Magnetic field generator and method for manufacturing a magnetic field generator, electromagnetic positioning system

Abstract

The application provides a magnetic field generator and a preparation method and an electromagnetic positioning system, and the magnetic field generator comprises a shell and a magnetic field generating unit arranged in the shell, and the magnetic field generating unit comprises one or more groups of three-axis orthogonal coil assemblies, each group of three-axis orthogonal coil assemblies is composed of three first coil assemblies, and the central axes of the three first coil assemblies are vertically intersected with each other in space. The application has the beneficial effects that: the three first coil assemblies are vertically intersected with each other to form a three-axis orthogonal group, an ideal orthogonal magnetic field base is constructed, the simplest solving model is obtained in mathematics, the complexity of iterative solving is effectively reduced, and the positioning calculation amount is maximally reduced; meanwhile, the three-axis orthogonal arrangement structure is compact in layout and high in space utilization, and the setting of the second coil assembly further improves the magnetic field uniformity and total magnetic sensitivity of the measurement domain, so that the optimal positioning effect is obtained in the measurement region.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic field generation technology, and in particular to a magnetic field generator and its preparation method, as well as an electromagnetic positioning system. Background Technology

[0002] An electromagnetic positioning system is a high-precision instrument for measuring the three-dimensional coordinates and attitude angles of a target object, and it has important applications in industrial measurement and medical testing. This system obtains spatial pose information such as the sensor's three-dimensional coordinates and angular orientation by measuring changes in the magnetic field within the positioning area. Therefore, the magnetic field distribution in the measurement domain has a decisive influence on positioning accuracy, and the magnetic field generator is the core component of the electromagnetic positioning system.

[0003] Currently, electromagnetic positioning systems based on alternating magnetic fields on the market generally adopt a multi-sole coil layout for their magnetic field generators. However, different manufacturers have different arrangements of the solenoid coils, and a unified optimal architecture has not yet been formed.

[0004] For a single solenoid coil, the closer the sensor is to the coil axis, the higher the overall magnetic sensitivity and the higher the positioning accuracy. Figure 2 As shown, electromagnetic positioning systems rely on the combined action of multiple solenoid coils to determine the sensor's position. Therefore, the magnetic field generated by each solenoid coil within the positioning area should possess good magnetic sensitivity; that is, the sum of the angles between a point in the measurement domain and the axes of all solenoid coils should be as small as possible. However, due to the nonlinear distribution of the magnetic field of the solenoid coils, the sensor's pose and orientation information cannot be directly calculated using mathematical analytical methods. Only iterative solutions can obtain results closest to the true values. The accuracy of the iterative solution depends on the high-quality magnetic field signals provided by each coil within the measurement domain, which places comprehensive demands on the spatial arrangement and magnetic field distribution characteristics of the coils.

[0005] However, current products cannot meet these requirements simultaneously, resulting in slow convergence of iterative solutions and limited accuracy, which has become a bottleneck restricting further improvement in the measurement accuracy of electromagnetic positioning systems.

[0006] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0007] To address the problems in the prior art, the present invention provides a magnetic field generator, comprising: a housing and a magnetic field generating unit disposed within the housing, wherein the magnetic field generating unit comprises one or more sets of triaxial orthogonal coil assemblies, each set of the triaxial orthogonal coil assemblies being composed of three first coil assemblies, the central axes of the three first coil assemblies being perpendicularly intersecting each other in space.

[0008] As a further improvement of the present invention, the magnetic field generating unit further includes an auxiliary coil assembly, which consists of one or more second coil assemblies, wherein the central axis of each second coil assembly is orthogonal to the central axis of at least one first coil assembly in the triaxial orthogonal coil assembly; or the central axes of any two of the second coil assemblies are orthogonal to each other.

[0009] As a further improvement of the present invention, the total number of the first coil assemblies is six.

[0010] As a further improvement of the present invention, the total number of the first coil assembly and the second coil assembly is at least six.

[0011] As a further improvement of the present invention, the total number of the first coil assembly and the second coil assembly is seven.

