Magnetic energy control method of MC-WPT system based on coordinate transformation principle

Abstract

The present invention provides a method for regulating magnetic energy of an MC-WPT system based on the principle of coordinate transformation, characterized in that it comprises the following steps: S1: establishing a Cartesian coordinate system according to the shape and position of a magnetic coupling mechanism in the MC-WPT system, and determining the area where the original magnetic field is located and the area where the transformed magnetic field is located; S2: determining the coordinate mapping relationship between the area where the transformed magnetic field is located and the area where the original magnetic field is located; S3: calculating the Jacobian matrix expression according to the coordinate mapping relationship; S4: determining the electromagnetic parameters of the medium that needs to be added to the area where the original magnetic field is located; S5: adding the corresponding medium to the area where the original magnetic field is located according to the electromagnetic parameters of the medium obtained in step S4. The effect is that the method can arbitrarily regulate the magnetic field distribution as needed, thereby effectively improving the energy efficiency and spatial capability of the magnetic coupling wireless power transmission system; the magnetic field convergence effect is not affected by the position of the energy transmitting coil and the energy receiving coil, and the aggregation effect is obvious.

Description

Technical Field

[0001] The present invention relates to wireless power transmission technology, and in particular to a magnetic energy control method of a MC-WPT system based on the coordinate transformation principle. Background Art

[0002] Magnetic Coupling Wireless Power Transfer (MC-WPT) uses the law of electromagnetic induction to achieve energy transmission between the primary and secondary coils, and can achieve wireless transmission of electrical energy without relying on transmission lines. Wireless power transmission technology has attracted more and more attention due to its unique advantages such as convenience and safety. However, the use of the law of electromagnetic induction to achieve wireless power transmission will generate leakage magnetic field in space, which will inevitably cause MC-WPT technology to have problems such as short transmission distance and low transmission efficiency.

[0003] In order to alleviate the above problems and improve the transmission distance and transmission efficiency of the MC-WPT system, many solutions have been proposed. One of the methods starts with optimizing the topological structure of the circuit and performs reactive compensation on the MC-WPT system to improve the transmission efficiency. However, this method is only based on circuit optimization and does not change the magnetic field distribution between coils. The transmission distance is limited and there is still a lot of energy loss between coils. Another method is to optimize the magnetic coupling mechanism, optimize the magnetic field distribution by optimizing the design of the primary and secondary coils, thereby improving the transmission distance and efficiency of the system. However, once the magnetic coupling mechanism is set, the effective energy transmission range is fixed. In some application scenarios, it is difficult to arbitrarily change the shape of the magnetic coupling mechanism to meet the adjustment of the magnetic field transmission direction and range. In addition, there is another way to add relays to the primary coil and the secondary coil, which can change the magnetic field distribution to a certain extent, enhance the coupling between the primary and secondary coils, and thus improve the energy efficiency and transmission distance of the system. However, adding relays will make the coil structure complicated, and the relays will bring additional losses. More importantly, the relay can only change the magnetic field distribution to a certain extent, and the magnetic field direction is fixed, so the control area is limited. Summary of the invention

[0004] Based on the above problems, the purpose of the present invention is to propose a magnetic energy control method for the MC-WPT system based on the coordinate transformation principle, which satisfies the arbitrary control of the magnetic field distribution by adding media with different electromagnetic parameters, thereby effectively improving the energy efficiency and spatial capability of the magnetically coupled wireless power transmission system.

[0005] In order to achieve the above object, the specific technical solutions adopted by the present invention are as follows:

[0006] A magnetic energy control method for a MC-WPT system based on the coordinate transformation principle includes the following steps:

[0007] S1: Establish a Cartesian coordinate system in space, and determine the area where the original magnetic field is located and the area where the transformed magnetic field is located according to the expected field energy control effect;

[0008] S2: Determine the coordinate mapping relationship between the area where the transformed magnetic field is located and the area where the original magnetic field is located;

[0009] S3: Calculate the Jacobian matrix expression according to the coordinate mapping relationship;

[0010] S4: According to Determine the electromagnetic parameters of the medium that needs to be added to the area where the original magnetic field is located, where The form of the third-order matrix that needs to add the magnetic permeability of the medium is expressed as, The third-order matrix form that represents the dielectric constant of the medium needs to be added, The third-order matrix form of air permeability is: represents the third-order matrix form of the dielectric constant of air, Λ represents the Jacobian matrix, Λ T represents the transpose of the Jacobian matrix, |Λ| represents the determinant value of the Jacobian matrix;

[0011] S5: Add corresponding medium into the area where the original magnetic field is located according to the medium electromagnetic parameters obtained in step S4.

