Electromagnetic tracking system magnetic field generator and control method

Abstract

The present application relates to electromagnetic tracking system magnetic field generating device and control method, the magnetic field generating device includes a plurality of transmitting coils arranged in a tile, and an equivalent transmitting unit is formed by at least three transmitting coils adjacent to each other; The center of the transmitting coil in the equivalent transmitting unit is concentric and the size is the same; The equivalent transmitting unit is used to excite at a certain moment, and the equivalent transmitting unit is equivalent to an independent transmitting unit; The equivalent transmitting units excited at adjacent moments have multiplexed transmitting coils. The control method is to make the equivalent transmitting units excited at adjacent moments generate alternating magnetic field through the adjustable pulse width alternating pulse signal. The equivalent transmitting unit and the multiplexed form of the transmitting coil of the present application can increase the magnetic field intensity in the tracking area, reduce the field intensity decay rate in the tracking area, and further improve the positioning and tracking performance. The alternating pulse signal can realize stable control of the magnetic field generated by the transmitting coil, and the remaining magnetic field is quickly eliminated between the switching of different excitation moments, thereby improving the tracking and positioning efficiency.

Description

Technical Field

[0001] This invention relates to the field of positioning and motion tracking, specifically to an electromagnetic tracking system that uses a magnetic field to determine the position and orientation of an object. Background Technology

[0002] Positioning and motion tracking systems can express and describe the location and orientation of target nodes in real time. Today, there are various positioning and motion tracking technologies, among which electromagnetic tracking systems are widely used due to their advantage of not being affected by line-of-sight obstruction. For example, in the medical field, stereotactic navigation has extremely high requirements for precise positioning; fixing sensors to the target point allows for real-time dynamic tracking and positioning of the target point.

[0003] Despite the significant advantage of electromagnetic tracking and positioning technology being unaffected by line-of-sight, its effective tracking range still needs improvement compared to other motion tracking technologies such as optical tracking and positioning. The limited effective measurement range is primarily due to the use of rapidly decaying magnetic signals as the positioning medium in electromagnetic tracking and positioning systems. This results in extremely weak magnetic signals in the far field, making signal acquisition difficult. Furthermore, the gradient change in the far field is too gradual, making it impossible to obtain significantly different magnetic signals between two nearby points. This is detrimental to electromagnetic tracking and positioning systems that rely on magnetic gradient changes for precise positioning. Additionally, current electromagnetic tracking and positioning technology is based on a far-field model of a magnetic dipole, leading to poor accuracy in modeling the magnetic field in the near field. These drawbacks mean that current electromagnetic tracking and positioning systems only perform well at medium distances, with unsatisfactory positioning results at close and long distances.

[0004] In summary, the effective tracking and positioning range and accuracy of an electromagnetic tracking and positioning system are closely related to the spatial magnetic field distribution constructed by the magnetic field generator. It is necessary to ensure a high-intensity magnetic field throughout the entire measurement space, optimize the magnetic field attenuation characteristics to ensure a significant magnetic gradient change throughout the entire measurement space, and finally, rationally arrange the emission sources to limit non-tracking areas while ensuring a compact and small-scale magnetic field generator structure. Summary of the Invention

[0005] This invention provides a magnetic field generating device and control method for an electromagnetic tracking system. By using a multi-source equivalent and multiplexing method, it solves the problem of ensuring a high-intensity magnetic field and optimizing attenuation characteristics during axial measurement, thereby optimizing the spatial magnetic field distribution.

[0006] The present invention discloses an equivalent method for the transmitting unit and a multiplexing form for the transmitting coil in a magnetic field generating device, which can increase the magnetic field strength within the positioning and tracking area, reduce the field strength attenuation rate within the positioning and tracking area, and thus improve positioning and tracking performance. Through the excitation control unit, stable control of the magnetic field generated by the transmitting coil can be achieved, as well as rapid elimination of the residual magnetic field between different excitation times, thereby improving tracking and positioning efficiency.

