System and method for accurately positioning near-field target pose through orthogonal electromagnetic signal group

Abstract

The invention discloses a system and method for accurately positioning a near-field target pose through an orthogonal electromagnetic signal group, and the system comprises a magnetic field generator module which comprises a transmitting coil array composed of a plurality of transmitting coils fixed at respective preset positions, and each transmitting coil transmits at different frequencies at the same time to form a non-interfering space magnetic field; the magnetic sensing receiving module is fixed on the ultrasonic probe and comprises a receiving coil, and the receiving coil can sense the change of a space magnetic field and generate an induced electromotive force analog signal; the signal preprocessing module is used for obtaining actually measured potential values of the receiving coil at different preset space point locations under each frequency channel; the signal calibration module is used for comparing the theoretical potential value with the actually measured potential value, determining the induction coefficient of each frequency channel and calibrating the attitude of the transmitting coil; and the signal analysis module is used for determining the accurate pose of the receiving coil according to the determined induction coefficient, the calibrated attitude of the transmitting coil and the actually measured potential value of the receiving coil.

Description

Technical Field

[0001] This invention relates to an electromagnetic detection system, and more particularly to a system and method for accurately locating the pose of a near-field target using orthogonal electromagnetic signal groups. Background Technology

[0002] This section provides only background information relevant to this disclosure and is not necessarily prior art.

[0003] Precise sensor positioning, such as for the accurate location of ultrasound probes and surgical instruments, has significant application value. Specifically, precise positioning of the ultrasound probe facilitates rapid location of target areas based on image orientation, assisting doctors in making more accurate judgments based on ultrasound images.

[0004] Currently, the methods for precise positioning of sensors are mainly divided into two categories:

[0005] 1. Sensor position detection via optical tracking systems is characterized by high accuracy and robustness to environmental conditions. The main limitations of this method are the need for a direct line of sight between the optical marker and the camera sensor, and its secure mounting within the operating room. Furthermore, camera-based systems can expose user privacy to varying degrees, potentially impacting user willingness to use them.

[0006] 2. Detecting the sensor position using an ultrasonic tracking system is characterized by its relatively simple principle and algorithm, and low implementation difficulty. The main limitations of this method are low measurement accuracy and large errors; furthermore, ultrasonic measurements are significantly affected by environmental noise, resulting in poor robustness.

[0007] Meanwhile, the current solution does not involve real-time and accurate detection of the sensor's location.

[0008] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0009] Purpose of the invention: The technical problem to be solved by the present invention is to provide a system and method for accurately locating the pose of a near-field target by means of orthogonal electromagnetic signal groups, which addresses the shortcomings of the prior art.

[0010] To address the aforementioned technical problems, a first aspect of the present invention discloses a system for accurately locating the pose of a near-field target using orthogonal electromagnetic signal groups, comprising:

[0011] The magnetic field generator module includes an array of multiple transmitting coils fixed at their respective preset positions, with each transmitting coil serving as a frequency channel; the multiple transmitting coils emit simultaneously to generate multiple spatial magnetic fields of different frequencies that do not interfere with each other.

[0012] A magnetic sensing receiving module is fixed on an ultrasonic probe; the magnetic sensing receiving module contains a receiving coil, which can sense changes in the spatial magnetic field and generate a corresponding induced electromotive force analog signal.

[0013] The signal preprocessing module is used to obtain the measured potential value of the receiving coil at different preset spatial points under each frequency channel based on the simulated induced electromotive force signal generated by the receiving coil at different preset spatial points.

[0014] The signal calibration module is used to compare the theoretical potential value with the measured potential value for each frequency channel, and determine the inductance coefficient of each frequency channel and calibrate the attitude of the transmitting coil for each frequency channel based on the comparison results.

[0015] The signal analysis module is used to determine the orientation of the receiving coil based on the determined inductance coefficient, the calibrated orientation of the transmitting coil, and the measured potential value of the receiving coil.

[0016] Specifically, each of the transmitting coils is composed of multiple turns of enameled wire.

[0017] Furthermore, the magnetic field generator module further includes: a control unit; a signal generator configured to generate multiple orthogonal frequency-division multiplexed sinusoidal signals of different frequencies under the drive of the control unit, wherein each frequency signal is orthogonal to the others and transmitted in parallel; a first power amplifier configured to receive each frequency signal from the signal generator and amplify each frequency signal; and a bandpass filter configured to receive the amplified frequency signals from the first power amplifier, remove low-frequency and high-frequency noise from the amplified frequency signals, and send the frequency signals after filtering out low-frequency and high-frequency noise to the corresponding transmitting coils in the transmitting coil array to generate multiple spatial magnetic fields of different frequencies that do not interfere with each other.

[0018] In this embodiment, the gain of the sinusoidal signal is adjusted by a first power amplifier on the hardware circuit. The purpose of amplifying the signal is to ensure the strength of the spatial magnetic field by increasing the signal amplitude.

[0019] Furthermore, the receiving coil can sense changes in the spatial magnetic field and generate a corresponding induced electromotive force analog signal, including:

[0020] Based on Faraday's law of electromagnetic induction, when the magnetic induction intensity B caused by a target object in the detection area changes with time t, according to the differential relationship: An induced electromotive force ε is generated in a coil with N turns; the rate of change of magnetic flux in the sensor coil is nonlinearly positively correlated with the conductivity, permeability and velocity of the target object. The mapping relationship between the electrical signal and the target parameters can be quantified by establishing a numerical model of the Maxwell equations.

[0021] Specifically, the signal preprocessing module includes an RC bandpass filter, a second power amplifier, an analog-to-digital converter, and a frequency division processing unit;

[0022] The RC bandpass filter is configured to perform high-pass and low-pass filtering on the induced electromotive force analog signal, allowing only signals within a specific frequency range to pass through, while removing signals that affect the received electromagnetic induction analog signal.

[0023] The second power amplifier is configured to amplify the filtered analog signal and adjust it to the amplitude range of the analog-to-digital converter input;

[0024] The analog-to-digital converter is configured to convert the amplified analog signal into a discrete digital signal;

[0025] The frequency division processing unit is configured to separate or extract digital signals with different frequency components from the digital signal output by the analog-to-digital converter, i.e., digital signals with different frequency channels.

[0026] In this embodiment, the system performs the same processing on the simulated induced electromotive force signals generated by the receiving coil at different preset spatial points by the signal preprocessing module, thereby obtaining the measured electromotive force values ​​of the receiving coil at different preset spatial points under different frequency channels.

[0027] Specifically, separating or extracting digital signals of different frequency components from the digital signal output by the analog-to-digital converter includes: sampling the digital signal output by the analog-to-digital converter 330 at at least three times the highest transmission frequency, performing frequency division processing using a fast Fourier transform algorithm, and extracting the amplitude of each frequency component.

