Low frequency magnetic field generator for rat electromagnetic experiment and method for measuring uniform area thereof

Abstract

The present application relates to a kind of low-frequency magnetic field generator for rat electromagnetic experiment and its uniform area measuring method, the method includes the following steps: S1, analysis display terminal calculates the magnetic induction intensity distribution of Helmholtz coil under given condition, and according to the change of magnetic induction intensity relative error determines the uniform area of magnetic field distribution, is recorded as reference area, corresponding boundary is reference boundary;S2, using magnetic field probe coil measures the magnetic induction intensity on reference boundary;S3, least square method is applied to obtain the measured boundary of magnetic field distribution uniform area;S4, according to the average absolute percentage error of magnetic induction intensity at measured boundary and reference boundary determines its actual uniform boundary;S5, analysis display terminal displays the actual uniform area of Helmholtz coil magnetic field distribution under given current amplitude and frequency, for rat electromagnetic experiment.Compared with prior art, the present application has the advantages of obtaining accurate magnetic field uniform area, reducing test workload and the like.

Description

Technical Field

[0001] This invention relates to the field of magnetic field generator technology, and in particular to a low-frequency magnetic field generator for electromagnetic experiments on rats and a method for measuring the uniform region thereof. Background Technology

[0002] Rapid economic development and the increase in power construction projects such as power grids and rail transit have made the impact of environmental electromagnetic fields, which are closely related to people's lives, on organisms a public health concern. Environmental electromagnetic fields include extremely low frequency (ULF) electromagnetic fields and radio frequency (RF) electromagnetic fields. ULF electromagnetic fields, with frequencies ranging from 3 to 3000 Hz, are mainly emitted or leaked during the transmission, conversion, and use of electrical energy. Related research indicates that organisms, as independent and complex electromagnetically compatible systems, can function independently of other organisms, a phenomenon resulting from long-term evolution. However, when this external environment is disrupted, a series of life activities of organisms will be affected to varying degrees. When electromagnetic fields affect the circulatory, immune, and nervous systems, they alter cell membrane permeability, causing some cells to die or their function to be enhanced. Macroscopically, this manifests as changes in various systems of the body, leading to different degrees and modes of biological mutations, often manifesting as non-thermal biological effects. That is, after absorbing electromagnetic energy, the organism does not convert it into energy that causes changes in body temperature, but produces biological effects other than temperature changes. The extent and scope of this impact, and how to assess it, are all pressing issues that need to be addressed.

[0003] A Helmholtz coil consists of a pair of parallel, coaxial circular coils connected together, with the distance between them equal to the radius of the coils. This allows currents of the same direction and magnitude to flow through both coils, generating a wide, uniform magnetic field region near their common axis. It features a wide spatial range, a stable and uniform magnetic field distribution, and ease of use. Furthermore, it can superimpose two-dimensional and three-dimensional magnetic fields on top of a one-dimensional magnetic field, providing either alternating current or direct current magnetic fields. The current and magnetic field exhibit a very stable linear relationship, making it widely used in research on electromagnetic effects in organisms. However, compared to its own size, the uniform magnetic field region of a Helmholtz coil-based magnetic field generator is relatively low, and changes in the frequency of the input current affect this region. Additionally, if rats move within a non-uniform magnetic field region during long-term experiments, it can negatively impact the accurate acquisition of electromagnetic effects from the rats. Therefore, constructing a high-performance, low-frequency magnetic field generator with variable frequency and magnetic field strength suitable for rat electromagnetic experiments and accurately determining its uniform region are urgent problems to be solved. Summary of the Invention

[0004] The purpose of this invention is to overcome the defects of the prior art by providing a low-frequency magnetic field generator for rat electromagnetic experiments and a method for measuring its uniform region.

[0005] The objective of this invention can be achieved through the following technical solutions:

[0006] A low-frequency magnetic field generator for electromagnetic experiments on rats, the low-frequency magnetic field generator comprising:

[0007] Programmable AC power supply, used to output AC current signals with adjustable frequency and current amplitude;

[0008] A power amplifier, connected to a programmable AC power supply, is used to receive AC current signals, amplify the current signals, and transmit them through a transmission cable.

[0009] A Helmholtz coil, connected to a power amplifier, is used to generate a magnetic field through a current signal;

[0010] A magnetic field detection coil, connected to a Helmholtz coil, is used to acquire the voltage signal on the Helmholtz coil. A signal acquisition module, connected to the magnetic field detection coil, is used to filter and perform analog-to-digital conversion on the voltage signal.

