A circuit and method for determining position and trajectory based on magnetic field variation characteristics.

Abstract

This invention discloses a circuit and method for determining position and trajectory based on magnetic field variation characteristics, relating to the field of position and trajectory monitoring. The key technical points are: it includes a magnetic field generation and control module for generating a changing magnetic field, and a magnetic field sensing and recording module for acquiring and recording the magnetic field strength; in the magnetic field generation and control module, a control digital circuit is connected to the input terminals of several current source circuits, and the output terminal of each current source circuit is connected to an electromagnetic coil; in the magnetic field sensing and recording module, the output terminal of the magnetic field sensor group is connected to a signal amplification circuit, and the output terminal of the signal amplification circuit is connected to a digital acquisition and recording circuit. The position and trajectory determination circuit of this invention measures position by applying an additional magnetic field and utilizing the magnetic field variation characteristics, unaffected by external environmental interference.

Description

Technical Field

[0001] This invention relates to the field of position and trajectory monitoring, and more specifically, to a circuit and method for determining position and trajectory based on magnetic field variation characteristics. Background Technology

[0002] Position and trajectory determination technologies are increasingly being used across various industries. In interventional medicine, it is necessary to track the position of instruments inserted into the human body and plan their movement routes to ensure surgical safety; in industrial applications, it is necessary to detect the trajectory of moving parts in equipment to ensure the reliability of production lines.

[0003] Currently used positioning technologies include satellite positioning, radio positioning, optical positioning, acoustic positioning, and inertial positioning. Satellite positioning is easily affected by weather and geographical conditions, resulting in lower accuracy; radio positioning is susceptible to interference from other electronic devices and obstacles, also leading to lower accuracy; optical positioning utilizes cameras or optical sensors to acquire visual information, requiring precise line-of-sight and lighting conditions; acoustic positioning is easily affected by noise and obstacles, making it difficult to distinguish nearby targets; and inertial positioning accumulates errors over time. Trajectory determination, on the other hand, involves tracking the position of a moving target over a period of time and drawing its path to obtain its trajectory.

[0004] The above positioning technologies cannot obtain accurate location information of the target object and are easily affected by external factors. The trajectories drawn by these methods have high errors. At present, there is a lack of a high-precision position and trajectory determination technology suitable for short-distance movement. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a circuit and method for determining position and trajectory based on magnetic field change characteristics.

[0006] The above-mentioned technical objective of the present invention is achieved through the following technical solution: the circuit and method for determining position and trajectory based on magnetic field change characteristics include a magnetic field generation and control module for generating a changing magnetic field and a magnetic field sensing and recording module for acquiring and recording magnetic field strength; in the magnetic field generation and control module, a control digital circuit is connected to the input terminals of several current source circuits, and the output terminal of each current source circuit is connected to an electromagnetic coil; in the magnetic field sensing and recording module, the output terminal of the magnetic field sensor group is connected to a signal amplification circuit, and the output terminal of the signal amplification circuit is connected to a digital acquisition and recording circuit.

[0007] The number of electromagnetic coils should be no less than four, and each electromagnetic coil is uniformly distributed in a non-planar space; in order to reduce the amount of data calculation in the later stage, the electromagnetic coils are hollow cylindrical coils, and the axial direction of each coil is consistent in the space.

[0008] When the magnetic field generation and control module is working, the control digital circuit controls each current source circuit to output a high-speed periodically changing current that changes asynchronously, and each electromagnetic coil generates a real-time changing magnetic field, which together form a changing spatial magnetic field.

[0009] The magnetic field sensor group consists of multiple scalar magnetic field sensors arranged in a row at uniform intervals and fixed together by a flexible material. The signal output lines of each magnetic field sensor need to have sufficient length margin. When the circuit is working, the magnetic field sensor group is located in the spatial magnetic field formed by each electromagnetic coil. The signal amplification circuit and the digital acquisition and recording circuit are placed at a certain distance outside the electromagnetic coil area.

[0010] In the magnetic field sensing and recording module, each scalar magnetic field sensor converts the acquired magnetic field signal into an electrical signal and sends it to a multi-channel signal amplification circuit for amplification. The amplified continuous electrical signals are sampled by a multi-channel digital acquisition unit to obtain several sets of discrete digital signals. The embedded processor inside the digital acquisition unit then calculates the discrete digital signals into magnetic field strength. The recording and storage unit records the magnetic field strength and sampling time of all sensors at each sampling time.

