CN108042094B - Positioning system and positioning method for freedom degree of wireless capsule endoscope 5 - Google Patents
Positioning system and positioning method for freedom degree of wireless capsule endoscope 5 Download PDFInfo
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- A61B1/31—Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes; Illuminating arrangements therefor for the rectum, e.g. proctoscopes, sigmoidoscopes, colonoscopes
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Abstract
The invention provides a positioning system of 5 degrees of freedom of a wireless capsule endoscope and a positioning method thereof, comprising a transmitting coil, a sampling module, a position and direction calculating module, a wireless transmitting module, an external wireless receiving module and a wireless capsule endoscope positioned in a human body, wherein the transmitting coil is arranged outside the human body and is in triaxial quadrature; therefore, an equation set is established to calculate the three-dimensional position and the three-dimensional posture, the method is convenient to integrate, the single-shaft induction coil occupies little space of the wireless capsule endoscope, the wireless capsule endoscope can be positioned in real time and continuously, the follow-up operation is convenient, the safety and the reliability are realized, and the cost is low.
Description
[ field of technology ]
The invention relates to a magnetic positioning technology, in particular to a positioning system and a positioning method for the degree of freedom of a wireless capsule endoscope 5.
[ background Art ]
Currently, after the wireless capsule endoscope enters the alimentary canal of a human body, the wireless capsule endoscope freely moves under the combined action of gravity and peristalsis of the gastrointestinal tract, and the wireless capsule endoscope lacks real-time and accurate positioning. Therefore, the pose control work of the wireless capsule endoscope cannot be effectively performed; because the image has no position and direction matching information of the lens, digestive tract reconstruction work cannot be carried out; without real-time positioning data, the physician cannot confirm whether the capsule is stuck during the examination.
The Given Imaging company has used the radio frequency technology to locate the wireless capsule endoscope earlier, including Chongqing Jinshan technology Co. And (3) sticking 8 or more wireless radio frequency antennas on the surface of a human body, receiving radio frequency signals emitted by the in-vivo wireless capsule endoscope, establishing an equation set according to a radio frequency signal propagation model, and solving the equation set through an algorithm to obtain the position of the wireless capsule endoscope. The method has low positioning precision, the average positioning precision is 37.7 mm, and the clinical application effect is poor.
A wireless capsule endoscope permanent magnet positioning method is proposed, a small permanent magnet is embedded in the wireless capsule endoscope, or a permanent magnet ring is sleeved outside the capsule, a magnetic field sensor array is arranged around a human body to collect a multipoint magnetic field, an equation set is established according to a permanent magnet space distribution model, and the position of the wireless capsule endoscope is obtained by solving the equation set through an algorithm; the permanent magnet positioning has the advantages of high precision and high speed. However, the permanent magnet positioning has a relatively large defect that the positioning distance is short, and the effective detection distance of the permanent magnet capable of being put into the existing capsule is about 10cm, so that the requirement of human body size is difficult to meet.
It has also been proposed to arrange two triaxial induction coils in the capsule, and to make the permanent magnet reciprocate outside the capsule under the action of the vibration module to generate a varying magnetic field, and the two triaxial induction coils in the capsule output induced electromotive force; however, two triaxial induction coils occupy more space of the capsule.
Imaging examinations such as X-ray imaging, CT (computed tomography) imaging and MRI (magnetic resonance) imaging can also be used to locate wireless capsule endoscopes. However, X-ray imaging and CT imaging have radiation damage, and are not suitable for long-time positioning; MRI imaging is currently costly.
[ invention ]
In order to solve the defects in the prior art, the invention provides a wireless capsule endoscope 5 degree-of-freedom positioning system and a positioning method thereof based on an alternating magnetic field, wherein the wireless capsule endoscope adopts a triaxial transmitting coil and a uniaxial induction coil. The single-shaft coil occupies little space of the wireless capsule endoscope, is convenient to integrate, can be positioned in real time, is safe and reliable, has low cost, and has the advantage of providing convenience for subsequent operation.