[0012] As a further improvement of the present invention, the total number of the first coil assembly and the second coil assembly is eight, including six first coil assemblies and two second coil assemblies. The central axes of every three first coil assemblies intersect each other perpendicularly in space, and the central axes of the two second coil assemblies are orthogonal to each other.

[0013] As a further improvement of the present invention, the housing includes a front shell and a rear shell fixedly installed with the front shell. The back of the front shell is provided with a plurality of mounting slots. The first coil assembly and the second coil assembly are respectively embedded in the corresponding mounting slots, and the central axis of the first coil assembly or the second coil assembly coincides with the central axis of the corresponding mounting slot.

[0014] As a further improvement of the present invention, the first coil assembly and the second coil assembly respectively include a solenoid coil and a coil retainer, and each solenoid coil is respectively sleeved on the corresponding coil retainer; each coil retainer is fixed to the corresponding mounting groove with glue.

[0015] As a further improvement of the present invention, the housing is provided with a mounting hole for the drive cable to pass through. One end of the drive cable extends into the housing through the mounting hole and is electrically connected to each of the solenoid coils, while the other end is exposed outside.

[0016] As a further improvement of the present invention, the magnetic field generator also includes a memory electrically connected to the drive cable.

[0017] As a further improvement of the present invention, the magnetic field generator further includes a control circuit, which is communicatively connected to the memory; the control circuit is used to receive the magnetic moment parameters of each of the solenoid coils transmitted externally, and write the magnetic moment parameters into the memory.

[0018] This invention also discloses a method for preparing a magnetic field generator, comprising: Step 1: Set up a housing, the housing having multiple mounting slots, the multiple mounting slots including orthogonal mounting slot groups, the number of orthogonal mounting slot groups being one or more groups, each group of orthogonal mounting slot groups consisting of three mounting slots, and the axes of the three mounting slots in the group intersecting perpendicularly to each other. Step 2: Embed each coil assembly into the corresponding mounting slot, so that the central axis of each coil assembly coincides with the central axis of the corresponding mounting slot. The three coil assemblies embedded in the same set of three mounting slots constitute a set of triaxial orthogonal coil assemblies. Then, fix each coil assembly to its corresponding mounting slot with glue. The coil assembly includes a solenoid coil and a coil retainer for fixing the solenoid coil.

[0019] As a further improvement of the present invention, in step 1, the plurality of mounting slots further include auxiliary mounting slots, and the coil assembly embedded in the auxiliary mounting slot is an auxiliary coil assembly. The central axis of the auxiliary mounting slot is orthogonal to the central axis of at least one mounting slot in the triaxial orthogonal mounting slot group; or when there are two auxiliary mounting slots, the central axes of the two auxiliary mounting slots are orthogonal to each other.

[0020] As a further improvement of the present invention, in step 1, the preparation method further includes: Step 3: Calibrate each solenoid coil to obtain the magnetic moment parameters of each solenoid coil, and write the magnetic moment parameters into the memory through the control circuit.

[0021] As a further improvement of the present invention, the number of mounting slots is six, the number of coil assemblies is six, and the six coil assemblies are arranged in a one-to-one correspondence with the six mounting slots.

[0022] As a further improvement of the present invention, the number of mounting slots is seven, the number of coil assemblies is seven, and the seven coil assemblies are arranged in a one-to-one correspondence with the seven mounting slots.

[0023] As a further improvement of the present invention, the number of mounting slots is eight, the number of orthogonal mounting slot groups is two groups, each group of orthogonal mounting slot groups consists of three mounting slots, and the axes of the three mounting slots in the group intersect each other perpendicularly; the number of auxiliary mounting slots is two, and the central axes of the two auxiliary mounting slots are orthogonal to each other; the number of coil assemblies is eight, and the eight coil assemblies are arranged in a one-to-one correspondence with the eight mounting slots.

[0024] The present invention also discloses an electromagnetic positioning system, including the magnetic field generator described in the present invention.