[0028] A second aspect of the present invention discloses a method for accurately locating the pose of a near-field target using orthogonal electromagnetic signal groups, implemented using the system described above. The method includes:

[0029] Step 1: Input N sinusoidal signals of different frequencies into the corresponding transmitting coils in the transmitting coil array, with each transmitting coil corresponding to a frequency channel; these frequency signals are orthogonal to each other, achieving parallel transmission and forming multiple spatial magnetic fields of different frequencies that do not interfere with each other;

[0030] Step 2: Place the receiving coil fixed on the ultrasonic probe at M different preset spatial points in sequence. The receiving coil generates a corresponding induced electromotive force analog signal by sensing the change in the spatial magnetic field at each preset spatial point.

[0031] Step 3: Based on the simulated induced electromotive force signals generated by the receiving coil at different preset spatial points, obtain the measured potential values ​​of the receiving coil at different preset spatial points for each frequency channel.

[0032] Step 4: Compare the theoretical potential value with the measured potential value for each frequency channel. Based on the comparison results, determine the inductance coefficient of each frequency channel and calibrate the attitude of the transmitting coil for each frequency channel. Then, determine the attitude of the receiving coil based on the determined inductance coefficient, the calibrated attitude of the transmitting coil, and the measured potential value of the receiving coil.

[0033] Specifically, in step 4, the calculation process for the theoretical potential value under each frequency channel is as follows:

[0034] First, a magnetic dipole model is established: the transmitting coil is equivalent to a magnetic dipole, and the magnetic induction intensity generated by the transmitting coil of frequency channel i at the spatial point (x,y,z) is calculated using the Biot-Savart law. Let the magnetic induction intensity The components in the X, Y, and Z axes are respectively B ix B iy and B ix Then we have:

[0035]

[0036] In equation (1), (a i ,b i ,c i (m) represents the center coordinates of the transmitting coil for frequency channel i. i ,n i ,p i ) represents the direction vectors of the X, Y, and Z axes of the transmitting coil corresponding to frequency channel i; r i For distance, its formula is: B T is the magnetic flux density coefficient.

[0037] Then, based on Faraday's law of electromagnetic induction, the theoretical potential value generated by the magnetic field change corresponding to the induced frequency channel i through the receiving coil located at the spatial point (x,y,z) is obtained:

[0038]

[0039] In equation (2), For the characteristic parameters of the receiving coil, The calculation formula is shown in equation (3).

[0040]

[0041] In equation (3), ω i Here, N represents the frequency corresponding to frequency channel i, and N is the number of turns in the receiving coil. The effective area of ​​the receiving coil is calculated as shown in equation (4):

[0042]

[0043] In equation (4), S is the maximum area of ​​the receiving coil; (α i ,β i ,γ i ) is the normalized direction vector of the angle between the magnetic field and the maximum area S of the current receiving coil when the transmitting coil of the corresponding frequency channel i emits a magnetic field and the center of the receiving coil is located at the spatial point (x,y,z). i ,β i ,γ i It can be given by equation (5):

[0044]

[0045] In equation (5), (v x ,v y ,v z ) represents the direction vectors of the X, Y, and Z axes of the receiving coil; L ix L iy L iz They are respectively:

[0046]

[0047] By (v x ,v y ,v z The values ​​ε are assigned to (1, 0, 0), (0, 1, 0), and (0, 0, 1) respectively. Combining formulas (1) to (6), the theoretical potential value ε is obtained when the transmitting coil of the corresponding frequency channel i emits a magnetic field, and the center of the receiving coil is located at the spatial point (x, y, z) with its axis along the X, Y, and Z directions respectively. ix , ε iy and ε iz .

[0048] Specifically, determining the inductance coefficient for each frequency channel includes the following steps:

[0049] The theoretical potential value ε is calculated when the transmitting coil of the corresponding frequency channel i emits a magnetic field, and the receiving coil is located at point j among M preset spatial points, with its axis along the X, Y, and Z directions, respectively. ijx , ε ijy and ε ijz ;

[0050] Given the corresponding frequency channel i, the theoretical potential value ε corresponding to the receiving coil being located at all of the M preset spatial points, with the receiving coil axis set along the X, Y, and Z directions. ijx , ε ijy and ε ijz Then, combining the measured potential values ​​ε' corresponding to the frequency channel i, the receiving coil located at all of the M preset spatial points, and the receiving coil axis along the X, Y, and Z directions respectively. ijx ,ε' ijy and ε' ijz The inductance coefficient k of frequency channel i along the X, Y, and Z axes ix k iy k iz Perform calibration.

[0051] More specifically, the calculation yields the theoretical potential value ε when the transmitting coil of the corresponding frequency channel i emits a magnetic field, and the receiving coil is located at point j among M preset spatial points, with its axis along the X, Y, and Z directions respectively. ijx , ε ijy and ε ijz Specifically:

[0052] The transmitting coil corresponding to frequency channel i is equivalent to a magnetic dipole. The position of the transmitting coil at point j(x) of frequency channel i is calculated using the Biot-Savart law. j ,y j ,z j The magnetic induction intensity generated at point ) Let the magnetic induction intensity The components in the X, Y, and Z axes are respectively B ijy B ijy B ijz Then we have:

[0053]

[0054] In equation (7), (a i ,b i ,c i (m) represents the center coordinates of the transmitting coil for frequency channel i. i ,n i ,p i) represents the direction vectors of the X, Y, and Z axes of the transmitting coil corresponding to frequency channel i; r ij For distance, its formula is: B T is the magnetic flux density coefficient.

[0055] Then, based on Faraday's law of electromagnetic induction, we obtain that the center is located at point j(x). j ,y j ,z j The theoretical potential value generated in the receiving coil at point ) is:

[0056]

[0057] In equation (8), Centered at point j(x) j ,y j ,z j The characteristic parameters of the receiving coil at point ) The calculation formula is shown in equation (9).

[0058]

[0059] In equation (9), ω i Here, N represents the frequency corresponding to frequency channel i, and N is the number of turns in the receiving coil. Centered at j(x) j ,y j ,z j The effective area of ​​the receiving coil at point () is calculated as shown in equation (10):

[0060]

[0061] In equation (10), S is the maximum area of ​​the receiving coil; (α ij ,β ij ,γ ij ) is the normalized direction vector of the angle between the magnetic field and the maximum area S of the current receiving coil when the transmitting coil (111) of the corresponding frequency channel i emits a magnetic field and the center of the receiving coil is located at point j. ij ,β ij ,γ ij According to equation (11):

[0062]

[0063] In equation (11), (v jx ,v jy ,v jz Centered at point j(x) j ,y j ,z jThe direction vectors of the X, Y, and Z axes of the receiving coil; L ijx L ijy and L ijz They are respectively:

[0064]

[0065] By (v jx ,v jy ,v jz The values ​​are assigned to (1, 0, 0), (0, 1, 0), and (0, 0, 1) respectively. Combining formulas (7) to (12), the theoretical potential value ε is obtained when the transmitting coil of the corresponding frequency channel i emits a magnetic field and the receiving coil is located at point j among the M preset spatial points, with its axis along the X, Y, and Z directions respectively. ijx , ε ijy and ε ijz .