In order to achieve the above purpose, the invention adopts the following technical scheme:
the invention provides a first vision-improving and wireless capsule endoscope 5-degree-of-freedom positioning system, which comprises a transmitting coil, a sampling module, a position and direction calculation module, an external wireless receiving module and a wireless capsule endoscope, wherein the transmitting coil, the sampling module, the position and direction calculation module, the external wireless receiving module and the wireless capsule endoscope are arranged outside a human body and are in triaxial orthogonality; the transmitting coil consists of a triaxial orthogonal coil I, a triaxial orthogonal coil II and a triaxial orthogonal coil III, the coil I, the coil II and the coil III sequentially transmit signals with fixed frequencies, the coil I, the coil II and the coil III sequentially transmit signals with 6 different frequencies and amplitudes to form a period, namely, each coil transmits signals with 2 different frequencies and amplitudes in one period.
Further, the wireless capsule endoscope further comprises a signal amplifying module and an analog-to-digital conversion module; the single-shaft induction coil is directly connected with the signal amplification module, and the signal amplification module is directly connected with the wireless transmission module.
Further, the wireless capsule endoscope is also provided with an acquisition filter module for filtering noise of acquired signals, and the external wireless receiving module is also connected with a receiving filter module for filtering noise of received sampling signals.
Further, the uniaxial induction coil is arranged on or in a direction parallel to a central axis of the wireless capsule endoscope.
Further, the coil I transmits 2 signals with different frequencies and amplitudes at fixed time intervals; then, the coil II transmits 2 signals with different frequencies and amplitudes from the coil I according to fixed time intervals; finally, the coil III transmits 2 signals with different frequencies and amplitudes from the coil I and the coil II at fixed time intervals.
Further, the coil I, the coil II and the coil III sequentially emit signals with 1 different frequency and amplitude; then, the coil I, the coil II and the coil III sequentially emit a signal with different frequency and amplitude from the previous signal.
The second object of the present invention is to provide a method for positioning the degree of freedom of a wireless capsule endoscope 5, in which a single-axis induction coil and a wireless transmission module are provided, comprising the steps of:
the method comprises the following steps that 1, a three-axis orthogonal transmitting coil is arranged outside a human body, and the transmitting coil consists of a three-axis orthogonal coil I, a three-axis orthogonal coil II and a three-axis orthogonal coil III;
step 2, taking a coordinate system OXYZ established by three axes of the transmitting coil as a reference coordinate system, wherein the coordinate of a center point of the single-axis induction coil in the OXYZ coordinate system is (x, y, z), and converting the coordinate into the position of the center of the wireless capsule endoscope in the reference coordinate system; the direction vector of the uniaxial induction coil in the OXYZ coordinate system is (vx, vy, vz) and represents the direction of the wireless capsule endoscope; the coordinates (x, y, z) and the direction vectors (vx, vy, vz) of the center point of the single-axis induction coil are positioning parameters;
step 3, after power-on, the coil I, the coil II and the coil III of the transmitting coil sequentially transmit 2 signals with different frequencies and amplitudes in each period;
step 4, an amplifying module in the wireless capsule endoscope amplifies the output voltage of the single-shaft induction coil;
step 5, the analog-to-digital conversion module in the wireless capsule endoscope samples the amplified output voltage;
step 6, a wireless transmitting module in the wireless capsule endoscope transmits a sampling signal;
step 7, the in-vitro wireless receiving module receives the sampling signal and sends the sampling signal to the position and direction calculating module;
and 8, calculating the position and direction information of the wireless capsule endoscope by a position and direction calculation module, wherein the process is as follows:
solving 6 unknown parameters (x, y, z, vx, vy, vz) of the position and the direction of the wireless capsule endoscope;
each axis of the triaxial transmitting coil is equivalent to a magnetic dipole, and the magnetic dipole generates magnetic flux density at the center of the uniaxial induction coil inside the wireless capsule endoscope according to the Bioshaval lawThree orthogonal components along the X, Y, Z axis of the reference coordinate system ozz are shown in equations (1), (2), (3):
wherein (x, y, z) is the position of the center of the uniaxial induction coil, (m, n, p) is the direction vector of each axis of the transmission coil, (a, B, c) is the position of the transmission coil, B T Is a constant related to the transmit coil, L is the distance of the sense coil from the transmit coil, L is as shown in equation (4):
