Portable system and method for position and orientation of remote objects
View Patent ↗The present invention describes an electromagnetically positioning system, which can measure a position and orientation of a remote object in an isolated targeted examination area with time. Specifically, the remote object is a remote miniaturized examination device. During the location process, both the electromagnetically positioning system and the remote miniaturized examination device can have expected or unexpected, controlled and can-not-be-controlled movement. By implementing the electromagnetically positioning system, disclosed herein, position and orientation information of the remote miniaturized examination device can be linked with time, any information collected by the remote miniaturized examination device, for example, the photo images collected, can be associated kinetically with time and positioning information of the examination device, when the remote miniaturized examination device travels inside an isolated target examination area.
1. A method to determining a position and orientation of a remote object in a target area, comprising:
providing a portable external magnetic field generation assembly,
bringing the portable external magnetic field generation assembly near to the target area,
or placing the portable external magnetic field generation assembly near to the target area to cover the remote area, without additional physical mechanical fixtures, and
generating pulsed magnetic fields respectively in three dimensions;
introducing a remote object enclosing a 3-dimensional magnetic field sensor into the enclosed or semi-enclosed target area in a digestive channel,
sensing the pulsed magnetic fields generated externally by the portable external magnetic field generation assembly by the 3-dimensional magnetic field while the remote object is traveling in the enclosed or semi-enclosed target area at a rate;
measuring the position and orientation of the remote object with an acceptable position accuracy threshold under a confined measurement time limit less than 50 ms;
executing one or more computer processors configured to performing the steps of
determining three pure magnetic fields generated by a three-dimensional magnetic excitation assembly;
calculating the position of the remote object; and
determining orientation of the remote object,
wherein the step of calculating the position of the remote object includes
determining a current position data P (a, b, c) of the remote object in three coordinates by equation (6)
p=A 1/3 /[(( Bx/mx ) 2 +( By/my ) 2 +Bz 2 )/6] −1/6 (6)
x
a=±p √{square root over ((( Bx/mx ) 2 p 6 /A 2 −1)/3)}
b=±p √{square root over ((( By/my ) 2 p 6 /A 2 −1)/3)}
c=±p √{square root over (( Bz 2 p 6 /A 2 −1)/3)} (7)
wherein p is a distance between
the external magnetic field generation assembly, which located at a position O
and the remote object, which is located at the position P (a, b, c);
Bx is the magnetic field generated in x direction;
By is the magnetic field generated in y direction;
Bz is the magnetic field generated in z direction;
mx is a ratio of magnetic moment from x coil to z coil,
my is a ratio of magnetic moment from y coil to z coil,
wherein magnetic moment of each coil is proportional to
a coil current and an open cross section area of its respective coil and a number of wire turns,
and x coil, z coil and y coil are in the portable external magnetic field generation assembly;
A is defined by
A=μ 0 /4π| {right arrow over (M)}|
μ 0 is the vacuum magnetic permeability, M is a magnetic moment of an individual excitation coil.
2. The method of claim 1 , wherein the step of determining three pure magnetic fields generated by three-dimensional magnetic excitation assembly is accomplished by
measuring an environmental magnetic field data and removing the environmental magnetic field data from measured total magnetic field data of the three-dimensional magnetic assembly, including
measuring an environmental magnetic field vector every time before or/and after a pulsed magnetic field from an excited coil, calibrating the magnetic field vector generated by the external magnetic field generation assembly by removing the environmental magnetic field vector;
a time interval between the environmental magnetic field detection and the pulsed magnetic field from an excited coil shall be less than the half of the period of varying environmental magnetic field.
3. The method of claim 1 , wherein the step of determining three pure magnetic fields generated by three-dimensional magnetic excitation assembly is accomplished by
measuring the magnetic field generated by each coil in the magnetic generation assembly in a positive and negative direction, and adding results of the two total magnetic field data lead to cancellation of the environmental magnetic field.
4. The method of claim 1 , wherein the step of determining three pure magnetic fields generated by three-dimensional magnetic excitation assembly is accomplished by
a combinatorial sequencing method to measure total magnetic fields three times, and among which at least one electrical current direction for one of the coils is different from the previous sequence.
5. The method of claim 1 , wherein the step of calculating the position of the remote object further includes
determining the orientation of remote miniaturized examination
B
ext
=
[
0
0
B
z
]
B
int
=
[
B
x
′
B
y
′
B
z
′
]
B
z
′
=
-
sin
(
β
)
B
x
B
y
′
=
sin
(
α
)
cos
(
β
)
B
y
B
z
′
=
cos
(
α
)
cos
(
β
)
B
z
B
ext
=
[
0
B
y
0
]
B
int
=
[
B
x
′
B
y
′
B
z
′
]
B
x
′
=
cos
(
β
)
sin
(
γ
)
B
y
wherein the position O is a position of the external magnetic field generation assembly, a line from O to P forms angles α, β, γ, with three axes x, y and z, respectively, in the three coordinates.
6. The method of claim 1 , wherein the wherein the acceptable position accuracy target of the 0.5 mm.
7. The method of claim 1 , wherein the target area is a digestive channel and remote object travels at a rate of 10 mm/s.