CN106983487A - The alignment system and its localization method of Wireless capsule endoscope three-dimensional position and 3 d pose - Google Patents

Abstract

The invention provides the alignment system and its localization method of Wireless capsule endoscope three-dimensional position and 3 d pose, including being arranged at outside human body and the orthogonal transmitting coil of three axles, external wireless receiving module, external pose computing module and positioned at internal Wireless capsule endoscope, using the transmitting coil that one three axle of setting outside human body are orthogonal, the orthogonal induction coil of two axles is only arranged in Wireless capsule endoscope, transmitting coil is placed near human body, the coil I of transmitting coil, the signal of the respective fixed frequency of coil II and coil III sequential transmissions, three axle transmitting coils have launched a signal and have been referred to as a cycle, the voltage signal of two axle induction coils, three groups of different frequencies of inductive output in a cycle, so as to set up the calculating that equation group carries out three-dimensional position and 3 d pose, the integrated convenience of this method, it is small that two axle induction coils take Wireless capsule endoscope space, energy real-time continuous is positioned to Wireless capsule endoscope, facilitate subsequent operation, it is safe and reliable, it is with low cost.

Description

The alignment system and its positioning of Wireless capsule endoscope three-dimensional position and 3 d pose Method

【Technical field】

The present invention relates to the positioning of three-dimensional localization techniques, more particularly to Wireless capsule endoscope three-dimensional position and 3 d pose System and its localization method.

【Background technology】

Currently, one of clinical Wireless capsule endoscope shortcoming be exactly can not actively it is controlled, to realize this actively it is controlled Function simultaneously facilitates Clinical practice, and the three-dimensional position and 3 d pose information of Wireless capsule endoscope want Real-time Feedback to give control system System；Meanwhile, Wireless capsule endoscope vision guided navigation in the alimentary canal of reconstruction is also required to three-dimensional position and 3 d pose information, doctor It is raw to facilitate manipulation wireless capsule sight glass.

For problem above, generally using X-ray imaging, CT (computed tomography) and MRI, (nuclear-magnetism is common in the prior art Shaking) imaging technique carries out three-dimensional reconstruction and positions Wireless capsule endoscope, this speed and essence by reconstruction technique indirect addressing Degree is all affected, and ray has infringement, should not position for a long time.

The Given Imaging companies of Israel propose a kind of applied to the wireless of Wireless capsule endoscope positioning earliest Radio frequency (RF) signal framing technology.It utilizes Wireless capsule endoscope hair in 8 wireless radio frequency antenna receiving body outside human body The radio frequency signal penetrated, and utilize the position of algorithm acquisition Wireless capsule endoscope.This method directly make use of wireless capsule Endoscope transmits the radio frequency signal of image, has the disadvantage that positioning precision is low, and average positioning precision is 37.7 millimeters, clinical practice Effect is bad.

Also it is proposed that positioning Wireless capsule endoscope using permanent magnetism location technology.Put inside Wireless capsule endoscope Permanent magnet is put as magnetic marker, arranges that multiple magnetic field sensors measure the magnetic field of difference in human peripheral, is calculated with algorithm Three-dimensional position and alignment lenses (two dimension) direction of Wireless capsule endoscope.The technology has precision high, fast excellent of locating speed Point, but the direction change information that Wireless capsule endoscope is rotated around the spindle can not be determined, this one-dimensional loss of learning cannot be utilized The image that Wireless capsule endoscope is shot carries out alimentary canal three-dimensional reconstruction；Further, since the magnetic field intensity of permanent magnet increases with distance Plus rapid decay, the coverage between magnetic field sensor and magnetic marker is difficult to meet human dimension requirement.

Also it has been proposed that the localization method based on permanent magnetism and induction coil, i.e., using mechanical arm control permanent magnet position and Direction, allows permanent magnet reciprocating magnetic field for producing change, the triaxial induction coil in capsule in the presence of shock module Export induced electromotive force.The method needs to arrange that two triaxial induction coils could be positioned in Wireless capsule endoscope, to increase The volume of big Wireless capsule endoscope.

【The content of the invention】

It is not enough in order to solve prior art, it is an object of the invention to provide one kind only with a two axle induction coils, Integrated convenience, it is small to take Wireless capsule endoscope space, can real-time continuous Wireless capsule endoscope is positioned, facilitate subsequent operation Wireless capsule endoscope three-dimensional position and 3 d pose alignment system and its localization method.

