Magnetic field generating device of planar electric coil

Abstract

The application relates to the electromagnetic field, in particular to a magnetic field generating device of a planar electric coil. The device comprises at least two parallel arranged coil layers, a plurality of planar electric coils with same or different sizes and configurations arranged on the coil layers, a circuit system for supplying power to the planar electric coils, and a control system for controlling the circuit system. The planar electric coils are formed by winding a single wire segment at least two turns on the same plane, and the planar electric coils in the same coil layer have no interference. In the direction perpendicular to the coil layer, the planar electric coils in different layers have overlapping projections in the direction parallel to the plane of the coil layer. The time-varying spatial gradient magnetic field is obtained by combining the current size of each planar electric coil and / or the power supply switch. The application realizes the vector superposition of the magnetic field by the coil arranged in a multi-layer stacked array, so as to obtain stronger magnetic field strength and gradient. The coil has good consistency through the process of the printed circuit, thereby effectively improving the uniformity and precision of the generated magnetic field.

Description

Technical Field

[0001] This invention relates to the field of electromagnetics, and more particularly to a magnetic field generating device for a planar electric coil. Background Technology

[0002] There are many ways to use coils to create a magnetic field.

[0003] In their paper titled "Time-optimal Control for Bilinear Nonnegative-in-control Systems: Application to Magnetic Manipulation" published in IFAC-PapersOnLine 2017, Zemánek et al. used a single-layer conventional winding array, which, due to configuration and boundary conditions, could not effectively generate the required magnetic field strength and gradient in the confined region.

[0004] In their paper "Development of an Enhanced Electromagnetic Actuation System With Enlarged Workspace," published in Transactions on Mechatronics, 22(5), 2265–2276, Niu, F. et al. used a conventionally wound iron-core electromagnetic coil composed of six orthogonally arranged slanted Cartesian coordinates to form a magnetic field driving source. Due to its spatial configuration and large working space (a 110 mm diameter spherical space), the generated magnetic field is a global magnetic field, and the movement and deformation capabilities of the magnetic structures within the region tend to be similar, which cannot effectively realize different forms of movement and deformation of the magnetic structures in different regions.

[0005] In addition, Chinese patent CN101851577A uses multi-layer masking technology to fabricate a single-layer planar coil. The single-layer planar coil is limited by the configuration and boundary conditions (e.g., adjacent coils will be activated if they are too close). Similarly, it cannot effectively generate the required magnetic field strength and gradient in the confined area.

[0006] Currently, there is also a technology that uses Helmholtz coils to generate magnetic fields. The main problem with this technology is that the generated magnetic field is almost uniformly distributed in space, making it impossible to achieve magnetic field changes at specific points or to achieve independent control of multiple targets. In addition, it is heavy and requires a large amount of space. Summary of the Invention

[0007] The present invention provides a magnetic field generating device for a planar electric coil to solve the above-mentioned technical problems.

[0008] To solve the above-mentioned technical problems, the present invention provides a magnetic field generating device for planar electric coils, comprising at least two parallel coil layers, a plurality of planar electric coils of the same or different sizes and configurations disposed on the coil layers, a circuit system for supplying power to the planar electric coils, and a control system for the control circuit system. The planar electric coils are formed by winding a single line segment at least two turns in the same plane, and there is no interference between the planar electric coils in the same coil layer. The planar electric coils in at least two of the coil layers overlap in projection parallel to the plane of the coil layer. A time-varying spatial gradient magnetic field is obtained by combining the current magnitude of each planar electric coil and / or the power supply switch.

[0009] Preferably, the planar coil, circuit system and control system are manufactured using printed circuit board technology.

[0010] Preferably, the circuit configuration of the planar coil is that it is wound along a regular contour line, with gaps between adjacent turns.

[0011] Preferably, the regular outline is circular, elliptical, or polygonal, with a circular outline being the most desirable.

[0012] Preferably, on the coil layer, the centroid of the planar electric coil is used as the location point to be planned as needed.

[0013] Preferably, the location points are arranged in an array.

[0014] Preferably, the number of stacked coil layers is 2 to 6.

[0015] Preferably, from top to bottom, the position where the magnetic field superposition change between the planar electric coils of the first coil layer is minimized and mapped to the second coil layer is set as the centroid of the planar electric coil.

[0016] Preferably, the planar coils in the same coil layer have the same radius and the same profile.