[0066] More specifically, when the corresponding frequency channel i is obtained, the receiving coil is located at all of the M preset spatial points, and the receiving coil axis is set along the X, Y, and Z directions, the theoretical potential value ε is... ijx , ε ijy and ε ijz Then, combining the measured potential values ​​ε' corresponding to the frequency channel i, the receiving coil located at all of the M preset spatial points, and the receiving coil axis along the X, Y, and Z directions respectively. ijx ,ε' ijy and ε' ijz The inductance coefficient k of frequency channel i along the X, Y, and Z axes ix k iy k iz The calibration process is as follows:

[0067] For each frequency channel i, establish the first error function E. ik :

[0068]

[0069] Minimize the first error function E using the Levenberg-Marquardt algorithm. ik The inductance coefficient k of each frequency channel i along the X, Y, and Z axes is obtained. ix k iy and k iz The values ​​are denoted as k'. ix 、k' iy and k' iz .

[0070] Specifically, the calibration of the transmit coil attitude for each frequency channel includes:

[0071] The attitude parameters (a) of the transmitting coil corresponding to frequency channel i i ,b i ,c i ,m i ,n i ,p i () is considered an unknown parameter, where the value of the inductance coefficient k' of each frequency channel i on the X, Y, and Z axes is... ix 、k' iy and k' iz The center coordinates and direction vector (x) of the receiving coil placed at each preset spatial point j. j ,y j ,z j ,v jx ,v jy ,v jz When the magnetic field is determined, by combining formulas (1) to (6), the theoretical potential value ε corresponding to the transmitting coil transmitting the magnetic field corresponding to the frequency channel i, and the receiving coil being located at point j among the M preset spatial points, with its axis along the X, Y, and Z directions respectively, is obtained. ijx , ε ijy and ε ijz The attitude parameters (a) of each transmitting coil with respect to the corresponding frequency channel i i ,b i ,c i ,m i ,n i ,p i The relation is denoted as ε. ijx (a i ,b i ,c i ,m i ,n i ,p i ), ε ijy (a i ,b i ,c i ,m i ,n i ,p i ) and ε ijz (a i ,b i ,c i ,m i ,n i ,p i ).

[0072] For each frequency channel i, establish a second error function E. ip :

[0073]

[0074] Minimize the second error function E using the Levenberg-Marquardt algorithm. ip The attitude parameters (a) of the transmitting coil corresponding to each frequency channel i are obtained. i ,b i ,c i ,m i ,n i ,p i The value of ) is denoted as (a' i ,b' i ,c' i ,m' i ,n' i ,p' i ).

[0075] Specifically, determining the pose of the receiving coil based on the determined inductance coefficient, the calibrated transmitting coil attitude, and the measured potential value of the receiving coil includes:

[0076] The pose of the receiving coil (x,y,z,v) x ,v y ,v z The position of the receiving coil is treated as an unknown parameter, and a two-stage optimization algorithm is used to solve for the pose of the receiving coil.

[0077] In the first stage, based on the measured potential value ε' of the receiving coil under each frequency channel i obtained in step 3... i And the values ​​of the inductance coefficients k' of each frequency channel i along the X, Y, and Z axes as determined in step 4. ix 、k' iy and k' iz The attitude parameter values ​​(a') of the transmitting coil corresponding to each frequency channel i i ,b' i ,c' i ,m' i ,n' i ,p' i Combining formulas (1) to (6), we obtain the theoretical potential value ε corresponding to the transmitting coil transmitting magnetic field of the corresponding frequency channel i, and the center of the receiving coil located at (x,y,z) with its axis along the X, Y, and Z directions, respectively. ix , ε iy and ε iz The poses (x, y, z, v) of each relative to the receiving coil x ,v y ,v z The relation, denoted as ε ix (x,y,z,v x ,v y ,v z ), ε iy(x,y,z,v x ,v y ,v z ) and ε iz (x,y,z,v x ,v y ,v z ).

[0078] For each frequency channel i, the following equation (15) is constructed:

[0079]

[0080] A particle swarm optimization (PSO) algorithm is used to traverse the three-dimensional space for a global search. The six position parameters of the receiving coil calculated by the PSO algorithm are substituted into equation (15) to finally obtain the pose (x, y, z, v) of the receiving coil. x ,v y ,v z The initial value of ).

[0081] The second stage, a local optimization algorithm, improves the solution accuracy by precisely calculating the specific coordinates and angles of the receiving coil. Using the output of the particle swarm optimization algorithm as initial values, the Levenberg-Marquardt algorithm is employed to minimize the third error function E'. ip E' ip The formula for calculation is:

[0082]

[0083] Minimize the third error function E' using the Levberg-Marquardt algorithm. ip Find the six-degree-of-freedom pose parameters (x, y, z, v) of the receiving coil when the error is minimized. x ,v y ,v z The precise value of the nine-channel induced potential value is ultimately used to achieve a precise conversion from the nine-channel induced potential value to the spatial position and attitude angle.

[0084] Specifically, the number M of the preset spatial points is at least 1000, preferably 1444; the number N of the transmitting coils is at least 6, preferably 9; and the axis of the receiving coil is set at 90 degrees to the longitudinal axis of the ultrasonic probe.

[0085] Beneficial effects:

[0086] This invention proposes a system for accurately locating the pose of a near-field target using orthogonal electromagnetic signal groups. Based on the magnetic field strength and frequency measured by electromagnetic sensors, a series of signal processing methods are used to achieve a non-contact, portable, and miniaturized sensor positioning method. This system can accurately detect the sensor position in real time, thus overcoming the shortcomings of existing sensor positioning methods. Attached Figure Description

[0087] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0088] Figure 1 This is a schematic diagram of the workflow of the system provided by the present invention.

[0089] Figure 2 This is an installation diagram of the system provided in the first embodiment of the present invention.

[0090] Figure 3 This is a schematic diagram of the magnetic dipole model provided in the first embodiment of the present invention.

[0091] The reference numerals in the attached figures are as follows: 100, magnetic field generator module; 110, transmitting coil array; 111, transmitting coil; 112, magnetically transparent mounting component; 120, spatial magnetic field; 130, control unit; 140, signal generator; 150, first power amplifier; 160, bandpass filter; 200, magnetic sensing receiving module; 210, receiving coil; 300, signal preprocessing module; 310, bandpass filter; 320, second power amplifier; 330, analog-to-digital converter; 340, frequency division processing unit; 400, signal calibration module; 500, signal analysis module; 700, bed board. Detailed Implementation

[0092] Example 1

[0093] The following specific embodiment will further illustrate the system and method for accurately locating the pose of a near-field target using orthogonal electromagnetic signal groups, as proposed in this invention.