[0025] The beneficial effects of this invention are as follows: This invention constructs an ideal orthogonal magnetic field base by forming a triaxial orthogonal group through the pairwise perpendicular intersection of three first coil components. Mathematically, this yields the simplest solution model, effectively reducing the complexity of iterative solutions and minimizing the computational load for positioning. Simultaneously, the compact triaxial orthogonal arrangement layout maximizes space utilization. The inclusion of the second coil components further improves the magnetic field uniformity and total magnetic sensitivity in the measurement domain, thereby achieving optimal positioning performance within the measurement area. In other words, by improving the coil layout, this invention can achieve the highest total magnetic sensitivity in the measurement area, thus achieving optimal positioning performance; while maintaining two sets of triaxial orthogonal coils and one set of mutually orthogonal coils minimizes the computational load for positioning. Attached Figure Description

[0026] Figure 1 This is an overall structural diagram of the magnetic field generator of the present invention; Figure 2 This is a schematic diagram of the magnetic field sensitivity distribution of a single solenoid coil; Figure description: 10-front shell, 20-mounting slot, 30-sowary coil, 40-coil holder, 50-memory, 60-drive cable. Detailed Implementation

[0027] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0028] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components.

[0029] The present invention discloses a magnetic field generator, comprising: a housing and a magnetic field generating unit disposed within the housing. The magnetic field generating unit includes one or more sets of triaxial orthogonal coil assemblies, each set of triaxial orthogonal coil assemblies being composed of three first coil assemblies, the central axes of the three first coil assemblies being perpendicularly intersecting each other in space.

[0030] The magnetic field generating unit also includes an auxiliary coil assembly, which includes one or more second coil assemblies. The central axis of each second coil assembly is orthogonal to the central axis of at least one first coil assembly in the triaxial orthogonal coil assembly; or the central axes of any two of the second coil assemblies are orthogonal to each other; the total number of first coil assemblies and second coil assemblies is at least six.

[0031] The first coil assembly and the second coil assembly each include a solenoid coil 30 and a coil holder 40. The solenoid coil 30 is a hollow structure, and each solenoid coil 30 is respectively sleeved on the corresponding coil holder 40. The coil holder 40 is used to determine the position and central axis direction of the solenoid coil 30 in the housing.

[0032] The housing includes a front shell 10 and a rear shell fixedly mounted to the front shell 10. The back of the front shell 10 has multiple mounting slots 20. A first coil assembly and a second coil assembly are respectively embedded in their corresponding mounting slots 20, and the central axis of the first or second coil assembly coincides with the central axis of the corresponding mounting slot 20. The inner wall of the mounting slot 20 provides radial support and axial positioning for the solenoid coil. Each coil retainer 40 is fixed to its corresponding mounting slot 20 with adhesive.

[0033] The housing has mounting holes for the drive cable 60 to pass through. One end of the drive cable 60 extends into the housing through the mounting holes and is electrically connected to each solenoid coil 30, while the other end remains exposed. The drive cable 60 is used to transmit control signals to each solenoid coil 30. To avoid affecting the magnetic field, the housing is made of plastic.

[0034] In one embodiment of the present invention, the total number of first coil assemblies is six. These include two sets of triaxial orthogonal coil assemblies, each set consisting of three first coil assemblies, the central axes of which intersect each other perpendicularly in space.

[0035] In one embodiment of the present invention, the total number of first coil assemblies and second coil assemblies is seven. The triaxial orthogonal coil assemblies form a group (i.e., three first coil assemblies), whose central axes extend along the X-axis, Y-axis, and Z-axis directions, respectively. The auxiliary coil assemblies consist of four second coil assemblies, wherein their central axes are orthogonal to the central axis of at least one of the first coil assemblies in the triaxial orthogonal coil assemblies. Specifically, the central axes of two of the second coil assemblies are parallel to the X-axis direction, and the other two are parallel to the Y-axis direction, such that the magnetic field direction generated by each auxiliary coil is orthogonally superimposed with the magnetic field direction generated by the corresponding first coil assembly, thereby forming a composite magnetic field covering multiple orthogonal directions within the measurement domain.