[0017] Here, the radius refers to the radius of the circle when the outline is circular, and the radius of the circumcircle when the outline is non-circular.

[0018] Preferably, the odd-numbered coil layers have the same position point arrangement, and the even-numbered coil layers have the same position point arrangement; the planar electric coils of the odd-numbered coil layers and the planar electric coils of the even-numbered coil layers are nested.

[0019] Nesting refers to the overlapping of planar coils when they are nested together in a plane.

[0020] Preferably, the planar coils at corresponding positions in the odd-numbered coil layers are connected in series, and the planar coils at corresponding positions in the even-numbered coil layers are connected in series.

[0021] Preferably, the coil layer is provided with through holes for electrical connection or conduction.

[0022] Preferably, multiple planar coils form a module, and at least one module is assembled to form the magnetic field generating device.

[0023] Preferably, the modules are spliced ​​together using a planar and / or inclined plane method.

[0024] The control method for the magnetic field generating device of the above-mentioned planar electric coil includes the following steps:

[0025] First, the coil layers in the magnetic field generating device of the planar electric coil are grouped according to the arrangement, and the input current of the coil layers in the same group is the same;

[0026] Then, calculate the elementary magnetic field matrix of the same group of coil layers.

[0027] Finally, substituting the elementary magnetic field matrix and preset magnetic field distribution matrix Calculate the required input current for each group of coil layers.

[0028] Preferably, the elementary magnetic field matrix of a certain arrangement The calculation is obtained using equation (1):

[0029] Given that the arrangement has a total of l layers, where the i-th layer has m coil configurations, and the j-th coil configuration among the m coil configurations has n coils, then when a current of I is passed through (I is...<l×m×n> A matrix of size × 1, where the current flowing through the k-th coil is I. k The magnetic field strength that can be generated for:

[0030]

[0031] in Let be the spatial magnetic field strength when the current flowing through the p-th coil is 1A; The elementary magnetic field matrix generated when each coil carries a 1A current is 3×<l×m×n> A matrix, where the three values ​​in each row represent The three components in the x, y, and z directions.

[0032] Preferably, the required current I is calculated using equation (2) based on the preset magnetic field:

[0033]

[0034] in Representing singular value decomposition, U, ∑, and V are 3×3, 3×, and ∑ respectively.<l×m×n> ,<l×m×n> ×<l×m×n> matrix.

[0035] Compared with the prior art, the planar electric coil magnetic field generating device provided by the present invention has the following advantages:

[0036] 1. This invention achieves vector superposition of magnetic fields by using multi-layer stacked array coils to obtain stronger magnetic field strength and gradient, and realizes the generation of the required magnetic field strength and gradient within a confined area;

[0037] 2. The present invention also uses the printed circuit process to make the coil have better consistency, which can avoid the deviation caused by the coil winding, thereby effectively improving the uniformity and accuracy of the generated magnetic field. Attached Figure Description

[0038] Figure 1 a and Figure 1 b is a diagram illustrating the principle and magnetic field effect of the magnetic field generating device described in this embodiment of the invention;

[0039] Figures 2a to 2c These are schematic diagrams of the coil structures for various circuit configurations in this invention;

[0040] Figure 3 This is a schematic diagram of the planar coil arrangement described in Embodiment 1 of the present invention;

[0041] Figure 4 for Figure 3 Front view;

[0042] Figure 5 This refers to the method used in Example 1 for controlling a local planar coil;

[0043] Figure 6 According to Figure 5 The effect diagram of the local time-varying spatial gradient magnetic field achieved by the control method;

[0044] Figure 7 This is a coil layer design diagram of the magnetic field generating device of the planar electric coil described in Embodiment 2 of the present invention;

[0045] Figure 8 This is a schematic diagram of the planar coils corresponding to the odd-numbered or even-numbered layers in Embodiment 2 of the present invention connected in series through a central through-hole. Detailed Implementation

[0046] To illustrate the technical solutions of the invention in more detail, specific embodiments are listed below to demonstrate the technical effects; it should be emphasized that these embodiments are used to illustrate the invention and not to limit the scope of the invention.

[0047] The present invention provides a magnetic field generating device for planar electric coils, wherein the planar electric coil is defined as follows: the planar electric coil is mainly distributed in a plane (the size in the third-dimensional direction perpendicular to the plane is much smaller than the size in the plane).