magnetic flux densityIncluded angle with the direction vector of the uniaxial induction coil, magnetic flux density +.>The projection vector on the induction coil unit direction vector is as shown in formula (5):
wherein (vx, vy, vz) is the unit direction vector of the uniaxial induction coil,three orthogonal components along the X, Y, Z axis of the reference coordinate system ozz are shown in equations (6), (7), and (8), respectively:
the uniaxial induction coil outputs a voltage signal, and the induced electromotive force generated by the uniaxial induction coil is shown as formula (9) according to faraday's law of electromagnetic induction:
wherein N is the number of turns of the uniaxial induction coil, phi is the magnetic flux passing through the curved surface S, and t is the time;
since the uniaxial induction coil is small, the volume thereof can be ignored, and the magnetic flux density of the uniaxial induction coil is considered to be equal everywhere, so that the formula (9) becomes the formula (10):
because ofThe direction is the same as that of the uniaxial induction coil, so that the following formula (11) is obtained:
if a sinusoidal signal of known frequency is emitted, other signals of known frequency can of course be used, which cannot be used to define the signal employed for the emission, the magnetic flux density is described as shown in equation (12):
wherein,for maximum amplitude when the magnetic flux density is taken as a vector, ω is the angular frequency of the sinusoidal signal, +.>Is the initial phase of the sinusoidal signal;
thus, a relation between the output voltage value and the magnetic flux density of the uniaxial induction coil can be obtained, as shown in formula (13):
wherein B' max Is thatThe maximum amplitude of the projection vector on the unit direction vector (vx, vy, vz) where the uniaxial induction coil is located;
the output voltage signal of the single-axis induction coil is a cosine signal with the same frequency as the transmitting signal, and the amplitude of the signal is taken to establish an equation set, so that E T = - ωn·s, equation (14) is obtained:
ε max ＝-ωN·B' max ·S＝E T ·B' max (14)
wherein ε max Is the maximum value of the induced electromotive force;
the amplitude of the cosine signal is extracted by the fast Fourier transform, and other methods can be used, so that the mode of extracting the amplitude of the cosine signal cannot be limited;
the triaxial transmitting coils sequentially transmit sinusoidal signals with respective amplitude and frequency, and in one period, the uniaxial induction coil outputs 6 groups of voltage signals, so that 6 equations can be established, and 6 unknown parameters describing the position and the direction of the wireless capsule endoscope are solved; since the direction vector (vx, vy, vz) of the single axis induction coil is a unit vector, a constraint equation is added as shown in equation (15):
vx 2 +vy 2 +vz 2 ＝1 (15)
setting epsilon i ' max (i=1, 2, 3, 4, 5, 6) is the output voltage amplitude of the uniaxial induction coil in the wireless capsule endoscope, ε imax Is a theoretical expression of the amplitude, and the definition error E is shown in formula (16):
the optimization algorithm, such as the Levenberg-Marquardt algorithm, can be used, but other methods can be used, and the adopted optimization algorithm can not be limited by the optimization algorithm; minimizing E, the position and direction parameters (x, y, z, vx, vy, vz) of the wireless capsule endoscope can be solved;
and 9, the position and direction calculation module sends the pose information of the wireless capsule endoscope to the display terminal to reflect the pose of the current wireless capsule endoscope in real time, so that the wireless capsule endoscope is convenient for an operator to observe or subsequently apply.
Further, the step 5 further includes: the acquisition filtering module arranged in the wireless capsule endoscope carries out noise filtering on the sampled signals.
Further, the step 7 further includes: the external wireless receiving module is also connected with a receiving filtering module for filtering noise of the received sampling signals.
Further, the transmitting frequency and amplitude modes of the coil I, the coil II and the coil III of the transmitting coil in the step 3 are as follows: firstly, a coil I transmits 2 signals with different frequencies and amplitudes at fixed time intervals; then, the coil II transmits 2 signals with different frequencies and amplitudes from the coil I according to fixed time intervals; finally, the coil III transmits 2 signals with different frequencies and amplitudes from the coil I and the coil II at fixed time intervals.
Further, the transmitting frequency and amplitude modes of the coil I, the coil II and the coil III of the transmitting coil in the step 3 are as follows: firstly, a coil I, a coil II and a coil III sequentially transmit signals with 1 different frequency and amplitude; then, the coil I, the coil II and the coil III sequentially emit a signal with different frequency and amplitude from the previous signal.
