Electromagnetic positioning method and system in strong magnetic field environment and storage medium thereof

Abstract

The invention discloses an electromagnetic positioning method and system in a strong magnetic field environment and a storage medium thereof. The method comprises the steps that sine wave current with fixed frequency is adopted to sequentially, circularly and alternately pass through four groups of magnetic source micro electromagnetic coils in sequence to excite sine wave magnetic fields in three dimensions; acquiring magnetic field data information of a positioning target in the sine wave magnetic field, and acquiring the magnetic field data information of the positioning target in the corresponding sine wave magnetic field based on the fact that one group of magnetic source micro electromagnetic coils are electrified each time, the magnetic field data information comprises a three-dimensional magnetic field component sensed by the positioning target in the sine wave magnetic field; fitting the three-dimensional magnetic field component of each dimension, and decomposing the three-dimensional magnetic field component to obtain independent magnetic field signals of four groups of magnetic source micro electromagnetic coils at the positioning target; and obtaining the position and attitude information of the positioning target according to the independent magnetic field signal. Compared with the prior art, the method has the following beneficial effects that the method can cyclically and alternately excite three-dimensional sine wave magnetic fields with fixed frequency, so that a positioning target can generate three-dimensional data to facilitate positioning calculation. In addition, a function fitting mode is adopted to assist in positioning calculation, after n-point data fitting, the standard deviation of an equivalent magnetic field measurement value can be reduced to # imgabs0 # of a direct measurement result, the signal-to-noise ratio is remarkably improved, superimposed magnetic field signal data with high accuracy are extracted, and the precision of a positioning system can be improved. According to the positioning method, the system is high in anti-interference capability, the calculation result is more accurate, the overall power consumption is low, and the cost is low.

Description

Technical Field

[0001] The present invention relates to the technical field of medical equipment, and in particular to an electromagnetic positioning method and system in a strong magnetic field environment and a storage medium thereof. Background Art

[0002] With the continuous development of medical technology, magnetically controlled capsule endoscopes, as a new type of painless, active digestive tract examination method, are gradually being widely used in clinical diagnosis and physical examination screening. The magnetically controlled device controls the strong magnetic field gradient generated by the magnet (electromagnet, permanent magnet or a combination of the two) to exert force and torque on the permanent magnet built into the capsule endoscope, thereby realizing remote non-contact control of the capsule endoscope. Precise control of the magnetically controlled device can be achieved through high-precision robotic arms, motors, etc., but the capsule endoscope swallowed into the body is blocked by the human body, and its position and posture are difficult to obtain accurately. As a result, the magnetic control of the capsule depends on the experience of the operating technician and doctor, and the automated quantitative intelligent control of the capsule is also difficult to implement.

[0003] In the existing technology of capsule endoscope positioning, the radio frequency positioning solution uses electromagnetic waves to position the capsule, which is not affected by the strong magnetic field of the magnetic control device, the magnetic field of the permanent magnet inside the capsule, etc. However, electromagnetic wave signals are significantly attenuated in human tissue, and the human tissue environment is unevenly distributed. The positioning accuracy of the capsule in the body is usually not high, and it is difficult to achieve the requirements of precise control.

[0004] Another type of existing technology is the magnetic positioning solution, including passive magnetic sensor array positioning and active magnetic source signal positioning. Magnetic sensor array positioning achieves the positioning function by measuring the spatial magnetic field distribution and separating the magnetic field component of the permanent magnet built into the capsule. Due to the small size of the magnet in the capsule, it is usually difficult to accurately detect the weak magnetic field of the capsule magnet in a strong magnetic field environment, making it difficult to effectively locate. Moreover, when the capsule is slightly far away from the array, the positioning effect is poor, and it is difficult to meet the 30-40cm height requirement for quantitative magnetic control under a strong magnetic field.

[0005] Active magnetic source signal positioning generates a magnetic field signal with unique characteristics through the magnetic source device, detects the spatial magnetic field through the magnetic sensor inside the capsule and separates the magnetic source signal, and realizes the positioning function of the capsule through optimization solution. The strong magnetic field environment of the magnetic control device requires the MEMS magnetic sensor in the capsule to have a large range to avoid oversaturation, and requires the magnetic source magnetic field signal to be strong to provide the signal-to-noise ratio accuracy required for magnetic positioning.

[0006] The existing magnetic positioning technology for capsule endoscopes in the human body mainly uses square wave pulse current to pass through the magnetic source coil to generate a corresponding square wave pulse magnetic field. The square wave pulse magnetic field has high power consumption and insufficient positioning endurance, which cannot meet the actual positioning needs. At the same time, it takes a certain amount of time for the square wave type sudden power supply to reach stability, that is, there is a step-like sudden change in the coil power supply (in fact, affected by the induced magnetic field, the current and magnetic field cannot change suddenly, but require a delay process, corresponding to the delay time), resulting in a long waiting time to measure the stable magnetic field amplitude, that is, the positioning cycle is long. On the one hand, it cannot meet the positioning frame rate requirements. On the other hand, due to the long positioning cycle, if the positioning target moves within a positioning cycle. The range is large, it will cause a large positioning error. In the prior art, there is also a method of using non-stationary curve characteristics to calibrate the curve transformation coefficient to obtain the amplitude of the square wave magnetic field. Although this can shorten the positioning cycle, the square wave amplitude error obtained is large, which ultimately leads to inaccurate positioning.

[0007] In the existing magnetic positioning technology for capsule endoscopes in the human body, in order to effectively reduce the power consumption of the square wave pulse magnetic field signal of the magnetic source and the negative impact of the square wave-like mutation magnetic field on the positioning accuracy, positioning technologies with sinusoidal magnetic field signals as the magnetic source have emerged one after another. Each independent sinusoidal magnetic field signal is obtained through Fourier decomposition, and then the position and posture of the positioning target are solved.

[0008] On the one hand, when the positioning target is far away from the magnetic source, the magnetic field measurement values ​​measured by the magnetic sensor of the positioning target are widely dispersed and the signal-to-noise ratio is low. Directly using the magnetic field measurement values ​​measured by the magnetic sensor of the positioning target for decomposition results in large noise and low positioning accuracy.

[0009] On the other hand, the positioning method of obtaining each independent sinusoidal magnetic field signal through Fourier decomposition has a very complex solution process, and has high requirements on the signal frequency setting of the magnetic source coil. For example, the signal frequency of the magnetic source coil is in multiple relationship, so that the highest signal frequency f of the magnetic source coil k Large, and the maximum sampling frequency f of the magnetic sensor s is limited, which results in an inability to obtain enough samples n (n≤f s / f k ), so the measured value of the magnetic sensor cannot accurately restore the actual magnetic field value, which ultimately leads to low positioning accuracy. In order to obtain an independent signal with higher accuracy through Fourier decomposition, it is necessary to obtain a sufficient number of samples. Obviously, it is impossible to obtain such a large number of samples in one cycle. Therefore, Fourier decomposition requires multiple periodic signals, that is, the required positioning cycle is longer. If the range of movement of the positioning target is large within one positioning cycle, it will lead to a large positioning error.

[0010] In summary, the existing magnetic positioning technology cannot meet the actual positioning requirements of capsule endoscopes.

[0011] The existing technology uses a large-size electromagnetic coil magnetic source powered by a pulsed square wave to achieve the capsule positioning function in a strong magnetic field environment. However, the DC power supply method has high power consumption and poor anti-interference ability. When the magnetic sensor has a low signal-to-noise ratio and low effective accuracy, the positioning accuracy is not ideal. Moreover, when the magnetic control device moves and the capsule shakes, it is difficult for the positioning system to obtain accurate magnetic source signals for positioning. It is necessary to wait for the magnetic control device to stop and the capsule to stabilize before positioning again, which affects the real-time quantitative magnetic control of the capsule.

[0012] Due to the complexity and peristalsis of the human digestive tract, as well as the hardware limitations in a strong magnetic field environment, most of the digital accuracy of the magnetic sensor is occupied by the strong magnetic field background, and the actual positioning signal accuracy is very limited, making it difficult to stably and accurately position the capsule endoscope. How to accurately and reliably position the capsule endoscope in a strong magnetic field environment has become an urgent problem to be solved.

[0013] Therefore, it is necessary to develop and design a capsule endoscope positioning system in a strong magnetic field environment with low power consumption, high frame rate, high precision and high stability, and to develop hardware driving methods and software calculation methods that are compatible with it. This will help improve the intelligence and automation of capsule magnetic control, expand the application scenarios of capsule endoscopes, enhance their auxiliary diagnosis effects, and improve the user experience. Summary of the invention

[0014] The purpose of the present invention is to provide an electromagnetic positioning method, system and storage medium in a strong magnetic field environment to solve the technical problems in the prior art that the magnetic positioning technology of capsule endoscopes has high power consumption, poor positioning accuracy, and takes a long time to solve the positioning problem and has poor timeliness.