[0094] The system provided in this embodiment includes: a magnetic field generator module 100, comprising a transmitting coil array 110 consisting of nine transmitting coils 111 fixed at their respective preset positions, each transmitting coil 111 serving as a frequency channel; the nine transmitting coils 111 simultaneously transmit to generate nine spatial magnetic fields 120 of different frequencies that do not interfere with each other; a magnetic sensing receiving module 200, which is fixed on an ultrasonic probe; the magnetic sensing receiving module 200 includes a receiving coil 210, which can sense changes in the spatial magnetic field 120 and generate a corresponding induced electromotive force analog signal; and a signal preprocessing module. 300, used to obtain the measured potential value signal of the receiving coil 210 at different preset spatial points under each frequency channel based on the simulated induced electromotive force signal generated by the receiving coil 210 at different preset spatial points; calibration module 400, used to compare the theoretical potential value and the measured potential value under each frequency channel, and determine the induction coefficient of each frequency channel and calibrate the attitude of the transmitting coil 111 of each frequency channel based on the comparison result; signal analysis module 500, used to determine the position and orientation of the receiving coil 210 based on the determined induction coefficient, the calibrated attitude of the transmitting coil 111 and the measured potential value of the receiving coil 210.

[0095] Specifically, the magnetic field generator module 100 further includes: a control unit 130; a signal generator 140 configured to generate multiple orthogonal frequency division multiplexed sinusoidal signals of different frequencies under the drive of the control unit 130, wherein each frequency signal is orthogonal to the others and transmitted in parallel; a first power amplifier 150 configured to receive each frequency signal from the signal generator 140 and amplify each frequency signal; and a bandpass filter 160 configured to receive each amplified frequency signal from the first power amplifier 150, remove low-frequency noise and high-frequency noise from each amplified frequency signal, and send each frequency signal after filtering out low-frequency noise and high-frequency noise to the corresponding transmitting coil 111 in the transmitting coil 111 array.

[0096] In this embodiment, the control unit 130 is an STM32 microcontroller, and the signal generator 140 is an AD9833 module. The STM32 microcontroller drives the AD9833 module to generate nine sinusoidal signals ranging from 1000Hz to 1900Hz, spaced 100Hz apart. The output voltage amplitude of all sinusoidal signals is 0.35V. The first power amplifier 150 has an adjustable amplification range of 10-100 times, and the output voltage amplitude of all frequency signals after adjustment is 22V. More specifically, the STM32 microcontroller chip can be an STM32F103ZE.

[0097] Specifically, the signal preprocessing module 300 includes: an RC bandpass filter 310, configured to perform high-pass and low-pass filtering on the induced electromotive force analog signal, allowing only signals within a specific frequency range to pass through, while removing signals that affect the received electromagnetic induction analog signal; a second power amplifier 320, configured to amplify the filtered analog signal and adjust it to the amplitude range of the analog-to-digital converter 330 input; an analog-to-digital converter 330, configured to convert the amplified analog signal into discrete digital signals; and a frequency division processing unit 340, configured to separate or extract digital signals of different frequency components from the digital signal output by the analog-to-digital converter 330.

[0098] In this embodiment, the system performs the same processing on the analog signals of induced electromotive force generated by the receiving coil 210 at different preset spatial points by the signal preprocessing module 300, thereby obtaining the measured electromotive force values ​​of the receiving coil 210 at different preset spatial points under different frequency channels.

[0099] This embodiment uses an RC bandpass filter 310 on the hardware circuit to filter the acquired induced electromotive force analog signal, removing low-frequency and high-frequency noise and limiting the signal to a specific frequency range. In this embodiment, to filter out DC and interference components, the specific frequency range is set to 0.01Hz to 10Hz. The calculation method is as follows:

[0100]

[0101] Among them, f c R is the cutoff frequency, R is the resistance, and C is the capacitance. R = 100kΩ, C = 159μF and R = 100kΩ, C = 15.9μF are respectively used to achieve filtering from 0.01Hz to 10Hz.

[0102] The analog-to-digital converter 330 in this embodiment is a 16-bit analog-to-digital converter 330.

[0103] In this embodiment, the bandpass filter 160 includes a high-pass filter and a low-pass filter connected in series with the high-pass filter. It should be understood that the parameters of the filter and amplifier can be adjusted according to different environmental types.

[0104] Specifically, separating or extracting digital signals of different frequency components from the digital signal output by the analog-to-digital converter 330 includes: sampling the digital signal output by the analog-to-digital converter at a frequency of 5 kHz, performing frequency division processing using a fast Fourier transform algorithm, and extracting the amplitude of each frequency component.

[0105] like Figure 2As shown, the array of transmitting coils 111 is vertically fixed to the surface of the magnetically transparent mounting component; the array of transmitting coils 111 is fixed to the side of the bed by the magnetically transparent mounting component, perpendicular to the bed surface, and can slide within a limited range. The array of transmitting coils 111 remains in a fixed position during operation.

[0106] In this embodiment, the transmitting coil 111 array is a 3×3 array, consisting of nine identical transmitting coils 111. Each transmitting coil 111 is constructed by winding multiple turns of enameled wire, with 1000 turns, a wire diameter of 0.2 mm, an inner diameter of 100 mm, and a height of 50 mm. The axes of the transmitting coils 111 are placed perpendicular to the surface of the magnetically transparent mounting component, and the axes of the transmitting coils 111 are parallel to each other.

[0107] In this embodiment, the magnetically transparent mounting component 112 is an acrylic sheet. By using acrylic material, the influence of ferromagnetic materials on the magnetic field is avoided, ensuring that the signal emitted by the transmitting coil 111 array is more stable and repeatable. The acrylic sheet is 0.5cm thick, which effectively reduces vibration attenuation and dispersion. The acrylic sheet is 50cm × 50cm in size. It should be understood that the size of the acrylic sheet can be adjusted according to different types of bed boards 700.

[0108] In this embodiment, the transmitting coil 111 is fixed to the acrylic plate by nylon screws and nuts.

[0109] In this embodiment, the receiving coil 210 is fixed to the medical ultrasound probe with resin adhesive, and the axis of the receiving coil 210 is set at a 90-degree angle to the longitudinal axis of the ultrasound probe. The receiving coil 210 has 1000 turns, the enameled wire diameter is 0.1 mm, the coil diameter is 1.2 mm, and the height is 18 mm.

[0110] In this embodiment, the control unit 130 adopts an STM32 microcontroller, and the signal generator 140 adopts an AD9833 digital waveform generator chip; the multiplexed sinusoidal signals of different frequencies in step 2 are nine sinusoidal signals with a center frequency of 1000Hz to 1900Hz and an interval of 100Hz, and the output voltage amplitude of all sinusoidal signals is 0.35V.

[0111] In this embodiment, the output voltage amplitude of each sinusoidal signal after being amplified by the first power amplifier 150 is 24V.

[0112] The method for accurately locating the pose of a near-field target using orthogonal electromagnetic signal groups provided in this embodiment is implemented using the aforementioned system for accurately locating the pose of a near-field target using orthogonal electromagnetic signal groups. The method includes the following steps:

[0113] Step 1: Input nine sinusoidal signals of different frequencies into the corresponding transmitting coils 111 in the array of transmitting coils 111. Each transmitting coil 111 corresponds to a frequency channel. These frequency signals are orthogonal to each other, realize parallel transmission, and form nine spatial magnetic fields 120 of different frequencies that do not interfere with each other.

