles of the present invention have been described with reference to several specific embodiments, it should be understood that the present invention is not limited to the specific embodiments disclosed, and the division of each aspect does not mean that the features in these aspects cannot be combined for benefits. This division is only for the convenience of expression. The present invention aims to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A blind - area - free data fusion method for an optically pumped magnetometer based on multiple probes, characterized in that, Including: Using a sliding window method to repair the abnormal measurement values of the probe of the magnetometer; Performing weighted averaging on the repaired measurement values of multiple probes to obtain the fused magnetic field measurement data.

2. A method for blind - area - free data fusion of an optically pumped magnetometer based on multiple probes according to claim 1, characterized in that, The method for repairing outliers of the probe of the optically pumped magnetometer by using the sliding window method includes: setting the measured magnetic field values within the sliding window of the i-th probe as Calculating the standard deviation of multiple data points within the sliding window. If the standard deviation is greater than a preset threshold, it is determined that the measured magnetic field value of the i-th probe within the sliding window is an abnormal measured value; Calculating the mean value of the measured magnetic field values within the sliding window of other probes; calculating the difference between the mean value and the abnormal measurement value; subtracting the difference from the mean value to obtain the repaired value within the sliding window of the i-th probe; for the obtained repaired values within multiple sliding windows, splicing them together to obtain the measured magnetic field data after repair of the i-th probe.

3. A method for blind area-free data fusion of an optically pumped magnetometer based on multiple probes according to claim 2, characterized in that, The performing weighted averaging on the repaired multiple probes to obtain the fused magnetic field measurement data includes: Calculating the cosine value of the angle between the direction vector of each probe and the total geomagnetic field vector at each moment; Calculating the confidence of each probe at each moment based on the cosine value of the angle; Calculating the weight of each probe at each moment according to the confidence; Performing weighted averaging on the measured magnetic field data after repair of multiple probes based on the weight vectors of each probe at multiple moments to obtain the fused magnetic field measurement data.

4. A method for blind area-free data fusion of an optically pumped magnetometer based on multiple probes according to claim 3, characterized in that, The calculation formula of the cosine value of the angle is as follows: In the formula, arccos represents the inverse cosine function; represents the direction vector of the i-th probe; represents the measured value of the fluxgate magnetometer at time t.

5. A method for blind - area - free data fusion of an optically pumped magnetometer based on multiple probes according to claim 4, wherein, The calculation formula of the confidence of each probe is as follows: where c min and c max are the minimum and maximum values of the normal working range of the probe respectively.

6. A method for blind area-free data fusion of an optically pumped magnetometer based on multiple probes according to claim 5, characterized in that, The calculation formula of the weight of each probe is as follows: In the formula, N represents the total number of probes.

7. A blind - area - free data fusion system for an optically pumped magnetometer based on multiple probes, characterized in that, Including: An abnormal repair module configured to use a sliding window method to repair the abnormal measurement values of the probe of the magnetometer; A data fusion module configured to perform weighted averaging on the repaired measurement values of multiple probes to obtain the fused magnetic field measurement data.

8. A blind-zone-free data fusion system for an optically pumped magnetometer based on multiple probes according to claim 7, wherein The using a sliding window method to repair the abnormal values of the probe of the optically pumped magnetometer in the abnormal repair module includes: Let the measured magnetic field value within the sliding window of the \(i\)-th probe be Calculate the standard deviation of multiple data points within the sliding window. If the standard deviation is greater than a preset threshold, determine that the measured magnetic field value of the \(i\)-th probe within the sliding window is an abnormal measured value; calculate the mean value of the measured magnetic field values within the sliding windows of other probes; calculate the difference between the mean value and the abnormal measured value; obtain the repaired value within the sliding window of the \(i\)-th probe by subtracting the difference from the mean value; for the obtained repaired values within multiple sliding windows, splice them together to obtain the repaired measured magnetic field data of the \(i\)-th probe.

9. A blind - area - free data fusion system of an optically pumped magnetometer based on multiple probes according to claim 8, wherein, The performing weighted averaging on the repaired multiple probes to obtain the fused magnetic field measurement data in the data fusion module includes: calculating the cosine value of the angle between the direction vector of each probe and the total geomagnetic field vector at each moment; calculating the confidence of each probe at each moment based on the cosine value of the angle; calculating the weight of each probe at each moment according to the confidence; performing weighted averaging on the measured magnetic field data after repair of multiple probes based on the weight vectors of each probe at multiple moments to obtain the fused magnetic field measurement data.

10. A blind - area - free data fusion system for an optically pumped magnetometer based on multiple probes according to claim 9, wherein, The calculation formula of the cosine value of the angle in the data fusion module is as follows: wherein, arccos represents the inverse cosine function; represents the direction vector of the i-th probe; represents the measured value of the fluxgate magnetometer at time t; The calculation formula of the confidence of each probe is as follows: where c min and c max are the minimum and maximum values of the normal working range of the probe, respectively; The calculation formula of the weight of each probe is as follows: In the formula, N represents the total number of probes.

Images