[0015] To achieve one of the above-mentioned purposes of the invention, an embodiment of the present invention provides an electromagnetic positioning method in a strong magnetic field environment, the method comprising:

[0016] A fixed frequency sinusoidal current is used to cyclically and alternately pass through four groups of magnetic source micro-electromagnetic coils in sequence to excite a three-dimensional sinusoidal magnetic field;

[0017] Acquire magnetic field data information of the positioning target in the sinusoidal magnetic field, and acquire magnetic field data information of the positioning target in the corresponding sinusoidal magnetic field based on each time a group of the magnetic source micro-electromagnetic coils are energized, wherein the magnetic field data information includes a three-dimensional magnetic field component sensed by the positioning target in the sinusoidal magnetic field;

[0018] Fitting the three-dimensional magnetic field component of each dimension, and decomposing to obtain independent magnetic field signals of four groups of magnetic source micro-electromagnetic coils at the positioning target;

[0019] The position and posture information of the positioning target are obtained according to the independent magnetic field signal.

[0020] As a further improvement of the present invention, the method further comprises:

[0021] The frequency of the sinusoidal current is fixed to satisfy f ps ≤f≤f s / n, where f ps is the full-load positioning frame rate of the positioning system, f s is the sampling frequency of the magnetic sensor, and n is the number of samples that can be achieved within one cycle of a sinusoidal wave signal.

[0022] As a further improvement of the present invention, the method further comprises:

[0023] The fitting of the three-dimensional magnetic field component of each dimension specifically includes: performing function fitting on the magnetic field measurement values ​​of the dispersed three-dimensional magnetic field components to obtain the magnetic field intensity B in the corresponding dimension k；s (t);

[0024] The decomposition to obtain the independent magnetic field signals of the four groups of magnetic source micro-electromagnetic coils at the positioning target includes: the magnetic field strength B after decomposition and fitting k；s (t), obtain the magnetic induction intensity amplitude A of the independent magnetic field signals of the four groups of magnetic source micro electromagnetic coils at the positioning target k；s , the decomposition formula is:

[0025] B k；s (t) = A k；s sin(wt+b)+c k；s ;

[0026] Wherein, k represents the serial number of the magnetic source micro-electromagnetic coil, k=1, 2, 3, 4; s=1, 2, 3, represents the three dimensions of the sinusoidal magnetic field, representing the X direction, the Y direction, and the Z direction respectively; A k；s is the magnetic induction intensity amplitude of the independent magnetic field signals of the four groups of magnetic source micro-electromagnetic coils at the positioning target to be decomposed and determined, that is, the magnetic field measurement peak value; c k；s is the background magnetic field component when each group of magnetic source micro-electromagnetic coils is energized respectively; the signal angular frequency w and the signal phase b are known quantities directly obtained according to the frequency value and phase value of the current data.

[0027] As a further improvement of the present invention, the method further comprises:

[0028] The decomposition formula is linearized to obtain the linearized decomposition formula:

[0029]

[0030] Among them, β0；k；s X 0；k；s Characterizes the environmental magnetic field intensity at the positioning target when the four groups of magnetic source micro electromagnetic coils are powered on respectively; β 1；k；s X1 represents the three-dimensional magnetic field strength of the magnetic field signal at the positioning target when the four groups of magnetic source micro-electromagnetic coils are powered on respectively, that is, the three-dimensional magnetic field strength of the independent magnetic field signals of the four groups of magnetic source micro-electromagnetic coils at the positioning target;

[0031] Using a series of data at time t, {X j；k；s (t),B j；k；s (t)}, and solve the coefficient β through linear optimization j；k；s After that, it is easy to calculate the required magnetic induction intensity amplitude A k；s and background magnetic field c k；s .

[0032] As a further improvement of the present invention, the method further comprises:

[0033] The magnetic induction intensity amplitude A k；s Correction is performed, and the correction formula is Where Ik0 is the initial hardware parameter current peak value under ideal working conditions, Ik1 is the current peak value under actual working conditions, A 0；k；s is the magnetic field strength B after decomposition fitting k；s (t) The magnetic induction intensity amplitude A obtained k；s , A 1；k；s For the A 0；k；s The magnetic induction intensity amplitude is obtained after correcting the resistance and current change drift caused by the coil temperature change and the actual magnetic field intensity.

[0034] As a further improvement of the present invention, the method further comprises:

[0035] The magnetic induction intensity amplitude A k；s The matrix is ​​updated using a cyclic refresh mechanism, with 1x3 matrix elements updated each time, corresponding to the magnetic field generated at the magnetic sensor when the same set of coils is energized.

[0036] As a further improvement of the present invention, the method further comprises:

[0037] The magnetic induction intensity amplitude A k；s The matrix is ​​updated using a cyclic refresh mechanism, with 4x3 matrix elements updated each time, corresponding to the magnetic field generated at the magnetic sensor when the four sets of coils are energized.

[0038] As a further improvement of the present invention, the method further comprises:

[0039] Acquiring the position and attitude information of the positioning target according to the independent magnetic field signal specifically includes:

[0040] The geometric center is at the origin and the single coil is placed horizontally upward. The magnetic field components are in the cylindrical coordinate system. The following is expressed as

[0041]

[0042] Among them, the angular elliptic integral function

[0043]

[0044] Other parameters z ± =z±h, the coordinates of the spatial point (x, y, z) satisfy The basic parameters μ0 is the vacuum magnetic permeability, n is the number of coil turns per unit height, I is the peak current of the coil, a is the coil radius, and h is the half height of the coil;

[0045] The four coils are arranged in a horizontal 2x2 array in the Z=0 plane, with coil spacings of 2dx and 2dy respectively. The corresponding peak magnetic induction intensity can be expressed by the above formula:

[0046]

[0047] in, is the spatial position vector of the point to be located, and the coordinates of the center points of the four coils satisfy

[0048]

[0049] The peak magnetic induction intensity can be expressed as a matrix component form A k；s , where k = 1, 2, 3, 4, represents four groups of orthogonal magnetic source coil marks; s = 1, 2, 3, represents the three-dimensional magnetic field component marks measured by the magnetic sensor.

[0050] According to the peak value of magnetic induction intensity Obtain the theoretical value of the magnetic induction intensity peak matrix

[0051]

[0052] The position and attitude information of the positioning target is obtained by solving the corresponding relationship between the theoretical value of the magnetic induction intensity peak matrix and the magnetic field measurement peak in the independent magnetic field signal through a nonlinear optimization algorithm; wherein the corresponding relationship is:

[0053] At the spatial point (x, y, z), the theoretical value of the magnetic induction intensity peak matrix and the magnetic field measurement peak value satisfy the corresponding relationship

[0054]

[0055] in, A is the sensor attitude rotation matrix; k；s Measure the peak value of the magnetic field; is the theoretical value of the magnetic induction intensity peak matrix;

[0056] The nonlinear optimization algorithm is:

[0057]

[0058] As a further improvement of the present invention, the method further comprises:

[0059] The pitch angle pitch and the roll angle roll of the positioning target are obtained, and the yaw angle yaw and the position coordinates of the positioning target are calculated according to the pitch angle pitch, the roll angle roll of the positioning target and the independent magnetic field signal.

[0060] In order to achieve one of the above-mentioned objects of the invention, the present invention further provides an electromagnetic positioning system in a strong magnetic field environment, the system comprising:

[0061] A magnetic field generating component, comprising at least four groups of magnetic source micro-electromagnetic coils arranged in the same plane, wherein the magnetic source micro-electromagnetic coils are used to receive sinusoidal currents and generate three-dimensional sinusoidal magnetic fields;

[0062] A positioning target, comprising a three-dimensional magnetic sensor for sensing a three-dimensional magnetic field component within the sinusoidal magnetic field;

[0063] A positioning processing component, electrically connected to the magnetic field generating component through a switching switch and communicatively connected to the positioning target;

[0064] The positioning processing component is configured to implement the strong electromagnetic positioning method as described above.

[0065] As a further improvement of the present invention, the system also includes: the positioning processing component also includes a sinusoidal pulse width modulation module, the sinusoidal pulse width modulation module is electrically connected to the switching switch, the sinusoidal pulse width modulation module is used to receive direct current and convert it into alternating current of a preset frequency, and the sinusoidal pulse width modulation module outputs the alternating current to the coil through the switching switch.

[0066] As a further improvement of the present invention, the system further includes: the strong electromagnetic positioning system further includes a magnetic control device, the positioning target further includes a magnet, the magnetic control device magnetically cooperates with the magnet, and the magnetic control device is used to electromagnetically control the movement of the positioning target.

[0067] As a further improvement of the present invention, the system also includes: the magnetic control device includes a control magnet, a robotic arm and a motor, the control magnet is arranged at the end of the robotic arm, and the motor is electrically connected to the robotic arm and drives the robotic arm to move along a preset path.

[0068] As a further improvement of the present invention, the system further comprises: the positioning target further comprises an imaging unit and an inertial measurement unit, and the imaging unit and the inertial measurement unit are communicatively connected to the positioning processing component;

[0069] The imaging unit is used to capture images;

[0070] The inertial measurement unit is used to obtain inertial measurement data.