[0114] Step 2: The receiving coil 210 fixed on the ultrasonic probe is placed sequentially at 1444 different preset spatial points. The receiving coil 210 generates a corresponding induced electromotive force analog signal by sensing the change of the spatial magnetic field 120 at each preset spatial point.

[0115] It should be understood that the number of transmitting coils 111 can also be set to a number greater than or equal to 6, except for 9. The number of preset spatial points can also be set to a number greater than or equal to 6, except for 1444.

[0116] Specifically, the analog signal of induced electromotive force generated by the change in the spatial magnetic field 120 induced by the receiving coil 210 is based on Faraday's law of electromagnetic induction. When the magnetic induction intensity B in the detection area changes with time t, according to the differential relationship: The receiving coil 210 generates an induced electromotive force ε. The effective area of ​​the receiving magnetic field of the receiving coil 210 is expressed by the following formula: (α,β,γ) is the normalized direction vector of the angle between the magnetic field and the maximum area S of the receiving coil 210. The magnetic flux passing through the receiving coil 210 is expressed as follows: N is the number of turns of the coil. Since the coil is small, the magnetic flux density on the surface of the receiving coil 210 can be considered to be the same. Therefore, the above formula can be modified as follows:

[0117] Step 3: Based on the simulated induced electromotive force signals generated by the receiving coil 210 at different preset spatial points, obtain the measured potential values ​​of the receiving coil 210 at different preset spatial points under each frequency channel.

[0118] Specifically, each of the induced electromotive force analog signals undergoes noise reduction filtering and amplification processing. The noise reduction filtering is implemented using active filtering, employing an OP07 operational amplifier and an RC feedback network to form a second-order bandpass filter 160, which actively modulates the sinusoidal signal generated by the signal generator 140 to achieve frequency-selective amplification. The amplification processing involves adjusting the gain of the acquired induced voltage signal through an amplifier on the hardware circuit to increase the signal amplitude, bringing it closer to the input range of the analog-to-digital converter 330 and improving the sampling accuracy. The gain-adjusted signal is then sampled at 11kHz by the 16-bit analog-to-digital converter 330 to obtain a high-precision induced electromotive force digital signal.

[0119] The induced electromotive force (EMF) digital signal contains multiple sinusoidal components, which originate from sinusoidal excitation signals of different frequencies synchronously emitted by the transmitting coil 111. A window function is applied to the discretized induced EMF digital signal to reduce spectral leakage. A discrete Fourier transform is performed on the windowed signal to generate a frequency domain complex sequence. A one-sided amplitude spectrum is calculated based on the frequency domain complex sequence. Significant amplitude peaks are detected in the one-sided amplitude spectrum, and the sinusoidal signal amplitude corresponding to each frequency is extracted. Optionally, the window function is a Hanning window function.

[0120] The same processing is performed on all induced electromotive force simulation signals to obtain the measured potential values ​​of the receiving coil 210 at different preset spatial points under each frequency channel.

[0121] Step 4: Compare the theoretical potential value and the measured potential value for each frequency channel. Based on the comparison results, determine the inductance coefficient of each frequency channel and calibrate the attitude of the transmitting coil 111 for each frequency channel. Then, determine the pose of the receiving coil 210 based on the determined inductance coefficient, the calibrated attitude of the transmitting coil 111, and the measured potential value of the receiving coil 210.

[0122] Specifically, in step 4, the calculation process for the theoretical potential value under each frequency channel is as follows:

[0123] First, a magnetic dipole model is established, and the transmitting coil is equivalent to a magnetic dipole. The magnetic induction intensity generated by the transmitting coil of frequency channel i at the spatial point (x,y,z) is calculated using the Biot-Savart law. Let the magnetic induction intensity The components in the X, Y, and Z axes are respectively B ix B iy B ix Then we have:

[0124]

[0125] In equation (1), (a i ,b i ,c i (m) represents the center coordinates of the transmitting coil for frequency channel i. i ,n i ,p i ) represents the direction vectors of the X, Y, and Z axes of the transmitting coil corresponding to frequency channel i; r i For distance, its formula is: B T is the magnetic flux density coefficient.

[0126] Then, based on Faraday's law of electromagnetic induction, the theoretical potential value generated by the magnetic field change corresponding to the induced frequency channel i through the receiving coil located at the spatial point (x,y,z) is obtained:

[0127]

[0128] In equation (2), For the characteristic parameters of the receiving coil, The calculation formula is shown in equation (3).

[0129]

[0130] In equation (3), ω i Here, N represents the frequency corresponding to frequency channel i, and N is the number of turns in the receiving coil. The effective area of ​​the receiving coil is calculated as shown in equation (4):

[0131]

[0132] In equation (4), S is the maximum area of ​​the receiving coil 210; (α i ,β i ,γ i ) is the normalized direction vector of the angle between the magnetic field and the maximum area S of the current receiving coil when the transmitting coil 111 of the corresponding frequency channel i emits a magnetic field and the center of the receiving coil is located at the spatial point (x,y,z). i ,β i ,γ i According to equation (5):

[0133]

[0134] In equation (5), (v x ,v y ,v z ) represents the direction vectors of the X, Y, and Z axes of the receiving coil; L ix L iy L iz They are respectively:

[0135]

[0136] By (v x ,v y ,v z The values ​​ε are assigned to (1, 0, 0), (0, 1, 0), and (0, 0, 1) respectively. Combining formulas (1) to (6), the theoretical potential value ε is obtained when the transmitting coil 111 of the corresponding frequency channel i emits a magnetic field, and the center of the receiving coil 210 is located at the spatial point (x, y, z) and its axis is along the X, Y, and Z directions respectively. ix, ε iy and ε iz .

[0137] Specifically, in step 4, determining the inductance coefficient for each frequency channel involves:

[0138] First, calculate the theoretical potential values ​​ε corresponding to the frequency channel i, the receiving coil located at point j among M preset spatial points, and the receiving coil axis along the X, Y, and Z directions, respectively. ijx , ε ijy and ε ijz The calculation process is as follows:

[0139] The transmitting coil corresponding to frequency channel i is equivalent to a magnetic dipole. The position of the transmitting coil at point j(x) of frequency channel i is calculated using the Biot-Savart law. j ,y j ,z j The magnetic induction intensity generated at point ) Let the magnetic induction intensity The components in the X, Y, and Z axes are respectively B ijy B ijy B ijz Then we have:

[0140]

[0141] In equation (7), (a i ,b i ,c i (m) represents the center coordinates of the transmitting coil for frequency channel i. i ,n i ,p i ) represents the direction vectors of the X, Y, and Z axes of the transmitting coil corresponding to frequency channel i; r ij For distance, its formula is: B T is the magnetic flux density coefficient.

[0142] Then, based on Faraday's law of electromagnetic induction, we obtain that the center is located at point j(x). j ,y j ,z j The theoretical potential value generated in the receiving coil at point ) is:

[0143]

[0144] In equation (8), Centered at point j(x) j ,y j ,z j The characteristic parameters of the receiving coil at point ) The calculation formula is shown in equation (9).