The beneficial effects of the invention are as follows:
the invention is based on alternating magnetic field, arrange the transmitting coil of triaxial orthogonality near human body, arrange a single-axis induction coil in the wireless capsule endoscope, set up reference coordinate system OXYZ with three axes that the transmitting coil is located, the single-axis induction coil central point is (x, y, z) in the coordinate system of OXYZ, can convert it into the position in reference coordinate system of the wireless capsule endoscope center; the direction vector of the uniaxial induction coil in the OXYZ coordinate system is (vx, vy, vz) and can represent the direction of the wireless capsule endoscope; the coordinates (x, y, z) and the direction vectors (vx, vy, vz) of the center point of the single axis induction coil are parameters of the positioning.
The coil I, the coil II and the coil III of the transmitting coil sequentially transmit 6 signals with different frequencies and amplitudes, and the coil I, the coil II and the coil III transmit 6 signals, which is called a period; the tri-axial coils transmit signals corresponding to the same in different periods. The single-axis induction coil can output 6 voltage signals with different frequencies and amplitudes in one period, so that an equation set containing 6 equations can be established, and the equation set is solved by adopting an optimization algorithm to obtain positioning parameters, so that 5-degree-of-freedom (position: 3-degree-of-freedom, direction: 2-degree-of-freedom) measurement is realized.
Through adopting a triaxial transmitting coil, a unipolar induction coil, unipolar induction coil occupies wireless capsule endoscope space is few, and is integrated convenient, but real-time positioning, safe and reliable, low cost can provide convenience for follow-up operation.
[ description of the drawings ]
FIG. 1 is an enlarged schematic view of the in vitro triaxial transmitting coil and the internal uniaxial coil arrangement of a wireless capsule endoscope according to the present invention;
fig. 2 is a positioning flow chart of the present invention.
[ detailed description ] of the invention
In order that the above objects, features and advantages of the invention will be readily understood, a more particular description of the invention will be rendered by reference to the appended drawings.
The positioning system of the freedom degree of the wireless capsule endoscope 5 is shown in fig. 1, and comprises a transmitting coil, a sampling module, a position and direction calculation module, an external wireless receiving module and a wireless capsule endoscope which are arranged outside a human body and are orthogonal in three axes, wherein the wireless capsule endoscope is internally provided with a single-axis induction coil and a wireless transmitting module, and the single-axis induction coil is arranged in the wireless capsule endoscope as shown in a part a in fig. 1; the three-axis orthogonal transmitting coil and the single-axis induction coil arranged in the wireless capsule endoscope form a magnetic circuit through an alternating magnetic field, the sampling module is directly connected with the single-axis induction coil arranged in the wireless capsule endoscope, the wireless transmitting module arranged in the wireless capsule endoscope is connected with the external wireless receiving module through wireless signals, and the position and direction calculating module is directly connected with the external wireless receiving module; the transmitting coil consists of a triaxial orthogonal coil I, a triaxial orthogonal coil II and a triaxial orthogonal coil III, wherein the coil I, the coil II and the coil III sequentially transmit signals with fixed frequencies, the coil I, the coil II and the coil III sequentially transmit signals with 6 different frequencies and amplitudes to form a period, namely, each coil transmits signals with 2 different frequencies and amplitudes in one period; the transmitting coil and the wireless capsule endoscope form a magnetic circuit through an alternating magnetic field, the wireless capsule endoscope is connected with the external wireless receiving module through wireless signals, and the pose calculating module is directly connected with the external wireless receiving module.
The wireless capsule endoscope also comprises a signal amplification module and an analog-to-digital (AD) conversion module, wherein the single-shaft induction coil is directly connected with the signal amplification module, and the signal amplification module is directly connected with the wireless transmission module; the wireless capsule endoscope is also internally provided with an acquisition filter module for filtering noise of acquired signals, and the external wireless receiving module is also connected with a receiving filter module for filtering noise of received sampling signals.