[0071] The present invention also provides a storage medium, wherein the storage medium stores a computer program, and when the computer program is executed by a processor, the steps in the micro-electromagnetic positioning method as described above are implemented.

[0072] Compared with the prior art, the present invention has the following beneficial effects: the present invention can cyclically and alternately excite a three-dimensional sinusoidal magnetic field with a fixed frequency, so that the positioning target can generate three-dimensional data for easy positioning and solution. The present invention also uses function fitting to assist positioning and solution. After n-point data fitting, the standard deviation of the equivalent magnetic field measurement value can be reduced to the direct measurement result. The signal-to-noise ratio is significantly improved, and the superimposed magnetic field signal data with high accuracy is extracted, which can improve the accuracy of the positioning system. The positioning method and system of the present invention have strong anti-interference ability, more accurate solution results, lower overall power consumption and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Figure 1 It is a flow chart of an electromagnetic positioning method in a strong magnetic field environment according to one embodiment of the present invention.

[0074] Figure 2 It is a flow chart of fitting magnetic field data information in a strong magnetic field environment and decomposing it to obtain independent magnetic field signals in one embodiment of the present invention.

[0075] Figure 3 It is an exemplary typical magnetic field data characteristic diagram in one embodiment of the present invention.

[0076] Figure 4 is a characteristic diagram of the magnetic field component in one embodiment of the present invention.

[0077] Figure 5 The timing control logic of the non-interval cyclic alternating power supply in one embodiment of the present invention is shown in the figure.

[0078] Figure 6This is a timing logic diagram of power-on control for long-interval cyclic alternating power supply in one embodiment of the present invention.

[0079] Figure 7 This is a timing logic diagram of power-on control for short-interval cyclic alternating power supply in one embodiment of the present invention.

[0080] Figure 8 It is a flow chart for solving the position and posture information of the positioning target in one embodiment of the present invention.

[0081] Fig. 9 FIG. 4 is a matrix arrangement diagram of four groups of coils in one embodiment of the present invention.

[0082] Fig.10 It is a connection block diagram of a strong electromagnetic positioning system in one embodiment of the present invention.

[0083] Fig.11 It is a schematic diagram of a positioning processing component controlling a switching switch to switch on a conducting coil in one embodiment of the present invention.

[0084] Fig.12 It is a schematic diagram of a human body located on an examination table surface and being detected by a positioning target in one embodiment of the present invention.

[0085] Fig.13 It is a schematic diagram of reducing power consumption by changing the number of coil turns in one embodiment of the present invention.

[0086] Fig.14 It is a schematic diagram of the system structure for locating a target in one embodiment of the present invention.

[0087] Fig.15 It is a computer system structure block diagram of the storage medium suitable for implementing the implementation mode of the present application in the present invention. DETAILED DESCRIPTION

[0088] The present invention will be described in detail below in conjunction with the specific embodiments shown in the accompanying drawings. However, these embodiments do not limit the present invention, and any structural, methodological, or functional changes made by a person skilled in the art based on these embodiments are all within the scope of protection of the present invention.

[0089] like Figures 1 to 3 As shown, in one embodiment of the present invention, an electromagnetic positioning method in a strong magnetic field environment is provided, which can be applied to the positioning of capsule endoscopes during gastrointestinal medical examinations and auxiliary diagnosis. A target detection area is formed by a sinusoidal wave magnetic field of the strong electromagnetic positioning method, and the capsule endoscope is located and active in the target detection area. The strong electromagnetic positioning method can calculate the position and posture of the capsule endoscope in the target detection area; wherein, the capsule endoscope is identified as positioning target 2 in the target detection area.

[0090] S1: A fixed-frequency sinusoidal current is used to circulate alternately through four groups of magnetic source micro-electromagnetic coils in sequence to excite a three-dimensional sinusoidal magnetic field.

[0091] S2: Acquire the magnetic field data information of the positioning target in the sinusoidal magnetic field, and acquire the magnetic field data information of the positioning target in the corresponding sinusoidal magnetic field each time a group of the magnetic source micro-electromagnetic coils are energized, wherein the magnetic field data information includes the three-dimensional magnetic field components sensed by the positioning target in the sinusoidal magnetic field.

[0092] S3: Fitting the three-dimensional magnetic field component of each dimension, and decomposing to obtain independent magnetic field signals of four groups of magnetic source micro-electromagnetic coils at the positioning target.

[0093] S4: Obtaining the position and posture information of the positioning target according to the independent magnetic field signal.

[0094] The strong magnetic field environment refers to the strong magnetic field of the magnetron device, the permanent magnet magnetic field inside the capsule and other environmental magnetic fields relative to the magnetic field of the magnetic source coil.

[0095] In step S1, the positioning method cyclically and alternately excites four groups of magnetic source micro-electromagnetic coils to generate three-dimensional sinusoidal magnetic fields respectively. The sinusoidal magnetic fields of the four groups of magnetic source micro-electromagnetic coils excite the positioning target in different time periods to generate magnetic field data information, so that the magnetic field data information of each dimension can be separated in the generation stage for easy distinction, which is more conducive to subsequent calculations; at the same time, it can reduce the amount of calculation during positioning solution, thereby saving solution time and reducing solution power consumption; in the solution process, it has strong anti-interference ability, can eliminate background interference, has high data accuracy and low distortion rate, so the real-time positioning performance is better during repeated positioning.

[0096] The system is powered by a DC power supply to achieve the required variable frequency control. You can use a universal AC rectifier power supply or a USB or Type C power supply interface to obtain a standard voltage (e.g. 5V) DC power supply to reduce system cost. Convert DC power into a standard sinusoidal AC power with a specific amplitude (within the safe voltage range), frequency, and phase, and power the electromagnetic coil to generate a sinusoidal magnetic field signal.

[0097] Under the same signal peak, the power consumption of the sine wave signal is only 1 / 2 of that of the square wave pulse signal, which can effectively reduce the power consumption of the strong magnetic field positioning system. The sine wave electrical signal has no mutations, and will not cause magnetic field signal distortion and high-frequency harmonic interference to the inductive coil. There is no need to wait for the magnetic field delay to stabilize before performing magnetic field measurement, which can achieve better positioning stability and real-time performance. The sine wave magnetic field signal with a unique frequency can also avoid low-frequency interference from the movement of the magnetic control device and the jitter of the capsule, as well as interference from other external magnetic fields. By sampling the signal n times within a period and fitting the sine wave function, the statistical error of the signal measurement can be reduced, further improving the positioning accuracy.

[0098] Four sets of parallel flat structure magnetic source coils circulate and alternately apply sinusoidal current of a specific frequency.

[0099] I(t)=asin(wt+b),

[0100] Where a is the current peak value, w=2πf is the sine wave angular frequency, f is the sine wave frequency, and b is the sine wave phase. The peak value a and frequency f of the sine wave current are preset fixed values ​​of the hardware system.

[0101] The magnetic induction intensity vector of the sinusoidal magnetic field generated by the sinusoidal current passing through the coil is

[0102]

[0103] in, is the peak vector of magnetic induction intensity (including the three-axis magnetic field components in space), and k is the coil serial number (k=1, 2, 3, 4, corresponding to the 4 groups of electromagnetic coils used for positioning).

[0104] There is an optimized value for the initial phase of the sine wave. Usually, the phase of the sine wave can be set to b=0 through hardware control (in fact, b=nπ can also achieve the same effect, but b=0 is simpler and more natural), so that after each set of coils undergoes a complete cycle of power-on, it switches to the next set of coils for power supply, and the initial phase of the current is also 0. This processing method can reduce the sudden change of coil current caused by switching coil power supply due to non-zero initial phase, and reduce the distortion of the waveform of the magnetic field generated by the magnetic source coil to a certain extent.

[0105] The sine wave frequency f has a reasonable range of values, satisfying f ps ≤f≤f s / n. The lower limit of the sine wave frequency f is subject to the full-load positioning frame rate f of the positioning system. ps For example, if the positioning system wants to achieve a full-load positioning frame rate of 20fps, the sine wave frequency f must be no less than 20Hz. The upper limit of the sine wave frequency f is limited by the magnetic sensor sampling frequency f. s Limit, f≤f s / n, to ensure that n sampling times (for example, n ≥ 30) can be achieved within a sine wave signal cycle, thereby reducing the sine wave signal fitting variance and improving the positioning accuracy of the positioning system. For example, the magnetic sensor sampling frequency is 1kHz, the number of sampling points n = 30, then the sine wave frequency f k If the limit on the number of samples in a cycle is reduced, the frequency of the sine wave can be further increased to achieve the purpose of increasing the positioning frame rate (for example, if n=15 is set, the positioning frame rate can reach 66Hz).

