A full-automatic magnetic compensation method for a magnetic shielding cabin based on a Monte Carlo algorithm

Abstract

The application relates to a full-automatic magnetic compensation method of a magnetic shielding cabin based on a Monte Carlo algorithm. The method can simultaneously perform three-axis magnetic compensation in a full-automatic mode without decoupling the coupling of three-axis coils. First, three reference voltages are set as voltages for individually compensating three-axis residual magnetism to zero, then three random voltages in a certain interval are generated and input into the compensation coils with the three reference voltages as centers, and then a magnetic measuring sensor is used to measure the size of the residual magnetism. If the residual magnetism after compensation in three-axis directions is all zero, the algorithm stops, and stable voltages are output from the three axes. If the residual magnetism after compensation in three-axis directions is not all zero, three random voltages in a given interval are generated again and input into the compensation coils, and the above steps are repeated until the three-axis random voltages make the residual magnetism after compensation in three-axis directions all zero. If the above steps are repeated N times, and the measured residual magnetism is not reduced to 0, the voltage range generated by the random points is increased, the above steps are repeated, and the residual magnetism after compensation in three-axis directions is all zero.

Description

Technical Field

[0001] This invention relates to the field of active magnetic compensation in magnetically shielded cabins, specifically to a fully automatic magnetic compensation method for magnetically shielded cabins based on the Monte Carlo algorithm. Background Technology

[0002] Magnetism is a common physical quantity in daily life, with wide applications in geophysics, military, materials science, and medicine, such as geological exploration, geomagnetic navigation and anti-submarine warfare, flaw detection of metallic materials, and magnetocardiography (MCG). Accurate utilization of magnetic fields requires precise measurement, such as the precise measurement of magnetocardiography (MCG) and brain magnetocardiography (BEG). The magnetic fields generated by the heart and brain are approximately tens of finitesimals, six orders of magnitude smaller than the Earth's magnetic field and several orders of magnitude smaller than other magnetic interference sources. Therefore, measurements of MCG and BEG need to be conducted in an environment with extremely weak magnetic fields, typically within a magnetically shielded chamber.

[0003] Electrocardiography (ECG) of the heart and brain has stringent requirements for the magnetic field of the working environment. Passive magnetic shielding in a magnetically shielded chamber is insufficient to meet the conditions for extremely weak magnetic fields, thus necessitating the design of an active magnetic compensation system. Currently, there are two main methods for achieving active magnetic compensation: one is manual magnetic compensation using cross-modulation triaxial magnetic compensation, and the other is automatic compensation using a control algorithm-based method of sequential individual compensation of the three axes. The former method requires three signal generators as a foundation. The magnetic field signal output by the magnetometer is observed using an oscilloscope to determine if the magnetic field in the shielded chamber is compensated to zero. If the magnetic field is not zero, the output current of the signal generator is adjusted by a step size based on experience, according to the magnitude of the magnetic field, to compensate the magnetic field inside the shielded chamber to zero. This method suffers from low magnetic field compensation accuracy, cumbersome operation, and long compensation time. The latter method requires significant work to solve the decoupling problem of the triaxial compensation coils. This is because when the voltage required to achieve zero residual magnetism through sequential individual compensation of the three axes is simultaneously applied to the triaxial coils, the residual magnetism after compensation in all three directions is not zero due to coupling. Therefore, to achieve algorithmic compensation, decoupling processing using the algorithm must be performed first, requiring a large amount of preliminary work. Therefore, it is of great significance to study a method that can reduce labor costs, avoid decoupling processing, and provide fully automated and accurate magnetic field compensation. Summary of the Invention

[0004] To address the problems of traditional manual magnetic compensation methods for magnetically shielded chambers, which require observing the output of the magnetic sensors using instruments such as signal generators and oscilloscopes and adjusting the magnetic field of the compensation axis based on experience, resulting in cumbersome operation, long compensation time, and low accuracy, as well as the increased workload and difficulty in implementation caused by the need for preliminary decoupling processing in previous compensation algorithms, this invention provides a fully automatic magnetic compensation method for magnetically shielded chambers based on the Monte Carlo algorithm. This method can quickly and automatically compensate the residual magnetism in the magnetically shielded chamber to a zero-magnetic state without considering the decoupling problem of sequentially compensating the X, Y, and Z axis coils, thus providing a zero-magnetic environment for subsequent work.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A fully automated magnetic compensation method for a magnetically shielded cabin based on the Monte Carlo algorithm includes the following steps:

[0007] Step (1): First, perform data preprocessing, measure the voltage magnitude of a series of compensating magnetic fields generated by the three axes in the magnetic shielding cabin, fit the curve of the relationship between the compensating magnetic field and voltage based on the magnitude of the compensating magnetic field and voltage, and write it into the DSP control module.