[0048] The magnetic field generating device includes at least two parallel coil layers, several planar electric coils of the same or different sizes and configurations disposed on the coil layers, a circuit system for supplying power to the planar electric coils, and a control system for the control circuit system. That is to say, the configuration and size of all the planar electric coils in the magnetic field generating device can be evenly distributed in pairs. The most ideal circuit system and control system is that each planar electric coil is individually powered and the magnitude of the electric current is controlled.

[0049] like Figure 1 As shown in Figure a, the principle of obtaining a time-varying spatial gradient magnetic field by combining the current magnitudes of the planar coils and / or the power supply switches is illustrated using a simplified two-layer disc-shaped planar coil magnetic field generating device. The free ends of the two planar coils are the two power supply terminals. When current flows, the current directions of the upper and lower coils are in the same direction (both clockwise or both counterclockwise) to achieve a magnetic field enhancement effect. Figure 1 As shown in b, if the current flows in opposite directions in the upper and lower coils, a magnetic field cancellation effect is achieved.

[0050] For ease of design and layout, it is ideal for planar coils to be wound along a regular contour line. Additionally, gaps are provided between adjacent turns. The contour line can be circular, elliptical, or polygonal; see references for details. Figure 2a Disk configuration, Figure 2b Rectangular configuration Figure 2c Hexagonal configurations, etc. Planar coils are preferably arranged in an array within the same coil layer.

[0051] The planar coils in each layer overlap in projection parallel to the plane of the coil layer, forming a nested structure. A time-varying spatial gradient magnetic field can be generated by combining the power supply switching states and power supply current magnitudes of each coil. This invention achieves vector superposition of magnetic fields through a multi-layered stacked array of coils to obtain a stronger magnetic field strength and gradient.

[0052] In addition, the planar coil, circuit system and control system are made using printed circuit technology, that is, the planar coil circuit and auxiliary power supply and control circuit are printed using PCB (Printed Circuit Board) technology, which makes the planar coil have better consistency, avoids the deviation caused by coil winding, and thus effectively improves the uniformity and accuracy of the generated magnetic field.

[0053] In some embodiments, at the coil level, the centroid of the planar coil (i.e., the circle in a disk configuration, the geometric center in a rectangular configuration, etc.) is installed at a planned location point, and there is no interference between planar coils on the same coil layer. In other words, to achieve an array distribution of multiple planar coils in the same plane, it is necessary to first plan the location points of the planar coils in the plane according to actual driving requirements. Taking a disk configuration as an example, these points are the installation positions of the center points of the planar coils. To avoid interference between adjacent coils, the distance between each location point needs to be greater than the radius of the planar coil (for a disk configuration) or the radius of the closely spaced circumcircle of the planar coil (for other configurations). If planar coils with different circuit configurations need to be designed in the same plane, the goal is to achieve no interference between the planar coils.

[0054] In some embodiments, the number of stacked coil layers in the direction perpendicular to the coil layers is 2 to 6. Stacking 2 or more layers can achieve vector superposition of magnetic fields, but the number of stacked layers is limited by the processing capabilities of printed circuit technology, and the current maximum is 6 layers.

[0055] In some embodiments, the coil layer is provided with through holes for connection or conduction. Specifically, the through holes can be copper foil lines that conduct or connect conductive patterns in different layers of the circuit board to connect the complete circuit layout. That is to say, in addition to the method of independent power supply and control for each planar coil, planar coils on the same layer or planar coils on different layers can also be connected in series or in parallel, depending on the actual situation, to reduce the difficulty of circuit wiring and the complexity of circuit control.

[0056] In some embodiments, the location where the magnetic field superposition change between the planar electric coils of a certain coil layer is minimal and mapped to another coil layer is set as the centroid of the planar electric coil of that coil layer. That is, the magnetic field of other coil layers fills the gap in its own magnetic field regulation, so that there is no restricted area in the entire magnetic field generating device.

[0057] In some embodiments, the planar electric coils in the same coil layer have the same radius, which makes it easier to calculate the mutual interference points. The planar electric coils in the same coil layer also have the same outline, which makes it easier to calculate the magnetic field blank area.

[0058] In some embodiments, planar coils of odd-numbered coil layers are arranged vertically and vertically, and planar coils of even-numbered coil layers are arranged vertically and vertically. That is, planar coils of odd-numbered or even-numbered coils are used to enhance or weaken the magnetic field in the same area, and planar coils of odd-numbered and even-numbered coils are nested to fill the area where the magnetic field is restricted.