In order to realize foregoing invention purpose, the technical solution adopted by the present invention is：

First goal of the invention of the invention there is provided the alignment system of Wireless capsule endoscope three-dimensional position and 3 d pose, Including being arranged at outside human body and the orthogonal transmitting coil of three axles, external wireless receiving module, external pose computing module and being located at Internal Wireless capsule endoscope, the transmitting coil is made up of the orthogonal coil I of three axles, coil II and coil III, the line The signal of the respective fixed frequency of I, coil II and coil III sequential transmissions is enclosed, coil I, coil II, coil III have launched once Signal formation a cycle；The orthogonal induction coil of two axles is provided with the Wireless capsule endoscope, two axle is orthogonal The voltage signal of three groups of different frequencies of output in a cycle of induction coil correspondence transmitting coil, and the orthogonal line of induction of two axles The voltage signal number for enclosing every group of different frequency of output is two；Pass through between the transmitting coil and Wireless capsule endoscope Alternating magnetic field formation magnetic circuit, is connected, institute between the Wireless capsule endoscope and external wireless receiving module by wireless signal It is directly connected between rheme appearance computing module and external wireless receiving module.

Preferably, the Wireless capsule endoscope also includes signal amplification module, AD conversion module and wireless sending module, The orthogonal induction coil of two axle is directly connected to signal amplification module, and the signal amplification module and wireless sending module are straight Connect in succession.

There is provided Wireless capsule endoscope three-dimensional position and the localization method of 3 d pose, bag for the goal of the invention of invention second Include following steps：

Step 1, the orthogonal transmitting coil of three axles is set outside human body, sets two axles orthogonal in Wireless capsule endoscope Induction coil simultaneously enters in human body with Wireless capsule endoscope, and transmitting coil is by the orthogonal coil I of three axles, coil II and coil III is constituted；

The coordinate system OXYZ that three axles where step 2, transmitting coil are set up is used as reference frame, two axles of induction coil Intersection point be arranged on Wireless capsule endoscope central point, be used as the position of Wireless capsule endoscope, its table in reference frame The coordinate system O'u that two axles where being shown as (x, y, z), induction coil are set up_xu_y u_zAs object coordinates system, unit vector is used u_xAnd u_yIndicate the posture of Wireless capsule endoscope；

After step 3, upper electricity, coil I, coil II and the coil III of the transmitting coil sequential transmission within each cycle are each The signal of self-retaining frequency；

Amplification module in step 4, Wireless capsule endoscope amplifies the output voltage of induction coil；

Output voltage of the AD conversion module sampling by amplification in step 5, Wireless capsule endoscope；

Wireless sending module in step 6, Wireless capsule endoscope sends sampled signal；

Step 7, external wireless receiving module receive sampled signal, and are sent to pose computing module；

Step 8, pose computing module position fixing process it is as follows：

Solve 9 parameters (x, y, z, u_xx,u_xy,u_xz,u_yx,u_yy,u_yz), wherein (u_xx,u_xy,u_xz) and (u_yx,u_yy,u_yz) point U is not represented_xAnd u_yIn the projection components of the X, Y, Z axis of reference frame；

The transmitting coil of each axle is equivalent to magnetic dipole, according to Biot's Sa farr's law, magnetic dipole is wireless Three quadrature components such as formula (1) of the magnetic density along the X, Y, Z axis of reference frame that is produced at capsule endoscope position, (2), shown in (3)：

Wherein, (m, n, p) is the direction vector of each axle transmitting coil, and (x, y, z) is the position of induction coil, (a, b, c) It is the position of transmitting coil, B_TIt is a constant relevant with transmitting coil, L is distance of the induction coil to transmitting coil, and L is such as Shown in formula (4)：

Due to object coordinates, system is deflected, and the reference axis of object coordinates system and the reference axis of reference frame are not weighed Close, value of the transmitting coil in the magnetic density that Wireless capsule endoscope position is produced under object coordinates system is formula (5) institute Show：

Wherein, R is position and orientation matrix, shown in such as formula (6), due to there was only two induction coils, so B'_zNot excitation variable winding Output voltage；

Wherein

(u_xx,u_xy,u_xz)=u_x (7)

(u_yx,u_yy,u_yz)=u_y (8)

Induction coil output is induced voltage signal, the sense produced according to Faraday's electromagnetic induction law, induction coil Electromotive force is answered for shown in formula (9)：

Wherein, N is number of inductive coil turns, and φ is the magnetic flux through curved surface S；

In u_xAnd u_yOn direction, the relation between the voltage signal and magnetic density of induction coil output is as follows：

