A single-point magnetic gradient positioning method and device for a motion platform

Abstract

The application discloses a kind of single-point magnetic gradient positioning method and device for motion platform, install "H" shape magnetic sensor array in motion platform, utilize magnetic field gradient information in magnetic field X direction, calculate the position information and magnetic moment information of target;Using the position and magnetic moment information calculated, the magnetic anomaly Y direction gradient information that the point produces in the measurement point of the magnetic target is calculated by magnetic dipole target forward process;Using the measured Y direction gradient of the measurement point and model forward theory Y direction gradient, calculate the symmetric average absolute percentage error;Finally, whether the symmetric average absolute percentage error of the measurement point is minimum value is judged, to judge whether it is CPA point.The application is realized by the magnetic field gradient information at CPA point, the acquisition of target position and magnetic moment information, solve the problem that larger positioning error is caused by inconsistent measurement state in the magnetic positioning method based on multiple measurement points, improve the positioning performance of target.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of magnetic signal processing, and particularly relates to a single-point magnetic gradient positioning method for a motion platform. BACKGROUND

[0002] The magnetic field generated by the magnetic target is superimposed on the geomagnetic field, so that the magnetic field distribution of the space around the target changes and a magnetic anomaly is formed. Through detection and inversion of the magnetic anomaly, the target can be identified, positioned and tracked. The vector magnetic sensor can measure all information of the magnetic field, and has obvious advantages in target inversion positioning. However, the measurement of the vector magnetic sensor is greatly affected by the attitude of the sensor, for example, when the pitch angle of the magnetometer changes by 0.05°, the magnetic field component can produce an error of 50nT. In the process of magnetic field measurement and positioning based on the motion platform, the shaking of the motion platform can make the measurement states of the vector sensor array at different measurement points inconsistent. Therefore, the target positioning method using multiple measurement points is prone to produce large positioning errors in target positioning, which affects the positioning accuracy. SUMMARY

[0003] In order to overcome the shortcomings of the prior art, the application provides a single-point magnetic gradient positioning method and device for a motion platform. A "H" shaped magnetic sensor array is installed on the motion platform, and the array is constructed into a magnetic gradient measurement unit. It is assumed that the measurement point is the closest point on the magnetic measurement line (CPA), the position information and the magnetic moment information of the target are calculated according to the geometric relationship between the array baseline and the target gradient information by using the magnetic field gradient information in the X direction of the magnetic field. Then, the magnetic anomaly Y direction gradient information of the magnetic target at the measurement point is calculated by using the calculated position and magnetic moment information through the magnetic dipole target forward process. Again, the symmetric average absolute percentage error is calculated by using the measured Y direction gradient of the measurement point and the model forward theory Y direction gradient. Finally, it is judged whether the symmetric average absolute percentage error of the measurement point is the minimum value. If the error is the minimum value, the measurement point is the CPA point, and the calculated position and magnetic moment information of the target are correct values. If the error is not the minimum value, the measurement point is not the CPA point, and the calculated position and magnetic moment information are pseudo values. By using the application, the position and magnetic moment information of the target are obtained through the magnetic field gradient information at the CPA point, the problem of large positioning error caused by inconsistent measurement states in the magnetic positioning method based on multiple measurement points is solved, and the positioning performance of the target is improved.

[0004] The technical solution adopted by the application to solve the technical problems comprises the following steps:

[0005] Step 1: installing a "H" shaped magnetic sensor array on the motion platform;

[0006] Step 2: Calculate the magnetic field gradient information of the magnetic anomaly X direction and Y direction generated by the magnetic target at the measurement point using the measured data of the magnetic sensor array:

[0007] Magnetic anomaly X direction gradient Magnetic anomaly Y direction gradient

[0008] Where: S i represents the i-th sensor in the array; represents the X component of the magnetic field measured by the i-th sensor; represents the Y component of the magnetic field measured by the i-th sensor; represents the Z component of the magnetic field measured by the i-th sensor; l x represents the distance between the sensors on the same side of the array; L represents the baseline of the sensor array;

[0009] Step 3: Assuming that the measurement point is located at the nearest point of the survey line, i.e. the X coordinate value of the target is 0 at this time, the gradient of the magnetic anomaly in the X direction generated by the target is:

[0010]

[0011] Where: μ0 is the vacuum permeability; y and z are the position information of the target; R0 is the distance from the target to the center of the sensor array; M x , M y and M z are the magnetic moment components of the target;

[0012] Step 4: Calculate the position and magnetic moment information of the target using the geometric scale relationship of the sensor array:

[0013]

[0014]

[0015] Where: θ1 and θ2 respectively represent the angle between the distance from the target to the magnetic sensor array on both sides and the Y direction;

[0016] Step 5: Use the magnetic dipole model to forward the Y direction gradient value of the magnetic anomaly at the position of the sensor array generated by the target and

[0017] Step 6: Calculate the symmetric average absolute percentage error E index :

[0018]

[0019] Step 7: Determine the E indexwhether the E index is the minimum value, the measurement point is the CPA point, and the target position and magnetic moment information calculated are correct values; if the E index is not the minimum value, steps 1-5 are repeated.