[0007] The technical solution adopted by the present invention to achieve the above objectives is: an electromagnetic tracking system magnetic field generating device, comprising multiple transmitting coils arranged in a flat manner, wherein at least three adjacent transmitting coils constitute an equivalent transmitting unit; the transmitting coils in the equivalent transmitting unit are circular at their centers and have the same size;

[0008] The equivalent transmitting unit is used for excitation at a certain moment and is equivalent to an independent transmitting unit; the equivalent transmitting units excited at adjacent moments have multiplexed transmitting coils.

[0009] The part of the transmitting coil in the equivalent transmitting unit at time k+1 is the part of the transmitting coil in the equivalent transmitting unit at time k, so that the different equivalent transmitting units corresponding to the sequential excitation at different times generate multiple alternating magnetic fields, and each transmitting coil is excited multiple times in one tracking and positioning cycle.

[0010] In the equivalent transmitting unit, the center-to-center distance between any two adjacent transmitting coils that are concentric circles is a fixed value.

[0011] The equivalent transmitting unit contains N transmitting coils with the same size and a common center, where N≥3. Increasing the number of transmitting coils in the transmitting unit expands the magnetic field strength in the target area and reduces the field strength attenuation rate.

[0012] The equivalent transmitting unit contains N transmitting coils with a common center circle, where N≥3. The size of the transmitting coils is reduced so that the diameter of the circle containing the center of the transmitting coil is equal to the diameter of the circle containing the center of the transmitting coil when the size is not reduced, and the position of the center of the circle remains unchanged. That is, the size of the equivalent transmitting unit remains unchanged, so as to reduce the tracking error in the near field range.

[0013] The electromagnetic tracking system magnetic field generating device also includes an excitation control unit, which is used to achieve stable control of the magnetic field generated by the transmitting coil and rapid elimination of the residual magnetic field. The excitation control unit includes a microcontroller, a decoder, a full-bridge drive circuit, and current and magnetic field detection modules.

[0014] The microcontroller is used to generate logic pulse signals and control commands. The logic pulse signals are the pulse input waveforms required by the full-bridge drive circuit. Based on the feedback signals from the current and magnetic field detection module group, the microcontroller generates control commands and sends them to the decoder. The decoder controls the enable state of each full-bridge drive circuit to control the timing of the equivalent transmitter unit.

[0015] The decoder is used to generate an enable signal based on the control command in order to control the corresponding full-bridge drive circuit.

[0016] The full-bridge drive circuit is used to provide drive signals to the transmitting unit and control the excitation and triggering of a transmitting coil in the equivalent transmitting unit according to the enable signal;

[0017] The current and magnetic field detection module group includes a current sensor and a magnetic field sensor; the current sensor is connected in series between the full-bridge drive circuit and the transmitting coil, and the magnetic field sensor is located below the transmitting coil and coaxial with the transmitting coil; it is used to detect the excitation current value and the generated magnetic field strength value of the transmitting coil and feed them back to the microcontroller.

[0018] The microcontroller is used to add a reverse excitation signal by adjusting the control command at the end of each excitation signal cycle, so as to eliminate the residual magnetic field after the excitation cycle of the transmitting coil ends and shorten the switching time between adjacent excitation moments.

[0019] A control method for the magnetic field generator of an electromagnetic tracking system, wherein at a certain moment, an equivalent transmitting unit consisting of at least three adjacent transmitting coils is excited; the equivalent transmitting unit excited at adjacent moments generates an alternating magnetic field.

[0020] Based on the measured magnetic field and current values, the magnetic field strength of the equivalent transmitting unit is controlled as feedback values ​​to achieve stable control of the magnetic field generated by the transmitting coil. This includes the following steps:

[0021] The microcontroller generates logic pulse signals, which are the pulse input waveforms required by the full-bridge drive circuit.

[0022] The current and magnetic field detection module group detects the excitation current value and the generated magnetic field strength value of the transmitting coil and feeds them back to the microcontroller;

[0023] The microcontroller performs closed-loop control calculations for constant field strength output based on feedback signals from the current and magnetic field detection modules, generates control commands, and sends them to the decoder. The decoder controls the enable state of each full-bridge drive circuit to control the timing of the equivalent transmitter unit.

