Inter
national
J
our
nal
of
Electrical
and
Computer
Engineering
(IJECE)
V
ol.
9,
No.
3,
June
2019,
pp.
1541
1545
ISSN:
2088-8708,
DOI:
10.11591/ijece.v9i3.pp1541-1545
r
1541
W
ir
eless
po
wer
transfer
to
a
micr
o
implant
de
vice
fr
om
outside
of
human
body
Kazuya
Y
amaguchi,
Kazuma
Onishi,
and
K
enichi
Iida
Department
of
Control
Engineering,
National
Institute
of
T
echnology
,
Nara
Colle
ge
Article
Inf
o
Article
history:
Recei
v
ed
Jun
5,
2018
Re
vised
Oct
11,
2018
Accepted
Dec
18,
2018
K
eyw
ords:
W
ireless
po
wer
transfer
Biological
science
State
space
representation
ABSTRA
CT
This
paper
states
wireless
po
wer
transfer
(WPT)
from
an
A
C
po
wer
supply
to
a
micro
implant
de
vice
in
human
body
.
At
first,
an
equi
v
alent
circuit
of
WPT
which
contains
biomedical
tissue
is
constructed
with
an
A
C
po
wer
supply
,
parasitic
components,
load
resistance,
and
induct
ances.
Then
a
state
equation
whi
ch
stands
for
the
beha
vior
of
circuit
is
found,
and
the
e
xpression
of
ef
ficienc
y
is
deri
v
ed
as
the
ratio
of
the
po
wer
of
po
wer
supply
and
load.
Finally
an
e
xperiment
is
conducted
based
on
the
theoretical
calculation,
and
the
error
between
e
xperimental
and
calculated
result
is
computed
and
e
xamined.
Copyright
c
2019
Institute
of
Advanced
Engineering
and
Science
.
All
rights
r
eserved.
Corresponding
A
uthor:
Kazuya
Y
amaguchi,
Department
of
Control
Engineering,
National
Institute
of
T
echnology
,
Nara
Colle
ge,
22
Y
ata-cho,
Y
amatok
oriyama,
Nara,
Japan.
Email:
k-yamaguchi@ctrl.nara-k.ac.jp
1.
INTR
ODUCTION
W
ireless
Po
wer
T
ransfer
(WPT)
i
s
frequently
studied
and
applied
for
v
arious
fields,
for
e
xample
in-
dustry
,
manuf
acture,
mathematics,
medical
science,
and
information.
Th
e
basic
principle
of
tr
ansfer
has
been
found
in
19th
century
,
although
practical
applied
or
productization
is
later
.
In
2007,
a
WPT
system
with
mag-
netic
resonance
circuit
whose
transmitting
and
recei
ving
circuits
ha
v
e
same
resonant
frequenc
y
w
as
proposed
by
[1].
This
study
accomplished
highly
ef
ficient
ener
gy
transfer
on
the
situation
that
a
po
wer
supply
and
load
are
put
a
fe
w
meters
apart.
These
days,
man
y
papers
and
articles
ha
v
e
reported
v
arious
WPT
studies
and
practical
products.
WPT
for
electric
v
ehicles
is
cogitated
from
v
arious
vie
wpoints,
for
e
xample
a
design
of
coils
[2],
and
incorporating
solar
cells
[3].
Furthermore
a
method
to
dri
v
e
machines
is
e
xamined
by
actuating
the
rotor
with
piezoelectric
ener
gy
via
a
magnetic
relucta
n
c
e
coupling
[4].
The
necessity
of
IoT
is
mentioned
in
these
days,
and
hence
WPT
adopting
radio
frequenc
y
is
in
v
estig
ated
to
a
v
oid
replacing
or
rechar
ging
the
batteries
of
wireless
de
vices
in
IoT
[5].
Moreo
v
er
,
WPT
for
an
artificial
satellite
in
space
is
tried
to
e
xchange
ener
gy
wirelessly
without
going
to
space
[6],
and
then
micro
w
a
v
e
is
used
to
send
ener
gy
in
greatly
long
distance
such
as
this
situation.
F
or
realization
to
mak
e
these
systems,
man
y
approaches
are
in
v
estig
ated
in
terms
of
an
electric
ci
r
-
cuit,
and
mathematics.
The
resonant
frequencies
of
all
parts
which
compose
WPT
circuit
are
inte
grated,
and
impedance
of
load
is
matched
with
input
impedance
to
maximize
po
wer
of
load
[7].
The
coils
are
used
to
trans-
mit
ener
gy
via
electromagnetic
field,
and
therefore
the
proper
materials
which
are
used
to
mak
e
high
quality
coils
must
be
chosen
[8].
T
o
maximize
total
po
wer
of
load,
a
mathematical
model
is
structured
based
on
an
algorithmic
study
[9].
