CN113288008A - Magnetic capsule endoscope full-attitude determination method - Google Patents

Magnetic capsule endoscope full-attitude determination method Download PDF

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CN113288008A
CN113288008A CN202110570007.7A CN202110570007A CN113288008A CN 113288008 A CN113288008 A CN 113288008A CN 202110570007 A CN202110570007 A CN 202110570007A CN 113288008 A CN113288008 A CN 113288008A
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capsule endoscope
permanent magnet
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CN113288008B (en
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郭琳
叶波
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Hubei University
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    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
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    • A61B1/00—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
    • A61B1/04—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 combined with photographic or television appliances
    • A61B1/041—Capsule endoscopes for imaging
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B1/00—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
    • A61B1/00131—Accessories for endoscopes
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
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    • A61B1/00—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
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    • A61B1/00—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
    • A61B1/04—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 combined with photographic or television appliances
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    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
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    • A61B1/00—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
    • A61B1/273—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 upper alimentary canal, e.g. oesophagoscopes, gastroscopes
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Abstract

The invention discloses a method for measuring the whole posture of a magnetic capsule endoscope. Firstly, estimating the initial posture of the magnetic capsule endoscope; then adjusting the posture of the external large magnet to make the posture of the external large magnet consistent with the initial posture of the magnetic capsule endoscope; then, an external large magnet is used for controlling the magnetic capsule endoscope to rotate around the axial central shaft of the magnetic capsule endoscope, and the unit vector of the current radial magnetization direction of the permanent magnet in the rotated magnetic capsule endoscope is calculated
Figure DDA0003082299490000011
Finally calculating the magnetic capsule endoscopeAxial direction unit vector of permanent magnet in mirror
Figure DDA0003082299490000012
I.e. the current pose of the magnetic capsule endoscope is completely determined. The operation method is simple, has no accumulated error, and can solve the problem that the active movement and the positioning of the capsule need to be realized simultaneously in practical application.

Description

Magnetic capsule endoscope full-attitude determination method
Technical Field
The invention relates to the technical field of medical equipment, in particular to a method for measuring the whole posture of a magnetic capsule endoscope.
Background
A wireless capsule endoscope (hereinafter referred to as capsule endoscope) is used for medical examination of the digestive tract of a human body in a swallowing mode, is a non-invasive medical examination mode, and is a revolution and future development direction in the development history of the endoscope. Compared with the traditional medical endoscope, the capsule endoscope has the advantages of no wound, no pain, convenient operation, small size, safety, no cross infection and the like, greatly relieves the pain of patients, expands the examination visual field of doctors, fills the blind areas of gastroscopy and enteroscopy, has high diagnosis value especially for suspicious small intestine lesions, and has great market application value.
In the clinical use of the capsule lens, the rapid, accurate and complete determination of all the parameters of the spatial position and the posture of the capsule lens is one of the most critical problems. The following technical advantages can be brought by completely knowing the accurate position and posture information of the capsule endoscope in the digestive tract of the human body: the doctor is helped to judge the accurate shooting position and angle of the focus tissue picture, so as to make accurate judgment on the disease; necessary position and posture data are provided for actively controlling the movement of the capsule mirror, so that important technical support is provided for doctors to autonomously control the capsule mirror to carry out all-around examination and shooting or realize medical purposes such as examination and medicine application of a specified position or route.
At present, the rapid and accurate determination of the full parameters of the space attitude of the capsule mirror has difficulties. In the existing capsule mirror pose measuring method, a magnetostatic positioning mode that a small permanent magnet is placed in a capsule mirror is adopted, so that the method has the characteristics of no need of a power supply, simplicity in implementation and no damage to a human body, and is very suitable for the short-distance and high-precision positioning requirement of the capsule mirror.