[0024] The full-bridge drive circuit controls the excitation and triggering of a certain transmitting coil in the equivalent transmitting unit according to the enable signal.

[0025] The microcontroller performs rapid elimination of the residual magnetic field as follows: at the end of each excitation signal cycle, a reverse excitation signal is added by adjusting the control command to eliminate the residual magnetic field after the excitation cycle of the transmitting coil ends, thus shortening the switching time between adjacent excitation moments.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] 1. This invention employs a method of using multiple transmitting coils as equivalent to a large-size transmitting unit. The multiple transmitting units adopt a time-division excitation strategy with the same frequency but different timing. Without increasing the non-tracking area, the magnetic field strength of the magnetic field generating device in the target area is increased, thereby expanding the effective tracking and positioning range of the electromagnetic tracking and positioning system and improving the tracking and positioning accuracy of the target area.

[0028] 2. The equivalent transmitting unit used in this invention optimizes the attenuation characteristics of the axial magnetic field strength in the target area, reduces the attenuation rate of the magnetic field strength, and makes the magnetic field distribution in the target area more uniform. At the same time, in the weak magnetic region at a distance from the field generating device along the axis, there is a magnetic field gradient change that meets the tracking and positioning requirements, ensuring that the magnetic sensor can sense magnetic field signals of different intensities when making small movements in the far field, thereby obtaining better tracking and positioning performance in the far field.

[0029] 3. In this invention, the magnetic field generating device adopts a multiple-reuse method for multiple transmitting coils. Through reasonable arrangement, it achieves the effect of a strong spatial magnetic field using a smaller number of transmitting coils, thereby reducing the size of the magnetic field generating device and making the structure more compact.

[0030] 4. This invention has high scalability. Expansion method one: with the transmitter coil size unchanged, increasing the number of transmitter coils is equivalent to a larger transmitter unit, which can obtain a larger magnetic field strength and a smaller field strength attenuation rate in the tracking area, thereby obtaining better tracking and positioning accuracy. Expansion method two: reducing the transmitter coil size and increasing the number of transmitter coils while keeping the equivalent transmitter unit size unchanged can reduce the tracking error in the area near the magnetic field generating device, thereby increasing the tracking area.

[0031] 5. This invention transmits the excitation current value and the field strength value of the transmitting coil to the microcontroller, and through closed-loop feedback control, enables the transmitting unit to generate a stable magnetic field, meeting the requirements of high-precision measurement.

[0032] 6. The present invention, through the reverse excitation control method, can quickly eliminate the phenomenon of slow magnetic field decline in the transmitting unit due to inductive load, thereby increasing the transmitting efficiency of the transmitting unit and the detection efficiency of the tracking and positioning system, and improving the refresh rate of real-time position and orientation detection. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the equivalent transmitting unit and multiplexing excitation method of a magnetic field generator.

[0034] Figure 2 This is a schematic diagram of the circuit processing for an electromagnetic induction three-dimensional force sensor.

[0035] Figure 3 A comparison diagram of the attenuation characteristics of axial magnetic field strength of various equivalent transmitting units;

[0036] Figure 4 A schematic diagram of an expansion method for the equivalent transmitting unit of a magnetic field generator;

[0037] Figure 5 This is a schematic diagram of the second expansion method of the equivalent transmitting unit of the magnetic field generator;

[0038] Figure 6 A comparison diagram of near-field errors for two extended methods of the equivalent transmitting unit of a magnetic field generator.

[0039] Figure 7 This is a diagram illustrating a multiplexing example of an equivalent transmitting unit N=6 for a magnetic field generator.