Due to sensor coil very little, therefore its volume is ignored, it is believed that magnetic density is equal everywhere for induction coil, so public Formula (10) and (11) are changed into equation below (12) and (13),

Because the direction of induction coil is identical with the change in coordinate axis direction of object coordinates system, obtain equation below (14) and (15),

If the magnetic density launched under the sinusoidal signal of given frequency, object coordinates system can be described as equation below (16)：

So far, it can be deduced that the u of induction coil_x、u_yOn axle output voltage values and each axle of object coordinates system magnetic density it Between relational expression, shown in such as formula (17), (18)：

The output voltage signal of induction coil is the cosine signal with transmission signal same frequency, takes the amplitude of the signal to build Vertical equation group, if E_Tx=-ω_xN_x·S_x, E_Ty=-ω_yN_y·S_y, E_Tz=-ω_zN_z·S_z, obtain equation group (19), (20) such as Under：

ε_xmax=-ω N_x·B'_xmax·S_x=E_Tx·B'_xmax (19)

ε_ymax=-ω N_y·B'_ymax·S_y=E_Ty·B'_ymax (20)

Extracting the method for cosine signal amplitude and phase has Fast Fourier Transform (FFT) or Function Fitting method etc.；

If the transmitting coil of three axles encourages the sinusoidal signal of respective fixed frequency successively, the induction coil of two axles amounts to sense Should be to 6 groups of alternating signals, so as to set up 6 equations, due to solve 9 unknown parameters, so also needing to 3 equations； Due to u_xAnd u_yUnit vector is taken, and is mutually perpendicular to, so be further added by following 3 constraint equations, 3 equations (21), (22), (23) are as follows：

u_xx.u_yx+u_xy.u_yy+u_xz.u_yz=0 (23)

Three axles of transmitting coil are analyzed separately below：

Coil I corresponds to the X-axis of reference frame, and its position and direction parameter is

(a, b, c)=(0,0,0)

(m, n, p)=(1,0,0)

Carry it into formula (1), (2) and (3), obtain formula (24), (25) and (26) as follows：

Coil II corresponds to the Y-axis of reference frame, and its position and direction parameter is

(a, b, c)=(0,0,0)

(m, n, p)=(0,1,0)

Carry it into formula (1), (2) and (3), obtain formula (27), (28) and (29) as follows：

Coil III corresponds to the Z axis of reference frame, and its position and direction parameter is

(a, b, c)=(0,0,0)

(m, n, p)=(0,0,1)

Carry it into formula (1), (2) and (3), obtain formula (30), (31) and (32) as follows：

According to formula (5), (19) and (20), formula (33) is re-defined as follows：

Wherein, B_ixmax、B_iymaxAnd B_izmaxWhen being coil I, coil II and coil the III transmitting of three axle transmitting coils respectively, The amplitude of X, Y, Z axis three component of the magnetic density produced at induction coil along reference frame, is B_ix、B_iyWith B_izAmplitude；ε_ixmaxAnd ε_iymaxWhen being coil I, coil II and coil the III transmitting of three axle transmitting coils respectively, wireless capsule The u of two axle induction coils in endoscope_xAnd u_yThe theoretical amplitude of axle induced voltage, ε_izmaxThere is no induction coil output, so not Participate in calculating；

If ε '_ixmaxWith ε '_iymaxWhen being coil I, coil II and coil the III transmitting of transmitting coil respectively, in wireless capsule The u of two axle induction coils in sight glass_xAnd u_yThe real output value of axle induced voltage, i.e. measured value, define the formula (34) of error E It is as follows:

Using optimized algorithm such as Levenberg-Marquardt or Gauss-Newton algorithms etc., make E minimum, can be in the hope of Solve pose parameter (x, y, z, the u of Wireless capsule endoscope_xx,u_xy,u_xz,u_yx,u_yy,u_yz)；

The posture information of Wireless capsule endoscope is sent to display terminal by step 9, pose computing module, and reflection in real time is worked as The pose of preceding Wireless capsule endoscope, is easy to operator to observe or subsequent applications.

The beneficial effects of the invention are as follows：

The present invention is only arranged using the orthogonal transmitting coil of three axles is set outside human body in Wireless capsule endoscope The orthogonal induction coil of one two axle, transmitting coil is placed near human body, coil I, coil II and the coil III of transmitting coil The signal of the respective fixed frequency of sequential transmission, three axle transmitting coils have launched a signal and have been referred to as a cycle, the two axle lines of induction The voltage signal of three groups of different frequencies of inductive output in a cycle is enclosed, so that setting up equation group carries out Wireless capsule endoscope The calculating of three-dimensional position and 3 d pose, the integrated convenience of this method, two axle induction coils occupancy Wireless capsule endoscope space are small, Energy real-time continuous is positioned to Wireless capsule endoscope, facilitates subsequent operation, safe and reliable, with low cost.