[0012] Taking the spherical shell-shaped magnetic energy polymer material as an example, when the energy receiving coil in the magnetic coupling mechanism is located inside the spherical structure, the added medium is in the shape of a spherical shell; the inner diameter of the spherical shell-shaped medium material is determined to be R1 and the outer diameter is R2 according to the area where the original magnetic field is located; the coordinate expression of the point on the coordinate of the area where the original magnetic field is located is (x, y, z), and the coordinate expression of the point on the coordinate of the area where the transformed magnetic field is located is (x', y', z'), then the coordinate mapping relationship obtained in step S2 is:

[0013] Where a = R1 / (R2-R1), R1<r<R2, r is the radius of the location of the change point in the area where the original magnetic field is located.

[0014] For the design of spherical shell-shaped magnetic energy polymer material, the Jacobian matrix expression obtained in step S3 is:

[0015]

[0016] Optionally, a receiving coil is arranged inside the spherical shell medium, and when the magnetic field excited by the transmitting coil contacts the spherical shell material, the magnetic field is aggregated to the inside of the spherical shell due to the aggregation effect of the spherical shell material.

[0017] The effects of the present invention are:

[0018] The present invention proposes a magnetic energy control method for an MC-WPT system based on the coordinate transformation principle. The method can arbitrarily control the magnetic field distribution as needed, thereby effectively improving the energy efficiency and spatial capability of the magnetically coupled wireless power transmission system; the magnetic field convergence effect is not affected by the positions of the energy transmitting coil and the energy receiving coil, and the aggregation effect is obvious. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the specific implementation of the present invention or the technical solution in the prior art, the drawings required for use in the specific implementation or the description of the prior art are briefly introduced below.

[0020] Figure 1 Schematic diagram of coordinate transformation in general medium design process

[0021] Figure 2 A position relationship diagram of a magnetic field conversion region in a specific embodiment;

[0022] Figure 3 It is a schematic diagram of the change of magnetic field lines in a specific embodiment;

[0023] Figure 4 It is a schematic diagram of the structure of a spherical shell-shaped electromagnetic polymer medium in a specific embodiment;

[0024] Figure 5 This is the simulation effect diagram of magnetic field intensity distribution;

[0025] Figure 6 This is the simulation effect diagram of the magnetic field propagation direction;

[0026] Figure 7 This is a simulation diagram of the effect of the spherical shell material on the magnetic field excited by the coil. DETAILED DESCRIPTION

[0027] The following embodiments of the technical solution of the present invention are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and are therefore only used as examples, and cannot be used to limit the protection scope of the present invention.

[0028] It should be noted that, unless otherwise specified, the technical terms or scientific terms used in this application should have the common meanings understood by those skilled in the art to which the present invention belongs.

[0029] According to electromagnetic theory, if the magnetic field encounters a change in the propagation medium during the propagation process, refraction and scattering will occur on the surface of the medium, causing the direction and size of the magnetic field to change. These changes usually depend on the electromagnetic parameters of the medium, the dielectric constant ε and the magnetic permeability μ. The propagation medium in nature is usually an isotropic medium, that is, the dielectric constant and magnetic permeability remain unchanged. When the propagation medium changes during the propagation of the magnetic field, the propagation direction of the magnetic field will change. If the medium is an isotropic medium, the propagation direction of the magnetic field will continue to propagate in that direction after the change. Therefore, it can be imagined that if the magnetic permeability and dielectric constant at each position in a medium are different in size, which can be positive or negative, then the magnetic field cannot propagate in a single direction in the medium. Its propagation direction is determined by the electromagnetic parameters at each position in the medium. If we artificially design the electromagnetic parameters of the medium so that the magnetic field propagates in the direction we expect at a specific position in the medium, we can achieve artificial control of the magnetic field.

[0030] Therefore, based on the principle of electromagnetic coordinate transformation, the electromagnetic parameters of the medium can be designed to achieve arbitrary artificial control of the field. This method combines the change of the electromagnetic field vector line with the distortion of the coordinate space, and then establishes a corresponding relationship between the distortion of the space and the electromagnetic parameters of the medium. Through the relationship before and after the coordinate transformation, the electromagnetic parameters of the medium in the transformed space are obtained, and the magnetic field will propagate as needed after it propagates to the medium.

[0031] In combination with the above analysis, this embodiment provides a magnetic energy control method of a MC-WPT system based on the coordinate transformation principle, comprising the following steps:

[0032] S1: Establish a Cartesian coordinate system in space, and select two spatial regions as region S and region S' according to the expected field energy control effect. Region S is the region where the original magnetic field is located, and region S' is the region where the transformed magnetic field is located;

[0033] S2: Determine the coordinate mapping relationship between the area where the transformed magnetic field is located and the area where the original magnetic field is located: x'=f1(x, y, z), y'=f2(x, y, z), z'=f3(x, y, z);

[0034] S3: Calculate the Jacobian matrix expression according to the coordinate change expression

[0035]

[0036] S4: According to Determine the electromagnetic parameters of the medium that needs to be added to the area where the original magnetic field is located, where The third-order matrix form that represents the magnetic permeability of the medium that needs to be added is: The third-order matrix form that represents the dielectric constant of the medium needs to be added, The third-order matrix form of air permeability is: represents the third-order matrix form of the dielectric constant of air, Λ represents the Jacobian matrix, Λ T represents the transpose of the Jacobian matrix, |Λ| represents the determinant value of the Jacobian matrix;

[0037] S5: Add corresponding medium into the area where the original magnetic field is located according to the medium electromagnetic parameters obtained in step S4.