[0036] In another embodiment, the triaxial orthogonal coil assembly consists of two groups (i.e., six first coil assemblies), and the auxiliary coil assembly is composed of a second coil assembly whose central axis is orthogonal to the central axis of at least one of the first coil assemblies in one of the triaxial orthogonal coil assemblies.

[0037] In some locations, especially near the axis of the transmitting coil, the induced electromotive force of one or two transmitting coils may be very small, leading to a large error. To compensate for this excessive error, the present invention also designs a preferred embodiment in which the total number of first coil assemblies and second coil assemblies is eight. Specifically, the magnetic field generating unit includes six first coil assemblies and two second coil assemblies. The central axes of every three first coil assemblies intersect each other perpendicularly in space, corresponding to the X-axis, Y-axis, and Z-axis of the spatial rectangular coordinate system, respectively. The intersection point of these three axes is the geometric center of the three-axis orthogonal coil assembly. The central axes of the two second coil assemblies are mutually orthogonal. Figure 1 As shown, the first coil assemblies 1, 3, and 4 are orthogonal to each other, the first coil assemblies 5, 6, and 8 are orthogonal to each other, and the second coil assemblies 7 and 2 are orthogonal to each other.

[0038] In this invention, the total number of coil assemblies is set to at least six to meet the basic requirements of solving six degrees of freedom; when the number is more than six, the extra coil assemblies can provide redundant measurement information for error correction in iterative optimization, thereby improving positioning accuracy.

[0039] The above coil arrangement is merely an example. Those skilled in the art can select any arrangement that satisfies at least six coils and at least one set of triaxial orthogonal coils according to actual magnetic field requirements, and all such arrangements fall within the protection scope of this invention.

[0040] The magnetic field generator also includes a memory 50, which is electrically connected to the drive cable 60. The memory 50 is primarily used to store the magnetic moment parameters of each solenoid coil 30, such as the orientation relationship between coils, the equivalent radius and angle of each coil, etc. These magnetic moment parameters are obtained during the production calibration process of each solenoid coil 30. As a preferred embodiment, the memory 50 can be a circuit board with an EEPROM mounted on the front housing 10. Alternatively, the memory 50 can be an EEPROM chip, which is directly soldered to the connector of the drive cable 60.

[0041] After obtaining the parameters of the solenoid coil 30, the coil magnetic moment parameters are written into the EEPROM chip through other control circuits (such as the main control MCU). During real-time positioning calculation, the coil magnetic moment information is read from the EEPROM chip for positioning calculation.

[0042] Because the manufacturing process of the solenoid coil 30, housing, and coil holder 40 cannot perfectly match the design, there will be some deviation. Therefore, calibration is required before actual use. The actual magnetic field generated by the magnetic field generator is measured to iterate the true magnetic moment (including magnitude, position, and angle) of the transmitting coil (soleoid coil 30). The calibration process is as follows: Three magnetic field sensors are orthogonally arranged in the X, Y, and Z directions to collect triaxial magnetic field strength data. Simultaneously, an optical positioning device is used to obtain the spatial pose relationship between the magnetic field generator and the sensors. During calibration, the sensors are fixed to the end of a collaborative robotic arm, which moves the sensors above the magnetic field generator along a preset path, simultaneously collecting sensor pose information and corresponding magnetic field strength data at multiple spatial locations.

[0043] Subsequently, using a theoretical magnetic field model of the coil as the forward model, such as a magnetic dipole model or a coil magnetic field model based on the Biot-Savart law, the equivalent magnetic moment magnitude, spatial position, and attitude angle of the transmitting coil are taken as parameters to be determined. Through nonlinear least squares methods, such as the Gauss-Newton method or the Levenberg-Marquardt algorithm, the sum of squared errors between the theoretically calculated magnetic field and the actual measured magnetic field is minimized, thereby inversely calculating the actual magnetic moment parameters of each transmitting coil, including the magnetic moment magnitude, the coil center position, and the attitude angle corresponding to the coil axis. In actual solution processing, the coil's structural design parameters can be used as initial values ​​to improve the convergence speed and stability of parameter identification.