This
paper
focus
es
on
the
applications
for
medical
science,
especially
the
transmission
of
ener
gy
to
a
micro
implant
de
vice
from
outside.
The
ef
fect
to
human
body
must
be
considered
because
ener
gy
is
transmitted
to
human
body
via
electromagnetic
field
[10].
When
an
e
xperiment
with
respect
to
the
transmission
of
ener
gy
to
body
is
conducted,
an
e
xperimental
animal
is
used,
not
a
human
body
[11].
In
this
paper
,
biomedical
tissue
and
J
ournal
homepage:
http://iaescor
e
.com/journals/inde
x.php/IJECE
Evaluation Warning : The document was created with Spire.PDF for Python.
1542
r
ISSN:
2088-8708
a
micro
implant
de
vice
is
modeled
by
an
electric
circuit,
and
a
mathematical
equation
based
on
modern
control
theory
is
made
for
finding
an
e
xpression
of
ef
ficienc
y
.
M
oreo
v
er
an
e
xperimental
v
erification
is
conducted
with
an
electric
circuit
whose
elements
ha
v
e
practical
v
alues,
and
the
error
between
e
xperimental
and
theoretical
result
is
calculated.
2.
CALCULA
TION
OF
PO
WER
AND
EFFICIENCY
2.1.
Design
of
W
ir
eless
P
o
wer
T
ransfer
Cir
cuit
Which
Contains
Biomedical
T
issue
In
a
human
body
,
there
are
plasma
membrane,
intracellular
fluid,
and
e
xtracellular
fluid,
and
the
y
play
a
role
dif
ferent
electri
cal
characteristics
each
other
.
Current
can
flo
w
in
e
xtracellular
fluid,
and
moreo
v
er
current
which
has
high
frequenc
y
can
flo
w
into
intracellul
ar
fluid
by
going
o
v
er
plasma
membrane.
Therefore
intracellular
fluid
and
e
xtracellular
fluid
ha
v
e
resistances
R
i
and
R
e
,
and
plasma
membrane
has
capacitance
C
m
which
w
ork
as
a
high
pass
filter
.
In
terms
of
this
f
act
,
these
components
are
designed
as
an
electric
circuit
as
belo
w
[12].
Figure
1.
Equi
v
alent
circuit
of
biomedical
tissue
W
ith
Figure
1,
a
wireless
po
wer
transfer
circuit
for
char
ging
a
micro
implant
de
vice
is
designed
as
follo
ws.
Figure
2.
W
ireless
po
wer
transfer
circuit
which
contains
biomedical
tissue
In
Figure
2,
the
left
side
is
a
transmitting
circuit,
and
the
right
side
is
equi
v
alent
circuit
which
contains
biomedical
tissue
and
the
micro
implant
de
vice.
u
is
the
v
oltage
of
po
wer
supply
,
R
1
;
R
2
;
C
1
;
C
2
are
parasitic
components,
L
1
;
L
2
are
the
antennas,
M
is
mutual
inductance,
and
R
L
is
the
micro
implant
de
vice.
IJECE,
V
ol.
9,
No.
3,
June
2019
:
1541
–
1545
Evaluation Warning : The document was created with Spire.PDF for Python.
IJECE
ISSN:
2088-8708
r
1543
2.2.
Modeling
of
W
ir
eless
P
o
wer
T
ransfer
Cir
cuit
by
Usi
ng
a
State
Equation
which
has
State
V
ariables
V
oltage
and
Curr
ent
From
Figure
2,
a
state
equation
which
has
state
v
ariables
v
oltage
and
current
is
obtained
as
belo
w
[13].
_
x
=
Ax
+
B
u;
x
=
v
1
v
2
v
3
i
1
i
2
T
(1)
A
=
1
2
6
6
6
6
6
4
0
0
0
C
1
0
0
0
0
0
C
2
0
0
(
R
i
+
R
e
)
C
m
0
R
e
(
R
i
+
R
e
)
C
m
L
2
M
R
e
M
R
i
+
R
e
R
1
L
2
[
R
3
(
R
i
+
R
e
)+
R
i
R
e
]
M
R
i
+
R
e
M
L
1
R
e
L
1
R
i
+
R
e
R
1
M
[
R
3
(
R
i
+
R
e
)+
R
i
R
e
]
L
1
R
i
+
R
e
3
7
7
7
7
7
5
;
B
=
1
2
6
6
6
6
4
0
0
0
L
2
M
3
7
7
7
7
5
=
L
1
L
2
M
2
;
R
3
=
R
2
+
R
L
:
2.3.
Definition
and
calculation
of
po
wer
and
efficiency
The
v
ector
of
stationary
solution
x
ss
which
is
composed
of
v
oltage
v
1
;
v
2
;
v
3
and
current
i
1
;
i
2
is
found
by
solving
the
state
equation
(1).
x
ss
(
t
)
=
cos
!
t
+
sin
!
t
(2)
where
=
!