[0008] Step (2): The magnetic sensor measures the magnitude of the remanent magnetization corresponding to the three axes. Based on the relationship between the compensation magnetic field and the voltage, a reference voltage is set for each axis. The compensation magnetic field generated by the reference voltage makes the remanent magnetization in each direction in the magnetic shielding chamber zero, and is recorded as x0, y0 and z0 respectively. Then, a voltage range is set, and the voltage ranges of the three axes are [x0-a, x0+a], [y0-b, y0+b] and [z0-c, z0+c] respectively. Based on the Monte Carlo algorithm, the DSP control module randomly generates three voltage inputs in the three voltage ranges and inputs them to the compensation coil. Then, the magnetic sensor measures the remanent magnetization of the three axes in the magnetic shielding chamber.

[0009] Step (3): Determine whether the residual magnetism measured in step (2) is zero. If the residual magnetism is zero, the algorithm stops and the three-axis outputs a stable voltage. If it is not zero, repeat step (2) until the residual magnetism after the three-axis direction compensation is zero.

[0010] Step (4): Repeat step (3) N times. If the residual magnetism after triaxial direction compensation is not all zero, change the range of triaxial output voltage to [x0-μa,x0+μa], [y0-μb,y0+μb] and [z0-μc,z0+μc] according to the reference voltage set in step (1), where μ is greater than 1. Within this range, generate three random voltages based on the Monte Carlo algorithm, and then repeat step (3).

[0011] Step (5): If step (4) still cannot make the residual magnetism after triaxial compensation zero, increase the value of μ in step (4) and repeat steps (3) and (4) until the residual magnetism after triaxial compensation is zero.

[0012] Through the above five steps, rapid, fully automatic, three-axis simultaneous magnetic compensation of the magnetic shielding chamber is achieved.

[0013] Furthermore, in step (1), the sizes of a, b, and c are determined based on the sizes of x0, y0, and z0.

[0014] Furthermore, in step (4), the value of N is determined by the accuracy of the current source and the random voltage range in the hardware system. The larger the accuracy of the current source output and the random voltage range, the larger the value of N; the smaller the accuracy of the current source output and the random voltage range, the smaller the value of N.

[0015] The advantages of this invention compared to existing technologies are as follows: This invention presents a fully automatic magnetic compensation method for magnetically shielded chambers based on the Monte Carlo algorithm. Compared to traditional manual compensation methods that rely on oscilloscopes to observe the residual magnetism output from magnetometers, make rough estimates, and adjust the compensation axis magnetic field based on empirical step sizes, this method significantly reduces labor costs, accelerates compensation speed, and improves compensation accuracy. The automatic magnetic compensation system, with the Monte Carlo algorithm at its core, actively collects the residual magnetism within the magnetically shielded chamber and outputs the compensation current without the need for signal generators, oscilloscopes, or other instruments. This not only reduces system size but also provides more accurate compensation data and reduces human reading errors. Compared to other algorithm-based magnetic compensation systems, this invention eliminates the need for decoupling the three-axis coils, simplifying the algorithm's complexity, reducing the requirement for theoretical knowledge, and making it more suitable for engineering applications. Attached Figure Description

[0016] When considered in conjunction with the accompanying drawings, the invention will be better understood and its accompanying advantages readily apparent from the following detailed description. However, the accompanying drawings, which are provided to further illustrate the invention and form part of this invention, wherein:

[0017] Figure 1 This is a schematic diagram of the fully automatic magnetic compensation method for a magnetically shielded cabin based on the Monte Carlo algorithm of the present invention.

[0018] Figure 2 This is a hardware system block diagram of the fully automatic magnetic compensation method for a magnetically shielded cabin based on the Monte Carlo algorithm of the present invention.

[0019] Figure 3 This is a flowchart of the fully automatic magnetic compensation method for a magnetically shielded cabin based on the Monte Carlo algorithm of the present invention. Detailed Implementation

[0020] 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 protection scope of the present invention.