[0106] In actual application scenarios, the sine wave frequency can be set to 24Hz, so that the full-load positioning frame rate of the positioning system can reach 24fps. By controlling the power-on state of the magnetic source coil and only powering the coil in part of the cycle, the system power consumption can be reduced (at the same time, the system positioning frame rate is reduced accordingly). It is easy to reduce the system positioning frame rate to a divisor of 24, and realize integer frame rate positioning such as 24, 12, 8, 6, 4, 3, 2, 1fps, etc., so as to achieve accurate matching of the positioning frame rate of the capsule endoscope with the real-time reading image frame rate.

[0107] In step S2, the magnetic field data information of the positioning target in the sinusoidal magnetic field is obtained, and the magnetic field data information includes the three-dimensional magnetic field component sensed by the positioning target in the sinusoidal magnetic field. The three-dimensional magnetic field component sensed by the positioning target is the superposition magnetic field of the three-dimensional sinusoidal magnetic field and the ambient magnetic field respectively excited by the four groups of magnetic source micro-electromagnetic coils when the four groups of magnetic source micro-electromagnetic coils are respectively energized.

[0108] In one embodiment of the present invention, Figure 2 As shown, fitting the four-dimensional magnetic field component of each dimension in step S3 specifically includes:

[0109] The magnetic field strength B in the corresponding dimension is obtained by performing function fitting on the magnetic field measurement values ​​of the dispersed three-dimensional magnetic field components. k；s (t);

[0110] The decomposition to obtain independent magnetic field signals of four groups of magnetic source micro-electromagnetic coils at the positioning target includes:

[0111] The magnetic field strength B after decomposition fitting k；s (t), obtain the magnetic induction intensity amplitude A of the independent magnetic field signals of the four groups of magnetic source micro electromagnetic coils at the positioning target k；s , the decomposition formula is:

[0112] B k；s (t) = A k；s sin(wt+b)+c k；s ;

[0113] Wherein, k represents the serial number of the magnetic source micro-electromagnetic coil, k=1, 2, 3, 4; s=1, 2, 3, represents the three dimensions of the sinusoidal magnetic field, representing the X direction, the Y direction, and the Z direction respectively; A k；s is the magnetic induction intensity amplitude of the independent magnetic field signals of the four groups of magnetic source micro-electromagnetic coils at the positioning target to be decomposed and determined, that is, the magnetic field measurement peak value; c k；s is the background magnetic field component when each group of magnetic source micro-electromagnetic coils is energized respectively; the signal angular frequency w and the signal phase b are known quantities directly obtained according to the frequency value and phase value of the current data.

[0114] For the magnetic source of four sets of coils, the peak value of magnetic induction intensity A measured by the three-axis magnetic sensor k；s is a 4x3 matrix.

[0115] In one embodiment of the present invention, the decomposition formula may also be linearized to obtain a linearized decomposition formula:

[0116]

[0117] Among them, β 0；k；s X 0；k；s Characterizes the environmental magnetic field intensity at the positioning target when the four groups of magnetic source micro electromagnetic coils are powered on respectively; β 1；k；s X1 represents the three-dimensional magnetic field strength of the magnetic field signal at the positioning target when the four groups of magnetic source micro-electromagnetic coils are powered on respectively, that is, the three-dimensional magnetic field strength of the independent magnetic field signals of the four groups of magnetic source micro-electromagnetic coils at the positioning target;

[0118] Using a series of data at time t, {X j；k；s (t),B j；k；s (t)}, and solve the coefficient β through linear optimization j；k；s After that, it is easy to calculate the required magnetic induction intensity amplitude A k；s and background magnetic field c k；s This fitting process is performed independently for each of the 4x3=12 combinations of k and s, and the obtained magnetic induction intensity amplitude A k；s It is in the form of a 4x3 matrix.

[0119] The phase of the sinusoidal current of the coil is synchronized with the generated sinusoidal magnetic field. The phase information of the sinusoidal magnetic field measurement value can be directly obtained based on the known current phase (usually b=0 is set at the hardware level), reducing the algorithm complexity.

[0120] The magnetic field data measured by the magnetic sensor has the characteristics of periodic segmentation when the energized coil is switched. For example, the typical data characteristics are shown in Figure 3The magnetic field [Bx, By, Bz] measured by the three-axis magnetic sensor is divided into 4 groups by the coil identifier k, totaling 4x3=12 independent magnetic field components. The magnetic sensor measurement value conforms to the sine wave characteristics. When fitting according to the standard sine wave with phase b=0, the magnetic field amplitude can be negative, corresponding to the opposite direction of the magnetic sensor positive direction and the magnetic field direction.

[0121] like Figure 4 As shown in the figure, the characteristics of the magnetic field components are shown. For MEMS type micro magnetic sensors, the sampling frequency is limited, and the signal noise affects the accuracy of direct measurement. The amplitudes of the 4x3 groups of magnetic field signal data measured are orders of magnitude different. The small amplitude of some components leads to a too low signal-to-noise ratio, resulting in a large variance in the positioning results and low positioning accuracy. In addition, interference signals of other frequencies will also affect the accuracy of the direct measurement results. After fitting the n-point data, the standard deviation of the equivalent magnetic field measurement value can be reduced to the direct measurement result. The signal-to-noise ratio is significantly improved. Therefore, function fitting for magnetic field measurements is very valuable.

[0122] Function fitting can effectively suppress high-frequency noise and eliminate low-frequency background interference. Therefore, for positioning application scenarios with strict low-power requirements, using sinusoidal power supply to generate magnetic source magnetic field and using function fitting method to suppress high-frequency noise signals and separate low-frequency background signals at one time, and extracting high-accuracy coil magnetic field signal data is crucial to improving the accuracy of the positioning system.

[0123] Furthermore, the sinusoidal current of the coil is synchronized with the generated sinusoidal magnetic field. The phase and frequency of the corresponding independent magnetic field signal after separation can be directly obtained based on the known current phase and frequency. That is, the phase and frequency of the independent magnetic field signal are preset known quantities, and the magnetic induction intensity amplitude A of the independent magnetic field signal needs to be solved. k；s In the present invention, the superimposed magnetic field signal data B is decomposed according to the preset frequency s (t), other unimportant signals are thrown to c s (i.e. background magnetic field) item, including low-frequency and high-frequency signals (that is, signals that do not belong to the frequency of independent magnetic field signals).

[0124] The four groups of coils are energized alternately in a cycle, and the three-axis magnetic sensor obtains the time series data of the magnetic field measurement value at the spatial position, including the three-dimensional components of the magnetic field [Bx, By, Bz], as well as the identifier of the kth coil currently energized and the real-time current Ik. Ik can be used to online correct the resistance and current change drift caused by the temperature change of the coil and the actual magnetic field strength generated. The initial hardware parameter current peak value of Ik under ideal working conditions is Ik0, and the current peak value under actual working conditions (the peak value can be obtained by fitting the current series data Ik through a fitting method similar to step S3, or directly obtained through hardware) is Ik1, then the peak value of the magnetic induction intensity under actual working conditions needs to be corrected to Among them A 0；k；s is the magnetic field strength B after decomposition and fitting based on the phase information and angular frequency of the independent magnetic field signal k；s (t) The magnetic induction intensity amplitude A obtained k；s , A 1；k；s For the A 0；k；s The magnetic induction intensity amplitude is obtained after correcting the resistance and current change drift caused by the coil temperature change and the actual magnetic field intensity.

[0125] For low-power micro-electromagnetic portable positioning systems, after being worn for a certain period of time, the actual coil temperature tends to be stable human body temperature, with small changes, and the drift caused by temperature is also relatively small. However, setting the ideal operating temperature to about 37°C for Ik0 calibration can omit the above temperature-induced magnetic field theoretical value correction.

[0126] The timing control logic of the cyclic alternating power supply is shown in Figure 5-7 , the four coils are switched in sequence for a complete cycle, and only one coil is powered in each cycle, which can avoid the 4 times power consumption problem required for the four coils to be powered at the same time. Compared with the simultaneous power supply solution, the coil current and magnetic field strength signal-to-noise ratio can be increased by about 2 times under the same power consumption, thereby improving the positioning performance indicators of the system.

[0127] The switching interval time dt of each coil power supply can be 0( Figure 5 ), or a smaller interval other than 0 ( Figure 6 , Figure 7 ), reducing the interference of the magnetic field between the coils. Switching near the current phase b=0 can further minimize the interference amplitude. Therefore, the power supply switching time interval dt=0 can be set to increase the magnetic field refresh frequency, thereby increasing the frame rate of the positioning system.