The existing magnetostatic-based capsule mirror pose measurement method is to use a permanent magnet as a magnetic source, utilize a magnetic dipole model and a correction model thereof, and calculate 6 pose parameters (3 position parameters and 3 pose parameters) of a capsule by adopting a nonlinear optimization algorithm. The magnetic positioning precision is better; however, the 3 attitude parameters (m, n, p) have a constraint relation (m)2+n2+p21) and therefore can only determine two-dimensional pose parameters in practice, and not all three-dimensional posesAnd (4) state parameters, namely the roll angle in the attitude parameters of the capsule mirror cannot be obtained. The reason is that the internal permanent magnet of the existing capsule mirror is generally an annular magnet with axial magnetism, the central axis of the magnet is arranged in the same direction as the central axis of the capsule mirror, and when the capsule mirror rotates around the self axial direction, the magnetic field direction of the axial magnetic permanent magnet is not changed, so that the posture change (namely the roll angle change) of the capsule mirror cannot be detected according to the magnetic field change.
Although some algorithms can also achieve six-dimensional magnetic positioning of rectangular permanent magnets, the rectangular permanent magnets are not well combined with capsule mirrors due to their form factor and are not suitable for use in capsule mirrors. Meanwhile, the capsule mirror working environment is completely visually isolated from the outside, so that most measurement means relying on video recognition gestures are ineffective.
Another type of existing capsule mirror pose determination method adopts three-axis angular velocity data to participate in pose solution. However, such methods have cumulative errors, namely: when the data of the angular velocity instrument is converted into an angle, an integral accumulated error exists, and the accumulated error is larger and larger along with the time, so that the measurement error is larger. Although the prior art can measure the geomagnetic vector by using a triaxial geomagnetic sensor and calibrate the angle to eliminate the accumulated error, the geomagnetic sensor cannot be used because a strong external magnetic field for driving the capsule to move exists in the use environment of the active capsule.
Therefore, how to rapidly and completely measure all the attitude parameters of the capsule mirror is a technical problem to be solved urgently by those skilled in the art.
Disclosure of Invention
In order to solve the technical problems, the invention provides a method for measuring the whole attitude of a magnetic capsule endoscope, which can simply, accurately and completely measure all attitude parameters and position parameters of the capsule endoscope.
The invention provides a method for measuring the whole posture of a magnetic capsule endoscope, which adopts the magnetic capsule endoscope, wherein a permanent magnet arranged in the capsule endoscope is a small permanent magnet which is magnetized in the radial direction; the small permanent magnet is cylindrical or annular and is fixedly arranged in the magnetic capsule endoscope or fixed on the wall of the annular magnetic capsule endoscope shell, and the axial direction of the small permanent magnet is consistent with the axial direction of the magnetic capsule endoscope; a large permanent magnet is arranged outside the capsule endoscope and is a cylindrical strong permanent magnet which is magnetized in the radial direction;
the method comprises the following steps:
step 1: estimating the initial attitude of the magnetic capsule endoscope, and determining the unit vector of the radial magnetization direction of the small permanent magnet in the magnetic capsule endoscope
Figure BDA0003082299470000021
And axial direction unit vector
Figure BDA0003082299470000022
The specific implementation comprises the following substeps:
step 1.1: calculating the unit vector of the radial magnetization direction of the small permanent magnet
Figure BDA0003082299470000023
Step 1.2: controlling the rotation of the magnetic capsule endoscope by using an external large permanent magnet according to the radial magnetization direction vector of the small permanent magnet;
step 1.3: calculating the unit vector of the radial magnetization direction of the small permanent magnet after rotation
Figure BDA0003082299470000024
Step 1.4: by
Figure BDA0003082299470000031
And
Figure BDA0003082299470000032
calculating the estimated axial direction unit vector of the magnetic capsule endoscope
Figure BDA0003082299470000033
Step 2: adjusting the posture of the external large permanent magnet to make the posture of the external large permanent magnet consistent with the current posture of the magnetic capsule endoscope;
and step 3: the magnetic capsule endoscope is controlled to rotate around the axial central shaft of the magnetic capsule endoscope by using an external large permanent magnet;
and 4, step 4: calculating the unit vector of the current radial magnetization direction of the small permanent magnet in the rotated magnetic capsule endoscope
Figure BDA0003082299470000034
And 5: calculating the axial direction unit vector of the magnetic capsule endoscope
Figure BDA0003082299470000035
Figure BDA0003082299470000036
I.e. the current pose of the capsule endoscope is completely determined.