[0021] This invention presents a fully automatic magnetic compensation method for a magnetically shielded cabin based on the Monte Carlo algorithm. It eliminates the need for signal generators and oscilloscopes, and eliminates the need for pre-processing algorithm decoupling. Based on a hardware system including a DSP control module, amplification and filtering module, A / D data acquisition module, D / A data output module, power amplification module, and current source module, it performs fully automatic simultaneous triaxial magnetic compensation. First, three reference voltages are set based on voltages that individually compensate the residual magnetism of each of the three axes to zero. Then, using the Monte Carlo algorithm, three voltage input compensation coils are randomly generated within a certain range along the three axes, centered on the reference compensation voltages. The magnitude of the compensated residual magnetism is then measured using a magnetometer. If the residual magnetism after compensation in all three axes is zero, the algorithm stops, and the three axes output stable voltages. If the residual magnetism after compensation in all three axes is not zero, another voltage input compensation coil is randomly generated within a given range using the Monte Carlo algorithm. This process is repeated until the randomly generated voltages in all three axes reduce the compensated residual magnetism to zero. This process is repeated N times, where the value of N is determined by the accuracy of the current source and the random voltage range in the hardware system. If the residual magnetism does not decrease to 0, increase the voltage range generated by the random point and repeat the above steps until the residual magnetism after compensation in all three axes is zero. This invention achieves fully automatic simultaneous magnetic field compensation in three axes, with each axis compensating to the zero compensation point. Compared with traditional manual magnetic compensation, it greatly reduces labor costs, has a faster compensation speed, is simpler to operate, and is smaller in size.

[0022] like Figure 1 As shown, the directions of the three-axis coils are first defined as X, Y, and Z axes. The system implementing this invention includes a magnetic shielding chamber 1, an X-axis coil 2, a Y-axis coil 3, a Z-axis coil 4, a magnetometer sensor 5, and a hardware system control and processing unit 6. The X-axis coil 2, Y-axis coil 3, and Z-axis coil 4 are located on the inner wall of the magnetic shielding chamber 1. The winding direction of a pair of coils in the X-axis coil 2 is the same (either clockwise or counterclockwise), the winding direction of a pair of coils in the Y-axis coil 3 is the same (either clockwise or counterclockwise), and the winding direction of a pair of coils in the Z-axis coil 4 is the same (either clockwise or counterclockwise). The magnetometer sensor 5 is located at the center of the magnetic shielding chamber 1. The hardware system control and processing unit 6 is located outside the magnetic shielding chamber 1 and is connected to the magnetometer sensor 5 and the X-axis coils 2, Y-axis coil 3, and Z-axis coil 4 at the center of the magnetic shielding chamber 1. The magnetic shielding chamber 1 has a cubic structure.

[0023] like Figure 2As shown, the hardware system control and processing section 6 includes a DSP control module, an amplification and filtering module, an A / D data acquisition module, a D / A data output module, a power amplification module, and a current source module. It replaces instruments such as signal generators and oscilloscopes used for manual magnetic field compensation. First, the DSP control module outputs three random voltages based on the set initial reference voltage. These voltages are then fed into the current source module via the D / A data output module and the power amplification module. The current source module outputs three currents to the triaxial compensation coil based on the three voltage values. The compensation coil generates a compensation magnetic field, and a magnetometer measures the magnitude of the residual magnetism in the three directions after compensation. After passing through the amplification and filtering module and the A / D data acquisition module, the voltage corresponding to the residual magnetism is input into the DSP control module for further control.

[0024] like Figure 3 As shown, the fully automatic magnetic compensation method for a magnetically shielded cabin based on the Monte Carlo algorithm of the present invention includes the following steps in its specific implementation:

[0025] Step (1): First, perform data preprocessing, measure the voltage magnitude of a series of compensating magnetic fields generated by the three axes inside the magnetic shielding chamber 1, and use MATLAB to fit the curve of the relationship between the compensating magnetic field and voltage according to the magnitude of the compensating magnetic field and voltage. Write this relationship into the DSP control module for setting the initial reference value of the Monte Carlo algorithm, and then initialize the system.

[0026] Step (2): The magnetic sensor 5 measures the residual magnetism in the three-axis direction inside the magnetic shielding chamber 1. After passing through the amplification and filtering module and the A / D data acquisition module, the DSP control module reads the magnitude of the acquired voltage. According to the magnitude of the residual magnetism and the relationship between the compensation magnetic field and the voltage, the Monte Carlo algorithm sets the reference voltage for each of the three axes. The compensation magnetic field generated by the reference voltage makes the residual magnetism in the corresponding direction of the magnetic shielding chamber 1 zero, which are recorded as x0, y0 and z0 respectively. Then, the voltage range is set. The voltage range of the three axes is [x0-a, x0+a], [y0-b, y0+b] and [z0-c, z0+c] respectively, where the magnitudes of a, b and c are determined according to the magnitudes of x0, y0 and z0. Then, based on the Monte Carlo algorithm, three random voltage values ​​are generated in the three intervals. The D / A data output module, the power amplification module and the current source module are simultaneously input to the three-axis compensation coil to perform active magnetic compensation of the magnetic shielding chamber 1. Then, the magnetic sensor 5 measures the magnitude of the residual magnetism after compensation in the three-axis direction.