[0040] Figure 8 This is a schematic diagram of the excitation control unit;

[0041] Figure 9 This is a schematic diagram of a feedback control magnetic field strength method;

[0042] Figure 10 A schematic diagram of a reverse pulse to eliminate the residual magnetic field;

[0043] Figure 11 This is a schematic diagram of the excitation control process of a magnetic field generator. Detailed Implementation

[0044] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0045] This invention proposes a magnetic field generating device for an electromagnetic tracking system based on multiple transmitting coils coupled into an equivalent transmitting unit. The equivalent transmitting unit can contain 3, 4, 6, 8, or even N transmitting coils, with multiplexing relationships between the coils. This results in a more compact magnetic field generating device that exhibits a high-intensity spatial magnetic field distribution with better gradient changes within the space of interest. The magnetic field generating device control method of this invention uses a microprocessor's pulse control signal to control a full-bridge drive circuit to output an alternating pulse signal with adjustable pulse width and period to generate a magnetic field for the transmitting unit. A short-duration reverse pulse is cleverly introduced to solve the problem of residual magnetic field generated by the previous transmitting unit during time-division switching.

[0046] An electromagnetic tracking system magnetic field generating device comprises an equivalent transmitting unit and a multiplexed transmitting coil arranged according to a certain rule, wherein:

[0047] The equivalent transmitting unit consists of six small equilateral triangles formed by three adjacent transmitting coils arranged in an equilateral triangle, and two large equilateral triangles formed by six adjacent transmitting coils arranged in an equilateral triangle. The transmitting coils in each equilateral triangle are excited at the same time, which is equivalent to an independent transmitting unit, increasing the magnetic field strength in the tracking area and reducing the field strength attenuation rate in the tracking area.

[0048] In the multiplexing of the transmitting coils, the eight transmitting units are sequentially excited at eight different times to generate multiple magnetic fields. The transmitting units excited at adjacent times have multiplexing transmitting coils, and each transmitting coil is excited multiple times within a tracking and positioning cycle.

[0049] The equivalent transmitting unit consists of transmitting coils 1, 2, and 4 forming the first transmitting unit, which is simultaneously excited at the first moment; transmitting coils 2, 4, and 5 forming the second transmitting unit, which is simultaneously excited at the second moment; and transmitting coils 2, 3, and 5 forming the third transmitting unit, which is simultaneously excited at the third moment. In this way, by sequentially exciting the eight transmitting units at different moments, the alternating magnetic field required by the electromagnetic tracking system is generated.

[0050] Extension Method 1: The equivalent transmitting unit can be composed of N transmitting coils of the same size. The N transmitting coils are arranged in a circular shape by connecting their center points to form a larger equivalent transmitting unit, resulting in a larger magnetic field strength and a smaller field strength attenuation rate in the tracking area; adjacent different transmitting units have multiplexed transmitting coils.

[0051] Extension Method 2: It can also be equivalently constructed by N transmitting coils smaller than those in Extension Method 1. The N transmitting coils are arranged in a ring shape by connecting their center points. The resulting equivalent transmitting unit has the same size as the transmitting unit described in Extension Method 1, which reduces the tracking error in the area near the magnetic field generating device and increases the tracking area. Adjacent different transmitting units have multiplexed transmitting coils.

[0052] An electromagnetic tracking system magnetic field generating device includes an excitation control unit. The excitation control unit comprises a microcontroller, a decoder, a full-bridge drive circuit, and current and magnetic field detection modules. It generates periodic pulse excitation signals to sequentially excite transmitting units at different times. In the excitation control unit, the output of the microcontroller is connected to the input of the decoder; the output of the microcontroller is connected to the logic control terminal of the full-bridge drive circuit; the output of the decoder is connected to the enable terminal of the full-bridge drive circuit; the output of each full-bridge inverter circuit is connected to each transmitting coil; and current and magnetic field sensor circuits are connected to the input of the microcontroller.

[0053] The excitation control unit detects the excitation current value and the generated magnetic field strength value of the transmitting coil through the current and magnetic field detection modules, and uses these as feedback quantities to control the transmitting coil and the transmitting unit to generate a stable magnetic field.

[0054] The excitation control unit eliminates the residual magnetic field after the excitation cycle of the transmitting coil ends by using a short-time reverse excitation signal, thus shortening the switching time between adjacent excitation moments.