The invention can solve the problem of integral accumulated error in the existing method for calculating the attitude angle according to the angular velocity data, solve the problem that the existing magnetostatic positioning method can not completely measure all attitude parameters of the capsule endoscope and mainly solve the problem that the rotation angle of the capsule endoscope around the self axial direction can not be measured. The invention can completely measure all attitude parameters of the capsule endoscope; the operation method is simple, and no accumulated error exists; meanwhile, the external permanent magnet in the method can be simultaneously used for actively controlling the capsule endoscope, and the problem that the active movement of the capsule endoscope and the positioning of the capsule endoscope need to be simultaneously realized in practical application can be well solved.
Drawings
FIG. 1 is a schematic diagram of the spatial relationship between the permanent magnet inside the capsule mirror and the external large magnet, the human body and the magnetic sensor array according to the embodiment of the present invention;
FIG. 2 is a flow chart of a method embodying the present invention;
FIG. 3 is a schematic diagram of an external large magnet controlled magnetic capsule endoscope rotation according to an embodiment of the present invention;
fig. 4 is a schematic diagram of the spatial relationship between the magnetic sensor array and the xyz coordinate system and the rotation direction of the small permanent magnet according to the embodiment of the present invention.
Detailed Description
In order to facilitate the understanding and implementation of the present invention for those of ordinary skill in the art, the present invention is further described in detail with reference to the accompanying drawings and examples, it is to be understood that the embodiments described herein are merely illustrative and explanatory of the present invention and are not restrictive thereof.
The invention provides a method for measuring the whole posture of a magnetic capsule endoscope, which adopts the magnetic capsule endoscope; the permanent magnet arranged in the capsule endoscope is a small permanent magnet which is magnetized in the radial direction; the small permanent magnet is cylindrical or annular and is fixedly arranged in the magnetic capsule endoscope or fixed on the wall of the annular magnetic capsule endoscope shell, and the axial direction of the small permanent magnet is consistent with the axial direction of the magnetic capsule endoscope; the exterior of the capsule endoscope is provided with a large permanent magnet which is a cylindrical strong permanent magnet magnetized in the radial direction, as shown in figure 1.
Referring to fig. 2, the method for measuring the full attitude of the magnetic capsule endoscope provided by the invention specifically comprises the following steps:
step 1: estimating the initial attitude of the magnetic capsule endoscope, and determining the unit vector of the radial magnetization direction of the small permanent magnet in the magnetic capsule endoscope
Figure BDA0003082299470000041
And axial direction unit vector
Figure BDA0003082299470000042
The specific implementation comprises the following substeps:
step 1.1: calculating unit vector of radial magnetization direction of small permanent magnet
Figure BDA0003082299470000043
The specific process is as follows:
(1) by means of the array of magnetic sensors,detecting to obtain the current magnetic induction intensity generated by the small magnet
Figure BDA0003082299470000044
Wherein N (more than or equal to 5) is the number of the three-axis magnetic sensors in the magnetic sensor array. As shown in fig. 4, a three-dimensional rectangular coordinate system oyx is established by taking the plane of the sensor array as the XOY plane. The current value of the magnetic induction at the nth magnetic sensor is denoted as
Figure BDA0003082299470000045
Wherein, B0，nx、B0，ny、B0，nzRespectively represent the magnetic induction intensity components of the nth magnetic sensor in three directions of an x axis, a y axis and a z axis in a coordinate system OXYZ. The magnetic sensor array is fixed to the outside of the human body (e.g., below the human body), as shown in fig. 1.