[0059] In some embodiments, planar coils at corresponding positions in the odd-numbered coil layers are connected in series, and planar coils at corresponding positions in the even-numbered coil layers are connected in series. This simplifies the control system.

[0060] In some embodiments, multiple planar coils form a module, and at least one module is spliced ​​together to form the magnetic field generating device, thereby expanding the effective driving area and space. In some embodiments, the modules can be spliced ​​together in a planar and / or inclined manner, which provides more flexibility. If a planar splicing is used, the magnetic field generation range can be effectively expanded. If an inclined splicing is used, the effective range can be expanded and a superimposed magnetic field can be generated.

[0061] Furthermore, the module provided by this invention is suitable for in-plane driving and load transport of magnetic microstructures (including microparticles, microrobots, biological particles, etc.), and can also be used for motion and deformation driving of microstructures with motion capabilities (soft robots, etc.). The advantages of the module provided by this invention are: the driving method is cable-free remote control, which can effectively reduce contact; each individual coil 10 in the array and interlayer stacking can realize the opening and closing state of the magnetic field and change the strength and gradient of the generated magnetic field by the magnitude of the supply current; furthermore, the combination of the magnetic fields of each coil can be used to generate a local magnetic field. The generated local magnetic field can realize different forms of motion and deformation of the magnetic structure in different regions. For example, it can drive the overall motion of an entire octopus, and can also realize the individual motion control of each claw of an octopus-structured microrobot.

[0062] It should be noted that the magnetic field strength decreases exponentially with the square of the distance from the magnetic field source, meaning the magnetic field decays rapidly. In this invention, a local magnetic field refers to a region where a single maximum magnetic field strength exists. The module in this invention can generate multiple local magnetic fields.

[0063] The specific embodiments of the planar electric coil magnetic field generating device provided by the present invention will be described in detail below with reference to the accompanying drawings. Any parts not mentioned below refer to the content described above.

[0064] Example 1

[0065] like Figure 3 and 4As shown, the magnetic field generating device of the planar electric coil includes four parallel coil layers 10. From top to bottom, each of the odd-numbered coil layers 10 has 16 planar electric coils A21 with the same radius arranged in a 4x4 matrix, with no interference between the planar electric coils A21. Each of the even-numbered coil layers 10 has 9 planar electric coils B22 with the same radius arranged in a 3x3 matrix, with no interference between the planar electric coils B22. The planar electric coils A21 and B22 of the odd-numbered coil layers 10 are arranged vertically and vertically respectively. The center of the planar electric coil A21 is its centroid, located at a designed 4x4 evenly distributed position. The same applies to the planar electric coil B22. (Continue to see...) Figure 4 Planar coil A 21 and planar coil B 22 are nested, and the centroid of planar coil B 22 is precisely where the magnetic field superposition change of the odd-numbered coil layers is minimal.

[0066] Perform magnetic field control analysis on one of the repeating regions of the structure, such as... Figure 5 As shown in diagram a, each odd-numbered coil layer contains four planar coils A with smaller radii, labeled A1, A2, A3, and A4 in counter-clockwise order. Each even-numbered coil layer contains one planar coil A with a larger radius, labeled B1. See also... Figure 4 It can be seen that A1 of the first coil layer and A1 of the third coil layer are connected in series, while A2 of the first coil layer and A2 of the third coil layer are connected in series, and A3 and A4 are similarly connected. That is, the planar coils at corresponding positions in the odd-numbered coil layers are connected in series sequentially. B1 of the second coil layer and B1 of the fourth coil layer are connected in series, meaning the planar coils at corresponding positions in the even-numbered coil layers are connected in series sequentially. The planar coils are then processed as follows... Figure 5 Control of the power supply switch status as shown in b.

[0067] Based on the above structure, the generated magnetic field was calculated: using the magnetic dipole model, and based on key parameters such as the number of turns of the coil, wire diameter, and wire spacing, a mathematical model of the spatial magnetic field distribution under elementary current (1A) excitation was established according to the Biot-Savart law. Based on the principle of spatial vector superposition of magnetic induction intensity, a mathematical model of the spatial magnetic field distribution generated by the combined coil under arbitrary excitation current is established. Where I i / I j Let m and n be the currents passing through the i-th and j-th type A / B coil elements, respectively, and m and n be the number of type A and type B coils, respectively. The final result is as follows: Figure 6 The front and front views of the simulated time-varying spatial gradient magnetic field are shown in the four states.