Continuing with fig. 1, the uniaxial induction coil is disposed on or parallel to the central axis of the wireless capsule endoscope; as shown in part b of fig. 1, the uniaxial induction coil is arranged in a direction parallel to the central axis of the wireless capsule endoscope; as shown in part c of fig. 1, the uniaxial induction coil is arranged on the central axis of the wireless capsule endoscope.
The transmitting frequency and amplitude in the coil I, the coil II and the coil III of the transmitting coil are transmitted in two modes, and one mode is as follows: firstly, a coil I transmits 2 signals with different frequencies and amplitudes at fixed time intervals; then, the coil II transmits 2 signals with different frequencies and amplitudes from the coil I according to fixed time intervals; finally, the coil III transmits 2 signals with different frequencies and amplitudes from the coil I and the coil II at fixed time intervals. Another way is: firstly, a coil I, a coil II and a coil III sequentially transmit signals with 1 different frequency and amplitude; then, the coil I, the coil II and the coil III sequentially emit a signal with different frequency and amplitude from the previous signal.
As shown in fig. 2, the positioning method of the degree of freedom of the wireless capsule endoscope 5 according to this embodiment is provided with a single-axis induction coil and a wireless transmission module, and includes the following steps:
the method comprises the following steps that 1, a three-axis orthogonal transmitting coil is arranged outside a human body, and the transmitting coil consists of a three-axis orthogonal coil I, a three-axis orthogonal coil II and a three-axis orthogonal coil III;
step 2, taking a coordinate system OXYZ established by three axes of the transmitting coil as a reference coordinate system, wherein the coordinate of a center point of the single-axis induction coil in the OXYZ coordinate system is (x, y, z), and converting the coordinate into the position of the center of the wireless capsule endoscope in the reference coordinate system; the direction vector of the uniaxial induction coil in the OXYZ coordinate system is (vx, vy, vz) and represents the direction of the wireless capsule endoscope; the coordinates (x, y, z) and the direction vectors (vx, vy, vz) of the center point of the single-axis induction coil are positioning parameters;
step 3, after power-on, the coil I, the coil II and the coil III of the transmitting coil sequentially transmit 2 signals with different frequencies and amplitudes in each period;
step 4, an amplifying module in the wireless capsule endoscope amplifies the output voltage of the single-shaft induction coil;
step 5, the analog-to-digital (AD) conversion module in the wireless capsule endoscope samples the amplified output voltage, and the step 5 also comprises a collection filtering module arranged in the wireless capsule endoscope for noise filtering of the sampled signals;
step 6, a wireless transmitting module in the wireless capsule endoscope transmits a sampling signal;
step 7, the in-vitro wireless receiving module receives the sampling signal and sends the sampling signal to the position and direction calculating module; in the step, the external wireless receiving module is also connected with a receiving filtering module for filtering noise of the received sampling signal;
and 8, calculating the position and direction information of the wireless capsule endoscope by a position and direction calculation module, wherein the process is as follows:
solving 6 unknown parameters (x, y, z, vx, vy, vz) of the position and the direction of the wireless capsule endoscope;
each axis of the triaxial transmitting coil is equivalent to a magnetic dipole, and the magnetic dipole generates magnetic flux density at the center of the uniaxial induction coil inside the wireless capsule endoscope according to the Bioshaval lawThree orthogonal components along the X, Y, Z axis of the reference coordinate system ozz are shown in equations (1), (2), (3):
where (x, y, z) is the position of the center of the uniaxial induction coil, (m, n,p) is the direction vector of each axis of the transmitting coil, (a, B, c) is the position of the transmitting coil, B T Is a constant related to the transmit coil, L is the distance of the sense coil from the transmit coil, L is as shown in equation (4):
magnetic flux densityIncluded angle with the direction vector of the uniaxial induction coil, magnetic flux density +.>The projection vector on the induction coil unit direction vector is as shown in formula (5):
wherein (vx, vy, vz) is the unit direction vector of the uniaxial induction coil,three orthogonal components along the X, Y, Z axis of the reference coordinate system ozz are shown in equations (6), (7), and (8), respectively:
the uniaxial induction coil outputs a voltage signal, and the induced electromotive force generated by the uniaxial induction coil is shown as formula (9) according to faraday's law of electromagnetic induction:
wherein N is the number of turns of the uniaxial induction coil, phi is the magnetic flux passing through the curved surface S, t is time, and the induced electromotive force epsilon is the change rate of the magnetic flux density;
since the uniaxial induction coil is small, the volume thereof can be ignored, and the magnetic flux density of the uniaxial induction coil is considered to be equal everywhere, so that the formula (9) becomes the formula (10):
because ofThe direction is the same as that of the uniaxial induction coil, so that the following formula (11) is obtained:
if a sinusoidal signal of known frequency is emitted, other signals of known frequency can of course be used, which cannot be used to define the signal employed for the emission, the magnetic flux density is described as shown in equation (12):
wherein,for maximum amplitude when the magnetic flux density is taken as a vector, ω is the angular frequency of the sinusoidal signal, +.>Is the initial phase of the sinusoidal signal;
thus, a relation between the output voltage value and the magnetic flux density of the uniaxial induction coil can be obtained, as shown in formula (13):
wherein B' max Is thatThe maximum amplitude of the projection vector on the unit direction vector (vx, vy, vz) where the uniaxial induction coil is located;
the output voltage signal of the single-axis induction coil is a cosine signal with the same frequency as the transmitting signal, and the amplitude of the signal is taken to establish an equation set, so that E T = - ωn·s, equation (14) is obtained:
ε max ＝-ωN·B' max ·S＝E T ·B' max (14)
wherein ε max Is the maximum value of the induced electromotive force;
the amplitude of the cosine signal is extracted by the fast Fourier transform, and other methods can be used, so that the mode of extracting the amplitude of the cosine signal cannot be limited;
the triaxial transmitting coils sequentially transmit sinusoidal signals with respective amplitude and frequency, and in one period, the uniaxial induction coil outputs 6 groups of voltage signals, so that 6 equations can be established, and 6 unknown parameters describing the position and the direction of the wireless capsule endoscope are solved; since the direction vector (vx, vy, vz) of the single axis induction coil is a unit vector, a constraint equation is added as shown in equation (15):
vx 2 +vy 2 +vz 2 ＝1 (15)
set epsilon' imax (i=1, 2, 3, 4, 5, 6) is the output voltage amplitude of the uniaxial induction coil in the wireless capsule endoscope, ε imax Is a theoretical expression of the amplitude, and the definition error E is shown in formula (16):
the optimization algorithm, such as the Levenberg-Marquardt algorithm, can be used, but other methods can be used, and the adopted optimization algorithm can not be limited by the optimization algorithm; minimizing E, the position and direction parameters (x, y, z, vx, vy, vz) of the wireless capsule endoscope can be solved;
and 9, the position and direction calculation module sends the pose information of the wireless capsule endoscope to the display terminal to reflect the pose of the current wireless capsule endoscope in real time, so that the wireless capsule endoscope is convenient for an operator to observe or subsequently apply.
The above embodiments are merely preferred embodiments of the present invention, and are not intended to limit the scope of the present invention, except as exemplified in the detailed description, all equivalent changes according to the principles of the present invention shall be included in the scope of the present invention.
Claims (11)
1. The utility model provides a wireless capsule endoscope 5 positioning system of degree of freedom, including setting up outside the human body and triaxial quadrature transmitting coil, position and direction calculation module, external wireless receiving module and be located internal wireless capsule endoscope, its characterized in that:
the wireless capsule endoscope is internally provided with a single-axis induction coil, a sampling module and a wireless transmitting module, wherein a magnetic circuit is formed by a triaxial orthogonal transmitting coil and the single-axis induction coil arranged in the wireless capsule endoscope through an alternating magnetic field, the sampling module is directly connected with the single-axis induction coil arranged in the wireless capsule endoscope, the wireless transmitting module arranged in the wireless capsule endoscope is connected with an external wireless receiving module through wireless signals, and the position and direction calculating module is directly connected with the external wireless receiving module;
the transmitting coil consists of a coil I, a coil II and a coil III which are orthogonal in triaxial, the coil I, the coil II and the coil III sequentially transmit signals with respective frequencies, and the coil I, the coil II and the coil III sequentially transmit signals with 6 different frequencies and amplitudes to form a period, namely, each coil transmits signals with 2 different frequencies and amplitudes in one period.