[0145]

[0146] In equation (9), ω i Here, N represents the frequency corresponding to frequency channel i, and N is the number of turns in the receiving coil. Centered at point j(x) j ,y j ,z j The effective area of ​​the receiving coil at point () is calculated as shown in equation (10):

[0147]

[0148] In equation (10), S is the maximum area of ​​the receiving coil 210; (α ij ,β ij ,γ ij ) is the normalized direction vector of the angle between the magnetic field and the maximum area S of the current receiving coil when the transmitting coil (111) of the corresponding frequency channel i emits a magnetic field and the center of the receiving coil is located at point j. ij ,β ij ,γ ij It can be given by equation (11):

[0149]

[0150] In equation (11), (v jx ,v jy ,v jz Centered at point j(x) j ,y j ,z j The direction vectors of the receiving coil along the X, Y, and Z axes at point L; ijx L ijy L ijz They are respectively:

[0151]

[0152] By (v jx ,v jy ,v jz The values ​​are assigned to (1, 0, 0), (0, 1, 0), and (0, 0, 1) respectively. Combining formulas (7) to (12), the theoretical potential value ε is obtained when the transmitting coil 111 of the corresponding frequency channel i emits a magnetic field, and the receiving coil 210 is located at point j among the M preset spatial points, with its axis along the X, Y, and Z directions respectively. ijx , ε ijy and ε ijz .

[0153] Given the corresponding frequency channel i, the theoretical potential value ε corresponding to the receiving coil being located at all of the M preset spatial points, with the receiving coil axis set along the X, Y, and Z directions. ijx , ε ijy and ε ijz Then, combining the measured potential values ​​ε' corresponding to the frequency channel i, the receiving coil located at all of the M preset spatial points, and the receiving coil axis along the X, Y, and Z directions respectively. ijx ,ε' ijy and ε' ijz The inductance coefficient k of frequency channel i along the X, Y, and Z axes ix k iy k iz The calibration process is as follows:

[0154] For each frequency channel i, establish the first error function E. ik :

[0155]

[0156] Minimize the first error function E using the Levenberg-Marquardt algorithm. ik The inductance coefficient k of each frequency channel i along the X, Y, and Z axes is obtained. ix k iy and k iz The values ​​are denoted as k'. ix 、k' iy and k' iz .

[0157] Specifically, in step 4, calibrating the transmit coil attitude of each frequency channel includes:

[0158] The attitude parameters (a) of the transmitting coil corresponding to frequency channel i i ,b i ,c i ,m i ,n i ,p i () is considered an unknown parameter, where the value of the inductance coefficient k' of each frequency channel i on the X, Y, and Z axes is... ix 、k' iy and k' iz The center coordinates and direction vector (x) of the receiving coil placed at each preset spatial point j. j ,y j ,z j ,v jx ,v jy ,v jzWhen the frequency channel i is determined, the theoretical potential value ε is obtained by combining formulas (1) to (6) when the transmitting coil 111 corresponding to the frequency channel i emits a magnetic field and the receiving coil 210 is located at point j among the M preset spatial points, with its axis along the X, Y, and Z directions respectively. ijx , ε ijy and ε ijz The attitude parameters (a) of each transmitting coil with respect to the corresponding frequency channel i i ,b i ,c i ,m i ,n i ,p i The relation is denoted as ε. ijx (a i ,b i ,c i ,m i ,n i ,p i ), ε ijy (a i ,b i ,c i ,m i ,n i ,p i ) and ε ijz (a i ,b i ,c i ,m i ,n i ,p i ).

[0159] For each frequency channel i, establish a second error function E. ip :

[0160]

[0161] Minimize the second error function E using the Levenberg-Marquardt algorithm. ip The attitude parameters (a) of the transmitting coil (111) corresponding to each frequency channel i are obtained. i ,b i ,c i ,m i ,n i ,p i The value of ) is denoted as (a' i ,b' i ,c' i ,m' i ,n' i ,p' i ).

[0162] In this embodiment, the orientation of the receiving coil 210 is determined based on the determined inductance coefficient, the calibrated orientation of the transmitting coil 111, and the measured potential value of the receiving coil 210, including:

[0163] The pose of the receiving coil (x,y,z,v) x ,v y ,v z The position of the receiving coil is treated as an unknown parameter, and a two-stage optimization algorithm is used to solve for the pose of the receiving coil.

[0164] In the first stage, based on the measured potential value ε' of the receiving coil under each frequency channel i obtained in step 3... i And the values ​​of the inductance coefficients k' of each frequency channel i along the X, Y, and Z axes as determined in step 4. ix 、k' iy and k' iz The attitude parameter values ​​(a') of the transmitting coil corresponding to each frequency channel i i ,b' i ,c' i ,m' i ,n' i ,p' i Combining formulas (1) to (6), we obtain the theoretical potential values ​​ε corresponding to the frequency channel i, with the center of the receiving coil located at (x, y, z), and the axis of the receiving coil along the X, Y, and Z directions, respectively. ix , ε iy and ε iz The poses (x, y, z, v) of each relative to the receiving coil x ,v y ,v z The relation is denoted as ε. ijx (a i ,b i ,c i ,m i ,n i ,p i ), ε ijy (a i ,b i ,c i ,m i ,n i ,p i ) and ε ijz (a i ,b i ,c i ,m i ,n i ,p i ).

[0165] For each frequency channel i, the following equation (15) is constructed:

[0166]

[0167] A particle swarm optimization (PSO) algorithm is used to traverse the three-dimensional space for a global search. The six position parameters of the receiving coil calculated by the PSO algorithm are substituted into equation (15) to finally obtain the pose (x, y, z, v) of the receiving coil. x ,v y ,v z The initial value of ).

[0168] The second stage, a local optimization algorithm, improves the solution accuracy by precisely calculating the specific coordinates and angles of the receiving coil. Using the output of the particle swarm optimization algorithm as initial values, the Levenberg-Marquardt algorithm is employed to minimize the third error function E'. ip E' ip The formula for calculation is:

[0169]

[0170] Minimize the third error function E' using the Levberg-Marquardt algorithm. ip Find the six-degree-of-freedom pose parameters (x, y, z, v) of the receiving coil when the error is minimized. x ,v y ,v z The precise value of the nine-channel induced potential value is ultimately used to achieve a precise conversion from the nine-channel induced potential value to the spatial position and attitude angle.

[0171] In its specific implementation, this application provides a computer storage medium and a corresponding data processing unit. The computer storage medium is capable of storing a computer program, which, when executed by the data processing unit, can run the invention's content regarding a system for accurately locating the pose of a near-field target using orthogonal electromagnetic signal groups, as well as some or all of the steps in various embodiments. The storage medium can be a magnetic disk, optical disk, read-only memory (ROM), or random access memory (RAM), etc.