【Brief description of the drawings】

Fig. 1 is the amplification of two axial coils inside external three axles transmitting coil of the invention and its corresponding Wireless capsule endoscope Structural representation；

Fig. 2 is the positioning flow figure of the present invention.

【Embodiment】

In order to facilitate the understanding of the purposes, features and advantages of the present invention, below in conjunction with the accompanying drawings to the present invention Embodiment be described in detail.

The alignment system of Wireless capsule endoscope three-dimensional position and 3 d pose, as shown in figure 1, including being arranged at outside human body And three orthogonal transmitting coils of axle, external wireless receiving module, external pose computing module and in internal wireless capsule Sight glass, the transmitting coil is made up of the orthogonal coil I of three axles, coil II and coil III, the coil I, coil II and coil The signal of the respective fixed frequency of III sequential transmissions, coil I, coil II, coil III have launched a signal formation a cycle； The orthogonal induction coil of two axles, the orthogonal induction coil correspondence emission lines of two axle are provided with the Wireless capsule endoscope The voltage signal of three groups of different frequencies of output in a cycle of circle, and every group of different frequency of the orthogonal induction coil output of two axles The voltage signal number of rate is two；By alternating magnetic field formation magnetic circuit between the transmitting coil and Wireless capsule endoscope, Connected between the Wireless capsule endoscope and external wireless receiving module by wireless signal, the pose computing module and body It is directly connected between outer wireless receiving module.

Wherein, Wireless capsule endoscope also includes signal amplification module, AD conversion module and wireless sending module, described two The orthogonal induction coil of axle is directly connected to signal amplification module, and the signal amplification module is directly connected to AD conversion module, The AD conversion module is directly connected to wireless sending module.

The Wireless capsule endoscope three-dimensional position and the localization method of 3 d pose of the embodiment, as shown in Fig. 2 including with Lower step：

Step 1, the orthogonal transmitting coil of three axles is set outside human body, sets two axles orthogonal in Wireless capsule endoscope Induction coil simultaneously enters in human body with Wireless capsule endoscope, and transmitting coil is by the orthogonal coil I of three axles, coil II and coil III is constituted；

The coordinate system OXYZ that three axles where step 2, transmitting coil are set up is used as reference frame, two axles of induction coil Intersection point be arranged on Wireless capsule endoscope central point, be used as the position of Wireless capsule endoscope, its table in reference frame The coordinate system O'u that two axles where being shown as (x, y, z), induction coil are set up_x u_y u_zAs object coordinates system, with unit to Measure u_xAnd u_yIndicate the posture of Wireless capsule endoscope；

After step 3, upper electricity, coil I, coil II and the coil III of the transmitting coil sequential transmission within each cycle are each The signal of self-retaining frequency；

Amplification module in step 4, Wireless capsule endoscope amplifies the output voltage of induction coil；

Output voltage of the AD conversion module sampling by amplification in step 5, Wireless capsule endoscope；

Wireless sending module in step 6, Wireless capsule endoscope sends sampled signal；

Step 7, external wireless receiving module receive sampled signal, and are sent to pose computing module；

Step 8, pose computing module position fixing process it is as follows：

Solve 9 parameters (x, y, z, u_xx,u_xy,u_xz,u_yx,u_yy,u_yz), wherein (u_xx,u_xy,u_xz) and (u_yx,u_yy,u_yz) point U is not represented_xAnd u_yIn the projection components of the X, Y, Z axis of reference frame；

The transmitting coil of each axle is equivalent into magnetic dipole, and according to Biot's Sa farr's law, magnetic dipole is in wireless glue Three quadrature components such as formula (1) of the magnetic density along the X, Y, Z axis of reference frame that Nang Neikuijingweizhichu is produced, (2), shown in (3)：

Wherein, (m, n, p) is the direction vector of each axle transmitting coil, and (x, y, z) is the position of induction coil, (a, b, c) It is the position of transmitting coil, B_TIt is a constant relevant with transmitting coil, L is distance of the induction coil to transmitting coil, and L is such as Shown in formula (4)：

Due to object coordinates, system is deflected, and the reference axis of object coordinates system and the reference axis of reference frame are not weighed Close, value of the transmitting coil in the magnetic density that Wireless capsule endoscope position is produced under object coordinates system is formula (5) institute Show：