[0020] Step 8: output the target position and magnetic moment information corresponding to the minimum value of the E index .

[0021] Preferably, the average absolute percentage error E index is obtained based on the measured gradient and the theoretical forward gradient.

[0022] The present application also provides a device based on the single-point magnetic gradient positioning method for a motion platform, which comprises:

[0023] a magnetic signal acquisition unit for obtaining a magnetic signal;

[0024] a magnetic field gradient calculation unit for calculating the gradient values of the magnetic field in the X and Y directions;

[0025] a magnetic sensor array scale unit for inverting the target position and magnetic moment information;

[0026] a target positioning information output unit for outputting the target position and magnetic moment information based on the decision condition.

[0027] The present application has the following advantages:

[0028] The present application provides a single-point magnetic gradient positioning method for a motion platform, which gives a closed-form solution of the target position and magnetic moment information at the CPA point by using the particularity of the nearest point (CPA) position on the magnetic field survey line and the geometric scale relationship between the array base line and the target magnetic field gradient. Meanwhile, the symmetry average absolute percentage error value of the measured magnetic anomaly Y-direction gradient and the forward magnetic anomaly Y-direction gradient is used to effectively determine whether the measurement point is at the CPA point. In the present application, the magnetic field gradient of a single measurement point is used to realize real-time positioning of the target, solve the problem of large positioning error caused by the inconsistent measurement state of the vector sensor array for a motion platform at different measurement points, and improve the performance of target positioning. Meanwhile, a closed-form solution of the target position and magnetic moment is given, and real-time calculation of the target position information can be realized. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a flowchart of the method of the present application.

[0030] Figure 2 is a schematic diagram of target positioning of the present application.

[0031] Figure 3The gradient in the X direction of the magnetic anomaly is measured in an embodiment of the present invention.

[0032] Figure 4 This is the gradient of the magnetic anomaly in the Y direction measured in an embodiment of the present invention.

[0033] Figure 5 This is the target positioning result obtained in an embodiment of the present invention. Detailed Implementation

[0034] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0035] The purpose of this invention is to address the problems in existing magnetic field vector measurement and positioning based on moving platforms by proposing a single-point magnetic gradient positioning method and device for moving platforms. This solves the problem of large positioning errors caused by the shaking of the moving platform and improves the positioning accuracy of the target. For the acquisition of magnetic field gradient information in the positioning method, a corresponding "I"-shaped magnetic sensor array is designed. Through the geometric relationship of the magnetic sensors, single-point positioning of the target by the moving platform is achieved.

[0036] like Figure 1 As shown, a single-point magnetic gradient localization method for a motion platform includes the following steps:

[0037] Step 1: Install an I-shaped magnetic sensor array on the motion platform;

[0038] Step 2: Using the measurement data from the magnetic sensor array, calculate the magnetic field gradient information in the X and Y directions of the magnetic anomaly generated by the magnetic target at the measurement point:

[0039] Magnetic anomaly X-direction gradient Magnetic anomaly gradient in the Y direction

[0040] Wherein: S i This represents the i-th sensor in the array; This represents the X component of the magnetic field measured by the i-th sensor; This represents the Y component of the magnetic field measured by the i-th sensor; This represents the Z component of the magnetic field measured by the i-th sensor; l x This represents the distance between sensors on the same side of the array; L represents the baseline of the sensor array.

[0041] Step 3: Assuming the measurement point is located at the closest point on the survey line, i.e., the target's X-coordinate is 0 at this time, the gradient of the magnetic anomaly generated by the target in the X direction is:

[0042]

[0043] Where: μ0 is the vacuum permeability; y and z are the position information of the target; R0 is the distance from the target to the center of the sensor array; M x , M y , and M z are the magnetic moment components of the target;

[0044] Step 4: Calculate the position and magnetic moment information of the target using the geometric scale relationship of the sensor array:

[0045]

[0046] Where: θ1 and θ2 represent the angles between the distances from the target to the two sides of the magnetic sensor array and the Y direction, respectively;

[0047] Step 5: Use the magnetic dipole model to forward the magnetic anomaly Y direction gradient value of the target at the sensor array position and

[0048] Step 6: Calculate the symmetric average absolute percentage error E index :

[0049]

[0050] Step 7: Determine whether the E index of the measurement point is the minimum value; if the E index of the measurement point is the minimum value, the measurement point is the CPA point, and the calculated target position and magnetic moment information are correct values; if the E index of the measurement point is not the minimum value, repeat steps 1-5;

[0051] Step 8: Output the target position and magnetic moment information corresponding to the minimum value of the measurement point E index .