[0011] The analysis and display terminal is connected to the programmable AC power supply and the signal acquisition module, respectively. It is used to set the current amplitude and frequency, and to calculate the magnetic induction intensity distribution of the Helmholtz coil based on the filtered and analog-to-digital converted voltage signal using built-in software.

[0012] Furthermore, the Helmholtz coil comprises two identical circular coils placed in parallel, the distance between the two identical circular coils being equal to their radius.

[0013] A method for measuring the uniform region of a low-frequency magnetic field generator used in electromagnetic experiments on rats, the method comprising the following steps:

[0014] S1. The analysis and display terminal calculates the magnetic induction intensity distribution of the Helmholtz coil when given current amplitude and frequency input, and determines the uniform magnetic field distribution area of ​​the Helmholtz coil based on the change of the relative error of magnetic induction intensity, which is denoted as the reference area, and the corresponding boundary is the reference boundary.

[0015] S2. Use a magnetic field detection coil to measure the magnetic induction intensity on the reference boundary of a region with a uniform magnetic field distribution of a Helmholtz coil.

[0016] S3. The least squares method is used to obtain the measured boundary of the region with uniform magnetic field distribution of the Helmholtz coil.

[0017] S4. Determine the actual uniform boundary based on the average absolute percentage error of the magnetic induction intensity at the measured boundary and the reference boundary of the uniform magnetic field distribution region of the Helmholtz coil.

[0018] S5. The analysis and display terminal displays the actual uniform region of the magnetic field distribution of the Helmholtz coil under a given current amplitude and frequency, for use in electromagnetic experiments on rats.

[0019] Furthermore, the formula for calculating the magnetic flux density distribution of the Helmholtz coil in step S1 is as follows:

[0020]

[0021]

[0022]

[0023] In the formula, r is the distance from spatial point P to the central axis of the Helmholtz coil; z is the distance from the projection of spatial point P onto the central axis to the center of the Helmholtz coil; and B... r (r,z) and B z (r,z) represent the radial and axial magnetic induction in the cylindrical coordinate system of the spatial point P, respectively; I represents the current amplitude; R is the radius of the Helmholtz coil; n represents the order; and k represents the parameter.

[0024] Furthermore, the formula for calculating the relative error e of magnetic induction intensity in step S1 is as follows:

[0025]

[0026] In the formula, B0 represents the magnetic induction intensity at the center point of the Helmholtz coil, and B represents the magnetic induction intensity at any point inside the Helmholtz coil; when the change in the relative error of the magnetic induction intensity is less than 1%, it is determined to be a region with a uniform magnetic field distribution of the Helmholtz coil.

[0027] Furthermore, step S3 specifically includes:

[0028] S301. For a certain boundary segment, based on the position coordinates of the magnetic field detection coil x = [x0, x1, ..., x6] T and corresponding magnetic induction intensity Construct orthogonal polynomials {P} L (x)};

[0029] S302. Calculate the coefficients of the fitted curve. And gradually put Adding it to the fitting curve function F(x) yields the measured boundary of the region with uniform magnetic field distribution of the Helmholtz coil.

[0030] Furthermore, the recurrence relation for the orthogonal polynomial is:

[0031]

[0032] In the formula, P k (x) is a k-th degree polynomial with a leading coefficient of 1, a k and β k Here, L represents the polynomial coefficients, and L is the number of orthogonal polynomials.

[0033] According to P k The orthogonality of (x) leads to P k (x) and a k and β k The relation is:

[0034]

[0035] a k and β k Substituting the expression into the orthogonal polynomial {P} L The recursive formula of (x)} is obtained step by step to obtain {P}. L (x)} completes the construction of orthogonal polynomials.

[0036] Furthermore, the expressions for the fitting curve coefficients and the measured boundary are as follows:

[0037]

[0038] In the formula, f represents a function with x as its independent variable.

[0039] Furthermore, step S4 specifically includes:

[0040] S401. Calculate the average absolute percentage error of the magnetic induction intensity at the measured boundary and the reference boundary. The formula for calculating the average absolute percentage error is as follows:

[0041]

[0042] In the formula, m represents the number of points, B i 'B' represents the measured magnetic field strength at the boundary. i Indicates the magnetic flux density at the reference boundary;

[0043] S402. Determine the actual boundary of the uniform magnetic field distribution area of ​​the Helmholtz coil based on the change of the mean absolute percentage error. If the mean absolute percentage error is greater than 0.5%, the measured boundary is used as the new reference boundary. Determine the new measured point again and repeat steps S3 and S4 until the mean absolute percentage error is less than 0.5%.