[0128] When the positioning system reduces the positioning frame rate, all coils are in a no-load state during some periodic periods, which can further reduce the power consumption of the system. There are two ways to reduce the positioning frame rate: long interval mode and short interval mode. The power control timing logic diagram of the long interval mode is shown in Figure 6 After the four coils are energized alternately once, they are kept in an unloaded state for a long interval, and then energized alternately again. See the timing logic diagram of the short interval energization control. Figure 7 , the four groups of coils are energized alternately at shorter and more uniform intervals. The short interval method is more conducive to data stability when the magnetic field measurement data is reused, and the stability of the positioning solution results is better. Both methods can achieve the purpose of reducing the positioning frame rate and reducing the power consumption of the coil. For example, the situation shown in the figure can further reduce the power consumption of the magnetic source coil to 1 / 3 of the full load, thereby improving the endurance of the positioning system. At the same time, the positioning frame rate is reduced from 24fps to 8fps. According to a similar method, positioning with lower power consumption and lower frame rate can be achieved, and the real-time performance of positioning is also reduced.

[0129] Correspondingly, the positioning unit can also synchronously adopt a frequency reduction mechanism to detect and collect magnetic field signals, thereby saving the communication timing and energy consumption of the capsule endoscope.

[0130] In one embodiment of the present invention, the peak value of magnetic induction intensity A k；s The matrix is ​​updated using a cyclic refresh mechanism, with 1x3 matrix elements updated each time, corresponding to the magnetic field generated at the magnetic sensor when the same set of coils is energized. The four sets of coils are energized alternately, and the above matrix elements are also updated cyclically. When the positioning frame rate is high and the movement of the positioning target is relatively stable, it can be approximately considered that the 4x3 matrix elements are measured simultaneously. Small disturbances of the positioning target can be suppressed by filtering the positioning results. The filtering algorithm can use mean smoothing filtering, Kalman filtering, etc., all of which can achieve good results.

[0131] The cyclic refresh mechanism of the peak value of magnetic induction intensity can perform a positioning solution every time it is updated, without waiting for the entire 4x3 matrix to be fully refreshed. It can avoid energizing the four sets of coils at the same time, significantly saving the power consumption of the magnetic source coil system. At the same time, it maintains the effect of approximately equivalent magnetic field generation and detection, and does not affect the real-time positioning and does not reduce the positioning frame rate.

[0132] In one embodiment of the present invention, a positioning period of the micro-electromagnetic positioning method is T=T1+d t , where T1 is the power supply time of each group of the four magnetic source micro electromagnetic coils, d t The switching interval time for supplying power to each group of the four groups of magnetic source micro electromagnetic coils.

[0133] Enter the mth positioning cycle, m≥4, the time of the mth positioning cycle T=T1+d t , where T1 is the power supply time of each group of the three magnetic source micro electromagnetic coils, d t a switching interval for supplying power to each of the three groups of magnetic source micro-electromagnetic coils;

[0134] The method of using a fixed frequency sinusoidal current to cyclically and alternately pass through four groups of magnetic source micro-electromagnetic coils in sequence to excite a three-dimensional sinusoidal magnetic field includes:

[0135] The first group of magnetic source micro-electromagnetic coils is powered in the m-4th positioning period, the second group of magnetic source micro-electromagnetic coils is powered in the m-3th positioning period, the third group of magnetic source micro-electromagnetic coils is powered in the m-2th positioning period, the fourth group of magnetic source micro-electromagnetic coils is powered in the m-1th positioning period, the first group of magnetic source micro-electromagnetic coils is powered in the m-4+4nth positioning period, the second group of magnetic source micro-electromagnetic coils is powered in the m-3+4nth positioning period, the third group of magnetic source micro-electromagnetic coils is powered in the m-2+4nth positioning period, and the fourth group of magnetic source micro-electromagnetic coils is powered in the m-1+4nth positioning period, where n≥1.

[0136] The peak value of magnetic induction intensity A k；s The matrix adopts a cyclic refresh mechanism to update, specifically including, in the current m-4+4nth positioning cycle, the magnetic induction intensity peak value A k；s Including the peak value A of the magnetic induction intensity obtained when the first group of magnetic source micro-electromagnetic coils are powered during the m-4+4n positioning cycle 1；s , the peak value of magnetic induction intensity A obtained when the second group of magnetic source micro-electromagnetic coils are powered during the m-7+4n positioning cycle 2；s , the peak value of magnetic induction intensity A obtained when the third group of magnetic source micro-electromagnetic coils are powered in the m-6+4n positioning cycle 3；s , the peak value of magnetic induction intensity A obtained when the fourth group of magnetic source micro-electromagnetic coils are powered in the m-5+4n positioning cycle 3；s , that is, in the current m-4+4nth positioning cycle, the peak value of the magnetic induction intensity A k；s The peak value of magnetic induction intensity A obtained when the first group of magnetic source micro-electromagnetic coils are powered in the m-8+4nth positioning cycle in the matrix 1；s Updated to the peak value of magnetic induction intensity A obtained when the first group of magnetic source micro-electromagnetic coils are powered in the m-4+4nth positioning cycle 1；s Similarly, in the current m-3+4nth positioning cycle, the peak value of the magnetic induction intensity A k；s Including the peak value A of the magnetic induction intensity obtained when the first group of magnetic source micro-electromagnetic coils are powered during the m-4+4n positioning cycle 1；s , the peak value of magnetic induction intensity A obtained when the second group of magnetic source micro-electromagnetic coils are powered during the m-3+4n positioning cycle 2；s , the peak value of magnetic induction intensity A obtained when the third group of magnetic source micro-electromagnetic coils are powered in the m-6+4n positioning cycle 3；s , the peak value of magnetic induction intensity A obtained when the fourth group of magnetic source micro-electromagnetic coils are powered in the m-5+4n positioning cycle 3；s, that is, in the current m-3+4n positioning cycle, the peak value of the magnetic induction intensity A k；s The peak value of magnetic induction intensity A obtained when the second group of magnetic source micro-electromagnetic coils are powered in the m-7+4n positioning cycle in the matrix 1；s Updated to the peak value of magnetic induction intensity A obtained when the second group of magnetic source micro-electromagnetic coils are powered in the m-3+4n positioning cycle 1；s .

[0137] In one embodiment of the present invention, the peak value of magnetic induction intensity A k；s The matrix is ​​updated using a cyclic refresh mechanism, with 4x3 matrix elements updated each time, corresponding to the magnetic field generated at the magnetic sensor when the four coils are powered on. The four coils are powered on alternately, and the matrix elements are also updated cyclically. In this case, in each positioning cycle, the four coils are powered on alternately once, and a 4x3 peak value of magnetic induction intensity A is obtained. k；s matrix.

[0138] See Figure 6 As shown in the long interval mode power-on control timing logic diagram, after the four sets of coils are alternately energized once, they are kept in a no-load state for a long interval, and then alternately energized once again. Since a long interval of no-load state is maintained between each positioning cycle, the 4x3 matrix elements obtained in adjacent positioning cycles cannot be considered to be measured simultaneously. Therefore, in this implementation, 4x3 matrix elements are updated in each positioning cycle to ensure the real-time positioning under low frame rate conditions and obtain better positioning effects.

[0139] In one embodiment of the present invention, step S4 of obtaining the position and attitude information of the positioning target according to the independent magnetic field signal specifically includes:

[0140] When the size of the magnetic source coil is large, the spatial distribution of the magnetic induction intensity will cause large deviations if the magnetic dipole is directly used to approximate it, resulting in distortion of the positioning trajectory. Therefore, the ideal solenoid model with multiple turns of circular wire magnetic fields superimposed is used to calculate the magnetic field. Specifically, for a single coil with its geometric center at the origin and placed horizontally upward, the magnetic field components in the cylindrical coordinate system are The following is expressed as

[0141]

[0142] Among them, the angular elliptic integral function

[0143]

[0144] Other parameters z ± =z±h, the coordinates of the spatial point (x, y, z) satisfy The basic parameters μ0 is the vacuum magnetic permeability, n is the number of coil turns per unit height, I is the peak current of the coil, a is the coil radius, and h is the half height of the coil.

[0145] The coil layout of the four-coil system in counterclockwise order is as follows Fig. 9 As shown, the four coils are arranged in a horizontal 2x2 array in the Z=0 plane, and the coil spacing is 2dx and 2dy respectively. The corresponding peak value of magnetic induction intensity can be expressed by the above formula:

[0146]

[0147] in, is the spatial position vector of the point to be located, and the coordinates of the center points of the four coils satisfy

[0148]

[0149] The peak value of magnetic induction intensity can be expressed as matrix component form A k；s , where k = 1, 2, 3, 4, represents four groups of orthogonal magnetic source coil marks; s = 1, 2, 3, represents the three-dimensional magnetic field component marks measured by the magnetic sensor.

[0150] According to the peak value of magnetic induction intensity Obtain the theoretical value of the magnetic induction intensity peak matrix

[0151]

[0152] Specifically, the peak magnetic induction intensity It can be expressed as a matrix component form Where k is the magnetic source coil number, and s is the three-dimensional component measured by the three-axis magnetic sensor. For the magnetic source of four sets of coils, is a 3x3 matrix. It should be noted that the magnetic induction intensity Equivalent to the theoretical value of the magnetic induction intensity peak matrix

[0153] Four sets of orthogonal coils can obtain 4x3=12 independent magnetic induction intensity components A k；s , including a certain amount of redundancy to avoid the signal-to-noise ratio of some magnetic field components being too low (e.g. Figure 4 B shown in 1；3 , B 4；3 The large positioning error caused by the positioning error is sufficient to calculate the 6DOF position and attitude information of the magnetic sensor at its spatial position and avoid the blind area of ​​poor positioning.