Wherein, R is position and orientation matrix, shown in such as formula (6), due to there was only two induction coils, so B'_zNot excitation variable winding Output voltage；

Wherein

(u_xx,u_xy,u_xz)=u_x (7)

(u_yx,u_yy,u_yz)=u_y (8)

Induction coil output is induced voltage signal, the sense produced according to Faraday's electromagnetic induction law, induction coil Electromotive force is answered for shown in formula (9)：

Wherein, N is number of inductive coil turns, and φ is the magnetic flux through curved surface S；

In u_xAnd u_yOn direction, the relation between the voltage signal and magnetic density of induction coil output is as follows：

Due to sensor coil very little, therefore its volume is ignored, it is believed that magnetic density is equal everywhere for induction coil, so public Formula (10) and (11) are changed into equation below (12) and (13),

Because the direction of induction coil is identical with the change in coordinate axis direction of object coordinates system, obtain equation below (14) and (15),

If launching the sinusoidal signal of given frequency, it is also possible to other signals, the invention is not restricted to this, under object coordinates system Magnetic density can be described as equation below (16)：

So far, it can be deduced that the u of induction coil_x、u_yOn axle output voltage values and each axle of object coordinates system magnetic density it Between relational expression, shown in such as formula (17), (18)：

The output voltage signal of induction coil is the cosine signal with transmission signal same frequency, takes the amplitude of the signal to build Vertical equation group, if E_Tx=-ω_xN_x·S_x, E_Ty=-ω_yN_y·S_y, E_Tz=-ω_zN_z·S_z, obtain equation group (19), (20) such as Under：

ε_xmax=-ω N_x·B'_xmax·S_x=E_Tx·B'_xmax (19)

ε_ymax=-ω N_y·B'_ymax·S_y=E_Ty·B'_ymax (20)

Extracting the method for cosine signal amplitude and phase has Fast Fourier Transform (FFT) or Function Fitting method, it is also possible to other Method, the invention is not restricted to this,

The transmitting coil of three axles encourages the sinusoidal signal of respective different frequency successively, and two axle induction coils are amounted to and sensed 6 groups of alternating signals, so as to set up 6 equations, due to solve 9 unknown parameters, so also needing to 3 equations；Due to u_xAnd u_yTake unit vector, and be mutually perpendicular to, so be further added by following 3 constraint equations, 3 equations (21), (22), (23) it is as follows：

u_xx.u_yx+u_xy.u_yy+u_xz.u_yz=0 (23)

Three axles of transmitting coil are analyzed separately below：

Coil I corresponds to the X-axis of reference frame, and its position and direction parameter is

(a, b, c)=(0,0,0)

(m, n, p)=(1,0,0)

Carry it into formula (1), (2) and (3), obtain formula (24), (25) and (26) as follows：

Coil II corresponds to the Y-axis of reference frame, and its position and direction parameter is

(a, b, c)=(0,0,0)

(m, n, p)=(0,1,0)

Carry it into formula (1), (2) and (3), obtain formula (27), (28) and (29) as follows：

Coil III corresponds to the Z axis of reference frame, and its position and direction parameter is

(a, b, c)=(0,0,0)

(m, n, p)=(0,0,1)

Carry it into formula (1), (2) and (3), obtain formula (30), (31) and (32) as follows：

According to formula (5), (19) and (20), formula (33) is re-defined as follows：

Wherein, B_ixmax、B_iymaxAnd B_izmaxWhen being coil I, coil II and coil the III transmitting of three axle transmitting coils respectively, The amplitude of X, Y, Z axis three component of the magnetic density produced at induction coil along reference frame, is B_ix、B_iyWith B_izAmplitude；ε_ixmaxAnd ε_iymaxWhen being coil I, coil II and coil the III transmitting of three axle transmitting coils respectively, wireless capsule The u of two axle induction coils in endoscope_xAnd u_yThe theoretical amplitude of axle induced voltage, ε_izmaxThere is no induction coil output, so not Participate in calculating；

If ε_i'_xmaxAnd ε_i'_ymaxWhen being coil I, coil II and coil the III transmitting of transmitting coil respectively, in wireless capsule The u of two axle induction coils in sight glass_xAnd u_yThe real output value of axle induced voltage, i.e. measured value, define the formula (34) of error E It is as follows:

Utilize optimized algorithm such as Levenberg-Marquardt or Gauss-Newton algorithms, it is also possible to other methods, this Invention not limited to this, makes E minimum, can solve pose parameter (x, y, z, the u of Wireless capsule endoscope_xx,u_xy,u_xz,u_yx, u_yy,u_yz)；

The posture information of Wireless capsule endoscope is sent to display terminal by step 9, pose computing module, and reflection in real time is worked as The pose of preceding Wireless capsule endoscope, is easy to operator to observe or subsequent applications.