[0055] Combination Figure 1 and Figure 2Specific implementation scheme one: A magnetic field generating device based on a time-division excitation strategy that converts multiple transmitting coils into an equivalent transmitting unit. This invention adopts a combination of three equivalent transmitting coils and six equivalent transmitting coils. The multiple transmitting coils in the equivalent transmitting unit are arranged according to the fact that their center points are located at the points where the circle is equally divided in the equivalent ring. For example, the line connecting the center points of the three transmitting coils will form an equilateral triangle, forming an equivalent transmitting unit. At the first moment, the first transmitting unit composed of transmitting coils 1, 2, and 4 is turned on to generate the first time-varying magnetic field, while the other coils are inactive. At the second moment, the second transmitting unit composed of transmitting coils 2, 4, and 5 is turned on to generate the second time-varying magnetic field, while the other coils are inactive. This process continues, sequentially activating transmitting coils 2, 3, and 5; transmitting coils 5, 7, and 8; transmitting coils 4, 5, and 7; transmitting coils 4, 6, and 7; transmitting coils 2, 4-8; and transmitting coils 1-5 and 7. A total of eight conducting groups constitute one tracking and positioning cycle to complete the tracking and positioning of one point.

[0056] This invention employs a multiplexing approach for transmitting coils. For example, transmitting coil 1 belongs to both the first and eighth conducting units, and transmitting coil 2 belongs to the first, second, third, seventh, and eighth conducting units. This multiplexing principle, through rational arrangement, achieves the target magnetic field strength using as few transmitting coils as possible, reducing the overall size of the magnetic field generator, lowering power consumption, and reducing circuit complexity. In this invention, eight transmitting coils achieve the effect that might have previously required thirty.

[0057] Combination Figure 3 Explanation of Implementation Scheme 2: Comparing the advantages and disadvantages of a single transmitting coil versus three equivalent transmitting coils versus six equivalent transmitting coils in the non-equivalent case in terms of magnetic field strength and gradient, it can be seen that as the number of equivalent transmitting coils increases, the spatial magnetic field strength increases, and the magnetic field attenuation rate from the magnetic source to the external radiation direction decreases.

[0058] Combination Figure 3 and Figure 4 Specific implementation scheme three: A method for expanding the transmitting unit is proposed. This method increases the number of transmitting coils to N while keeping the size of the transmitting coil unchanged. The N transmitting coils are arranged in a circular shape by connecting their center points to form a large-size equivalent transmitting unit, thereby increasing the magnetic induction intensity in the region of interest and improving the linear characteristics of magnetic field attenuation from the magnetic source to the outside.

[0059] Combination Figure 5 and Figure 6The fourth implementation scheme is described, which proposes another method for expanding the transmitter unit. This method reduces the size of the transmitter coil and increases the number to N while keeping the equivalent transmitter unit size unchanged. The N transmitter coils are then arranged in a circular shape by connecting their center points to form an equivalent transmitter unit, thereby increasing the model accuracy in the near-field region of interest and thus improving the solution accuracy.

[0060] Combination Figure 7 The fifth specific implementation scheme describes an example of a magnetic field generating device with an equivalent number of transmitting coils N=6, based on the two equivalent transmitting unit expansion methods and the transmitting coil multiplexing method.

[0061] Combination Figure 8 and Figure 2 In implementation scheme six, the microcontroller's I / O ports are connected as control signals to the decoder's inputs. The decoder's outputs are connected to the enable interface of the full-bridge driver circuit, with a TTL control level. The microcontroller controls the timing of the transmitting units by controlling whether each full-bridge driver circuit is enabled through the decoder. The microcontroller outputs a pair of logically opposite pulse control signals to the logic control input interface of the full-bridge driver circuit, also at a TTL level. The microprocessor can modulate the pulse period and pulse width of the pulse signals.

[0062] The microprocessor's pulse control signal controls the full-bridge drive circuit to output an alternating pulse signal with adjustable pulse width and period to generate a magnetic field for the transmitting unit. Each excitation cycle is 2 and 1 / 2 cycles. Through the enable signal of the decoder, the microprocessor uses time-division control to select and activate each transmitting unit individually, thus periodically energizing the eight transmitting units. The pulse begins with a high level of 1 / 4 cycle, followed by two complete cycles of alternating pulse signals, and ends with a low level of 1 / 4 cycle. This pulse waveform drives the transmitting unit, which generates an alternating magnetic field waveform.

