Circuit and method for position and track judgment based on magnetic field change characteristics

Abstract

The invention discloses a circuit and method for judging a position and a track based on magnetic field change characteristics, and relates to the field of position and track monitoring, and the circuit and method are characterized in that the circuit comprises a magnetic field generation and regulation module for generating a change magnetic field and a magnetic field sensing and recording module for collecting and recording the magnetic field intensity; in the magnetic field generation and regulation module, a control digital circuit is respectively connected with input ends of a plurality of current source circuits, and an output end of each current source circuit is respectively connected with an electromagnetic coil; in the magnetic field sensing and recording module, the output end of a magnetic field sensor group is connected to a signal amplification circuit, and the output end of the signal amplification circuit is connected with a digital acquisition and recording circuit. According to the position and track judgment circuit, the magnetic field is additionally applied, position measurement is carried out through the magnetic field change characteristics, and interference of the external environment is avoided.

Description

Technical Field

[0001] The present invention relates to the field of position and trajectory monitoring, and more specifically, to a circuit and method for position and trajectory judgment based on magnetic field variation characteristics. Background Art

[0002] Position and trajectory judgment technology is increasingly being used in all walks of life. In the field of interventional medicine, it is necessary to track the position of instruments that intervene in the human body and plan the movement route to ensure the safety of the operation; in the industrial field, it is necessary to detect the trajectory of moving parts in the equipment to ensure the reliability of the production line.

[0003] Currently, the commonly used positioning technologies include: satellite positioning, radio positioning, optical positioning, acoustic positioning and inertial positioning technology. Satellite positioning technology is easily affected by weather and geographical environment, and has low accuracy; radio positioning technology is interfered by other electronic devices and obstacles, and has low accuracy; optical positioning technology uses cameras or optical sensors to obtain visual information, and has high requirements for sight and light; acoustic positioning technology is easily interfered by noise and obstacles, and it is difficult to distinguish adjacent targets; inertial positioning technology will accumulate errors over time. The trajectory judgment method is to track the position of the moving target over a period of time, draw its path, and obtain the trajectory.

[0004] The above positioning technologies are unable to obtain accurate location information of the target object and are easily interfered by external factors. The trajectories drawn by these methods have high errors. Currently, there is a lack of a high-precision position and trajectory judgment technology suitable for short-distance movement. Summary of the invention

[0005] In view of the deficiencies in the prior art, the object of the present invention is to provide a circuit and method for determining position and trajectory based on magnetic field variation characteristics.

[0006] The above technical purpose of the present invention is achieved through the following technical solutions: the circuit and method for position and trajectory judgment 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 collecting and recording the magnetic field strength; in the magnetic field generation and control module, the control digital circuit is respectively connected to the input ends of several current source circuits, and the output end of each current source circuit is respectively connected to an electromagnetic coil; in the magnetic field sensing and recording module, the output end of the magnetic field sensor group is connected to a signal amplification circuit, and the output end of the signal amplification circuit is connected to the digital collection and recording circuit.

[0007] The number of the electromagnetic coils should be no less than 4, and each electromagnetic coil is evenly distributed in the non-planar space; in order to reduce the amount of data calculation in the later stage, the electromagnetic coil is a hollow cylindrical coil, and the axial direction of each coil placed in space is consistent.

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

[0009] The magnetic field sensor group is composed of a plurality of scalar magnetic field sensors arranged in a row at even intervals and fixed together by soft materials. The signal output line of each magnetic field sensor needs to have a sufficiently long 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 collected magnetic field signal into an electrical signal and sends it to a multi-channel signal amplification circuit for amplification processing; the amplified multiple continuous electrical signals are sampled by a multi-channel digital acquisition unit to obtain a plurality of discrete digital signals; the discrete digital signals are then calculated as magnetic field strength by an embedded processor inside the digital acquisition unit; and the recording storage unit records the magnetic field strength and sampling time at the locations of all sensors at each sampling moment.