[0011] Finally, an external processor calls the data stored in the recording and storage unit to calculate the static position of all magnetic field sensors at each moment; when the sensors are in motion, their motion trajectory can be obtained.

[0012] A method for determining position and trajectory based on magnetic field variation characteristics includes the following steps:

[0013] Step S1: Write a program for the control unit in the digital control circuit to make each current source circuit output a power frequency AC current with a different phase.

[0014] Step S2: Write the driver program for the digital acquisition unit to enable intermittent block sampling. The number of samples in each sampling block shall not be less than the number of electromagnetic coils. In this invention, the number of samples is N, and after N consecutive samples, there is a short pause. The sampling period is 0.02s of the power frequency current period, the continuous sampling time interval is 0.02s / N, the pause period is 0.08s of 4 power frequency current periods, and the total duration of one sampling block is 0.1s.

[0015] Step S3: Based on the relationship between the amplified electrical signal of the scalar magnetic field sensor and the actual magnetic field strength, fit the formula for the actual magnetic field strength expressed by the amplified electrical signal;

[0016] Step S4: Write a program for the embedded processor in the digital acquisition unit to calculate the magnetic field strength from the acquired amplified electrical signal using a fitting formula.

[0017] Step S5: When the magnetic field strength of continuously sampled magnetic fields in the same sampling channel changes significantly, the sampling value that has changed is skipped, and sampling is performed again.

[0018] Step S6: Write a program for the recording and storage unit so that the recording and storage unit saves the sampling time and the magnetic field value calculated by the embedded processor in each sampling block, with the data of the same sampling channel at each sampling time as a small group and the data of all sampling channels as a large group, according to the time order of the sampling blocks.

[0019] Step S7: Write a program for the external processor to call the magnetic field data of the same group stored in the recording and storage unit, calculate the coordinates of the current position of the corresponding magnetic field sensor, and perform the calculation process of all groups within the same large group synchronously; the calculation order of the large groups is in the order of being saved in the recording and storage unit; after each calculation is completed, save the corresponding sampling time and sensor position information.

[0020] Step S8: Plot the coordinates of each magnetic field sensor at any given time in the actual arrangement order on the display to obtain the spatial attitude of the magnetic field sensor group at that time; plot the attitude of the sensor group at each time in chronological order to obtain the motion trajectory.

[0021] Step S7 specifically involves:

[0022] Step S7.1: First, extract the current value sequence output by the N current source circuits controlled by the digital control circuit to the external processor. The current value sequence is as follows:

[0023] I(t) = [I1(t), I2(t), ..., I N (t)] T

[0024] The current value of each current source is a function of time t, and the current sequence at all sampling times is known.

[0025] Step S7.2: Next, calculate the vector magnetic field component matrix contributed by the N electromagnetic coils at positions (x, y, z) from the current sequence:

[0026]

[0027] In the formula, B xj B yj B zj These are the magnetic field components of the j-th coil at position (x, y, z).

[0028] Calculate the vector magnetic field expression for the spatial magnetic field generated by all electromagnetic coils at position (x, y, z):

[0029]

[0030] The expression for the magnetic field strength at position (x,y,z) is obtained as follows:

[0031]

[0032] Step S7.3: Within the same sampling block, the total sampling time is 0.02s. The magnetic field sensor group moves slowly, and the displacement difference caused by N consecutive samplings is negligible. Therefore, it is assumed that the position of all sampling times within the same sampling block is located at the position of the first sampling.

[0033] Read the data stored in the recording storage unit, where one sensor is within the sampling block t1, t2, t3, ..., t N The magnetic field strength values ​​B1, B2, B3, ..., B were collected at the sampling times respectively. N Substituting the expression for magnetic field strength, we obtain a set of equations for the location of this sensor:

[0034]

[0035] Solve the above system of equations to obtain the position coordinates of the magnetic field sensor at time t1, and save the time and coordinate data.

[0036] Step S7.4: Simultaneously perform step S7.3 on the data collected by the other magnetic field sensors in the same sampling block to obtain the position coordinates of all sensors at time t1.