[0063] Combination Figure 8 and Figure 9Specific implementation scheme seven describes a method where a constantan wire sampling resistor is added between the full-bridge drive circuit and the transmitting unit in the excitation circuit to measure the current value of each excitation current. A Hall effect magnetic field sensor is installed coaxially below the transmitting unit to measure the magnetic field strength of each transmitting unit. The analog signal output is connected to the microcontroller's I / O port for ADC analog signal acquisition. The measured magnetic field and current values ​​are used as feedback values ​​to control the magnetic field strength of the transmitting unit. The magnetic field strength control loop acts as the outer loop of the control system to regulate the magnetic field strength; the current change generated by the outer loop controller serves as the control input for the inner current loop of the control system, enabling closed-loop current control. The method used is as follows: under the premise that the overall excitation cycle of the transmitting unit remains unchanged, the enable duration of the full-bridge circuit is adjusted by the decoder controlled by the microcontroller, which can increase or decrease the pulse enable duration within the excitation cycle of the transmitting unit. When the pulse conduction duration within the transmitting unit is increased, the current within the transmitting unit will continuously increase, and the magnetic field will also increase accordingly, and vice versa, thereby adjusting the magnetic field strength of the transmitting unit. By controlling the pulse enable duration within the excitation cycle of the transmitting unit, the magnetic field strength of the transmitting unit can be stably output.

[0064] Combination Figure 10 Specific implementation plan eight describes the transmitting unit as a coil winding, which is an inductive load and serves as an energy storage component. After energizing the transmitting unit, the magnetic field does not immediately decrease to zero but requires a slow, gradual decline over a certain period. (Combined with...) Figure 7 The excitation control in this design employs time-sharing control, with the transmitting units being excited sequentially. However, the residual magnetic field from the previous transmitting unit can interfere with the measurement of the excitation magnetic field in the next transmitting unit. To eliminate the residual magnetic field as quickly as possible, this patent proposes a control method. After excitation is completed, a reverse excitation pulse is added to the transmitting unit based on the current direction, magnitude, and magnetic field strength. The reverse pulse voltage quickly eliminates the magnetic field within the transmitting unit, thus not affecting the excitation and measurement of the magnetic field in the next transmitting unit.

[0065] Combination Figure 11 Specific implementation scheme nine is described below. The microcontroller generates a timing control signal and two logically opposite pulse control signals. The timing control signal is input to a decoder, which generates a control signal for the full-bridge drive circuit. The logic control signal is used as the input to the full-bridge drive circuit and amplified. After the current sensor measures the current in the current circuit, the amplified logic control signal activates different excitation coils in a time-division multiplexing manner to generate the required alternating magnetic field. At the same time, a magnetic field sensor measures the magnitude of the alternating magnetic field, and together with the acquired current value, it is used as feedback input to the microcontroller to control the pulse width of the enable signal input to the full-bridge drive circuit, thereby achieving closed-loop control and stabilizing the emitted magnetic field.

Claims

1. A magnetic field generating device for an electromagnetic tracking system, comprising multiple transmitting coils arranged in a flat configuration, characterized in that: An equivalent transmitting unit is formed by at least three adjacent transmitting coils; the transmitting coils in the equivalent transmitting unit are circular at their centers and have the same size; The equivalent transmitting unit is used for excitation at a certain moment and is equivalent to an independent transmitting unit; the equivalent transmitting units excited at adjacent moments have multiplexed transmitting coils; It also includes an excitation control unit for achieving stable control of the magnetic field generated by the transmitting coil and rapid elimination of the residual magnetic field. The excitation control unit includes a microcontroller, a decoder, a full-bridge drive circuit, and current and magnetic field detection modules. The microcontroller is used to generate logic pulse signals and control commands. The logic pulse signals are the pulse input waveforms required by the full-bridge drive circuit. Based on the feedback signals from the current and magnetic field detection module group, the microcontroller generates control commands and sends them to the decoder. The decoder controls the enable state of each full-bridge drive circuit to control the timing of the equivalent transmitter unit. The decoder is used to generate an enable signal based on the control command in order to control the corresponding full-bridge drive circuit. The full-bridge drive circuit is used to provide drive signals to the transmitting unit and control the excitation and triggering of a transmitting coil in the equivalent transmitting unit according to the enable signal; The current and magnetic field detection module group includes a current sensor and a magnetic field sensor; the current sensor is connected in series between the full-bridge drive circuit and the transmitting coil, and the magnetic field sensor is located below the transmitting coil and is coaxial with the transmitting coil; It is used to detect the excitation current value and the generated magnetic field strength value of the transmitting coil, and feed them back to the microcontroller.