[0044] After obtaining the actual magnetic moment parameters of each transmitting coil, the host computer or calibration control program can organize the parameters corresponding to each coil into a fixed data format, including coil number, magnetic moment magnitude, position coordinates, attitude angle, check code, etc., and send them to the control circuit of the magnetic field generator via serial port, USB, CAN, or other communication interfaces. After receiving the data, the control circuit performs format verification and confirmation. Once confirmed to be correct, it writes the set of coil magnetic moment parameters into a predetermined storage address in the EEPROM, thus achieving parameter solidification and storage.

[0045] To enable data exchange between the control circuit and the EEPROM chip, the two are electrically connected via a data bus.

[0046] It should be noted that the communication protocol of the data bus is not limited to a specific form. Preferably, the control circuit and the EEPROM chip communicate using an I2C bus or an SPI bus.

[0047] To simplify the wiring layout within the housing and reduce the number of connection terminals, the control circuit and the EEPROM chip are connected using a one-wire communication protocol. Furthermore, this one-wire bus serves as both a data line and a power line; that is, the control circuit transmits read / write commands and data to the EEPROM and provides operating voltage to the EEPROM chip through this one-wire bus, thus eliminating the need for an additional independent power supply cable for the EEPROM chip.

[0048] During real-time positioning calculations, after the system starts or enters positioning mode, the control circuit first reads the actual magnetic moment parameters of each coil from the EEPROM chip and loads them into the positioning calculation module. Then, the control circuit drives each transmitting coil to operate according to a preset timing sequence, and the sensor collects the corresponding magnetic field data. When calculating the sensor position and attitude, the positioning algorithm no longer uses ideal design parameters, but instead calls the actual coil magnetic moment magnitude, position, and angle parameters stored in the EEPROM chip as magnetic field model parameters, thereby establishing a calculation model that more closely resembles the real magnetic field and improving positioning accuracy. Version numbers and checksums can also be added during the reading process; if the checksum fails, a prompt for recalibration or the use of default parameters is displayed.

[0049] This invention also discloses a method for preparing a magnetic field generator, comprising: Step 1: Set up a housing with multiple mounting slots 20 inside. The multiple mounting slots 20 include orthogonal mounting slot groups. The number of orthogonal mounting slot groups is one or more groups. Each orthogonal mounting slot group consists of three mounting slots 20, and the axes of the three mounting slots 20 in the group intersect each other perpendicularly.

[0050] Step 2: Embed each coil assembly into its corresponding mounting slot 20, so that the central axis of each coil assembly coincides with the central axis of the corresponding mounting slot 20. The three coil assemblies embedded in the same set of three mounting slots 20 constitute a set of triaxial orthogonal coil assemblies. Then, fix each coil assembly to its corresponding mounting slot 20. The coil assembly includes a solenoid coil 30 and a coil holder 40 for fixing the solenoid coil 30.

[0051] As a second embodiment, in step 1, the plurality of mounting slots 20 further include auxiliary mounting slots, and the coil assembly embedded in the auxiliary mounting slot is an auxiliary coil assembly. The central axis of the auxiliary mounting slot is orthogonal to the central axis of at least one mounting slot in the triaxial orthogonal mounting slot group; or when there are two auxiliary mounting slots, the central axes of the two auxiliary mounting slots are orthogonal to each other.

[0052] As a third embodiment, in step 1, the preparation method further includes: Step 3: Calibrate each solenoid coil 30 to obtain the magnetic moment parameters of each solenoid coil 30, and write the magnetic moment parameters into the memory 50 through the control circuit.

[0053] In the fourth embodiment, there are six mounting slots 20 and six coil assemblies, with each of the six coil assemblies corresponding to one of the six mounting slots 20.

[0054] In the fifth embodiment, there are seven mounting slots 20 and seven coil assemblies, with each of the seven coil assemblies corresponding to one of the seven mounting slots 20.

[0055] As a sixth embodiment, there are eight mounting slots 20, two sets of orthogonal mounting slots, each set of orthogonal mounting slots consisting of three mounting slots 20, and the axes of the three mounting slots 20 in the set intersect each other perpendicularly; there are two auxiliary mounting slots, and the central axes of the two auxiliary mounting slots are orthogonal to each other; there are eight coil assemblies, and the eight coil assemblies are arranged in a one-to-one correspondence with the eight mounting slots 20.