[0037] Step S7.5: Finally, encapsulate steps S7.1-S7.4 into a functional module, so that the external processor can call the module cyclically throughout the entire circuit from turn-on to turn-off.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] 1. The position and trajectory determination circuit of the present invention measures the position by applying an additional magnetic field and utilizing the characteristics of magnetic field changes, and is not affected by the external environment.

[0040] 2. The position and trajectory determination circuit of the present invention provides a spatial magnetic field through several electromagnetic coils, which can flexibly change the spatial layout according to the specific use case, and will not affect the environment during non-working periods.

[0041] 3. The position and trajectory determination circuit of the present invention uses several scalar magnetic field sensors to measure the spatial magnetic field strength, which has a low cost.

[0042] 4. The position and trajectory determination method of the present invention uses the formula of the spatial magnetic field strength of the electromagnetic coil to solve the equation system in reverse to calculate the position coordinates, which has the advantage of high accuracy.

[0043] 5. In the position and trajectory determination method of the present invention, the number of equations in the same equation group is greater than the number of unknowns. Even if the current source circuit and electromagnetic coil of a certain branch have an open circuit fault, the circuit and method can still continue to be used. Attached Figure Description

[0044] Figure 1 This invention relates to a magnetic field generation and control module for the position and trajectory determination circuit.

[0045] Figure 2 This invention relates to a magnetic field sensing and recording module for a position and trajectory determination circuit.

[0046] Figure 3 This is a schematic diagram showing the spatial distribution of the modules of the position and trajectory determination circuit of the present invention.

[0047] In the diagram: 1. Control digital circuit; 2. Current source circuit; 3. Electromagnetic coil; 4. Magnetic field sensor group; 5. Signal amplification circuit; 6. Digital acquisition unit; 7. Recording and storage unit. Detailed Implementation

[0048] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0049] Example:

[0050] The specific implementation of the position and trajectory determination circuit includes a magnetic field generation and control module for generating a changing magnetic field, and a magnetic field sensing and recording module for acquiring and recording the magnetic field strength; such as Figure 1 As shown, in the magnetic field generation and control module, the control digital circuit is connected to the input terminals of several current source circuits, and the output terminal of each current source circuit is connected to an electromagnetic coil; for example... Figure 2 As shown, in the magnetic field sensing and recording module, the output of the magnetic field sensor group is connected to a signal amplification circuit, and the output of the signal amplification circuit is connected to a digital acquisition and recording circuit.

[0051] To ensure a unique solution for the position coordinates in the later stages, the number of electromagnetic coils should be no less than four. For sensors with large movement distances, the measurement range can be expanded by increasing the number of electromagnetic coils. The electromagnetic coils are uniformly distributed in a non-planar spatial configuration. If a planar distribution is used, the spatial magnetic field is completely symmetrical on both sides of the plane. When the magnetic field sensor is not in a planar position, it is impossible to determine which side of the plane the measured position is on. For cases involving only planar motion or where the target only moves on a fixed side, the electromagnetic coils can be arranged coplanarly. Uniform distribution is used to balance the magnetic field distribution, expand the magnetic field range under the same current, and save resources. To reduce the amount of data calculation in the later stages, the electromagnetic coils are hollow cylindrical coils, and the axial direction of each coil is consistent. This invention uses hollow cylindrical coils to simplify the later calculation process. Other coils, such as iron-core coils or irregularly shaped coils, only require changes to the magnetic field component matrix and are all within the scope of this invention.

[0052] When the magnetic field generation and control module is working, the control digital circuit controls each current source circuit to output a high-speed periodically changing current that changes asynchronously. Each electromagnetic coil generates a real-time changing magnetic field, which together form a changing spatial magnetic field.

[0053] like Figure 3 As shown, the magnetic field sensor group consists of multiple scalar magnetic field sensors arranged in a row at uniform intervals, fixed together by a flexible material. When measuring a target object, each scalar magnetic field sensor is fixed to the object, and sufficient length slack is required for the signal output lines of each magnetic field sensor. When the circuit is working, the magnetic field sensor group or the object with the sensors fixed is located within the spatial magnetic field formed by each electromagnetic coil. The effect is best within the spatial range surrounded by the electromagnetic coils. The signal amplification circuit and the digital acquisition and recording circuit are placed at a certain distance outside the electromagnetic coil area to reduce the interference of the magnetic field on the circuit.