(2) According to the magnetic induction intensity detected in (1)
Figure BDA0003082299470000046
By using the method of the magnetic dipole model, the small magnet is taken as a point source, and the unit vector of the magnetization direction of the small magnet is calculated
Figure BDA0003082299470000047
(i.e., m)0 2+n0 2+p0 21). The specific method comprises the following steps:
establishing an objective function:
Figure BDA0003082299470000048
wherein,
Figure BDA0003082299470000049
b0，n＝B0，nxyn-B0， nyxn，
Figure BDA00030822994700000410
(xn，yn，zn) Is the position coordinates of the nth magnetic sensor in the OXYZ coordinate system, (a, b, c) is the position coordinates of the small magnet in the OXYZ coordinate system, m0′＝m0/p0，n0′＝n0/p0。
Secondly, solving the objective function by utilizing a nonlinear optimization algorithm to obtain an attitude parameter m of the small magnet (namely the magnetic capsule endoscope)0' and n0′。
Calculating unit vector of magnetization direction of small magnet according to the following formula
Figure BDA0003082299470000051
Figure BDA0003082299470000052
m0＝m0′p0
n0＝n0′p0
Step 1.2: controlling the rotation of the magnetic capsule endoscope by using an external large magnet according to the radial magnetization direction vector of the small magnet;
in this embodiment, the manner of controlling the rotation of the magnetic capsule endoscope by the external large magnet is as follows: first, the external large magnet is placed so that the radial magnetization direction of the large magnet is in the same direction as the radial magnetization direction (i.e., vector) of the small magnet
Figure BDA00030822994700000510
) In the same direction, as shown in fig. 3(a), the external large magnet is then controlled to rotate counterclockwise by a slight angle of 2 ° about its own axial central axis, resulting in rotation of the magnetic field generated by the external large magnet, which drives the small magnet (together with the magnetic capsule endoscope) to rotate clockwise about its own axial central axis (the direction of rotation of the magnetic capsule endoscope is opposite to that of the external large magnet, as shown in fig. 3 (b)).
Step 1.3: calculating the unit vector of the radial magnetization direction of the small permanent magnet after rotation
Figure BDA0003082299470000053
(m1 2+n1 2+p1 21). The specific process is as follows: shielding or removing the magnetic field of the external large magnet, and then obtaining the current magnetic induction intensity generated by the rotated small magnet through the magnetic sensor array
Figure BDA0003082299470000054
Then calculating the unit vector of the current magnetization direction of the small magnet according to the following steps
Figure BDA0003082299470000055
Establishing an objective function:
Figure BDA0003082299470000056
wherein,
Figure BDA0003082299470000057
b1，n＝B1，nxyn-B1， nyxn，
Figure BDA0003082299470000058
Figure BDA0003082299470000059
is the coordinate (x) of the small magnet after rotationn，yn，zn) M, the magnetic induction vector generated at the nth magnetic sensor1′＝m1/p1，n1′＝n1/p1。
Secondly, solving the objective function by utilizing a nonlinear optimization algorithm to obtain the attitude parameter m of the rotated small magnet (namely the magnetic capsule endoscope)1' and n1′。
Calculating the unit vector of the magnetization direction of the small magnet after rotation according to the following formula
Figure BDA0003082299470000061
Figure BDA0003082299470000062
m1＝m1′p1
n1＝n1′p1
Step 1.4: by
Figure BDA0003082299470000063
And
Figure BDA0003082299470000064
calculating the estimated axial direction unit vector of the magnetic capsule endoscope
Figure BDA0003082299470000065
The calculation formula is as follows:
r＝n0p1-n1p0
s＝m1p0-m0p1
t＝m0n1-m1n0
Figure BDA0003082299470000066
Figure BDA0003082299470000067
Figure BDA0003082299470000068
wherein,
Figure BDA0003082299470000069
and
Figure BDA00030822994700000610
respectively represent unit vectors of the magnetization directions of the small magnets before and after rotation,
Figure BDA00030822994700000611
is the predicted axial direction unit vector (i.e. the unit vector of the magnetic capsule endoscope)
Figure BDA00030822994700000612
)。
Step 2: adjusting the posture of the external big magnet to make the posture of the external big magnet consistent with the initial posture of the magnetic capsule endoscope, namely: the axial direction of the external large magnet and the estimated axial direction of the magnetic capsule endoscope (i.e. the axial direction of the magnetic capsule endoscope)
Figure BDA00030822994700000613
) Similarly, as shown in FIG. 1, and the radial magnetization direction of the outer large magnet is the same as the current radial magnetization direction of the permanent magnet (i.e., the radial magnetization direction of the outer large magnet)
Figure BDA00030822994700000614
) In the same direction as shown in FIG. 3 (a).
And step 3: the magnetic capsule endoscope is controlled to rotate around the axial central shaft of the magnetic capsule endoscope by an external large magnet.