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

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

[0013] Step S1: Write a program to control the control unit in the digital circuit so that each current source circuit outputs industrial frequency alternating current with different phases.

[0014] Step S2: Write a driver for the digital acquisition unit so that the sampling mode is intermittent block processing sampling; the number of sampling times in each sampling block is not less than the number of electromagnetic coils. The sampling times of the present invention is the number of coils N, and there is a short pause after N consecutive samplings; the sampling period is the power frequency current cycle of 0.02s, the continuous sampling time interval is 0.02s / N, the intermittent period is 4 cycles of the power frequency current of 0.08s, and the total duration of a sampling block is 0.1s.

[0015] Step S3: fitting a formula for the actual magnetic field strength represented by the amplified electrical signal according to the relationship between the electrical signal amplified by the scalar magnetic field sensor and the actual magnetic field strength;

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

[0017] Step S5: When the magnetic field intensity continuously sampled by the same sampling channel changes significantly, the sampling value that exceeds the change is re-sampled.

[0018] Step S6: Write a program for the recording storage unit so that the recording storage unit saves the sampling time in each sampling block and the magnetic field value calculated by the embedded processor in the time sequence of the 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.

[0019] Step S7: Write a program for the external processor to call the magnetic field data of the same group saved in the record storage unit, calculate the coordinates of the current location of the corresponding magnetic field sensor, and the calculation process of all group data in the same large group is carried out synchronously; the calculation order of each large group is carried out in the order saved in the record storage unit; each time the calculation is completed, the corresponding sampling time and sensor position information are saved.

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

[0021] The step S7 is specifically as follows:

[0022] Step S7.1: First, extract the current value sequence output by the N current source circuits controlled by the control digital 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 moments is known.

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

[0026]

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

[0028] Calculate the vector magnetic field expression of the spatial magnetic field generated by each electromagnetic coil at the position (x, y, z):

[0029]

[0030] Get the expression of magnetic field strength at position (x, y, z):

[0031]

[0032] Step S7.3: In the same sampling block, the sampling time is 0.02s in total. The magnetic field sensor group moves slowly, and the displacement difference caused by N consecutive samplings can be ignored. Therefore, it is considered that the positions of all sampling moments in the same sampling block are located at the position of the first sampling.

[0033] Read the data stored in the record storage unit, where one sensor is within the sampling block t1, t2, t3, ..., t N At the sampling time, the magnetic field intensity values ​​B1, B2, B3, ..., B N , substituting into the magnetic field strength expression, we get a set of equations for the location of the sensor:

[0034]

[0035] Solve the above 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: synchronously perform step S7.3 on the data collected by the remaining magnetic field sensors in the same sampling block to obtain the position coordinates of all sensors at time t1.

[0037] Step S7.5: Finally, steps S7.1-S7.4 are encapsulated as a functional module, so that the external processor cyclically calls the module during the period from the entire circuit being connected to being disconnected.

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

[0039] 1. The position and trajectory judgment 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 judgment circuit of the present invention provides a spatial magnetic field through a plurality of electromagnetic coils, and can flexibly change the spatial layout according to specific usage conditions, and will not affect the environment during non-working time periods.

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

[0042] 4. The position and trajectory determination method of the present invention utilizes the electromagnetic coil spatial magnetic field strength formula to reversely solve the equation group to calculate the position coordinates, which has the advantage of high precision.

[0043] 5. In the position and trajectory determination method of the present invention, the number of equations in the same set of equations is greater than the unknown quantities. Even if a current source circuit and an electromagnetic coil of a branch have a circuit breaker failure, the circuit and method can still be used. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a magnetic field generation and control module of the position and trajectory judgment circuit of the present invention;

[0045] Figure 2 A magnetic field sensing and recording module of the position and trajectory determination circuit of the present invention;

[0046] Figure 3 Schematic diagram of the spatial distribution of modules of the position and trajectory judgment circuit of the present invention.