[0054] In the magnetic field sensing and recording module, each scalar magnetic field sensor converts the acquired magnetic field signal into an electrical signal, which is then amplified by a multi-channel signal amplifier circuit. The amplified continuous electrical signals are sampled by a multi-channel digital acquisition unit to obtain several sets of discrete digital signals. The embedded processor within the digital acquisition unit then calculates the magnetic field strength from these discrete digital signals. The recording and storage unit records the magnetic field strength and sampling time at each sampling moment for all sensors. Due to the limited memory of the embedded processor and its slow performance in complex calculations, an external processor is used to retrieve the data stored in the recording and storage unit to calculate the static position of all magnetic field sensors at each moment. When the sensors are in motion, their trajectories can be obtained.

[0055] The position and trajectory measurement method of the present invention includes the following steps:

[0056] Step S1: Write the program for the control unit in the digital control circuit. To simplify the program and subsequent algorithms, each current source circuit outputs a power frequency AC current with a different phase. This invention uses power frequency currents with different phases. If the phase and period are equal, even if the amplitudes are unequal, the equations in the later solution system will be in a geometric relationship, and the solution will not be unique, making it impossible to calculate the position. Using other asynchronously changing high-speed periodic currents, such as AC currents with different periods and waveforms, follows the same principle and all fall within the scope of protection of this invention.

[0057] Step S2: Write the driver program for the digital acquisition unit to enable intermittent block sampling. To ensure a solution to the equation system, increase the number of equations. The number of samples within each sampling block should not be less than the number of electromagnetic coils. In this invention, the number of samples is N, the number of coils. After N consecutive samples, there is a short pause. It is necessary to avoid the existence of the same magnetic field distribution at different sampling times within the same sampling block, i.e., the equation system should not contain geometric equations. Therefore, the current sequence input at different sampling times within the same sampling block cannot be the same or geometrically proportional. Thus, the interval between any sampling times within the sampling block should not be an integer multiple of the current period output by the current source circuit. If the sampling interval is too short, close to the total sampling time within the sampling block, the effect of the slight movement of the sensor group itself during continuous sampling cannot be ignored in the later calculations. The solution obtained by this method will have a large error. Therefore, the sampling interval between adjacent sampling blocks should be long enough to ensure that the sensor group moves more significantly. The above problems should also be avoided for cases where the current source circuit outputs other periodically changing currents. To simplify the algorithm, the sampling period is taken as the power frequency current period of 0.02s, the continuous sampling time interval is 0.02s / N, the intermittent period is taken as 4 periods of power frequency current of 0.08s, and the total duration of one sampling block is 0.1s.

[0058] Step S3: Due to the differences in the working principles of different scalar magnetic field sensors on the market, the output electrical signal and the actual magnetic field strength are not necessarily linearly related.

[0059] For scalar magnetic field sensors where the manufacturer provides the relationship between the output electrical signal and the actual magnetic field strength, the relationship between the amplified electrical signal and the actual magnetic field is replaced by the amplification relationship from the signal amplification circuit. For unknown scalar magnetic field sensors, the relationship between the amplified electrical signal and the actual magnetic field is obtained through experimental measurement. The specific experimental measurements are as follows:

[0060] First, fix a scalar magnetic field sensor near an electromagnetic coil in the magnetic field generation and control module, and connect its output to a signal amplification circuit. Write a program to control the digital circuit, turn on the power to the magnetic field generation and control module, making the current of other electromagnetic coils zero, and increase the input current of this electromagnetic coil from zero to the upper limit. Record the correspondence between the electrical signal output by the signal amplification circuit and the current flowing through the electromagnetic coil. Remove the scalar magnetic field sensor and the signal amplification circuit, and take another highly integrated scalar magnetic field sensor with built-in signal processing. Fix the measuring end in the same position, and increase the input current of the electromagnetic coil from zero to the upper limit. Record the correspondence between the magnetic field value measured by the highly integrated scalar magnetic field sensor and the current flowing through the coil. Alternatively, calculate the theoretical magnetic field strength at the sensor location for each current value based on the structural dimensions of the electromagnetic coil. The calculation formula is the same as the magnetic field strength expression in step S7.2. Finally, obtain a table comparing the amplified electrical signal of the scalar magnetic field sensor with the actual magnetic field strength.