[0056] The present invention also discloses an electromagnetic positioning system, which includes the aforementioned magnetic field generator.

[0057] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A magnetic field generator, characterized in that, include: The housing and a magnetic field generating unit disposed within the housing, the magnetic field generating unit comprising one or more sets of triaxial orthogonal coil assemblies, each set of the triaxial orthogonal coil assemblies consisting of three first coil assemblies, the central axes of the three first coil assemblies intersecting perpendicularly in space.

2. The magnetic field generator according to claim 1, characterized in that: The magnetic field generating unit further includes an auxiliary coil assembly, which includes one or more second coil assemblies. The central axis of each second coil assembly is orthogonal to the central axis of at least one first coil assembly in the triaxial orthogonal coil assembly; or the central axes of any two of the second coil assemblies are orthogonal to each other.

3. The magnetic field generator according to claim 1, characterized in that: The total number of the first coil assembly is six.

4. The magnetic field generator according to claim 2, characterized in that: The total number of the first coil assembly and the second coil assembly is eight, including six first coil assemblies and two second coil assemblies. The central axes of every three first coil assemblies intersect each other perpendicularly in space, and the central axes of the two second coil assemblies are orthogonal to each other.

5. The magnetic field generator according to claim 2, characterized in that: The housing includes a front shell (10) and a rear shell fixedly installed with the front shell (10). The back of the front shell (10) is provided with a plurality of mounting slots (20). The first coil assembly and the second coil assembly are respectively embedded in the corresponding mounting slots (20), and the central axis of the first coil assembly or the second coil assembly coincides with the central axis of the corresponding mounting slot (20). The first coil assembly and the second coil assembly each include a solenoid coil (3) and a coil holder (40), and each solenoid coil (3) is respectively sleeved on the corresponding coil holder (40); each coil holder (40) is fixedly connected to the corresponding mounting groove (20).

6. The magnetic field generator according to claim 5, characterized in that: The magnetic field generator also includes a control circuit, which is communicatively connected to a memory (50); the control circuit is used to receive the magnetic moment parameters of each of the solenoid coils (3) sent from the outside and write the magnetic moment parameters into the memory (50).

7. A method for preparing a magnetic field generator, characterized in that, include: Step 1: Set up a housing, the housing having multiple mounting slots (20) inside, the multiple mounting slots (20) including orthogonal mounting slot groups, the number of orthogonal mounting slot groups is one or more groups, each group of orthogonal mounting slot groups consists of three mounting slots (20), and the axes of the three mounting slots (20) in the group intersect each other perpendicularly. Step 2: Each coil assembly is embedded in the corresponding mounting slot (20) so that the central axis of each coil assembly coincides with the central axis of the corresponding mounting slot (20). The three coil assemblies embedded in the same set of three mounting slots (20) constitute a set of triaxial orthogonal coil assemblies. Then, each coil assembly is fixedly connected to the corresponding mounting slot (20). The coil assembly includes a solenoid coil (30) and a coil holder (40) for fixing the solenoid coil (30).

8. The preparation method according to claim 7, characterized in that, In step 1, the plurality of mounting slots (20) further include auxiliary mounting slots, and the coil assembly embedded in the auxiliary mounting slot is an auxiliary coil assembly. The central axis of the auxiliary mounting slot is orthogonal to the central axis of at least one mounting slot in the triaxial orthogonal mounting slot group; or when there are two auxiliary mounting slots, the central axes of the two auxiliary mounting slots are orthogonal to each other.

9. The preparation method according to claim 7, characterized in that, In step 1, the preparation method further includes: Step 3: Calibrate each of the solenoid coils (30) to obtain the magnetic moment parameters of each solenoid coil (30), and write the magnetic moment parameters into the memory (50) through the control circuit.

10. An electromagnetic positioning system, characterized in that: Includes the magnetic field generator according to any one of claims 1-6.

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