[0047] In the figure: 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 storage unit. DETAILED DESCRIPTION

[0048] The present invention is described in detail below in conjunction with the accompanying drawings and embodiments.

[0049] Example:

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

[0051] In order to ensure that there is a unique solution for the position coordinates in the later stage, the number of electromagnetic coils should be no less than 4. For sensors with a large movement distance, the measurement range can be expanded by increasing the number of electromagnetic coils, and each electromagnetic coil is evenly distributed in the non-plane space; if a plane distribution is adopted, the spatial magnetic field is completely symmetrical on both sides of the plane. When the magnetic field sensor is in a non-plane position, the measured position cannot be determined on which side of the plane it is on. For the case of only plane movement or the target only moving on the fixed side, the electromagnetic coils can be arranged in the same plane; the uniform distribution is to balance the magnetic field distribution, expand the magnetic field range under the same current, and save resources; in order to reduce the amount of data calculation in the later stage, the electromagnetic coil is a hollow cylindrical coil, and the axial direction of each coil space is consistent. The present invention uses a hollow cylindrical coil to simplify the later calculation process. Other coils such as iron core coils, irregular shape coils, etc., only need to change the magnetic field component matrix, which belongs to the protection scope of the present invention.

[0052] When the magnetic field generation and regulation module is working, the control digital circuit controls each current source circuit to output asynchronously changing high-speed periodic changing current, and each electromagnetic coil generates a real-time changing magnetic field to 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 even intervals and fixed together by soft materials. When measuring a target object, each scalar magnetic field sensor is fixed on the object, and the signal output line of each magnetic field sensor needs to leave a sufficient margin. When the circuit is working, the magnetic field sensor group or the object with the fixed sensor is located in the spatial magnetic field formed by each electromagnetic coil, and the effect is best within the space surrounded by the electromagnetic coil; 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 collected magnetic field signal into an electrical signal and sends it to a multi-channel signal amplification circuit for amplification processing; the amplified multiple continuous electrical signals are sampled by a multi-channel digital acquisition unit to obtain several groups of discrete digital signals; the embedded processor inside the digital acquisition unit calculates the discrete digital signals as magnetic field strength; the recording storage unit records the magnetic field strength and sampling time of all sensors at each sampling time. The embedded processor has a small memory and is slow to perform complex calculations, so an external processor finally calls the data stored in the recording storage unit to calculate the static position of all magnetic field sensors at each time; when the sensor is in motion, the motion trajectory can be obtained.

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

[0056] Step S1: Write a program to control the control unit in the digital circuit. To simplify the program and the later algorithm, each current source circuit outputs industrial frequency alternating currents of different phases. The present invention uses industrial frequency currents of different phases. If the phase and period are equal, even if the amplitudes are not equal, the equations in the later equations are geometrically proportional, and the solution is not unique and the position cannot be calculated. Other asynchronously changing high-speed periodic currents, such as alternating currents of different periods and different waveforms, etc., have the same principle and belong to the protection scope of the present invention.

[0057] Step S2: Write a driver for the digital acquisition unit, so that the sampling method is intermittent block processing sampling; in order to make the equation group have a solution, increase the number of equations, and the sampling times in each sampling block is not less than the number of electromagnetic coils. The sampling times of the present invention are the number of coils N, and a short pause is taken after N consecutive samplings; it is necessary to avoid the existence of the same distributed magnetic field at each sampling moment in the same sampling block, that is, there are geometric equations in the equation group, so in the same sampling block, the current sequence input at each sampling moment cannot be the same or geometric, so any sampling time interval in the sampling block should not be equal to an integer multiple of the current cycle output by the current source circuit; if the sampling interval is too short, close to the total sampling time in the sampling block, then the subsequent calculation cannot ignore the impact of the slight movement of the sensor group itself during the continuous sampling process, and the solution of this method will have a large error, so two adjacent groups of sampling blocks should be provided with a sufficiently long sampling interval to ensure that the sensor group moves more obviously; for the case where the current source circuit outputs other periodically changing currents, the above problems should also be avoided. To simplify the algorithm, the sampling period is taken as the power frequency current cycle of 0.02s, the continuous sampling time interval is 0.02s / N, the intermittent period is taken as 4 cycles of the power frequency current of 0.08s, and the total duration of a 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 is not necessarily linearly related to the actual magnetic field strength.