[0061] Based on the relationship between the amplified electrical signal of the scalar magnetic field sensor and the actual magnetic field strength, a formula for the actual magnetic field strength expressed by the amplified electrical signal is fitted.

[0062] Step S4: Write a program for the embedded processor in the digital acquisition unit to calculate the magnetic field strength from the acquired amplified electrical signal using a fitting formula.

[0063] Step S5: When the magnetic field strength of continuously sampled magnetic fields in the same sampling channel changes significantly, the sampling value that has changed is skipped, and sampling is performed again.

[0064] Step S6: Write a program for the recording and storage unit so that the recording and storage unit saves the sampling time and the magnetic field value calculated by the embedded processor in each sampling block, with the data of the same sampling channel at each sampling time as a small group and the data of all sampling channels as a large group, according to the time order of the sampling blocks.

[0065] Step S7: Write a program for the external processor to call the magnetic field data of the same group stored in the recording storage unit, calculate the coordinates of the current position of the corresponding magnetic field sensor, and perform the calculation process of all groups within the same large group synchronously; the calculation order of the large groups is in the order of being saved in the recording storage unit; after each calculation is completed, save the corresponding sampling time and sensor position information.

[0066] Step S8: Plot the coordinates of each magnetic field sensor at any given time in the actual arrangement order on the display to obtain the spatial attitude of the magnetic field sensor group at that time; plot the attitude of the sensor group at each time in chronological order to obtain the motion trajectory.

[0067] Step S7 is as follows:

[0068] Step S7.1: First, extract the current value sequence output by the N current source circuits controlled by the digital control circuit to the external processor. The current value sequence is as follows:

[0069] I(t) = [I1(t), I2(t), ..., I N (t)] T

[0070] The current value of each current source is a function of time t, and the current sequence at all sampling times is known.

[0071] Step S7.2: Next, calculate the vector magnetic field component matrix contributed by the N electromagnetic coils at positions (x, y, z) from the current sequence:

[0072] Establish a Cartesian coordinate system with the center of one of the closely spaced cylindrical electromagnetic coils as the origin and the Z-axis as the axis. Then, the magnetic field vector at any position (x0, y0, z0) of the electromagnetic coil is as follows:

[0073]

[0074] in,

[0075]

[0076] In the formula, μ0 is the free permeability; m is the number of layers in the electromagnetic coil; n i r is the number of turns in the i-th layer of the coil; i I is the spatial radius of the i-th layer of the coil; t This is the instantaneous current value; H i Let be the height of the i-th layer of the coil.

[0077] The vector magnetic field components generated by each electromagnetic coil can be calculated using the above formula. To avoid increasing the computational load by transforming the coordinate system later, the coordinate axes of each coil are aligned, with the origin being the center of each coil. This yields the magnetic field component matrix of N coils contributing to the spatial position (x, y, z):

[0078]

[0079] In the formula, B xj B yj B zj Let x represent the magnetic field components of the j-th coil at position (x, y, z). j y j z j Let x, y, z be the coordinates of the spatial position (x, y, z) relative to the center of the j-th coil. The center position of each coil is known, therefore x... j y j z j They can be represented by x, y, and z respectively.

[0080] The vector magnetic field expression for the spatial magnetic field generated by each electromagnetic coil at position (x, y, z) is calculated using the principle of vector superposition of magnetic induction intensity:

[0081]

[0082] The expression for the magnetic field strength at position (x,y,z) is obtained as follows:

[0083]

[0084] In practical applications, if the spatial arrangement of the electromagnetic coils is changed, the relative positions of the centers of all the coils will change, requiring modification of the above magnetic field strength expression. However, by powering, sampling, and calculating each coil in turn, that is, taking the center of each electromagnetic coil as the origin, the relative coordinates from the sensor to the center of each coil can be obtained, and the position of each electromagnetic coil can be deduced. By incorporating this process into the program of the external processor and control digital circuit, a high degree of intelligence can be achieved.