In this embodiment, the manner of controlling the rotation of the magnetic capsule endoscope by the external large magnet is as follows: the external large magnet is controlled to rotate clockwise by 4 degrees around the self axial central shaft, so that the magnetic field generated by the external large magnet rotates, and the rotating magnetic field drives the small magnet (together with the magnetic capsule endoscope) to rotate anticlockwise around the self axial central shaft, as shown in figure 4. (the rotation direction of the magnetic capsule endoscope is opposite to that of the external large magnet.)
And 4, step 4: calculating the unit vector of the current radial magnetization direction of the small magnet in the rotated magnetic capsule endoscope
Figure BDA0003082299470000071
The specific process is as follows:
shielding external large magnet magnetic field, and detecting by magnetic sensor arrayMeasuring the current value of the magnetic induction intensity generated by the small magnet after rotating in the step 3
Figure BDA0003082299470000072
And establishing an objective function:
Figure BDA0003082299470000073
wherein,
Figure BDA0003082299470000074
b2，n＝B2，nxyn-B2， nyxn，
Figure BDA00030822994700000712
is a small magnet in the coordinate (x)n，yn，zn) M, the magnetic induction intensity value generated at the nth magnetic sensor2′＝m2/p2，n2′＝n2/p2。
Solving the objective function by using a nonlinear optimization algorithm to obtain the current position coordinates (a, b, c) and the attitude parameter m of the rotated small magnet2' and n2′。
Calculating the unit vector of the current magnetization direction of the rotated small magnet according to the following formula
Figure BDA0003082299470000077
Figure BDA0003082299470000078
m2＝m2′p2；
n2＝n2′p2；
And 5: calculating the axial direction unit vector of the magnetic capsule endoscope
Figure BDA0003082299470000079
Figure BDA00030822994700000710
I.e. the current pose of the capsule endoscope is completely determined.
The calculation formula is as follows:
r＝n1p2-n2p1；
s＝m2p1-m1p2；
t＝m1n2-m2n1；
Figure BDA00030822994700000711
Figure BDA0003082299470000081
Figure BDA0003082299470000082
wherein,
Figure BDA0003082299470000083
and
Figure BDA0003082299470000084
unit vectors respectively representing the radial magnetization directions of the small magnets before and after the rotation (i.e., the second rotation) of step 3, as shown in fig. 4,
Figure BDA0003082299470000085
is the unit vector of the axial direction of the magnetic capsule endoscope (i.e. the
Figure BDA0003082299470000086
). The radial magnetization direction of the small magnet has a fixed relation with the magnetic capsule endoscope and is different from the axial direction of the magnetic capsule endoscope, so thatThereby, from
Figure BDA0003082299470000087
I.e. the current pose of the magnetic capsule endoscope is completely determined.
By
Figure BDA0003082299470000088
And
Figure BDA0003082299470000089
calculating the roll angle increment of a magnetic capsule endoscope
Figure BDA00030822994700000810
Figure BDA00030822994700000811
Is prepared from (A)
Figure BDA00030822994700000812
Delta theta) is the attitude of the magnetic capsule endoscope before rotation.
In this example, use
Figure BDA00030822994700000813
Updating
Figure BDA00030822994700000814
Repeating steps 3 to 5, the posture of the magnetic capsule endoscope can be completely determined continuously.