[0059] For sensors whose manufacturers have provided the relationship between their output electrical signals and actual magnetic field strength, the relationship between the amplified electrical signals and the actual magnetic field is replaced by the relationship between the amplified electrical signals and the actual magnetic field according to the amplification relationship of the signal amplification circuit; for unknown scalar magnetic field sensors, the relationship between the amplified electrical signals and the actual magnetic field is obtained through experimental measurement. The experimental measurement is as follows:

[0060] First, fix a scalar magnetic field sensor near an electromagnetic coil in the magnetic field generation and control module, and connect the output end to the signal amplification circuit; write a program to control the digital circuit, turn on the power of the magnetic field generation and control module, make the current of other electromagnetic coils 0, and increase the input current of the electromagnetic coil from 0 to the upper limit, and record the corresponding relationship between the electrical signal output by the signal amplification circuit and the current passed 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 0 to the upper limit, and record the corresponding relationship between the magnetic field value measured by the highly integrated scalar magnetic field sensor and the current passed through the coil; or calculate the theoretical magnetic field strength at the location of the sensor at each current value based on the structural size of the electromagnetic coil, and the calculation formula is the same as the magnetic field strength expression in step S7.2; finally, a set of comparison tables of the electrical signal amplified by the scalar magnetic field sensor and the actual magnetic field strength are obtained.

[0061] According to the relationship between the electrical signal amplified by the scalar magnetic field sensor and the actual magnetic field strength, a formula for the actual magnetic field strength represented 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 acquired amplified electrical signal into the magnetic field strength through a fitting formula.

[0063] Step S5: When the magnetic field intensity continuously sampled by the same sampling channel changes significantly, the sampling value that exceeds the change is re-sampled.

[0064] Step S6: Write a program for the recording storage unit so that the recording storage unit saves the sampling time in each sampling block and the magnetic field value calculated by the embedded processor in the time sequence of the 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.

[0065] Step S7: Write a program for the external processor, call the magnetic field data of the same group saved in the record storage unit, calculate the coordinates of the current location of the corresponding magnetic field sensor, and the calculation process of all group data in the same large group is carried out synchronously; the calculation order of each large group is carried out in the order saved in the record storage unit; each time the calculation is completed, the corresponding sampling time and sensor position information are saved.

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

[0067] Step S7 is specifically as follows:

[0068] Step S7.1: First, extract the current value sequence output by the N current source circuits controlled by the control digital 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 moments is known.

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

[0072] A Cartesian coordinate system is established with the center of one of the cylindrical electromagnetic coils with closely arranged turns as the origin and the axial direction as the Z axis. The magnetic field vector at any position (x0, y0, z0) of the electromagnetic coil is specifically:

[0073]

[0074] in,

[0075]

[0076] Where μ0 is the vacuum magnetic permeability; m is the number of layers of the electromagnetic coil; n i is the number of turns of the coil in layer i; r i is the spatial radius of the coil layer i; I t is the instantaneous current value; H i is the height of the i-th coil layer.

[0077] According to the above formula, the vector magnetic field component generated by each electromagnetic coil can be calculated. In order to avoid the increase of calculation amount in the later conversion of the component magnetic field coordinate system, the coordinate axis direction of each coil is consistent, and the origin is the center of each coil. The magnetic field component matrix contributed by N coils to the spatial position (x, y, z) is obtained:

[0078]

[0079] In the formula, B xj , B yj , B zj are the magnetic field components of the jth coil at position (x, y, z). j ,y j 、z j are the spatial positions (x, y, z) relative to the center of the jth coil. The center position of each coil is known, so x j ,y j 、z j They can be represented by x, y, and z respectively.