[0044] Furthermore, the determination of the new measured point specifically involves: if the magnetic induction intensity at the measured point is greater than the calculated magnetic induction intensity of the reference boundary, then the corresponding measured point is shifted outward by 0.01R as the new measured point; if the magnetic induction intensity at the measured point is less than the calculated magnetic induction intensity of the reference boundary, then the corresponding measured point is shifted inward by 0.01R as the new measured point, where R is the radius of the Helmholtz coil.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] I. This invention constructs a low-frequency magnetic field generator with variable frequency and magnetic field strength. Based on the calculation results of the magnetic field distribution theory of Helmholtz coil and its symmetry characteristics, its uniform boundary is divided. This can obtain a more accurate actual uniform magnetic field region of the low-frequency magnetic field generator while significantly reducing the workload of testing, thus providing support for accurately obtaining the electromagnetic effect performance of rats.

[0047] Second, this invention uses the least squares algorithm to fit the magnetic induction intensity at the boundary of the uniform magnetic field distribution region of the Helmholtz coil, which can further obtain a more accurate uniform magnetic field region. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the low-frequency magnetic field generator of the present invention;

[0049] Figure 2 This is a schematic diagram of the method flow of the present invention;

[0050] Figure 3 This is a schematic diagram of the uniform distribution of the magnetic field of the Helmholtz coil of the present invention.

[0051] The labels in the diagram indicate:

[0052] 1. Programmable AC power supply; 2. Power amplifier; 3. Helmholtz coil; 4. Magnetic field detection coil; 5. Signal acquisition module; 6. Analysis and display terminal. Detailed Implementation

[0053] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0054] Example

[0055] like Figure 1As shown, a low-frequency magnetic field generator for rat electromagnetic experiments is characterized in that the low-frequency magnetic field generator includes a programmable AC power supply 1, a power amplifier 2, a Helmholtz coil 3, a magnetic field detection coil 4, a signal acquisition module 5, and an analysis and display terminal 6 connected in sequence; the analysis and display terminal 6 is connected to the programmable AC power supply 1.

[0056] The system comprises: a programmable AC power supply 1, which outputs an AC current signal with adjustable frequency and current amplitude, and transmits it to a power amplifier 2; a power amplifier 2, which receives the AC current signal, amplifies it, and transmits it to a Helmholtz coil 3 via a transmission cable; a Helmholtz coil 3, which includes two identical circular coils placed in parallel with a distance equal to their radius, used to generate a magnetic field through the current signal; a magnetic field detection coil 4, which acquires the voltage signal on the Helmholtz coil 3 and transmits it to a signal acquisition module 5; a signal acquisition module 5, which filters and performs analog-to-digital conversion on the voltage signal and transmits it to an analysis and display terminal 6; and an analysis and display terminal 6, which sets the current amplitude and frequency and calculates the magnetic induction intensity distribution of the Helmholtz coil 3 based on the filtered and analog-to-digital converted voltage signal using built-in software.

[0057] like Figure 2 As shown, a method for measuring the uniform region of a low-frequency magnetic field generator used in rat electromagnetic experiments includes the following steps:

[0058] S1. The analysis and display terminal 6 calculates the magnetic induction intensity distribution of the Helmholtz coil 3 under a given current amplitude and frequency input, and determines the uniform magnetic field distribution area of ​​the Helmholtz coil 3 based on the change of the relative error of the magnetic induction intensity, which is denoted as the reference area, and the corresponding boundary is the reference boundary.

[0059] The formula for calculating the magnetic flux density distribution of Helmholtz coil 3 is as follows:

[0060]

[0061]

[0062]

[0063] In the formula, r is the distance from spatial point P to the central axis of Helmholtz coil 3; z is the distance from the projection of spatial point P onto the central axis to the center of Helmholtz coil 3; and B... r (r,z) and B z (r,z) represent the radial and axial magnetic induction in the cylindrical coordinate system of the spatial point P, respectively; I represents the current amplitude; R is the radius of the Helmholtz coil 3; and n is the order.

[0064] The formula for calculating the relative error e of magnetic induction intensity is:

[0065]

[0066] In the formula, B0 represents the magnetic induction intensity at the center point of the Helmholtz coil 3, and B represents the magnetic induction intensity at any point inside the Helmholtz coil 3; when the change in the relative error of the magnetic induction intensity is less than 1%, it is determined to be a region with a uniform magnetic field distribution of the Helmholtz coil 3.