[0052] The application also provides a device based on the single-point magnetic gradient positioning method for a motion platform, which comprises:

[0053] A magnetic signal acquisition unit for obtaining a magnetic signal;

[0054] A magnetic field gradient calculation unit for calculating the gradient values of the magnetic field in the X and Y directions;

[0055] A magnetic sensor array scale unit for inverting the target position and magnetic moment information;

[0056] A target positioning information output unit for outputting the target position and magnetic moment information based on the judgment condition. Specific embodiments:

[0058] AsFigures 2 to 4 As shown, the magnetic object is located at the origin position of the coordinate system, and its magnetic moment is 20A·m2. The vector magnetic sensor array group moves in the horizontal plane along the direction parallel to the X axis from the starting position (30, 5, 2)m to the end position (-30, 5, 2)m in a uniform speed manner. The distance between the magnetic target and the closest point of the survey line is R0=5.38m. The CPA point of the survey line, the target position and the magnetic moment information are obtained by the target single-point magnetic gradient positioning method and device provided by the application, as shown in Figure 5 As shown, the magnetic object is located at the origin position of the coordinate system, and its magnetic moment is 20A·m2. The vector magnetic sensor array group moves in the horizontal plane along the direction parallel to the X axis from the starting position (30, 5, 2)m to the end position (-30, 5, 2)m in a uniform speed manner. The distance between the magnetic target and the closest point of the survey line is R0=5.38m. The CPA point of the survey line, the target position and the magnetic moment information are obtained by the target single-point magnetic gradient positioning method and device provided by the application, as shown in Figure 5 As shown, the magnetic object is located at the origin position of the coordinate system, and its magnetic moment is 20A·m2. The vector magnetic sensor array group moves in

Claims

1. A single-point magnetic gradient positioning method for a motion platform, characterized in that, Includes the following steps: Step 1: Install an I-shaped magnetic sensor array on the motion platform; Step 2: Using the measurement data from the magnetic sensor array, calculate the magnetic field gradient information in the X and Y directions of the magnetic anomaly generated by the magnetic target at the measurement point: Magnetic anomaly X-direction gradient Magnetic anomaly gradient in the Y direction Wherein: S i This represents the i-th sensor in the array; This represents the X component of the magnetic field measured by the i-th sensor; This represents the Y component of the magnetic field measured by the i-th sensor; The i-th sensor measures the Z component of the magnetic field; l x This represents the distance between sensors on the same side of the array; L represents the baseline of the sensor array. Step 3: Assuming the measurement point is located at the closest point on the survey line, i.e., the target's X-coordinate is 0 at this time, then the gradient of the magnetic anomaly generated by the target in the X direction is: Where: μ0 is the vacuum permeability; y and z are the target's position information; R0 is the distance from the target to the center of the sensor array; M x M y and M z The magnetic moment component is the target. Step 4: Calculate the target's position and magnetic moment information using the geometric scale relationship of the sensor array: Where: θ1 and θ2 represent the angles between the distance from the target to the two sides of the magnetic sensor array and the Y direction, respectively; Step 5: Using the magnetic dipole model, obtain the gradient value of the magnetic anomaly in the Y direction at the sensor array location of the target through forward modeling. and Step 6: Calculate the symmetric mean absolute percentage error E using the measured magnetic anomaly gradient in the Y direction and the forward-modeled magnetic anomaly gradient in the Y direction at this measurement point. index : Step 7: Determine the E value of the measurement point. index Is it the minimum value? If the E value at this measurement point is... index If the value is the minimum, then the measurement point is the CPA point, and the calculated target position and magnetic moment information are correct; if the E value of the measurement point is the minimum, then the measurement point is the CPA point. index If it is not the minimum value, repeat steps 1-5; Step 8: Output measurement point E index The target position and magnetic moment information corresponding to the minimum value.

2. The single-point magnetic gradient positioning method for a motion platform according to claim 1, characterized in that, The mean absolute percentage error E index The gradient is obtained using measured gradients and forward modeling gradients.

3. A single-point magnetic gradient positioning device for a motion platform employing the positioning method as described in claim 1, comprising: A magnetic signal acquisition unit is used to acquire magnetic signals; The unit of measurement for magnetic field gradient, used to calculate the gradient value of a magnetic field in the X and Y directions; Magnetic sensor array scale unit, used to invert target position and magnetic moment information; The target positioning information output unit is used to output target position and magnetic moment information based on decision conditions.

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