In the present embodiment, N is 25, and the sensor coordinate (x) is known1，y1，z1)＝(-0.16，-0.1685，0.017)，(x2，y2，z2)＝(-0.08，-0.1685，0.017)，(x3，y3，z3)＝(0，-0.1685，0.017)，(x4，y4，z4)＝(0.08，-0.1685，0.017)，(x5，y5，z5)＝(0.16，-0.1685，0.017)，(x6，y6，z6)＝(-0.16，0.0885，0.017)，(x7，y7，z7)＝(-0.08，0.0885，0.017)，(x8，y8，z8)＝(0，0.0885，0.017)，(x9，y9，z9)＝(0.08，0.0885，0.017)，(x10，y10，z10)＝(0.16，0.0885，0.017)，(x11，y11，z11)＝(-0.16，0.0085，0.017)，(x12，y12，z12)＝(-0.08，0.0085，0.017)，(x13，y13，z13)＝(0，0.0085，0.017)，(x14，y14，z14)＝(0.08，0.0085，0.017)，(x15，y15，z15)＝(0.16，0.0085，0.017)，(x16，y16，z16)＝(-0.16，-0.0715，0.017)，(x17，y17，z17)＝(-0.08，-0.0715，0.017)，(x18，y18，z18)＝(0，-0.0715，0.017)，(x19，y19，z19)＝(0.08，-0.0715，0.017)，(x20，y20，z20)＝(0.16，-0.0715，0.017)，(x21，y21，z21)＝(-0.16，-0.1515，0.017)，(x22，y22，z22)＝(-0.08，-0.1515，0.017)，(x23，y23，z23)＝(0，-0.1515，0.017)，(x24，y24，z24)＝(0.08，-0.1515，0.017)，(x25，y25，z25)＝(0.16，-0.1515，0.017)。
In this embodiment, the coordinates of the central point of the magnetic capsule endoscope are the same as the coordinates of the central point of the small permanent magnet, and the theoretical values are all
Figure BDA0003082299470000091
The magnetic capsule endoscope posture is set to be in the same direction with the positive X axis in the axial direction (the camera head end of the magnetic capsule endoscope is in the positive direction), and the radial magnetization direction is in the same direction with the positive Z axis, namely: the theoretical value of (r, s, t) is (1, 0, 0), (m, n, p) is (0, 0, 1), and the theoretical value of roll angle is 0 degrees.
The magnetic induction intensity collected by the magnetic sensor array is
Figure BDA0003082299470000092
Figure BDA0003082299470000093
Figure BDA0003082299470000094
Figure BDA0003082299470000095
Figure BDA0003082299470000096
Figure BDA0003082299470000097
Figure BDA0003082299470000098
Figure BDA0003082299470000099
Figure BDA00030822994700000910
Figure BDA00030822994700000911
Figure BDA00030822994700000912
Figure BDA00030822994700000913
Figure BDA00030822994700000914
Figure BDA00030822994700000915
Figure BDA00030822994700000916
Figure BDA00030822994700000917
Figure BDA00030822994700000918
Figure BDA00030822994700000919
Figure BDA00030822994700000920
Figure BDA0003082299470000101
Figure BDA0003082299470000102
Figure BDA0003082299470000103
Figure BDA0003082299470000104
Figure BDA0003082299470000105
Figure BDA0003082299470000106
Figure BDA0003082299470000107
Figure BDA0003082299470000108
Figure BDA0003082299470000109
Figure BDA00030822994700001010
Figure BDA00030822994700001011
Data of the No. 1 sensor is removed by setting over-small (less than 1) and over-large (over-sensor range) values as invalid values
Figure BDA00030822994700001012
And
Figure BDA00030822994700001013
from the remaining 24 sensor data
Figure BDA00030822994700001014
And
Figure BDA00030822994700001015
calculating to obtain:
Figure BDA00030822994700001016
then is made of
Figure BDA00030822994700001017
And
Figure BDA00030822994700001018
calculating to obtain the initial estimated posture of the capsule lens
Figure BDA00030822994700001019
By
Figure BDA00030822994700001020
Calculating to obtain:
Figure BDA00030822994700001021
the coordinates (a, b, c) of the center position of the magnetic capsule endoscope are (0.002388, -0.002005, 0.118974). Then is made of
Figure BDA00030822994700001022
And
Figure BDA00030822994700001023
calculating to obtain axial unit vector in attitude parameter of capsule lens
Figure BDA00030822994700001024
By
Figure BDA00030822994700001025
And
Figure BDA00030822994700001026
the roll angle Δ θ is calculated to be 1.76 °, and is positive in the counterclockwise direction.
Due to theoretical value of position coordinates
Figure BDA00030822994700001027
Theoretical values of (r, s, t) are (1, 0, 0), (m, n, p) are (0, 0, 1), and theoretical values of roll angle are 0 °, so in this example, the capsule mirror is used
Figure BDA00030822994700001028
Figure BDA0003082299470000111
Axial unit vector error | (r) in capsule mirror attitude parameters2，s2，t2) - (1, 0, 0) | (0.0026, 0.0543, 0.0463) converted to (4.13 °, 3.11 °, 2.65 °) angular errors (of the axial vectors respectively included in the three axes XYZ); the roll angle error in the attitude parameters is 1.76 degrees Δ θ -0.
The shape of the small magnet according to the present invention may be a cube having a square or polygonal cross section.