[0154] The position and attitude information of the positioning target is obtained by solving the corresponding relationship between the theoretical value of the magnetic induction intensity peak matrix and the magnetic field measurement peak in the independent magnetic field signal through a nonlinear optimization algorithm; wherein the corresponding relationship is:

[0155] At the spatial point (x, y, z), the theoretical value of the magnetic induction intensity peak matrix and the magnetic field measurement peak value satisfy the corresponding relationship

[0156]

[0157] in, A is the sensor attitude rotation matrix; k；s Measure the peak value of the magnetic field; is the theoretical value of the magnetic induction intensity peak matrix;

[0158] in, is the sensor posture rotation matrix, which represents the spatial rotation operation of rotating the sensor from the standard posture aligned with the world coordinate system axis to the current posture. It is an orthogonal normalized matrix containing 3x3=9 non-independent elements. The actual independent degrees of freedom are 3, which can be uniquely determined by the three rotation Euler angles yaw, pitch, and roll (the order of Euler angle rotation only needs to be consistent in the formula system, and there is no special order requirement. Generally, the ZYX order can be selected).

[0159] The following parameter optimization problems are solved by nonlinear optimization algorithms (such as LM, PSO algorithm, etc.):

[0160]

[0161] In the nonlinear optimization algorithm, the position information X, Y, Z and 3DOF attitude angles yaw (yaw angle), pitch (pitch angle) and roll (roll angle) of the positioning target are calculated based on the known theoretical value of the magnetic induction intensity peak matrix and the known magnetic field measurement peak value.

[0162] In one embodiment of the present invention, it also includes: obtaining the pitch angle pitch and roll angle roll of the positioning target, and calculating the yaw angle yaw and the position coordinates of the positioning target according to the pitch angle pitch, roll angle roll of the positioning target and the independent magnetic field signal.

[0163] Specifically, the pitch and roll angles of the capsule endoscope (positioning target) can be directly obtained with high accuracy through additional devices such as IMU (inertial measurement unit). The pitch and roll angles are known input parameters, which can reduce the number of unknown parameters (from 6 to 4), further simplify the above nonlinear solution, and improve the efficiency of positioning. It should be noted that the accelerometer in the IMU can only give accurate attitude angles (pitch, roll) in a stable state of force balance. For application scenarios with high real-time requirements for magnetic control, it is more reliable to use a positioning method based on a pure magnetic sensor when the capsule is in motion.

[0164] The four sets of magnetic source coils in a planar layout have mirror symmetry in the magnetic source magnetic field distribution about the Z=0 plane. The above positioning results cannot distinguish the 3DOF position points (x, y, +z) and (x, y, -z) that are symmetrical about the Z=0 plane. The mirror symmetry can be eliminated by limiting the positioning area to a half space (for example, Z>0, corresponding to the actual working area above the examination table), so that the positioning solution result is uniquely determined. For example, if z<0 in the solution result (x, y, z), the position result is remapped to (x, y, -z); and the 3DOF attitude angle also needs to be processed symmetricly, and (roll, pitch, yaw) is remapped to (roll, PI+pitch, PI-yaw).

[0165] Through the above positioning solution method, target positioning based on the micro-electromagnetic positioning method in a strong magnetic field environment can be achieved.

[0166] Through the above strong magnetic field cycle positioning system and positioning method, the wireless capsule endoscope can achieve real-time stable tracking and positioning with high accuracy (<3mm) and high frame rate (~24fps) in a large range (radius>400mm) with low power consumption (for example, within 2-5W). By reducing the required positioning frame rate, the effective power-on time of the electromagnetic coil can be reduced, further reducing the system power consumption and improving the system's battery life. For example, by reducing the positioning frame rate to 1 / 2 of the full-load frame rate, the actual power consumption of the positioning system will also be reduced to about 1 / 2 of the full-load power consumption.

[0167] In an embodiment of the present invention, a method for reducing system power consumption for positioning a capsule endoscope in a strong magnetic field environment is provided.

[0168] Methods to reduce system power consumption include hardware structure improvements and software algorithm improvements, both of which can be enabled separately or simultaneously. Reducing system power consumption (e.g. <5W) can eliminate the coil cooling system, further saving hardware costs and eliminating the noise caused by heat dissipation mechanical components.

[0169] The hardware structure is improved by increasing the number of coil turns. The magnetic field strength B generated by the coil is proportional to the product of the number of turns N and the current strength I. When the number of coil turns changes, the magnetic field strength generated by the magnetic source coil remains unchanged, while reducing the power consumption of the coil. When pulse square wave power supply is used, the magnetic field waveform is delayed and deformed due to the increase in the number of coil turns. In the coil system powered by a sine wave, the current will not change suddenly, and there will be no such problem of delayed deformation of the magnetic field waveform that affects the positioning accuracy and real-time performance.

[0170] like Fig.13 As shown in the figure, when the power supply input voltage of the coil is constant, the number of coil turns increases by n times, the corresponding resistance R increases by n times, the current intensity decreases to 1 / n, and the power consumption decreases to 1 / n accordingly. For example, increasing the number of coil turns by 4 times can keep the magnetic field signal strength of the magnetic source coil approximately unchanged while reducing the power consumption to 25% of the previous value.

[0171] like Figure 6 , 7 As shown in the figure, the software algorithm improvement is achieved by reducing the positioning frame rate. When the positioning system reduces the positioning frame rate, all coils are in a no-load state during some cycles, which can further reduce the power consumption of the system.

[0172] like Figure 9-14 As shown, in one embodiment of the present invention, an electromagnetic positioning system in a strong magnetic field environment is also provided, which can excite the coil to generate a sinusoidal magnetic field, and the positioning target can obtain a three-dimensional magnetic field component in the sinusoidal magnetic field to facilitate positioning and solving to obtain the position information of the positioning target. Specifically including:

[0173] The magnetic field generating component 1 comprises at least four groups of magnetic source micro electromagnetic coils arranged in the same plane, wherein the magnetic source micro electromagnetic coils are used to receive sinusoidal currents and generate three-dimensional sinusoidal magnetic fields;

[0174] A positioning target 2, comprising a three-dimensional magnetic sensor 21, for sensing a three-dimensional magnetic field component within the sinusoidal magnetic field;

[0175] A positioning processing component 3 is electrically connected to the magnetic field generating component 1 through a switching switch 4 and is in communication connection with the positioning target 2;

[0176] The positioning processing component 3 is configured to implement the electromagnetic positioning method in a strong magnetic field environment as described in any of the above embodiments.

[0177] The positioning target 2 is a capsule endoscope, and the magnetic field generating component 1 is used as a sinusoidal magnetic field generating source, and is usually used as the coordinate center during the positioning process. The three-dimensional magnetic sensor 21 can be a MEMS microchip (such as Hall, AMR, TMR and other magnetic sensors), or a micro flux coil.

[0178] It should be noted that in a strong magnetic field environment, in order to avoid oversaturation of the magnetic sensor and cause failure of magnetic field measurement, the magnetic sensor is required to have a large range, for example, up to + / -30mT level. AKM AK09973D, Melexis MLX90397 and other three-dimensional magnetic sensors 21 have a range that meets the requirements and a high digital bit resolution. Optionally, an IMU device can be used to obtain information other than magnetic field data to enhance the system positioning performance.

[0179] The positioning processing component 3 can be electrically connected to the magnetic field generating component 1 through the switching switch 4 and communicated with the positioning target 2 to control the operation of the magnetic field generating component 1 and the positioning target 2. On the one hand, it controls the magnetic field generating component 1 to generate a sinusoidal magnetic field, and on the other hand, it controls the three-dimensional magnetic sensor 21 in the positioning target 2 to sense the sinusoidal magnetic field to generate a three-dimensional magnetic field component; finally, the positioning processing component 3 performs positioning solution to obtain position information.

[0180] The positioning processing component 3 controls the magnetic field generating component 1 to work by first controlling the switching switch 4 to connect the corresponding coil according to the program, and then controlling the output current signal to flow through the coil to excite the coil wound on the excitation core to generate a sinusoidal magnetic field. The program is a control logic that instructs the switching switch 4 to connect the four groups of coils in sequence at a preset time interval.

[0181] like Fig.11 As shown, in one embodiment of the present invention, the positioning processing component 3 further includes a sinusoidal pulse width modulation module 31, the sinusoidal pulse width modulation module 31 is electrically connected to the switch 4, the sinusoidal pulse width modulation module 31 is used to receive direct current and convert it into alternating current of a preset frequency, and the sinusoidal pulse width modulation module 31 outputs the alternating current to the coil through the switch 4. In this way, the alternating current can excite the coil to generate a sinusoidal magnetic field, and it should be noted that the alternating current can be a waveform of one cycle.