Embodiment described above is simply presently preferred embodiments of the present invention, and the practical range of the present invention is not limited with this, Except in the case of being enumerated in specific embodiment, all equivalence changes made according to the principle of the invention all should be covered by the present invention's In protection domain.

Claims (3)

1. the alignment system of Wireless capsule endoscope three-dimensional position and 3 d pose, including it is arranged at outside human body and three axles are orthogonal Transmitting coil, external wireless receiving module, external pose computing module and positioned at internal Wireless capsule endoscope, its feature exists In：

The transmitting coil is made up of the orthogonal coil I of three axles, coil II and coil III, the coil I, coil II and coil The signal of the respective fixed frequency of III sequential transmissions, coil I, coil II, coil III have launched a signal formation a cycle；

The orthogonal induction coil of two axles is provided with the Wireless capsule endoscope, the orthogonal induction coil correspondence of two axle is sent out The voltage signal of three groups of different frequencies of output in a cycle of ray circle, and every group of the orthogonal induction coil output of two axles not The voltage signal number of same frequency is two；

Between the transmitting coil and Wireless capsule endoscope by alternating magnetic field formation magnetic circuit, the Wireless capsule endoscope with Connected between external wireless receiving module by wireless signal, it is straight between the pose computing module and external wireless receiving module Connect in succession.

2. the alignment system of Wireless capsule endoscope three-dimensional position according to claim 1 and 3 d pose, its feature exists In the Wireless capsule endoscope also includes signal amplification module, AD conversion module and wireless sending module, and two axle is orthogonal Induction coil be directly connected to signal amplification module, the signal amplification module has AD conversion module to be directly connected to, the AD Modular converter is directly connected to wireless sending module.

3. the localization method of Wireless capsule endoscope three-dimensional position and 3 d pose, it is characterised in that comprise the following steps：

Step 1, the orthogonal transmitting coil of three axles, the sensing for setting two axles orthogonal in Wireless capsule endoscope are set outside human body Coil simultaneously enters in human body with Wireless capsule endoscope, and transmitting coil is by the orthogonal coil I of three axles, coil II and coil III groups Into；

The coordinate system OXYZ that three axles where step 2, transmitting coil are set up is used as reference frame, the friendship of two axles of induction coil Point is arranged on Wireless capsule endoscope central point, and as the position of Wireless capsule endoscope, it is expressed as in reference frame The coordinate system O'u that two axles where (x, y, z), induction coil are set up_x u_y u_zAs object coordinates system, unit vector u is used_x And u_yIndicate the posture of Wireless capsule endoscope；

After step 3, upper electricity, coil I, coil II and the coil III of the transmitting coil sequential transmission within each cycle are each solid Determine the signal of frequency；

Amplification module in step 4, Wireless capsule endoscope amplifies the output voltage of induction coil；

Output voltage of the AD conversion module sampling by amplification in step 5, Wireless capsule endoscope；

Wireless sending module in step 6, Wireless capsule endoscope sends sampled signal；

Step 7, external wireless receiving module receive sampled signal, and are sent to pose computing module；

Step 8, pose computing module position fixing process it is as follows：

Solve 9 parameters (x, y, z, u_xx,u_xy,u_xz,u_yx,u_yy,u_yz), wherein (u_xx,u_xy,u_xz) and (u_yx,u_yy,u_yz) difference table Show u_xAnd u_yIn the projection components of reference frame X, Y, Z axis；

The transmitting coil of each axle is equivalent to magnetic dipole, according to Biot's Sa farr's law, magnetic dipole is in wireless capsule Three quadrature components of the magnetic density along the X, Y, Z axis of reference frame produced at endoscope position for example formula (1), (2), (3) shown in：

$B_x=B_T\{\frac{3\[m(x-a)+n(y-b)+p(z-c)\](x-a)}{L^5}-\frac{m}{L^3}\}---\left(1\right)$

$B_y=B_T\{\frac{3\[m(x-a)+n(y-b)+p(z-c)\](y-b)}{L^5}-\frac{n}{L^3}\}---\left(2\right)$

$B_z=B_T\{\frac{3\[m(x-a)+n(y-b)+p(z-c)\](z-c)}{L^5}-\frac{p}{L^3}\}---\left(3\right)$