[0038] The coordinate transformation principle is applied in the process of designing magnetic energy regulation materials. The coordinate transformation principle is the key to designing magnetic energy regulation materials in this patent. The detailed design process of the coordinate transformation principle and general magnetic energy regulation materials is as follows:

[0039] The schematic diagram of the coordinate change principle is as follows Figure 1 As shown in the figure, the application of the coordinate change principle in the design of magnetic energy regulation materials is the transformation of the spatial region. Now we want to transform region S to region S', which is actually to transform all points in the spatial region S to region S'. Suppose there is a point (x, y, z) on region S and a corresponding point (x', y', z') on region S'. The mapping relationship between the two points is:

[0040]

[0041] Through this mapping relationship, the point (x, y, z) can be transformed to the point (x', y', z'). By changing all points in area S according to this mapping relationship, all points in area S can be transformed to area S', realizing the transformation from space area S to space area S'. In the process of selecting the transformation area S and area S' and transforming area S to area S' in coordinate transformation, the field energy change actually expected to be achieved is to transform the field energy inside area S to area S'.

[0042] According to the above mapping relationship, the Jacobian matrix is:

[0043]

[0044] Substituting the obtained Jacobian matrix into the equivalent electromagnetic parameter formula, the electromagnetic parameters of the designed material can be obtained.

[0045]

[0046]

[0047] The formulas for the above electromagnetic parameters are derived from the covariant form of Maxwell's equations, where Represents the magnetic permeability of the design material in the form of a third-order matrix; Represents the dielectric constant of the designed material in the form of a third-order matrix; and Represents the magnetic permeability and dielectric constant in the original environment of the system. Since the original environment is usually air, these two quantities are third-order unit matrices; Λ T is the transpose of the Jacobian matrix; |Λ| is the determinant of the Jacobian matrix.

[0048] The original magnetic field region and the transformed magnetic field region can be of any shape, and this embodiment takes a spherical region as an example. Figure 2 As shown, for the wireless power transmission system, in order to optimize the system performance and realize the aggregation control of the magnetic field, the transformation first selects the transformation area S, which is also the area where the dielectric material is placed; secondly, the transformed area S' is selected, and the area S' is the area of ​​field aggregation.

[0049] When solving the parameters of the dielectric material, the coordinate transformation principle is used to compress the area S into the area S'. The compression process is the distortion of space. The relationship between the distortion of space and the electromagnetic parameters of the medium can be used to obtain the electromagnetic parameters of the transformed medium. Placing the designed dielectric material in the area S can achieve the control effect of the external magnetic field. The expected effect after control is as follows: Figure 3 shown.

[0050] Specifically, the coordinate transformation and medium parameter derivation process are as follows:

[0051] like Figure 4 As shown in the figure, when the energy receiving coil in the magnetic coupling mechanism is located inside the spherical structure, the added medium is in the shape of a spherical shell. The inner diameter of the spherical shell medium material is determined to be R1 and the outer diameter is R2 according to the area where the original magnetic field is located. The point spherical coordinates on the spherical shell area are in the form of (r,θ, ), the points in the inner region of the spherical shell are (r',θ', ). To transform all points on the spherical shell region to the internal region of the spherical shell, the mapping relationship between the corresponding points is:

[0052]

[0053] Through the above mapping relationship, the spherical shell area can be transformed to the internal area of ​​the spherical shell, and the conversion relationship between the spherical coordinate system and the rectangular coordinate system is:

[0054]

[0055]

[0056] z=r cosθ

[0057] Therefore, the mapping relationship is converted to a rectangular coordinate system. If the coordinate expression of the point on the coordinates of the original magnetic field is (x, y, z), and the coordinate expression of the point on the coordinates of the transformed magnetic field is (x', y', z'), then the coordinate change expression obtained in step S2 is:

[0058] Where a = R1 / (R2-R1), R1<r<R2, r is the radius of the location of the change point in the area where the original magnetic field is located.

[0059] The Jacobian matrix expression after the above coordinate transformation can be obtained as follows:

[0060]

[0061] The coordinate transformation and the electromagnetic parameters of the medium are linked through the above formula. Since the medium in the space before the transformation is usually air, whose magnetic permeability and dielectric constant are both 1, the equivalent electromagnetic parameters of the medium after the electromagnetic coordinate transformation can be obtained.