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

[0081]

[0082] Get the expression of magnetic field strength at position (x, y, z):

[0083]

[0084] In actual use, if the spatial arrangement of the electromagnetic coils is changed, the relative positions of the centers of all coils will change, and the above-mentioned magnetic field strength expression needs to be modified. The relative coordinates of the sensor to the center of each coil can be obtained by powering, sampling, and calculating each coil in turn, that is, taking the center of each electromagnetic coil as the origin, and inferring the position of each electromagnetic coil. Incorporating this process into the external processor and the program that controls the digital circuit can achieve high intelligence.

[0085] Step S7.3: At any time t1, a magnetic field sensor at an unknown position (x, y, z) collects a magnetic field strength value B1. To solve the three position parameters, no less than three equations are required. To avoid the situation where the magnetic field near the position is a uniform magnetic field or the magnetic field strength is close to 0 at a certain time, the equation solution is not unique, so the sampling number is no less than the number of electromagnetic coils. The present invention takes N sampling times for the same position.

[0086] In the same sampling block, the sampling time is 0.02s in total. The sensor group moves slowly, and the displacement difference caused by N consecutive samplings can be ignored. Therefore, it is considered that the positions of all sampling moments in the same sampling block are located at the position of the first sampling.

[0087] Read the data stored in the record storage unit, where one sensor is within the sampling block t1, t2, t3, ..., t N At the sampling time, the magnetic field intensity values ​​B1, B2, B3, ..., B N , substituting into the magnetic field strength expression, we get a set of equations for the location of the sensor:

[0088]

[0089] Solve the above 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: synchronously perform step S7.3 on the data collected by the remaining 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 as a functional module, so that the external processor can call the module cyclically during the period from the entire circuit being connected to disconnected, that is, the position of each sensor is measured once every 0.1s, and finally the motion trajectory of the sensor group is obtained.

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

[0093] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A circuit for determining position and trajectory based on magnetic field variation characteristics, 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 collecting and recording the magnetic field strength; in the magnetic field generation and control module, the control digital circuit is respectively connected to the input ends of several current source circuits, and the output end of each current source circuit is respectively connected to an electromagnetic coil; in the magnetic field sensing and recording module, the output end of the magnetic field sensor group is connected to a signal amplification circuit, and the output end of the signal amplification circuit is connected to the digital collection and recording circuit.

2. A circuit for determining position and trajectory based on magnetic field variation characteristics according to claim 1, characterized in that: The number of the electromagnetic coils should be no less than 4, and each electromagnetic coil is evenly distributed in the non-planar space; in order to reduce the amount of data calculation in the later stage, the electromagnetic coil is a hollow cylindrical coil, and the axial direction of each coil placed in space is consistent.

3. A circuit for determining position and trajectory based on magnetic field variation characteristics according to claim 1, characterized in that: When the magnetic field generation and regulation module is working, the control digital circuit controls each current source circuit to output asynchronously changing high-speed periodic current, and each electromagnetic coil generates a real-time changing magnetic field to form a changing spatial magnetic field.

4. A circuit for determining position and trajectory based on magnetic field variation characteristics according to claim 1, characterized in that: The magnetic field sensor group is composed of a plurality of scalar magnetic field sensors arranged in a row at even intervals and fixed together by soft materials. The signal output line of each magnetic field sensor needs to have a sufficiently long 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.

5. The circuit for determining position and trajectory based on magnetic field variation characteristics according to claim 1, characterized in that: In the magnetic field sensing and recording module, each scalar magnetic field sensor converts the collected magnetic field signal into an electrical signal and sends it to a multi-channel signal amplification circuit for amplification processing; the amplified multiple continuous electrical signals are sampled by a multi-channel digital acquisition unit to obtain a plurality of discrete digital signals; the discrete digital signals are then calculated as magnetic field strength by an embedded processor inside the digital acquisition unit; and the recording storage unit records the magnetic field strength and sampling time at the locations of all sensors at each sampling moment.