Wherein, (m, n, p) is the direction vector of each axle transmitting coil, and (x, y, z) is the position of induction coil, and (a, b, c) is hair The position of ray circle, B_TIt is a constant relevant with transmitting coil, L is distance of the induction coil to transmitting coil, L such as formula (4) shown in：

$L=\sqrt{{(x-a)}^2+{(y-b)}^2+{(z-c)}^2}---\left(4\right)$

Due to object coordinates, system is deflected, and the reference axis of object coordinates system and the reference axis of reference frame are misaligned, hair Value of the ray circle in the magnetic density that Wireless capsule endoscope position is produced under object coordinates system is shown in formula (5)：

$\left\{\begin{array}{c}{B}_x^{\′}\\ B_y^{\′}\\ B_z^{\′}\end{array}\right\}=R\left\{\begin{array}{c}{B}_x\\ B_y\\ B_z\end{array}\right\}---\left(5\right)$

Wherein, R is position and orientation matrix, shown in such as formula (6), due to there was only two induction coils, so B'_zExcitation variable winding is not exported Voltage；

$R=\left[\begin{array}{ccc}{u}_{xx}& u_{xy}& u_{xz}\\ u_{yx}& u_{yy}& u_{yz}\\ u_{xy}{u}_{yz}-u_{xz}{u}_{yy}& u_{xz}{u}_{yx}-u_{xx}{u}_{yz}& u_{xx}{u}_{yz}-u_{xy}{u}_{yx}\end{array}\right]---\left(6\right)$

Wherein

(u_xx,u_xy,u_xz)=u_x (7)

(u_yx,u_yy,u_yz)=u_y (8)

Induction coil output is induced voltage signal, the induced electricity produced according to Faraday's electromagnetic induction law, induction coil Kinetic potential is shown in formula (9)：

Wherein, N is number of inductive coil turns, and φ is the magnetic flux through curved surface S；

In u_xAnd u_yOn direction, the relation between the voltage signal and magnetic density of induction coil output is as follows：

Due to sensor coil very little, therefore its volume is ignored, it is believed that magnetic density is equal everywhere for induction coil, so formula (10) and (11) are changed into equation below (12) and (13),

${\mathrm{\ϵ}}_x=-N_x\·\frac{d({\stackrel{\→}{B}}_x^{\′}\·{\stackrel{\→}{S}}_x)}{dt}---\left(12\right)$

${\mathrm{\ϵ}}_y=-N_y\·\frac{d({\stackrel{\→}{B}}_y^{\′}\·{\stackrel{\→}{S}}_y)}{dt}---\left(13\right)$

Because the direction of induction coil is identical with the change in coordinate axis direction of object coordinates system, obtain equation below (14) and (15),

${\stackrel{\→}{B}}_x^{\′}\·{\stackrel{\→}{S}}_x=B_x^{\′}{S}_x---\left(14\right)$

${\stackrel{\→}{B}}_y^{\′}\·{\stackrel{\→}{S}}_y=B_y^{\′}{S}_y---\left(15\right)$

If the magnetic density launched under the sinusoidal signal of given frequency, object coordinates system can be described as equation below (16)：

So far, it can be deduced that induction coil u_x、u_yPass on each axle of axle output voltage values and object coordinates system between magnetic density It is formula, shown in such as formula (17), (18)：

The output voltage signal of induction coil is the cosine signal with transmission signal same frequency, takes the amplitude of the signal come the side of foundation Journey group, if E_Tx=-ω_xN_x·S_x, E_Ty=-ω_yN_y·S_y, E_Tz=-ω_zN_z·S_z, obtain equation (19), (20) as follows：

ε_xmax=-ω N_x·B'_xmax·S_x=E_Tx·B'_xmax (19)

ε_ymax=-ω N_y·B'_ymax·S_y=E_Ty·B'_ymax (20)

Extracting the method for cosine signal amplitude and phase has Fast Fourier Transform (FFT) or Function Fitting method etc.；

If the transmitting coil of three axles encourages the sinusoidal signal of respective fixed frequency successively, two axle induction coils amount to and sense 6 Group alternating signal, so as to set up 6 equations, due to solve 9 unknown parameters, so also needing to 3 equations；Due to u_x And u_yUnit vector is taken, and is mutually perpendicular to, so following 3 constraint equations are further added by, 3 equations (21), (22), (23) It is as follows：