[0062]

[0063]

[0064]

[0065]

[0066] a 21 =a 12

[0067]

[0068]

[0069] a 31 =a 13

[0070] a 32 =a 23

[0071]

[0072]

[0073] From the equivalent electromagnetic parameters of the above medium, it can be seen that the electromagnetic parameters of the medium obtained by the coordinate transformation method are in the form of a third-order matrix. The electromagnetic parameters at each position are different and are related to the position. Therefore, when the field contacts the medium, it will propagate in the expected design direction, and the external field will converge to the inside to achieve field aggregation regulation. From the above analysis, it can be seen that in the specific implementation, the receiving coil is placed inside the spherical shell, and the transmitting coil is placed outside the spherical shell. The magnetic field excited by the transmitting coil is aggregated and regulated by the spherical shell material and converged to the receiving coil inside the spherical shell, so as to achieve the purpose of improving the magnetic field distribution and optimizing the performance of the MC-WPT system. .

[0074] In order to further verify the feasibility of the above method, this embodiment also establishes a model in COMSOL simulation software based on the electromagnetic parameter derivation of the above spherical shell medium, selects the inner diameter R1 of the spherical shell = 0.2m, and the outer diameter R2 = 0.3m. When there is a uniform magnetic field in space, the simulation effect is as follows: Figure 5 and Figure 6 As shown in Figure 2, the simulation effect of the material on the coil excitation magnetic field is shown in Figure 2. Figure 7 As shown, it can be seen that the simulation results are consistent with the theoretical derivation results, the propagation direction of the magnetic field is consistent with expectations, and when the magnetic field encounters the designed spherical shell medium during propagation, it gathers inside the spherical shell to achieve the concentration of the electromagnetic field.

[0075] From the above, it can be seen that the magnetic energy control method and parameter design method of the MC-WPT system based on the coordinate transformation principle proposed in the present invention can reduce magnetic leakage, reduce energy loss in the air gap, optimize magnetic field distribution, improve system performance without increasing additional system losses, and this method can be applied to various magnetically coupled wireless power transmission systems, and will not limit the position of the transmitting and receiving coils. The method proposed in this patent directly controls the propagation direction of the magnetic field emitted by the transmitting coil, so that most of the magnetic field converges and propagates to the receiving coil, which not only achieves the purpose of optimizing the performance of the MC-WPT system, but also makes up for the shortcomings of the current method.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some or all of the technical features can be replaced by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and such changes should be included in the scope of the claims and description of the present invention.

Claims

1. A magnetic energy control method for a MC-WPT system based on the coordinate transformation principle, characterized in that: The following steps are involved: S1: Establish a Cartesian coordinate system in space, and determine the area where the original magnetic field is located and the area where the transformed magnetic field is located according to the expected field energy control effect; S2: Determine the coordinate mapping relationship between the area where the transformed magnetic field is located and the area where the original magnetic field is located; S3: Calculate the Jacobian matrix expression according to the coordinate mapping relationship; S4: According to Determine the electromagnetic parameters of the medium that needs to be added to the area where the original magnetic field is located, where The form of the third-order matrix that needs to add the magnetic permeability of the medium is expressed as, The third-order matrix form that represents the dielectric constant of the medium needs to be added, The third-order matrix form representing the magnetic permeability of air is, represents the third-order matrix form of the dielectric constant of air, Λ represents the Jacobian matrix, Λ T represents the transpose of the Jacobian matrix, |Λ| represents the determinant value of the Jacobian matrix; S5: adding corresponding medium into the area where the original magnetic field is located according to the electromagnetic parameters of the medium obtained in step S4; When the energy receiving coil in the magnetic coupling mechanism is located inside the spherical structure, the added medium is in the shape of a spherical shell; the inner diameter of the spherical shell medium material is determined to be R1 and the outer diameter is R2 according to the area where the original magnetic field is located; the coordinate expression of the point on the coordinate of the area where the original magnetic field is located is (x, y, z), and the coordinate expression of the point on the coordinate of the area where the transformed magnetic field is located is (x', y', z'), then the coordinate mapping relationship obtained in step S2 is: Where a = R1 / (R2-R1), b = R1 2 / (R2-R1), R1<r<R2, r is the radius of the location of the change point in the original magnetic field area; The Jacobian matrix expression obtained in step S3 is:

2. The magnetic energy control method of the MC-WPT system based on the coordinate transformation principle according to claim 1 is characterized in that: A receiving coil is arranged inside the spherical shell medium. When the magnetic field excited by the transmitting coil contacts the spherical shell material, the magnetic field is aggregated into the inside of the spherical shell due to the aggregation effect of the spherical shell material.

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