[0182] The positioning processing component 3 can independently provide each group of coils with load-carrying sinusoidal alternating current of a specific frequency and amplitude through steps such as DC boosting and modulation by the sinusoidal pulse width modulation module 31 .

[0183] The system is powered by a DC power supply to achieve the required variable frequency control. You can use a universal AC rectifier power supply or a USB or Type C power supply interface to obtain a standard voltage (e.g. 5V) DC power supply to reduce system cost. Convert DC power into a standard sinusoidal AC power with a specific amplitude (within the safe voltage range), frequency, and phase, and power the electromagnetic coil to generate a sinusoidal magnetic field signal.

[0184] Under the same signal peak, the power consumption of the sine wave signal is only 1 / 2 of that of the square wave pulse signal, which can effectively reduce the power consumption of the strong magnetic field positioning system. The sine wave electrical signal has no mutations, and will not cause magnetic field signal distortion and high-frequency harmonic interference to the inductive coil. There is no need to wait for the magnetic field delay to stabilize before performing magnetic field measurement, which can obtain better positioning stability and real-time performance. The sine wave magnetic field signal with a unique frequency can also avoid low-frequency interference caused by the movement of the magnetic control device 5 and the jitter of the capsule, as well as interference from other external magnetic fields. By sampling the signal n times within a period and fitting the sine wave function, the statistical error of the signal measurement can be reduced, further improving the positioning accuracy.

[0185] like Fig.12 As shown, in one embodiment of the present invention, the electromagnetic positioning system in the strong magnetic field environment also includes a magnetic control device 5, and the positioning target 2 also includes a magnet. The magnetic control device 5 magnetically cooperates with the magnet, and the magnetic control device 5 is used to electromagnetically control the movement of the positioning target 2.

[0186] The magnetic control device 5 can magnetically sense the positioning target 2 when powered on, thereby controlling the movement of the positioning target 2 in the human body.

[0187] Furthermore, the magnetic control device 5 includes a control magnet, a mechanical arm and a motor. The control magnet is arranged at the end of the mechanical arm. The motor is electrically connected to the mechanical arm and drives the mechanical arm to move along a preset path.

[0188] The control magnet can be a permanent magnet, an electromagnet, or a combination of the two. The motor can control the movement of the robotic arm, thereby indirectly controlling the movement of the control magnet at the end of the robotic arm, and attracting the positioning target 2 to move by controlling the movement of the magnet above the human body. Specifically, the control magnet is precisely driven to achieve spatial position movement and posture conversion, thereby achieving a change in the spatial distribution of the magnetic field of the control magnet, and using remote non-contact magnetic force to drive the capsule endoscope in the human body to achieve position and posture changes, and complete the shooting and scanning of the inner wall of the digestive tract.

[0189] For example, the human body is located on the examination bed 7, the magnetic control device 5 is located in the space above the examination bed 7 and moves through the cooperation of the motor and the mechanical arm, the positioning target 2, i.e., the capsule is swallowed into the human body and controlled to move by the magnetic control device 5, and the magnetic field generating component 1 is set at the bottom of the examination bed 7, i.e., four groups of magnetic source micro-electromagnetic coils are arranged in a 2x2 matrix. The four groups of magnetic source micro-electromagnetic coils are wound with insulated copper wire, and the exemplary reference hardware parameters are as follows: the coil radius is about 75-150mm, the height is about 20-40mm, the number of turns is about 200-1000 turns, and the copper wire diameter is about 0.5-1.0mm. The DC power input interface can accept DC input from a USB or TypeC interface, and can be directly powered by a low-cost universal DC power supply, a computer USB interface, etc., and a power supply of about 5W can achieve normal positioning function.

[0190] When the magnetic control device 5 controls the movement of the positioning target 2, the magnetic field generating component 1 is independently controlled by the positioning processing component 3 and is excited to generate a sinusoidal magnetic field. Specifically, the positioning processing component 3 controls the magnetic field generating component 1 to generate a magnetic field through the sinusoidal pulse width modulation module 31, and then the positioning processing component 3 offsets the sinusoidal magnetic field and receives the three-dimensional magnetic field component of the positioning target 2, and obtains the position information of the positioning target 2 through fitting and solution.

[0191] It should be noted that the magnetic field strength B generated by the coil is proportional to the product of the number of turns N and the current strength I. When the number of turns of the coil changes, the magnetic field strength generated by the magnetic source coil remains unchanged, and the power consumption of the coil can be reduced. In the embodiment of the present invention, in the coil system powered by a sine wave, the current will not change suddenly, which can avoid the problem of delayed deformation of the magnetic field waveform affecting the positioning accuracy and real-time performance.

[0192] like Fig.13 As shown, in one embodiment, when the power supply input voltage of the coil is constant, the number of coil turns can be increased by n times, the corresponding resistance R increases by n times, the current intensity is reduced to 1 / n, and the power consumption is reduced to 1 / n accordingly. For example, increasing the number of coil turns to 4 times can keep the magnetic field signal strength of the magnetic source coil approximately unchanged while reducing the power consumption to 25% of the previous value.

[0193] like Fig.14 As shown, in one embodiment of the present invention, the positioning target 2 further includes an imaging unit 22 and an inertial measurement unit 23, and the imaging unit 22 and the inertial measurement unit 23 are communicatively connected to the positioning processing component 3;

[0194] The imaging unit 22 is used to capture images;

[0195] The inertial measurement unit 23 is used to obtain inertial measurement data.

[0196] The imaging unit 22 is not limited to one group, but may include multiple groups, for example, two groups of imaging units 22 distributed at both ends of the capsule can simultaneously, alternately or independently capture images of the digestive tract. The inertial measurement unit 23 is used to obtain inertial measurement data to assist in positioning calculation, so that the data of the position and posture of the positioning target 2 is more accurate.

[0197] In one embodiment of the present invention, a storage medium is provided, wherein the storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the strong electromagnetic positioning method in the above embodiment are implemented.

[0198] It should be noted that the storage medium shown may be a removable storage medium 611 .

[0199] Fig.15 The structure block diagram of a computer system for implementing the storage medium of an embodiment of the present application is schematically shown.

[0200] It should be noted that Fig.15 The computer system 6 of the storage medium shown is only an example and should not bring any limitation to the functions and scope of use of the embodiments of the present application.

[0201] like Fig.15 As shown, the computer system 6 includes a central processing unit 601 (CPU), which can perform various appropriate actions and processes according to the program stored in the read-only memory 602 (ROM) or the program loaded from the storage part 608 to the random access memory 603 (RAM). Various programs and data required for system operation are also stored in the random access memory 603. The central processing unit 601, the read-only memory 602 and the random access memory 603 are connected to each other through a bus 604. An input / output interface 605 (Input / Output interface, i.e., I / O interface) is also connected to the bus 604.

[0202] The following components are connected to the input / output interface 605: an input section 606 including a keyboard, a mouse, etc.; an output section 607 including a cathode ray tube (CRT), a liquid crystal display (LCD), etc., and a speaker, etc.; a storage section 608 including a hard disk, etc.; and a communication section 609 including a network interface card such as a local area network card, a modem, etc. The communication section 609 performs communication processing via a network such as the Internet. A drive 610 is also connected to the input / output interface 605 as needed. A removable medium 611, such as a magnetic disk, an optical disk, a magneto-optical disk, a semiconductor memory, etc., is installed on the drive 610 as needed so that a computer program read therefrom is installed into the storage section 608 as needed.

[0203] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described systems, systems and modules can refer to the corresponding processes in the aforementioned method implementation methods and will not be repeated here.

[0204] In several embodiments provided in the present application, it should be understood that the disclosed systems, systems and methods can be implemented in other ways. For example, the system implementation described above is only schematic, for example, the division of the modules is only a logical function division, and there may be other division methods in actual implementation, such as multiple modules or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, systems or modules, which can be electrical, mechanical or other forms. The modules described as separate components may or may not be physically separated, and the components displayed as modules may or may not be physical modules, that is, they may be located in one place, or they may be distributed on multiple network modules. Some or all of the modules can be selected according to actual needs to achieve the purpose of the present implementation scheme.

[0205] In addition, each functional module in each embodiment of the present application can be integrated into a processing module, or each module can exist physically separately, or two or more modules can be integrated into one module. The above-mentioned integrated module can be implemented in the form of hardware or in the form of hardware plus software functional modules. The above-mentioned integrated module implemented in the form of software functional modules can be stored in a computer-readable storage medium. The above-mentioned software functional modules are stored in a storage medium, including a number of instructions for a computer system (which can be a personal computer, a server, or a network system, etc.) or a processor (processor) to perform some steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a disk or an optical disk.

[0206] Finally, it should be noted that the above implementation modes are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned implementation modes, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned implementation modes, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various implementation modes of the present application.