In the steps 1.1, 1.3 and 4 related by the invention, the radial magnetization direction vector of the small magnet is calculated, and the radial magnetization direction vector can be replaced by the existing magnetic dipole model and the improvement method thereof or the existing arbitrary method for calculating the magnetization direction of the magnetic source according to the magnetic induction intensity.
In step 2 according to the present invention, the posture of the external large magnet may be made to coincide with the initial posture of the magnetic capsule endoscope, and the following may be performed: the axial direction of the external large magnet and the estimated axial direction axis of the magnetic capsule endoscope (i.e. the axis of the magnetic capsule endoscope)
Figure BDA0003082299470000112
) The two magnets are superposed (i.e. the external big magnet is coaxial with the magnetic capsule endoscope), and the radial magnetization direction of the big magnet and the radial magnetization direction of the small magnet (i.e. the radial magnetization direction of the small magnet)
Figure BDA0003082299470000113
) The opposite is true. (in this case, in step 3, the rotation direction of the small magnet and the rotation direction of the external large magnet are the same direction.)
In step 5 designed by the present invention, the method can also be carried out by
Figure BDA0003082299470000114
And
Figure BDA0003082299470000115
calculating axial direction unit vector of magnetic capsule endoscope
Figure BDA0003082299470000116
The calculation formula is as follows:
r＝n0p2-n2p0；
s＝m2p0-m0p2；
t＝m0n2-m2n0；
Figure BDA0003082299470000117
Figure BDA0003082299470000118
Figure BDA0003082299470000119
it should be understood that the above description of the preferred embodiments is given for clarity and not for any purpose of limitation, and that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (10)

1. A magnetic capsule endoscope full attitude determination method adopts a magnetic capsule endoscope; the permanent magnet arranged in the capsule endoscope is a small permanent magnet which is magnetized in the radial direction; the small permanent magnet is cylindrical or annular and is fixedly arranged in the magnetic capsule endoscope or fixed on the wall of the annular magnetic capsule endoscope shell, and the axial direction of the small permanent magnet is consistent with the axial direction of the magnetic capsule endoscope; a large permanent magnet is arranged outside the capsule endoscope and is a cylindrical strong permanent magnet which is magnetized in the radial direction;
characterized in that the method comprises the following steps:
step 1: estimating the initial attitude of the magnetic capsule endoscope, and determining the unit vector of the radial magnetization direction of the small permanent magnet in the magnetic capsule endoscope
Figure FDA0003082299460000011
And axial direction unit vector
Figure FDA0003082299460000012
The specific implementation comprises the following substeps:
step 1.1: calculating the unit vector of the radial magnetization direction of the small permanent magnet
Figure FDA0003082299460000013
Step 1.2: controlling the rotation of the magnetic capsule endoscope by using an external large permanent magnet according to the radial magnetization direction vector of the small permanent magnet;
step 1.3: calculating the unit vector of the radial magnetization direction of the small permanent magnet after rotation
Figure FDA0003082299460000014
Step 1.4: by
Figure FDA0003082299460000015
And
Figure FDA0003082299460000016
calculating the estimated axial direction unit vector of the magnetic capsule endoscope
Figure FDA0003082299460000017
Step 2: adjusting the posture of the external large permanent magnet to make the posture of the external large permanent magnet consistent with the current posture of the magnetic capsule endoscope;
and step 3: controlling the magnetic capsule endoscope to rotate around the axial central shaft by using an external large permanent magnet;
and 4, step 4: calculating the unit vector of the current radial magnetization direction of the small permanent magnet in the rotated magnetic capsule endoscope
Figure FDA0003082299460000018
And 5: calculating the axial direction unit vector of the magnetic capsule endoscope
Figure FDA0003082299460000019
Figure FDA00030822994600000110
I.e. the current pose of the capsule endoscope is completely determined.
2. The method for measuring the full attitude of a magnetic capsule endoscope according to claim 1, characterized in that: step 1.1, detecting the magnetic induction intensity generated by the small permanent magnet before rotating through a magnetic sensor array
Figure FDA00030822994600000111
According to
Figure FDA00030822994600000112
Regarding the small permanent magnet as a point source, and calculating the unit vector of the magnetization direction of the small permanent magnet
Figure FDA00030822994600000113
3. The method for measuring the full attitude of the magnetic capsule endoscope according to claim 2, characterized in that: the magnetic sensor array is composed of at least 5 triaxial magnetic sensors and is fixed outside the magnetic capsule endoscope.