6. A circuit for determining position and trajectory based on magnetic field variation characteristics according to claim 5, characterized in that: Finally, an external processor calls the data stored in the recording storage unit to calculate the static positions of all magnetic field sensors at each moment; when the sensor is in motion, the motion trajectory can be obtained.

7. A method for determining position and trajectory based on magnetic field variation characteristics, characterized in that: The following steps are involved: Step S1: writing a program to control the control unit in the digital circuit so that each current source circuit outputs industrial frequency alternating current of different phases; Step S2: Write a driver for the digital acquisition unit, so that the sampling mode is intermittent block processing sampling; the number of sampling times in each sampling block is not less than the number of electromagnetic coils, the number of sampling times of the present invention is the number of coils N, and a short break is made after N consecutive samplings; the sampling period is 0.02s of the power frequency current cycle, the continuous sampling time interval is 0.02s / N, the intermittent period is 0.08s of 4 cycles of the power frequency current, and the total duration of a sampling block is 0.1s; Step S3: fitting a formula for the actual magnetic field strength represented by the amplified electrical signal according to the relationship between the electrical signal amplified by the scalar magnetic field sensor and the actual magnetic field strength; Step S4: writing a program for the embedded processor in the digital acquisition unit to calculate the acquired amplified electrical signal into the magnetic field strength through a fitting formula; Step S5: when the magnetic field intensity continuously sampled by the same sampling channel changes significantly, re-sampling is performed after the sampling value of the change is exceeded; Step S6: Write a program for the recording storage unit so that the recording storage unit stores the sampling time in each sampling block and the magnetic field value calculated by the embedded processor, 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, in the time sequence of the sampling block; Step S7: Write a program for the external processor to call the magnetic field data of the same group stored in the record storage unit, calculate the coordinates of the current location of the corresponding magnetic field sensor, and the calculation process of all group data in the same large group is carried out synchronously; the calculation order of each large group is carried out in the order stored in the record 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 time in the display in the actual arrangement order to obtain the spatial posture of the magnetic field sensor group at that time; plot the posture of the sensor group at each time in time order to obtain the motion trajectory.

8. A method for determining position and trajectory based on magnetic field variation characteristics according to claim 7, characterized in that: The step S7 is specifically as follows: Step S7.1: First, extract the current value sequence output by the N current source circuits controlled by the control digital circuit to the external processor. The current value sequence is as follows: I(t)=[I1(t),I2(t),…,I N (t)] T The current value of each current source is a function of time t, and the current sequence at all sampling moments is known; Step S7.2: Then, the vector magnetic field component matrix contributed by the N electromagnetic coils at the positions (x, y, z) is calculated from the current sequence: In the formula, B xj , B yj , B zj are the magnetic field components of the jth coil at position (x, y, z); Calculate the vector magnetic field expression of the spatial magnetic field generated by each electromagnetic coil at the position (x, y, z): Get the expression of magnetic field strength at position (x, y, z): Step S7.3: In the same sampling block, the sampling time is 0.02s in total. The magnetic field sensor group moves slowly, and the displacement difference caused by N consecutive samplings can be ignored. Therefore, it is considered that the positions of all sampling moments in the same sampling block are located at the position of the first sampling. Read the data stored in the record storage unit, where one sensor is within the sampling block t1, t2, t3, ..., t N At the sampling time, the magnetic field intensity values ​​B1, B2, B3, ..., B N , substituting into the magnetic field strength expression, we get a set of equations for the location of the sensor: Solve the above equations to obtain the position coordinates of the magnetic field sensor at time t1, and save the time and coordinate data; Step S7.4: synchronously perform step S7.3 on the data collected by the remaining magnetic field sensors in the same sampling block to obtain the position coordinates of all sensors at time t1; Step S7.5: Finally, steps S7.1-S7.4 are encapsulated as a functional module, so that the external processor cyclically calls the module during the period from the entire circuit being connected to being disconnected.

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