[0067] S2. Use magnetic field detection coil 4 to measure the magnetic induction intensity on the reference boundary of the uniform magnetic field distribution area of ​​Helmholtz coil 3.

[0068] like Figure 2 As shown, starting from the saddle shape and symmetry of the reference boundary of the uniform magnetic field distribution region of the Helmholtz coil 3, the selected measurement points are the six equal division points from the raised point to the concave point on the saddle-shaped boundary within the 1 / 4 quadrant.

[0069] S3. The measured boundary of the uniform magnetic field distribution region of the Helmholtz coil 3 is obtained by applying the least squares method, as follows:

[0070] S301. For a certain boundary segment, based on the position coordinates x = [x0, x1, ..., x6] of the magnetic field detection coil 4. T and corresponding magnetic induction intensity Construct orthogonal polynomials {P} L The recurrence relation for (x)} is:

[0071]

[0072] In the formula, P k (x) is a k-th degree polynomial with a leading coefficient of 1, a k and β k Here, L represents the polynomial coefficients, and L is the number of orthogonal polynomials.

[0073] According to P k The orthogonality of (x) leads to P k (x) and a k and β k The relation is:

[0074]

[0075] a k and β k Substituting the expression into the orthogonal polynomial {P} L The recursive formula of (x)} is obtained step by step to obtain {P}. L (x)}, complete the construction of orthogonal polynomials;

[0076] S302. Calculate the coefficients of the fitted curve. And gradually put Adding these values ​​to the fitting curve function F(x) yields the measured boundary of the uniform magnetic field distribution region of the Helmholtz coil 3; the expressions for the fitting curve coefficients and the measured boundary are as follows:

[0077]

[0078] In the formula, f represents a function with x as its independent variable.

[0079] S4. Determine the actual uniform boundary based on the average absolute percentage error of the magnetic induction intensity at the measured boundary and the reference boundary of the uniform magnetic field distribution region of the Helmholtz coil 3, as follows:

[0080] S401. Calculate the average absolute percentage error of the magnetic induction intensity at the measured boundary and the reference boundary. The formula for calculating the average absolute percentage error is as follows:

[0081]

[0082] In the formula, m represents the number of points, B i 'B' represents the measured magnetic field strength at the boundary. i Indicates the magnetic flux density at the reference boundary;

[0083] S402. Determine the actual boundary of the uniform magnetic field distribution area of ​​Helmholtz coil 3 based on the change in mean absolute percentage error. If the mean absolute percentage error is greater than 0.5%, the measured boundary is used as the new reference boundary. New measured points are determined again, and steps S3 and S4 are repeated until the mean absolute percentage error is less than 0.5%. Specifically: if the magnetic induction intensity at the measured point is greater than the calculated magnetic induction intensity of the reference boundary, the corresponding measured point is shifted outward by 0.01R as the new measured point; if the magnetic induction intensity at the measured point is less than the calculated magnetic induction intensity of the reference boundary, the corresponding measured point is shifted inward by 0.01R as the new measured point, where R is the radius of Helmholtz coil 3.

[0084] S5. The analysis and display terminal 6 displays the actual uniform region of the magnetic field distribution of the Helmholtz coil 3 under a given current amplitude and frequency, for use in electromagnetic experiments on rats.

[0085] This invention constructs a low-frequency magnetic field generator with variable frequency and magnetic field strength. Based on the calculation results of the magnetic field distribution theory of Helmholtz coil and its symmetry characteristics, and combined with the measured results of the magnetic field detection coil and the least squares method, the actual uniform magnetic field region of the low-frequency magnetic field generator with variable frequency and magnetic field strength is obtained, providing support for accurately obtaining the electromagnetic effect performance of rats.