(
!
2
I
+
A
2
)
1
B
;
=
A
(
!
2
I
+
A
2
)
1
B
,
and
!
is
angular
frequenc
y
of
u
.
Moreo
v
er
column
v
ectors
and
are
e
xpressed
in
the
follo
wing.
=
1
2
3
4
5
T
;
=
1
2
3
4
5
T
Po
wer
transmission
ef
ficienc
y
load
and
ener
gy
loss
ef
ficienc
y
loss
are
e
xpressed
as
follo
ws.
load
=
P
load
P
in
=
R
L
(
2
5
+
2
5
)
4
loss
=
P
loss
P
in
=
!
2
(
R
i
R
e
)(
2
3
+
2
3
)
C
2
m
2
!
R
e
C
m
(
3
5
5
3
)
R
e
(
2
5
+
2
5
)
4
(3)
where
P
in
is
po
wer
of
u
,
P
load
is
po
wer
of
R
L
,
and
P
loss
is
po
wer
of
R
i
and
R
e
.
3.
EXPERIMENT
AL
VERIFICA
TION
3.1.
Condition
of
experiment
f
or
wir
eless
po
wer
transfer
by
using
the
equi
v
alent
cir
cuit
to
suppose
po
wer
transmission
f
or
a
micr
o
implant
de
vice
in
human
body
fr
om
outside
The
e
xperimental
circuit
is
sho
wn
in
Figure
3.
Figure
3.
Experimental
circuit
W
ir
eless
power
tr
ansfer
to
a
micr
o
implant...
(Kazuya
Y
ama
guc
hi)
Evaluation Warning : The document was created with Spire.PDF for Python.
1544
r
ISSN:
2088-8708
The
v
alues
of
elements
are
sho
wn
in
T
able
1.
T
able
1.
V
alues
of
Elements
V
alues
of
Elements
R
1
465
R
2
10
:
0
R
3
97
:
4
R
i
684
R
e
5
:
37k
L
1
66
:
0
H
L
2
66
:
4
H
M
9
:
27
H
C
1
84
:
0pF
C
2
85
:
5pF
C
m
11
:
7nF
3.2.
V
ariation
of
efficiency
v
ersus
fr
equency
of
a
po
wer
supply
The
v
ariation
of
ef
ficienc
y
is
in
v
estig
ated
by
changing
frequenc
y
of
the
po
wer
supply
u
.
The
calculated
and
e
xperimental
results
are
sho
wn
in
Figure
4.
Figure
4.
V
ariation
of
ef
ficienc
y
v
ersus
frequenc
y
of
a
po
wer
supply
3.3.
Discussion
Figure
4
sho
ws
that
the
optimal
frequenc
y
which
maximizes
ef
ficienc
y
is
f
opt
=
2
:
65[MHz]
,
and
the
error
between
calculation
and
e
xperiment
is
sho
wn
on
T
able
2.
T
able
2.
Ef
ficienc
y
and
Error
at
the
Optimal
Frequenc
y
f
opt
=
2
:
65[MHz]
load
loss
Experiment
6
:
85
10
3
6
:
05
10
2
Calculation
7
:
08
10
3
3
:
41
10
2
Error
[%]
3
:
19
+77
:
6
W
ith
r
espect
to
load
,
the
e
xperimental
maximum
v
alue
is
almost
same
as
theoretical
v
alue
which
is
found
by
equation
(3).
On
the
other
hand,
the
e
xperimental
maximum
loss
is
greatly
dif
ferent
for
calculation.
This
error
is
caused
by
the
approximation
which
depends
on
frequenc
y
and
impedance.
IJECE,
V
ol.
9,
No.
3,
June
2019
:
1541
–
1545
Evaluation Warning : The document was created with Spire.PDF for Python.
IJECE
ISSN:
2088-8708
r
1545
4.
CONCLUSION
This
study
tried
to
inspect
transmission
of
ener
gy
to
a
micro
implant
de
vice
wirelessly
.
An
equi
v
al
ent
circuit
which
supposes
the
micro
implant
de
vice
and
biomedical
tissue
w
as
designed,
and
an
equation
w
as
found
for
calculating
po
wer
and
ef
ficienc
y
.
Moreo
v
er
an
e
xperiment
w
as
performed
to
pro
v
e
the
appropriateness
of
calculation
and
detect
an
error
and
cause
of
it.
As
an
approach
to
consider
ef
fecti
v
e
situation
furthermore,
a
meat
of
animals
should
be
used
as
a
load
resistance.
The
influence
of
electromagnetic
field
must
be
considered
for
making
some
productions
which
char
ge
a
micro
implant
de
vice
through
human
body
.
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W
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(Kazuya
Y
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guc
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