[0172] Those skilled in the art will clearly understand that the technical solutions in the embodiments of the present invention can be implemented using computer programs and their corresponding general-purpose hardware platforms. Based on this understanding, the technical solutions in the embodiments of the present invention, or the parts that contribute to the prior art, can be embodied in the form of computer programs, i.e., software products. These computer program software products can be stored in a storage medium and include several instructions to cause a device containing a data processing unit (which may be a personal computer, server, microcontroller, MCU, or network device, etc.) to execute the methods described in various embodiments or certain parts of the embodiments of the present invention.

[0173] This invention provides a system and method for accurately locating the pose of a near-field target using orthogonal electromagnetic signal groups. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A system for accurately locating the pose of a near-field target using orthogonal electromagnetic signal groups, characterized in that, include: The magnetic field generator module (100) includes a transmitting coil array (110) consisting of multiple transmitting coils (111) fixed at their respective preset positions, each transmitting coil (111) serving as a frequency channel; the multiple transmitting coils (111) emit simultaneously to generate multiple spatial magnetic fields (120) of different frequencies that do not interfere with each other; A magnetic sensing receiving module (200) is fixed on an ultrasonic probe; the magnetic sensing receiving module (200) contains a receiving coil (210), which can sense the change of the spatial magnetic field (120) and generate a corresponding induced electromotive force analog signal. The signal preprocessing module (300) is used to obtain the measured potential value of the receiving coil (210) at different preset spatial points under each frequency channel based on the induced electromotive force simulation signal generated by the receiving coil (210) at different preset spatial points. The signal calibration module (400) is used to compare the theoretical potential value with the measured potential value under each frequency channel, and determine the inductance coefficient of each frequency channel and calibrate the attitude of the transmitting coil (111) of each frequency channel based on the comparison result. The signal analysis module (500) is used to determine the position of the receiving coil (210) based on the determined inductance coefficient, the calibrated attitude of the transmitting coil (111), and the measured potential value of the receiving coil (210).

2. The system for accurately locating the pose of a near-field target using orthogonal electromagnetic signal groups according to claim 1, characterized in that, The magnetic field generator module (100) further includes: Control unit (130); The signal generator (140) is configured to generate multiple orthogonal frequency division multiplexed sinusoidal signals of different frequencies under the drive of the control unit (130), wherein the frequency signals are mutually orthogonal and transmitted in parallel; A first power amplifier (150) is configured to receive each of the frequency signals from the signal generator (140) and amplify each of the frequency signals; A bandpass filter (160) is configured to receive the amplified frequency signals from the first power amplifier (150), remove low-frequency noise and high-frequency noise from the amplified frequency signals, and send the frequency signals after filtering out low-frequency noise and high-frequency noise to the corresponding transmitting coils (111) in the transmitting coil (111) array.

3. The system for accurately locating the pose of a near-field target using orthogonal electromagnetic signal groups according to claim 2, characterized in that, The signal preprocessing module (300) includes: An RC bandpass filter (310) is configured to perform high-pass and low-pass filtering on the induced electromotive force analog signal, allowing only signals within a specific frequency range to pass through; The second power amplifier (320) is configured to amplify the filtered analog signal and adjust it to the amplitude range of the analog-to-digital converter (330) input; An analog-to-digital converter (330) is configured to convert an amplified analog signal into a discrete digital signal; The frequency division processing unit (340) is configured to separate or extract digital signals of different frequency components from the digital signal output by the analog-to-digital converter (330).

4. The system for accurately locating the pose of a near-field target using orthogonal electromagnetic signal groups according to claim 3, characterized in that, Separating or extracting digital signals of different frequency components from the digital signal output by the analog-to-digital converter (330) includes: sampling the digital signal output by the analog-to-digital converter (330) at at least three times the highest transmission frequency, performing frequency division processing using a fast Fourier transform algorithm, and extracting the amplitude of each frequency component.

5. A method for accurately locating the pose of a near-field target using orthogonal electromagnetic signal groups, characterized in that, The method, implemented using any one of claims 1 to 4, comprises: Step 1: Input N sinusoidal signals of different frequencies into the corresponding transmitting coils (111) in the transmitting coil (111) array. Each transmitting coil (111) corresponds to a frequency channel. These frequency signals are orthogonal to each other, realize parallel transmission, and form multiple spatial magnetic fields (120) of different frequencies that do not interfere with each other. Step 2: The receiving coil (210) fixed on the ultrasonic probe is placed at M different preset spatial points in sequence. The receiving coil (210) generates a corresponding induced electromotive force analog signal by sensing the change of the spatial magnetic field (120) at each preset spatial point. Step 3: Based on the simulated induced electromotive force signals generated by the receiving coil (210) at different preset spatial points, obtain the measured potential values ​​of the receiving coil (210) at different preset spatial points under each frequency channel. Step 4: Compare the theoretical potential value and the measured potential value under each frequency channel. Based on the comparison results, determine the inductance coefficient of each frequency channel and calibrate the attitude of the transmitting coil (111) of each frequency channel. Then, determine the pose of the receiving coil (210) based on the determined inductance coefficient, the calibrated attitude of the transmitting coil (111) and the measured potential value of the receiving coil (210).

6. The method according to claim 5, characterized in that, The calculation process for the theoretical potential value under each frequency channel is as follows: First, a magnetic dipole model is established, and the transmitting coil (111) is equivalent to a magnetic dipole. The magnetic induction intensity generated by the transmitting coil (111) at the spatial point (x,y,z) of the corresponding frequency channel i is calculated by Biot-Savart law. Let the magnetic induction intensity The components in the X, Y, and Z axes are respectively B ix B iy and B ix Then we have: In equation (1), (a i ,b i ,c i ) represents the center coordinates of the transmitting coil (111) corresponding to frequency channel i, (m i ,n i ,p i ) represents the direction vectors of the X, Y, and Z axes of the transmitting coil (111) corresponding to frequency channel i; r i For distance, its formula is: B T It is the magnetic flux density coefficient; Then, based on Faraday's law of electromagnetic induction, the theoretical potential value generated by the magnetic field change corresponding to the induced frequency channel i through the receiving coil (210) centered at the spatial point (x,y,z) is obtained: In equation (2), For the characteristic parameters of the receiving coil (210), The calculation formula is shown in equation (3). In equation (3), ω i Let N be the frequency corresponding to frequency channel i, and N be the number of turns of the receiving coil (210). The effective area of ​​the receiving coil (210) is calculated as shown in equation (4): In equation (4), S is the maximum area of ​​the receiving coil (210); (α i ,β i ,γ i ) is the normalized direction vector of the angle between the magnetic field and the maximum area S of the current receiving coil when the transmitting coil (111) of the corresponding frequency channel i emits a magnetic field and the center of the receiving coil is located at the spatial point (x,y,z). i ,β i ,γ i According to equation (5): In equation (5), (v x ,v y ,v z ) represents the direction vectors of the X, Y, and Z axes of the receiving coil (210); L ix L iy and L iz They are respectively: By (v x ,v y ,v z The values ​​of (1, 0, 0), (0, 1, 0), and (0, 0, 1) are assigned respectively. Combining formulas (1) to (6), the theoretical potential value ε is obtained when the transmitting coil (111) of the corresponding frequency channel i emits a magnetic field, and the center of the receiving coil (210) is located at the spatial point (x, y, z) and its axis is along the X, Y, and Z directions respectively. ix , ε iy and ε iz .