$u_{xx}^2+u_{xy}^2+u_{xz}^2=1---\left(21\right)$

$u_{yx}^2+u_{yy}^2+u_{yz}^2=1---\left(22\right)$

u_xx.u_yx+u_xy.u_yy+u_xz.u_yz=0 (23)

Three axles of transmitting coil are analyzed separately below：

Coil I corresponds to the X-axis of reference frame, and its position and direction parameter is

(a, b, c)=(0,0,0)

(m, n, p)=(1,0,0)

Carry it into formula (1), (2) and (3), obtain formula (24), (25) and (26) as follows：

$B_{1x}=B_T(\frac{3x^2}{L^5}-\frac{1}{L^3})---\left(24\right)$

$B_{1y}=B_T\frac{3xy}{L^5}---\left(25\right)$

$B_{1Z}=B_T\frac{3xz}{L^5}---\left(26\right)$

Coil II corresponds to the Y-axis of reference frame, and its position and direction parameter is

(a, b, c)=(0,0,0)

(m, n, p)=(0,1,0)

Carry it into formula (1), (2) and (3), obtain formula (27), (28) and (29) as follows：

$B_{2x}=B_T\frac{3xy}{L^5}---\left(27\right)$

$B_{2y}=B_T(\frac{3y^2}{L^5}-\frac{1}{L^3})---\left(28\right)$

$B_{2Z}=B_T\frac{3yz}{L^5}---\left(29\right)$

Coil III corresponds to the Z axis of reference frame, and its position and direction parameter is

(a, b, c)=(0,0,0)

(m, n, p)=(0,0,1)

Carry it into formula (1), (2) and (3), obtain formula (30), (31) and (32) as follows：

$B_{3x}=B_T\frac{3xz}{L^5}---\left(30\right)$

$B_{3y}=B_T\frac{3yz}{L^5}---\left(31\right)$

$B_{3z}=B_T(\frac{3z^2}{L^5}-\frac{1}{L^3})---\left(32\right)$

According to formula (5), (19) and (20), formula (33) is re-defined as follows：

$\left\{\begin{array}{c}{\mathrm{\ϵ}}_{ixmax}\\ {\mathrm{\ϵ}}_{iymax}\\ {\mathrm{\ϵ}}_{izmax}\end{array}\right\}=R\left\{\begin{array}{c}{E}_{Tx}\·B_{ixmax}\\ E_{Ty}\·B_{iymax}\\ E_{Tz}\·B_{izmax}\end{array}\right\},i=1,2,3---\left(33\right)$

Wherein, B_ixmax、B_iymaxAnd B_izmaxWhen being coil I, coil II and coil the III transmitting of three axle transmitting coils respectively, in sense The amplitude of X, Y, Z axis three component of the magnetic density produced at coil along reference frame is answered, is B_ix、B_iyAnd B_iz's Amplitude；ε_ixmaxAnd ε_iymaxWhen being coil I, coil II and coil the III transmitting of three axle transmitting coils respectively, peeped in wireless capsule The u of two axle induction coils in mirror_xAnd u_yThe theoretical amplitude of axle induced voltage, ε_izmaxThere is no corresponding induction coil to export, so It is not involved in calculating；

If ε '_ixmaxWith ε '_iymaxWhen being coil I, coil II and coil the III transmitting of transmitting coil respectively, Wireless capsule endoscope The u of interior two axles induction coil_xAnd u_yThe real output value of axle induced voltage, i.e. measured value, the formula (34) for defining error E are as follows:

$E={(u_{xx}^2+u_{xy}^2+u_{xz}^2-1)}^2+{(u_{yx}^2+u_{yy}^2+u_{yz}^2-1)}^2$

$+{(u_{xx}.u_{yx}+u_{xy}.u_{yy}+u_{xz}.u_{yz})}^2+\underset{i=1}{\overset{3}{\Σ}}{({\mathrm{\ϵ}}_{ixmax}-{\mathrm{\ϵ}}_{ixmax}^{\′})}^2+{({\mathrm{\ϵ}}_{iymax}-{\mathrm{\ϵ}}_{iymax}^{\′})}^2---\left(34\right)$

Using optimized algorithm such as Levenberg-Marquardt or Gauss-Newton algorithms etc., make E minimum, can solve Pose parameter (x, y, z, the u of Wireless capsule endoscope_xx,u_xy,u_xz,u_yx,u_yy,u_yz)；

The posture information of Wireless capsule endoscope is sent to display terminal by step 9, pose computing module, in real time reflection currently without The pose of line capsule endoscope, is easy to operator to observe or subsequent applications.