[0027] Step (3): The residual magnetism measured at the end of step (2) is input into the DSP control module through the amplification and filtering module and the A / D data acquisition module. The DSP control module is then used to determine whether the residual magnetism of the three axes is zero. If the residual magnetism after the three-axis direction compensation is zero, the algorithm stops and the system outputs stable voltage values ​​for the three axes. If the residual magnetism after the three-axis direction compensation is not zero, the DSP control module based on the Monte Carlo algorithm randomly generates three more voltages in the three voltage ranges in step (2) and repeats the process described later in step (2). This continues until the randomly generated voltages of the three axes make the residual magnetism after the three-axis direction compensation zero.

[0028] Step (4): Repeat step (2) N times. The value of N is determined by the accuracy of the current source and the random voltage range in the hardware system. The larger the accuracy of the current source output and the random voltage range, the larger the value of N. The smaller the accuracy of the current source output and the random voltage range, the smaller the value of N. If the residual magnetism after the three-axis direction compensation is not all zero, change the range of the three-axis output voltage to [x0-μa,x0+μa], [y0-μb,y0+μb] and [z0-μc,z0+μc] according to the reference voltage set in step (1). μ is greater than 1. Generate three random voltages based on the Monte Carlo algorithm within this range. Repeat step (3) until three compensation voltages are found where the residual magnetism after the three-axis direction compensation is all zero.

[0029] Step (5): If step four still cannot make the residual magnetism after triaxial compensation zero, increase the value of μ in step four and repeat steps (3) and (4) until the residual magnetism after triaxial compensation is zero.

[0030] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

[0031] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A fully automated magnetic compensation method for a magnetically shielded cabin based on the Monte Carlo algorithm, characterized in that, The process of quickly and automatically compensating for residual magnetism in a magnetically shielded chamber to zero magnetic field includes the following steps: Step (1): First, perform data preprocessing, measure the voltage magnitude of a series of compensating magnetic fields generated by the three axes in the magnetic shielding cabin, fit the curve of the relationship between the compensating magnetic field and voltage based on the magnitude of the compensating magnetic field and voltage, and write it into the DSP control module. Step (2): The magnetic sensor measures the residual magnetism of the three axes. Based on the relationship between the compensating magnetic field and voltage, a reference voltage is set for each axis. The compensating magnetic field generated by the reference voltage makes the residual magnetism in each direction within the magnetic shielding chamber zero, and these are recorded sequentially as follows: x 0、 y 0 and z 0; then set another voltage range, the three-axis voltage ranges are [ x 0 -a,x 0 +a ]、[ y 0 -b,y 0 +b ]and[ z 0 - c,z 0 +c Based on the Monte Carlo algorithm, a DSP control module randomly generates three voltage inputs in three voltage ranges to the compensation coil, and then the magnetic sensor is used to measure the triaxial residual magnetism inside the magnetic shielding chamber. Step (3): Determine whether the residual magnetism measured in step (2) is zero. If the residual magnetism is zero, the algorithm stops and the three-axis outputs a stable voltage. If it is not zero, repeat step (2) until the residual magnetism after the three-axis direction compensation is zero. Step (4): Repeat step (3). N Next, if the residual magnetism after triaxial direction compensation is not all zero, then according to the reference voltage set in step (1), change the range of the triaxial output voltage to [ x 0 -μa,x 0 +μa ]、[ y 0 -μb,y 0 +μb ]and[ z 0 -μc,z 0 +μc ],in μ If the value is greater than 1, three random voltages are generated within this range based on the Monte Carlo algorithm, and then step (3) is repeated. Step (5): If step (4) still cannot make the residual magnetism after triaxial compensation zero, increase the value of μ in step (4) and repeat steps (3) and (4) until the residual magnetism after triaxial compensation is zero. Through the above five steps, rapid, fully automatic, three-axis simultaneous magnetic compensation of the magnetic shielding chamber is achieved.

2. The fully automated magnetic compensation method for a magnetically shielded cabin based on the Monte Carlo algorithm according to claim 1, characterized in that, In step (1) described above, a, b, c The size is set according to x 0 、y 0 and z It depends on the size of 0.

3. The fully automated magnetic compensation method for a magnetically shielded cabin based on the Monte Carlo algorithm according to claim 1, characterized in that, In step (4) described above, N The value is determined by the accuracy of the current source and the random voltage range in the hardware system. The larger the accuracy of the current source output and the random voltage range, the better. N The larger the value, the smaller the accuracy of the current source output and the smaller the random voltage range. N The smaller the value.

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