[0085] Step S7.3: At any time t1, a magnetic field sensor at an unknown location (x, y, z) collects the magnetic field strength value B1. To solve for the three position parameters, at least three equations are required. To avoid the situation where the magnetic field near this location is a uniform magnetic field or the magnetic field strength is close to 0 at a certain time, resulting in a non-unique solution to the equations, the number of samplings is no less than the number of electromagnetic coils. Therefore, this invention samples the same location N times.

[0086] Within the same sampling block, the total sampling time is 0.02s. The sensor group moves slowly, and the displacement difference caused by N consecutive samplings is negligible. Therefore, it is assumed that the position of all sampling times within the same sampling block is located at the position of the first sampling.

[0087] Read the data stored in the recording storage unit, where one sensor is within the sampling block t1, t2, t3, ..., t N The magnetic field strength values ​​B1, B2, B3, ..., B were collected at the sampling times respectively. N Substituting the expression for magnetic field strength, we obtain a set of equations for the location of this sensor:

[0088]

[0089] Solve the above system of equations to obtain the position coordinates of the magnetic field sensor at time t1, and save the time and coordinate data.

[0090] Step S7.4: Simultaneously perform step S7.3 on the data collected by the other magnetic field sensors in the same sampling block to obtain the position coordinates of all sensors at time t1.

[0091] Step S7.5: Finally, steps S7.1-S7.4 are encapsulated into a functional module, which is then repeatedly called by the external processor during the entire circuit's on-time and off-time. That is, the position of each sensor is measured once every 0.1 seconds, ultimately obtaining the motion trajectory of the sensor group.

[0092] The scalar magnetic field sensor used in this circuit and method is small in size and can be fixed in most medical devices and industrial moving parts. The number and distribution can be adjusted according to the actual use, so as to achieve the purpose of monitoring the position and movement trajectory of the target object.

[0093] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for determining position and trajectory based on magnetic field variation characteristics, characterized in that: Includes the following steps: Step S1: Write a program to control the control unit in the digital circuit so that each current source circuit outputs a power frequency AC current with a different phase. Step S2: Write the driver program for the digital acquisition unit to enable intermittent block sampling; the number of samplings N in each sampling block shall not be less than the number of electromagnetic coils, and there shall be a short pause after N consecutive samplings; the sampling period shall be 0.02s of the power frequency current period, the continuous sampling time interval shall be 0.02s / N, the pause period shall be 0.08s of 4 power frequency current periods, and the total duration of one sampling block shall be 0.1s; Step S3: Based on the relationship between the amplified electrical signal of the scalar magnetic field sensor and the actual magnetic field strength, fit the formula for the actual magnetic field strength expressed by the amplified electrical signal; Step S4: Write the program for the embedded processor in the digital acquisition unit to calculate the magnetic field strength from the acquired amplified electrical signal using a fitting formula; Step S5: When the magnetic field strength of continuously sampled magnetic fields in the same sampling channel changes significantly, the sampling value that has changed is skipped, and sampling is performed again. Step S6: Write a program for the recording and storage unit so that the recording and storage unit saves the sampling time and the magnetic field value calculated by the embedded processor in each sampling block, with the data of the same sampling channel at each sampling time as a small group and the data of all sampling channels as a large group, according to the time order of the sampling blocks; Step S7: Write a program for the external processor to call the magnetic field data of the same group stored in the recording storage unit, calculate the coordinates of the current position of the corresponding magnetic field sensor, and perform the calculation process of all groups within the same large group synchronously; the calculation order of the large groups is in the order of being saved in the recording storage unit. After each calculation is completed, the corresponding sampling time and sensor location information are saved; Step S8: Plot the coordinates of each magnetic field sensor at any given time in the actual arrangement order on the display to obtain the spatial attitude of the magnetic field sensor group at that time; plot the attitude of the sensor group at each time in chronological order to obtain the motion trajectory.