2. The system for locating the degree of freedom of a wireless capsule endoscope 5 of claim 1, wherein the wireless capsule endoscope further comprises a signal amplification module and an analog to digital conversion module; the single-shaft induction coil is directly connected with the signal amplification module, and the signal amplification module is directly connected with the sampling module.
3. The positioning system of the degree of freedom of the wireless capsule endoscope 5 according to claim 1 or 2, wherein the wireless capsule endoscope is further provided with an acquisition filter module for filtering the acquired signal, and the external wireless receiving module is further connected with a receiving filter module for noise filtering the received sampling signal.
4. The system for positioning the degrees of freedom of a wireless capsule endoscope 5 according to claim 1, wherein said single axis induction coil is arranged on or in a direction parallel to the central axis of the wireless capsule endoscope.
5. The system for locating the degrees of freedom of a wireless capsule endoscope 5 according to claim 1, wherein said coil I transmits 2 signals of different frequency and amplitude at fixed time intervals; then, the coil II transmits 2 signals with different frequencies and amplitudes from the coil I according to fixed time intervals; finally, the coil III transmits 2 signals with different frequencies and amplitudes from the coil I and the coil II at fixed time intervals.
6. The system for locating the degrees of freedom of a wireless capsule endoscope 5 according to claim 1, wherein said coil I, coil II, coil III sequentially emit signals of 1 different frequency and amplitude; then, the coil I, the coil II and the coil III sequentially emit a signal with different frequency and amplitude from the previous signal.
7. The method for positioning the degree of freedom of the wireless capsule endoscope 5 is characterized by comprising the following steps of:
the method comprises the following steps that 1, a three-axis orthogonal transmitting coil is arranged outside a human body, and the transmitting coil consists of a three-axis orthogonal coil I, a three-axis orthogonal coil II and a three-axis orthogonal coil III;
step 2, taking a coordinate system OXYZ established by three axes of the transmitting coil as a reference coordinate system, wherein the coordinate of a center point of the single-axis induction coil in the OXYZ coordinate system is (x, y, z), and converting the coordinate into the position of the center of the wireless capsule endoscope in the reference coordinate system; the direction vector of the uniaxial induction coil in the OXYZ coordinate system is (vx, vy, vz) and represents the direction of the wireless capsule endoscope; the coordinates (x, y, z) and the direction vectors (vx, vy, vz) of the center point of the single-axis induction coil are positioning parameters;
step 3, after power-on, the coil I, the coil II and the coil III of the transmitting coil sequentially transmit 2 signals with different frequencies and amplitudes in each period;
step 4, an amplifying module in the wireless capsule endoscope amplifies the output voltage of the single-shaft induction coil;
step 5, the analog-to-digital conversion module in the wireless capsule endoscope samples the amplified output voltage;
step 6, a wireless transmitting module in the wireless capsule endoscope transmits a sampling signal;
step 7, the in-vitro wireless receiving module receives the sampling signal and sends the sampling signal to the position and direction calculating module;
and 8, calculating the position and direction information of the wireless capsule endoscope by a position and direction calculation module, wherein the process is as follows:
solving 6 unknown parameters (x, y, z, vx, vy, vz) of the position and the direction of the wireless capsule endoscope;
each axis of the triaxial transmitting coil is equivalent to a magnetic dipole, and the magnetic dipole generates magnetic flux density at the center of the uniaxial induction coil inside the wireless capsule endoscope according to the Bioshaval law Three orthogonal components along the X, Y, Z axis of the reference coordinate system ozz are shown in equations (1), (2), (3):
wherein (x, y, z) is the position of the center of the uniaxial induction coil, (m, n, p) is the direction vector of each axis of the transmission coil, (a, B, c) is the position of the transmission coil, B T Is a constant related to the transmit coil, L is the distance of the sense coil from the transmit coil, L is as shown in equation (4):
magnetic flux densityIncluded angle with the direction vector of the uniaxial induction coil, magnetic flux density +.>The projection vector on the induction coil unit direction vector is shown in formula (5):
wherein (vx, vy, vz) is the unit direction vector of the uniaxial induction coil,three orthogonal components along the X, Y, Z axis of the reference coordinate system ozz are shown in equations (6), (7), and (8), respectively:
