Akai AP-D40

an
(a) HALL ELEMENT
OUT PUT
=> —
i2
>
(b)
COIL
CURRENT
i
|
=
CLOCK - WISE
(c)
REVOLUTION
O
TORQUE |
COUNTER
CLOCK-WISE
Fig.
10
Each
Output
Waveform
vs
Position
of
Magnetic
Polarity
Fig.
8
shows
the
4
coils
and
the
2
Hall
elements
on
the
base
board.
Fig.
8
(a)
shows
the
motor
drive
system
and
the
magnet
which
face
the
coils.
The
magnet
is
magnet-
ized
into
6
poles
arranged
alternately
N/S.
Changes
in
the
sine
wave’s
magnetic
field
which
accom-
panies
revolution
of
the
magnet
are
detected
by
the
Hall
elements,
amplified
by
an
amplifier
generating
torque
which
is
supplied
to
the
coil
and
then
the
magnet
revolves.
When
sine
wave
current
flows
into
the
coil,
with
@
as
the
revolution
angle
and
K
as
a
fixed
value,
the
torque
force
T
is:
Ti
=Kei,
sin
30
2.
eee
ee
eee
eee
()
the
coil
current
i,
with
I
as
a
fixed
value
is:
Fd
oc:
a
a
(2)
so from 1 and 2:
T,
SK
Sn?
30
hoes
eed
eases
(3)
Fig.
9
shows
the
changes
in
the
coil
current
i,
and
the
torque
T;
accompaning
changes
in
the
revolution
angle
6.
A
clockwise
revolution
torque
is
produced.
Also
the
coil’s
other
phase
is
out
90°
electrically.
As
the
phase
of
the
magnetic
field
detected
by
the
Hall
element
is
also
90°
out,
the
current
flowing
to
this
coil
is:
ip
ST
ead
assent
ied
tens
(4)
the
generated
torque
T2
is
Tz
=Krin
coS30
2...
ee
ee
eee
(5)
so
from
4
and
5:
T,
=
Kel*cos*
30
ii
aensa
deed
a4
(6)
Fig.
10
shows
the
relationship
between
the
output
from
the
two
Hall
elements,
current
i,
and
i,,
and
the
generated
torque
T,
and
T..
The
total
torque
generated
is
the
sum
of
torques
T,
and
T..
This
torque
To
is
Ty
=T,
+T2
=K°I
(sin?
36
+
cos?
36)
=K-I
As
shown
in
Fig.
10.
To
is
fixed
regardless
of
the
revolu-
tion
angle
6.
a
14