7. The method according to claim 6, characterized in that, Determining the inductance coefficient for each frequency channel includes: The transmitting coil (111) corresponding to frequency channel i is equivalent to a magnetic dipole. The position of the transmitting coil (111) at point j(x) corresponding to frequency channel i is calculated using the Biot-Savart law. j ,y j ,z j The magnetic induction intensity generated at point ) Let the magnetic induction intensity The components in the X, Y, and Z axes are respectively B ijy B ijy B ijz Then we have: In equation (1), (a i ,b i ,c i ) represents the center coordinates of the transmitting coil (111) corresponding to frequency channel i, (m i ,n i ,p i ) represents the direction vectors of the X, Y, and Z axes of the transmitting coil (111) corresponding to frequency channel i; r ij For distance, its formula is: B T It is the magnetic flux density coefficient; Then, based on Faraday's law of electromagnetic induction, we obtain that the center is located at point j(x). j ,y j ,z j The theoretical potential value generated in the receiving coil (210) at point ) is: In equation (8), Centered at point j(x) j ,y j ,z j The characteristic parameters of the receiving coil (210) of the receiver, The calculation formula is shown in equation (9). In equation (9), ω i Let N be the frequency corresponding to frequency channel i, and N be the number of turns of the receiving coil (210). Centered at point j(x) j ,y j ,z j The effective area of ​​the receiving coil (210) is calculated as shown in equation (10): In equation (4), S is the maximum area of ​​the receiving coil (210); (α ij ,β ij ,γ ij ) is the normalized direction vector of the angle between the magnetic field and the maximum area S of the current receiving coil when the transmitting coil (111) of the corresponding frequency channel i emits a magnetic field and the center of the receiving coil is located at point j. ij ,β ij ,γ ij According to equation (11): In equation (11), (v jx ,v jy ,v jz Centered at point j(x) j ,y j ,z j The direction vectors of the X, Y, and Z axes of the receiving coil (210) at point L; ijx L ijy and L ijz They are respectively: By (v jx ,v jy ,v jz The values ​​are assigned to (1, 0, 0), (0, 1, 0), and (0, 0, 1) respectively. Combining formulas (7) to (12), the theoretical potential values ​​ε corresponding to the X, Y, and Z directions of the receiving coil (210) when the transmitting coil (111) of the corresponding frequency channel i emits a magnetic field and the receiving coil (210) is located at point j among the M preset spatial points are obtained. ijx , ε ijy and ε ijz ; For each frequency channel i, establish the first error function E. ik : Minimize the first error function E using the Levenberg-Marquardt algorithm. ik The inductance coefficient k of each frequency channel i along the X, Y, and Z axes is obtained. ix k iy and k iz The values ​​are denoted as k'. ix 、k' iy and k' iz .

8. The method according to claim 7, characterized in that, The calibration of the transmit coil (111) attitude for each frequency channel includes: The attitude parameters (a) of the transmitting coil corresponding to frequency channel i i ,b i ,c i ,m i ,n i ,p i () is considered an unknown parameter, where the value of the inductance coefficient k' of each frequency channel i on the X, Y, and Z axes is... ix 、k' iy and k' iz The center coordinates and direction vector (x) of the receiving coil placed at each preset spatial point j. j ,y j ,z j ,v jx ,v jy ,v jz When the magnetic field is determined, by combining formulas (1) to (6), the theoretical potential value ε corresponding to the transmitting coil (111) corresponding to the frequency channel i is obtained, and the receiving coil (210) is located at point j among the M preset spatial points, with its axis along the X, Y, and Z directions respectively. ijx , ε ijy and ε ijz The attitude parameters (a) of each transmitting coil with respect to the corresponding frequency channel i i ,b i ,c i ,m i ,n i ,p i The relation is denoted as ε. ijx (a i ,b i ,c i ,m i ,n i ,p i ), ε ijy (a i ,b i ,c i ,m i ,n i ,p i ) and ε ijz (a i ,b i ,c i ,m i ,n i ,p i ); For each frequency channel i, establish a second error function E. ip : Minimize the second error function E using the Levenberg-Marquardt algorithm. ip The attitude parameters (a) of the transmitting coil (111) corresponding to each frequency channel i are obtained. i ,b i ,c i ,m i ,n i ,p i The value of ) is denoted as (a' i ,b' i ,c' i ,m' i ,n' i ,p' i ).

9. The method according to claim 8, characterized in that, Determining the pose of the receiving coil (210) based on the determined inductance coefficient, the calibrated attitude of the transmitting coil (111), and the measured potential value of the receiving coil (210) includes: The pose of the receiving coil (x,y,z,v) x ,v y ,v z ( ) represents an unknown parameter. A two-stage optimization algorithm is used to solve for the pose of the receiving coil. In the first stage, based on the measured potential value ε' of the receiving coil under each frequency channel i obtained in step 3... i And the values ​​of the inductance coefficients k' of each frequency channel i along the X, Y, and Z axes as determined in step 4. ix 、k' iy and k' iz The attitude parameter values ​​(a') of the transmitting coil corresponding to each frequency channel i i ,b' i ,c' u ,m' i ,n' i ,p' i Combining formulas (1) to (6), we obtain the theoretical potential value ε corresponding to the following conditions: when the transmitting coil (111) of the corresponding frequency channel i emits a magnetic field, and the center of the receiving coil (210) is located at (x,y,z) with its axis along the X, Y, and Z directions, respectively. ix , ε iy and ε iz The poses (x, y, z, v) of each relative to the receiving coil x ,v y ,v z The relation, denoted as ε ijx (a i ,b i ,c i ,m i ,n i ,p i ), ε ijy (a i ,b i ,c i ,m i ,n i ,p i ) and ε ijz (a i ,b i ,c i ,m i ,n i ,p i ); For each frequency channel i, the following equation (15) is constructed: A particle swarm optimization (PSO) algorithm is used to traverse the three-dimensional space for a global search. The six position parameters of the receiving coil calculated by the PSO algorithm are substituted into equation (15) to finally obtain the pose (x, y, z, v) of the receiving coil. x ,v y ,v z The initial value of ). The second stage, a local optimization algorithm, improves the solution accuracy by precisely calculating the specific coordinates and angles of the receiving coil. Using the output of the particle swarm optimization algorithm as initial values, the Levenberg-Marquardt algorithm is employed to minimize the third error function E'. ip E' ip The formula for calculation is: Minimize the third error function E' using the Levberg-Marquardt algorithm. ip Find the six-degree-of-freedom pose parameters (x, y, z, v) of the receiving coil when the error is minimized. x ,v y ,v z The precise value of ).

10. The method according to claim 5, characterized in that, The number M of the preset spatial points is at least 1000, preferably 1444; the number N of the transmitting coils (111) is at least 6, preferably 9; the axis of the receiving coil (210) is set at 90 degrees to the longitudinal axis of the ultrasonic probe.

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