the uniaxial induction coil outputs a voltage signal, and the induced electromotive force generated by the uniaxial induction coil is shown as formula (9) according to faraday's law of electromagnetic induction:
wherein N is the number of turns of the uniaxial induction coil, phi is the magnetic flux passing through the curved surface S, and t is the time;
since the uniaxial induction coil is very small, its volume can be ignored, and the magnetic flux density of the uniaxial induction coil is considered to be equal everywhere, so equation (9) becomes as shown in equation (10):
because ofThe direction is the same as that of the uniaxial induction coil, so that the following formula (11) is obtained:
if a sinusoidal signal of known frequency is emitted, the magnetic flux density is described as shown in equation (12):
wherein,for maximum amplitude when the magnetic flux density is taken as a vector, ω is the angular frequency of the sinusoidal signal, +.>Is the initial phase of the sinusoidal signal;
thus, a relation between the output voltage value and the magnetic flux density of the uniaxial induction coil can be obtained, as shown in formula (13):
wherein B' max Is thatThe maximum amplitude of the projection vector on the unit direction vector (vx, vy, vz) where the uniaxial induction coil is located;
the output voltage signal of the single-axis induction coil is a cosine signal with the same frequency as the transmitting signal, and the amplitude of the signal is taken to establish an equation set, so that E T = - ωn·s, equation (14) is obtained:
ε max ＝-ωN·B' max ·S＝E T ·B' max (14)
wherein ε max Is the maximum value of the induced electromotive force;
extracting the amplitude of the cosine signal by using fast Fourier transformation;
the triaxial transmitting coils sequentially transmit sinusoidal signals with respective amplitude and frequency, and in one period, the uniaxial induction coil outputs 6 groups of voltage signals, so that 6 equations can be established, and 6 unknown parameters describing the position and the direction of the wireless capsule endoscope are solved; since the direction vector (vx, vy, vz) of the single axis induction coil is a unit vector, a constraint equation is added as shown in equation (15):
vx 2 +vy 2 +vz 2 ＝1 (15)
set epsilon' imax (i=1, 2, 3, 4, 5, 6) is the output voltage amplitude of the uniaxial induction coil in the wireless capsule endoscope, ε imax Is a theoretical expression of the amplitude, and the definition error E is shown in formula (16):
the position and direction parameters (x, y, z, vx, vy, vz) of the wireless capsule endoscope can be solved by utilizing an optimization algorithm to minimize E;
and 9, the position and direction calculation module sends the pose information of the wireless capsule endoscope to the display terminal to reflect the pose of the current wireless capsule endoscope in real time, so that the wireless capsule endoscope is convenient for an operator to observe or subsequently apply.
8. The method for positioning the degrees of freedom of the wireless capsule endoscope 5 according to claim 7, wherein the step 5 further comprises: the acquisition filtering module arranged in the wireless capsule endoscope carries out noise filtering on the sampled signals.
9. The method for positioning the degrees of freedom of the wireless capsule endoscope 5 according to claim 7, wherein the step 7 further comprises: the external wireless receiving module is also connected with a receiving filtering module for filtering noise of the received sampling signals.
10. The method for positioning the degrees of freedom of the wireless capsule endoscope 5 according to claim 7, wherein the transmitting frequency and amplitude modes of the coil I, the coil II and the coil III of the transmitting coil in the step 3 are as follows: firstly, a coil I transmits 2 signals with different frequencies and amplitudes at fixed time intervals; then, the coil II transmits 2 signals with different frequencies and amplitudes from the coil I according to fixed time intervals; finally, the coil III transmits 2 signals with different frequencies and amplitudes from the coil I and the coil II at fixed time intervals.
11. The method for positioning the degrees of freedom of the wireless capsule endoscope 5 according to claim 7, wherein the transmitting frequency and amplitude modes of the coil I, the coil II and the coil III of the transmitting coil in the step 3 are as follows: firstly, a coil I, a coil II and a coil III sequentially transmit signals with 1 different frequency and amplitude; then, the coil I, the coil II and the coil III sequentially emit a signal with different frequency and amplitude from the previous signal.
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| CN111839431B (en) * | 2020-07-24 | 2024-03-01 | 福建世新机器人科技有限公司 | Wireless capsule robot system and control method |
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