2. The magnetic field generating device for the electromagnetic tracking system according to claim 1, characterized in that, The part of the transmitting coil in the equivalent transmitting unit at time k+1 is the part of the transmitting coil in the equivalent transmitting unit at time k, so that the different equivalent transmitting units corresponding to the sequential excitation at different times generate multiple alternating magnetic fields, and each transmitting coil is excited multiple times in one tracking and positioning cycle.

3. The magnetic field generating device for the electromagnetic tracking system according to claim 1, characterized in that, In the equivalent transmitting unit, the center-to-center distance between any two adjacent transmitting coils that are concentric circles is a fixed value.

4. The magnetic field generating device for the electromagnetic tracking system according to claim 1, characterized in that, The equivalent transmitting unit contains N transmitting coils with the same size and a common center, where N≥3. Increasing the number of transmitting coils in the transmitting unit expands the magnetic field strength in the target area and reduces the field strength attenuation rate.

5. The magnetic field generating device for the electromagnetic tracking system according to claim 1, characterized in that, The equivalent transmitting unit contains N transmitting coils with a common center circle, where N≥3. The size of the transmitting coils is reduced so that the diameter of the circle containing the center of the transmitting coil is equal to the diameter of the circle containing the center of the transmitting coil when the size is not reduced, and the position of the center of the circle remains unchanged. That is, the size of the equivalent transmitting unit remains unchanged, so as to reduce the tracking error in the near field range.

6. The magnetic field generating device for the electromagnetic tracking system according to claim 1, characterized in that, The microcontroller is used to add a reverse excitation signal by adjusting the control command at the end of each excitation signal cycle, so as to eliminate the residual magnetic field after the excitation cycle of the transmitting coil ends and shorten the switching time between adjacent excitation moments.

7. A control method for a magnetic field generating device in an electromagnetic tracking system, wherein the method is applied to the magnetic field generating device of the electromagnetic tracking system as described in claim 1, characterized in that, At a certain moment, an equivalent transmitting unit consisting of at least three adjacent transmitting coils is excited; the equivalent transmitting unit excited at adjacent moments generates an alternating magnetic field.

8. The control method for the magnetic field generating device of the electromagnetic tracking system according to claim 7, characterized in that, Based on the measured magnetic field and current values, the magnetic field strength of the equivalent transmitting unit is controlled as feedback values ​​to achieve stable control of the magnetic field generated by the transmitting coil. This includes the following steps: The microcontroller generates logic pulse signals, which are the pulse input waveforms required by the full-bridge drive circuit. The current and magnetic field detection module group detects the excitation current value and the generated magnetic field strength value of the transmitting coil and feeds them back to the microcontroller; The microcontroller performs closed-loop control calculations for constant field strength output based on feedback signals from the current and magnetic field detection modules, generates control commands, and sends them to the decoder. The decoder controls the enable state of each full-bridge drive circuit to control the timing of the equivalent transmitter unit. The full-bridge drive circuit controls the excitation and triggering of a certain transmitting coil in the equivalent transmitting unit according to the enable signal.

9. The control method for the magnetic field generating device of the electromagnetic tracking system according to claim 7, characterized in that, The microcontroller performs rapid elimination of the residual magnetic field as follows: at the end of each excitation signal cycle, a reverse excitation signal is added by adjusting the control command to eliminate the residual magnetic field after the excitation cycle of the transmitting coil ends, thus shortening the switching time between adjacent excitation moments.

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