4. The method for measuring the full attitude of a magnetic capsule endoscope according to claim 1, characterized in that: in step 1.2, firstly, the external large permanent magnet is placed, and the radial magnetization direction of the large permanent magnet and the radial magnetization direction of the small permanent magnet are enabled to be in the same direction; and then the external large permanent magnet is controlled to rotate by any small angle around the self axial central shaft, so that the magnetic field generated by the external large permanent magnet rotates, the rotating magnetic field drives the small permanent magnet and the magnetic capsule endoscope to rotate around the self axial central shaft together, and the rotating direction of the magnetic capsule endoscope is opposite to that of the external large magnet.
5. The method for measuring the full attitude of a magnetic capsule endoscope according to claim 1, characterized in that: in step 1.3, the magnetic induction intensity generated after the small permanent magnet rotates is detected through a magnetic sensor array
Figure FDA0003082299460000021
According to
Figure FDA0003082299460000022
Regarding the small permanent magnet as a point source, and calculating the unit vector of the magnetization direction of the small permanent magnet
Figure FDA0003082299460000023
6. The method for measuring the full attitude of a magnetic capsule endoscope according to claim 1, characterized in that: in step 1.4, the estimated axial direction unit vector of the magnetic capsule endoscope is calculated
Figure FDA0003082299460000024
Figure FDA0003082299460000025
Wherein r is n0p1-n1p0，s＝m1p0-m0p1，t＝m0n1-m1n0；
Figure FDA0003082299460000026
And
Figure FDA0003082299460000027
unit vectors representing the radial magnetization directions of the small permanent magnets before and after rotation, respectively.
7. The method for measuring the full attitude of a magnetic capsule endoscope according to claim 1, characterized in that: in step 2, the axial direction of the external large permanent magnet is made to be the same as the estimated axial direction of the capsule endoscope, and the radial magnetization direction of the external large permanent magnet is made to be the same as the current radial magnetization direction of the small permanent magnet.
8. The method for measuring the full attitude of a magnetic capsule endoscope according to claim 1, characterized in that: in step 3, the external large permanent magnet is controlled to rotate by a small angle around the self axial central shaft, so that a magnetic field generated by the external large permanent magnet rotates, the rotating magnetic field drives the small permanent magnet and the magnetic capsule endoscope to rotate around the self axial central shaft, and the rotating direction of the magnetic capsule endoscope is opposite to that of the external large magnet.
9. The method for measuring the full attitude of a magnetic capsule endoscope according to claim 1,the method is characterized in that: in step 4, the magnetic induction intensity generated by the small permanent magnet after rotating in step 3 is detected through a magnetic sensor array
Figure FDA0003082299460000031
According to
Figure FDA0003082299460000032
Regarding the small permanent magnet as a point source, and calculating the unit vector of the magnetization direction of the small permanent magnet after rotating in the step 3
Figure FDA0003082299460000033
Namely, it is
Figure FDA0003082299460000034
10. The method for measuring the full attitude of a magnetic capsule endoscope according to any one of claims 1 to 9, characterized in that: in step 5, calculating the unit vector of the magnetic capsule endoscope in the axial direction
Figure FDA0003082299460000035
Figure FDA0003082299460000036
Wherein r is n1p2-n2p1，s＝m2p1-m1p2，t＝m1n2-m2n1(ii) a The radial magnetization direction of the small permanent magnet has a fixed relation with the magnetic capsule endoscope and is different from the axial direction of the magnetic capsule endoscope, so that the vector of the radial magnetization direction of the small permanent magnet
Figure FDA0003082299460000037
And axial direction vector
Figure FDA0003082299460000038
Determining a current pose of the magnetic capsule endoscope; by
Figure FDA0003082299460000039
And
Figure FDA00030822994600000310
calculating the roll angle increment of the magnetic capsule endoscope
Figure FDA00030822994600000311
By
Figure FDA00030822994600000312
Determining the attitude of the magnetic capsule endoscope before rotation.
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