2. The method for determining position and trajectory based on magnetic field variation characteristics according to claim 1, characterized in that: Step S7 specifically involves: Step S7.1: First, extract the current value sequence output by the N current source circuits controlled by the digital control circuit to the external processor. The current value sequence is as follows: The current value of each current source is a function of time t, and the current sequence at all sampling times is known; Step S7.2: Next, calculate the vector magnetic field component matrix contributed by the N electromagnetic coils at positions (x, y, z) from the current sequence: In the formula, B xj B yj B zj These are the magnetic field components of the j-th coil at position (x, y, z); The vector magnetic field expression for the spatial magnetic field generated by all electromagnetic coils at position (x, y, z) is calculated as follows: The expression for the magnetic field strength at position (x, y, z) is obtained as follows: Step S7.3: Within the same sampling block, the total sampling time is 0.02s. The magnetic field sensor group moves slowly, and the displacement difference caused by N consecutive samplings is negligible. Therefore, it is assumed that the position of all sampling times within the same sampling block is located at the position of the first sampling. Read the data stored in the recording storage unit, where one sensor is within the sampling block t1, t2, t3, ..., t N Magnetic field strength values ​​B1, B2, B3, ..., B were collected at the sampling times respectively. N Substituting these equations into the expression for magnetic field strength, we obtain a set of equations for the location of this sensor: Solve the above system of equations to obtain the position coordinates of the magnetic field sensor at time t1, and save the time and coordinate data; Step S7.4: Simultaneously perform step S7.3 on the data collected by the other magnetic field sensors in the same sampling block to obtain the position coordinates of all sensors at time t1; Step S7.5: Finally, encapsulate steps S7.1-S7.4 into a functional module, so that the external processor can call the module cyclically throughout the entire circuit from turn-on to turn-off.

3. A circuit for determining position and trajectory based on magnetic field change characteristics, applied to the method for determining position and trajectory based on magnetic field change characteristics according to claim 1, characterized in that: It includes a magnetic field generation and control module for generating a changing magnetic field and a magnetic field sensing and recording module for acquiring and recording the magnetic field strength; in the magnetic field generation and control module, the control digital circuit is connected to the input terminals of several current source circuits, and the output terminal of each current source circuit is connected to an electromagnetic coil; in the magnetic field sensing and recording module, the output terminal of the magnetic field sensor group is connected to a signal amplification circuit, and the output terminal of the signal amplification circuit is connected to a digital acquisition and recording circuit.

4. The circuit for determining position and trajectory based on magnetic field change characteristics according to claim 3, characterized in that: The number of electromagnetic coils is no less than four, and each electromagnetic coil is uniformly distributed in a non-planar space; in order to reduce the amount of data calculation in the later stage, the electromagnetic coils are hollow cylindrical coils, and the axial direction of each coil is consistent in the space.

5. The circuit for determining position and trajectory based on magnetic field change characteristics according to claim 3, characterized in that: When the magnetic field generation and control module is working, the control digital circuit controls each current source circuit to output a high-speed periodically changing current that changes asynchronously, and each electromagnetic coil generates a real-time changing magnetic field, which together form a changing spatial magnetic field.

6. The circuit for determining position and trajectory based on magnetic field change characteristics according to claim 3, characterized in that: The magnetic field sensor group consists of multiple scalar magnetic field sensors arranged in a row at uniform intervals and fixed together by a flexible material. The signal output lines of each magnetic field sensor need to have sufficient length margin. When the circuit is working, the magnetic field sensor group is located in the spatial magnetic field formed by each electromagnetic coil. The signal amplification circuit and the digital acquisition and recording circuit are placed at a certain distance outside the electromagnetic coil area.

7. The circuit for determining position and trajectory based on magnetic field change characteristics according to claim 6, characterized in that: In the magnetic field sensing and recording module, each scalar magnetic field sensor converts the acquired magnetic field signal into an electrical signal and sends it to a multi-channel signal amplification circuit for amplification. The amplified continuous electrical signals are sampled by a multi-channel digital acquisition unit to obtain several sets of discrete digital signals. The embedded processor inside the digital acquisition unit then calculates the discrete digital signals into magnetic field strength. The recording and storage unit records the magnetic field strength and sampling time of all sensors at each sampling time.

8. The circuit for determining position and trajectory based on magnetic field change characteristics according to claim 7, characterized in that: Finally, an external processor calls the data stored in the recording and storage unit to calculate the static position of all magnetic field sensors at each moment; when the sensors are in motion, their motion trajectory can be obtained.

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