[0068] Example 2

[0069] like Figure 7 As shown, Embodiment Two is another arrangement method. The main difference from Embodiment One is that the odd-numbered coil layers have 27 planar coil layers A 21 evenly arranged, while the even-numbered coil layers have 12 planar coil layers B 22 arranged in 3 rows and 4 columns. The wire diameter in the design drawing is only 35 micrometers on each side, therefore it is only shown as a disk schematic. The extra lines in the drawing are wiring diagrams, used as wires to power the coils. The through-holes 30 on the coil layers are used for wire insertion, especially as shown in... Figure 8 As shown, the planar coil layer A in the odd-numbered coil layers is connected in series through the central wire, and the planar coil layer B in the odd-numbered coil layers is connected in series through the central wire. The ends of the wires are distributed on the ribbon cable terminals 40 at the edge, which facilitates the use of ribbon cables to power the device.

[0070] Example 3

[0071] If there is a single coil arrangement with l layers, where the i-th layer has m coil configurations, and the j-th coil configuration has n coils, then this arrangement will work when a current of I is applied to the coils (where I is...).<l×m×n> A matrix of size × 1, where the current flowing through the k-th coil is I. k The magnetic field strength that can be generated The (3×1 matrix) is:

[0072]

[0073]

[0074] in Let be the spatial magnetic field strength when the current flowing through the p-th coil is 1A; The elementary magnetic field matrix generated when each coil carries a 1A current is 3×<l×m×n> A matrix, where the three values ​​in each row represent The three components in the x, y, and z directions.

[0075] Furthermore, in order to achieve Given the magnetic field distribution, the required current I to flow through this arrangement is:

[0076]

[0077] in Representing singular value decomposition, U, ∑, and V are 3×3, 3×, and ∑ respectively.<l×m×n> ,<l×m×n> ×<l×m×n> matrix.

[0078] Obviously, those skilled in the art can make various modifications and variations to the invention without departing from the spirit and scope of the invention. Therefore, if these modifications and variations fall within the scope of the claims of the invention and their equivalents, the invention is also intended to include these modifications and variations.

Claims

1. A magnetic field generating device for a planar electric coil, characterized in that, It includes at least two parallel coil layers, several planar electric coils of the same or different sizes and configurations disposed on the coil layers, a circuit system for powering the planar electric coils, and a control system for the control circuit system. The planar electric coils are formed by winding a single line segment at least 2 turns in the same plane, and there is no interference between the planar electric coils in the same coil layer. In the direction perpendicular to the coil layer, the projections of the planar electric coils between different layers onto the plane parallel to the coil layer overlap. A time-varying spatial gradient magnetic field is obtained by combining the current magnitude of each planar electric coil and / or the power supply switch. On the coil layer, the centroid of the planar electric coil is used as the location point to be planned as needed; From top to bottom, the location where the magnetic field superposition change between the planar electric coils of the first coil layer is minimal, mapped onto the second coil layer, is set as the centroid of the planar electric coil; The odd-numbered coil layers have the same position point arrangement, and the even-numbered coil layers have the same position point arrangement; the planar coils of the odd-numbered coil layers and the planar coils of the even-numbered coil layers are nested. The planar electric coils at corresponding positions in the odd-numbered coil layers are connected in series, and the planar electric coils at corresponding positions in the even-numbered coil layers are connected in series.

2. The magnetic field generating device of the planar electric coil as described in claim 1, characterized in that, The planar coil is wound along a regular contour line with gaps between adjacent turns.

3. The magnetic field generating device of the planar electric coil as described in claim 1, characterized in that, The location points are arranged in an array.

4. The magnetic field generating device of the planar electric coil as described in claim 1, characterized in that, The planar electric coils in the same coil layer have the same radius and the same outline.

5. The magnetic field generating device of the planar electric coil as described in claim 1, characterized in that, The coil layer is provided with through holes for electrical connection or conduction.

6. The magnetic field generating device of the planar electric coil as described in claim 1, characterized in that, Multiple planar coils are assembled into modules, and at least one module is spliced ​​together to form the magnetic field generating device. The modules are spliced ​​together in a planar and / or inclined manner.

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