[0086] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for measuring a uniform region using a low-frequency magnetic field generator for rat electromagnetic experiments, characterized in that, The low-frequency magnetic field generator includes: A programmable AC power supply (1) is used to output AC current signals with adjustable frequency and current amplitude; The power amplifier (2) is connected to the programmable AC power supply (1) to receive AC current signals and amplify the current signals, and transmit them through the transmission cable. A Helmholtz coil (3) is connected to a power amplifier (2) to generate a magnetic field through a current signal; A magnetic field detection coil (4) is connected to a Helmholtz coil (3) to obtain the voltage signal on the Helmholtz coil (3); The signal acquisition module (5) is connected to the magnetic field detection coil (4) and is used to filter and convert the voltage signal into digital signals. The analysis display terminal (6) is connected to the programmable AC power supply (1) and the signal acquisition module (5) respectively. It is used to set the current amplitude and frequency, and to calculate the magnetic induction intensity distribution of the Helmholtz coil (3) based on the built-in software using the filtered and analog-to-digital converted voltage signal. The method includes the following steps: S1. The analysis and display terminal (6) calculates the magnetic induction intensity distribution of the Helmholtz coil (3) under a given current amplitude and frequency input, and determines the uniform magnetic field distribution area of ​​the Helmholtz coil (3) based on the change of the relative error of the magnetic induction intensity, which is denoted as the reference area and the corresponding boundary is the reference boundary. S2. Use the magnetic field detection coil (4) to measure the magnetic induction intensity on the reference boundary of the uniform magnetic field distribution area of ​​the Helmholtz coil (3); S3. The measured boundary of the uniform magnetic field distribution region of the Helmholtz coil (3) is obtained by applying the least squares method. S4. Determine the actual uniform boundary based on the average absolute percentage error of the magnetic induction intensity at the measured boundary and the reference boundary of the uniform magnetic field distribution area of ​​the Helmholtz coil (3). S5. The analysis and display terminal (6) displays the actual uniform region of the magnetic field distribution of the Helmholtz coil (3) under a given current amplitude and frequency, for use in rat electromagnetic experiments.

2. The method according to claim 1, characterized in that, The Helmholtz coil (3) comprises two identical circular coils placed in parallel, with the distance between the two identical circular coils equal to their radius.

3. The method according to claim 1, characterized in that, The formula for calculating the magnetic induction intensity distribution of the Helmholtz coil (3) in step S1 is as follows: In the formula, For spatial points The distance to the central axis of the Helmholtz coil (3); For spatial points The distance from the center of the Helmholtz coil (3) to the projection on the central axis. and They are spatial points Radial and axial magnetic induction in cylindrical coordinate system This represents the current amplitude, and R is the radius of the Helmholtz coil (3). Indicates the order, Indicates a parameter.

4. The method according to claim 3, characterized in that, The relative error of magnetic induction intensity in step S1 The calculation formula is: In the formula, This represents the magnetic flux density at the center point of the Helmholtz coil (3). The magnetic induction intensity at any point inside the Helmholtz coil (3) is indicated; when the relative error of the magnetic induction intensity is less than 1%, it is determined to be a region with a uniform magnetic field distribution of the Helmholtz coil (3).

5. The method according to claim 1, characterized in that, The specific steps of step S3 are as follows: S301. For a certain boundary segment, based on the position coordinates of the magnetic field detection coil (4) and corresponding magnetic induction intensity Construct orthogonal polynomials ; S302. Calculate the coefficients of the fitted curve. and gradually put Add to the fitted curve function In the middle, the measured boundary of the uniform magnetic field distribution region of the Helmholtz coil (3) is obtained.

6. The method according to claim 5, characterized in that, The recurrence relation for the orthogonal polynomial is: In the formula, For those with a leading coefficient of 1 polynomial of degree. and Here are the polynomial coefficients, and L represents the number of orthogonal polynomials; in accordance with The orthogonality of can be derived as follows: and and The relation is: Will and Substituting the expression into the orthogonal polynomial The recursive formula is used to obtain the results step by step. Complete the construction of orthogonal polynomials.

7. The method according to claim 6, characterized in that, The expressions for the fitted curve coefficients and the measured boundary are as follows: In the formula, The function is represented by the independent variable. .

8. The method according to claim 1, characterized in that, The specific steps of S4 are as follows: S401. Calculate the average absolute percentage error of the magnetic induction intensity at the measured boundary and the reference boundary. The formula for calculating the average absolute percentage error is as follows: In the formula, Indicates the number of points. This represents the measured magnetic flux density at the boundary. Indicates the magnetic flux density at the reference boundary; S402. Determine the actual boundary of the uniform magnetic field distribution area of ​​the Helmholtz coil (3) based on the change of the mean absolute percentage error. If the mean absolute percentage error is greater than 0.5%, the measured boundary is used as the new reference boundary. Determine the new measured point again and repeat steps S3 and S4 until the mean absolute percentage error is less than 0.5%.

9. The method according to claim 8, characterized in that, The determination of a new measured point specifically involves: if the magnetic induction intensity at the measured point is greater than the calculated magnetic induction intensity at the reference boundary, then the corresponding measured point is shifted outward. As a new measured point; if the magnetic induction intensity at the measured point is less than the calculated magnetic induction intensity of the reference boundary, then the corresponding measured point is shifted inward. As a new measured point, R is the radius of the Helmholtz coil (3).

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