Claims

1. An electromagnetic positioning method in a strong magnetic field environment, characterized in that: include: A fixed-frequency sinusoidal current is used to cyclically and alternately pass through four groups of magnetic source micro-electromagnetic coils in sequence to excite a three-dimensional sinusoidal magnetic field; Acquire magnetic field data information of the positioning target in the sinusoidal magnetic field, and acquire magnetic field data information of the positioning target in the corresponding sinusoidal magnetic field based on each time a group of the magnetic source micro-electromagnetic coils are energized, wherein the magnetic field data information includes a three-dimensional magnetic field component sensed by the positioning target in the sinusoidal magnetic field; Fitting the three-dimensional magnetic field component of each dimension, and decomposing to obtain independent magnetic field signals of four groups of magnetic source micro-electromagnetic coils at the positioning target; The position and posture information of the positioning target are obtained according to the independent magnetic field signal.

2. The electromagnetic positioning method in a strong magnetic field environment according to claim 1, characterized in that: The frequency of the sinusoidal current is fixed to satisfy f ps ≤f≤f s / n, where f ps is the full-load positioning frame rate of the positioning system, f s is the sampling frequency of the magnetic sensor, and n is the number of samples that can be achieved within one cycle of a sinusoidal wave signal.

3. The electromagnetic positioning method in a strong magnetic field environment according to claim 1, characterized in that: The fitting of the three-dimensional magnetic field component of each dimension specifically includes: performing function fitting on the magnetic field measurement values ​​of the dispersed three-dimensional magnetic field components to obtain the magnetic field intensity B in the corresponding dimension k；s (t); The decomposition to obtain the independent magnetic field signals of the four groups of magnetic source micro-electromagnetic coils at the positioning target includes: the magnetic field strength B after decomposition and fitting k；s (t), obtain the magnetic induction intensity amplitude A of the independent magnetic field signals of the four groups of magnetic source micro electromagnetic coils at the positioning target k；s , the decomposition formula is: B k；s (t)=A k；s sin(wt+b)+c k；s ; Wherein, k represents the serial number of the magnetic source micro-electromagnetic coil, k=1, 2, 3, 4; s=1, 2, 3, represents the three dimensions of the sinusoidal magnetic field, representing the X direction, the Y direction, and the Z direction respectively; A k；s The independent magnetic field signals of the four groups of magnetic source micro-electromagnetic coils at the positioning target to be determined by decomposition The magnetic induction intensity amplitude, that is, the peak value of the magnetic field measurement; c k；s is the background magnetic field component when each group of magnetic source micro-electromagnetic coils is energized respectively; the signal angular frequency w and the signal phase b are known quantities directly obtained according to the frequency value and phase value of the current data.

4. The electromagnetic positioning method in a strong magnetic field environment according to claim 3, characterized in that: The decomposition formula is linearized to obtain the linearized decomposition formula: Among them, β 0；k；s X 0；k；s Characterizes the environmental magnetic field intensity at the positioning target when the four groups of magnetic source micro electromagnetic coils are powered on respectively; β 1；k；s X1 represents the three-dimensional magnetic field strength of the magnetic field signal at the positioning target when the four groups of magnetic source micro-electromagnetic coils are powered on respectively, that is, the three-dimensional magnetic field strength of the independent magnetic field signals of the four groups of magnetic source micro-electromagnetic coils at the positioning target; Using a series of data at time t, {X j；k；s (t),B j；k；s (t)}, and solve the coefficient β through linear optimization j；k；s After that, it is easy to calculate the required magnetic induction intensity amplitude A k；s and background magnetic field c k；s .

5. The electromagnetic positioning method in a strong magnetic field environment according to claim 4, characterized in that: The magnetic induction intensity amplitude A k；s Correction is performed, and the correction formula is Where Ik0 is the initial hardware parameter current peak value under ideal working conditions, Ik1 is the current peak value under actual working conditions, A 0；k；s is the magnetic field strength B after decomposition fitting k；s (t) The magnetic induction intensity amplitude A obtained k；s , A 1；k；s For the A 0；k；s The magnetic induction intensity amplitude is obtained after correcting the resistance and current change drift caused by the coil temperature change and the actual magnetic field intensity.

6. The electromagnetic positioning method in a strong magnetic field environment according to claim 5, characterized in that: The magnetic induction intensity amplitude A k；s The matrix is ​​updated using a cyclic refresh mechanism, with 1x3 matrix elements updated each time, corresponding to the magnetic field generated at the magnetic sensor when the same set of coils is energized.

7. The electromagnetic positioning method in a strong magnetic field environment according to claim 5, characterized in that: The magnetic induction intensity amplitude A k；s The matrix is ​​updated using a cyclic refresh mechanism, with 4x3 matrix elements updated each time, corresponding to the magnetic field generated at the magnetic sensor when the four sets of coils are energized.

8. The electromagnetic positioning method in a strong magnetic field environment according to claim 5, 6 or 7, characterized in that: Acquiring the position and attitude information of the positioning target according to the independent magnetic field signal specifically includes: The geometric center is at the origin and the single coil is placed horizontally upward. The magnetic field components are in the cylindrical coordinate system. The following is expressed as Among them, the angular elliptic integral function Other parameters z ± =z±h, the coordinates of the spatial point (x, y, z) satisfy The basic parameters μ0 is the vacuum magnetic permeability, n is the number of coil turns per unit height, I is the peak current of the coil, a is the coil radius, and h is the half height of the coil; The four coils are arranged in a horizontal 2x2 array in the Z=0 plane, with coil spacings of 2dx and 2dy respectively. The corresponding peak magnetic induction intensity can be expressed by the above formula: in, is the spatial position vector of the point to be located, and the coordinates of the center points of the four coils satisfy The peak value of magnetic induction intensity can be expressed as matrix component form A k；s , where k = 1, 2, 3, 4, represents four groups of orthogonal magnetic source coil marks; s = 1, 2, 3, represents the three-dimensional magnetic field component marks measured by the magnetic sensor. According to the peak value of magnetic induction intensity Obtain the theoretical value of the magnetic induction intensity peak matrix The position and attitude information of the positioning target is obtained by solving the corresponding relationship between the theoretical value of the magnetic induction intensity peak matrix and the magnetic field measurement peak in the independent magnetic field signal through a nonlinear optimization algorithm; wherein the corresponding relationship is: At the spatial point (x, y, z), the theoretical value of the magnetic induction intensity peak matrix and the magnetic field measurement peak value satisfy the corresponding relationship in, A is the sensor attitude rotation matrix; k；s Measure the peak value of the magnetic field; is the theoretical value of the magnetic induction intensity peak matrix; The nonlinear optimization algorithm is:

9. The electromagnetic positioning method in a strong magnetic field environment according to claim 1, characterized in that: Also includes: The pitch angle pitch and the roll angle roll of the positioning target are obtained, and the yaw angle yaw and the position coordinates of the positioning target are calculated according to the pitch angle pitch, the roll angle roll of the positioning target and the independent magnetic field signal.

10. An electromagnetic positioning system in a strong magnetic field environment, characterized in that: include: A magnetic field generating component, comprising at least four groups of magnetic source micro-electromagnetic coils arranged in the same plane, wherein the magnetic source micro-electromagnetic coils are used to receive sinusoidal currents and generate three-dimensional sinusoidal magnetic fields; A positioning target, comprising a three-dimensional magnetic sensor for sensing a three-dimensional magnetic field component within the sinusoidal magnetic field; A positioning processing component, electrically connected to the magnetic field generating component through a switching switch and communicatively connected to the positioning target; The positioning processing component is configured to implement the electromagnetic positioning method in a strong magnetic field environment as described in any one of claims 1 to 9.

11. The electromagnetic positioning system in a strong magnetic field environment according to claim 10, characterized in that: The positioning processing component also includes a sinusoidal pulse width modulation module, which is electrically connected to a switching switch and is used to receive direct current and convert it into alternating current of a preset frequency. The sinusoidal pulse width modulation module outputs the alternating current to the coil through the switching switch.

12. The electromagnetic positioning system in a strong magnetic field environment according to claim 10, characterized in that: The strong electromagnetic positioning system further includes a magnetic control device, the positioning target further includes a magnet, the magnetic control device magnetically cooperates with the magnet, and the magnetic control device is used to electromagnetically control the movement of the positioning target.

13. The electromagnetic positioning system in a strong magnetic field environment according to claim 12, characterized in that: The magnetron device comprises a control magnet, a mechanical arm and a motor. The control magnet is arranged at the end of the mechanical arm. The motor is electrically connected to the mechanical arm and drives the mechanical arm to move along a preset path.

14. The electromagnetic positioning system in a strong magnetic field environment according to claim 10, characterized in that: The positioning target further includes an imaging unit and an inertial measurement unit, and the imaging unit and the inertial measurement unit are communicatively connected to the positioning processing component; The imaging unit is used to capture images; The inertial measurement unit is used to obtain inertial measurement data.

15. A storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the electromagnetic positioning system in a strong magnetic field environment as claimed in any one of claims 1 to 9 are implemented.

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