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12. APPLICATIONS
41
12.1 SELECTION
OF SERVOMOTOR
AND Servopock
1
12.1.1
CONFIRMATION
OF MACHINE
SPECIFICATIONS
To control
machines,
they must
be designed
based
upon
the full knowledge
of the required
specifications
of machines,
taking
into account
the performance
necessary
for control,
workability,
safety
environment
and
other
conditions.
As basic
items,
the specifications
and
dimensions
of the target
machine
must
be studied,
examined
and determined.
As the
calculation
data
for the selection
of servomotor
and
for the start
and stop
time,
the follow-
ing items
must
be considered.
• Positioning
speed:
V [m/rain
• Weightof movingpart: W [kg]
• Coefficient
of friction:
/2
I
• Efficiency
of machine:
z/
• Load
GD 2 (converted
to motor
shaft):
GD2L [kg • m 2]
• Load
torque
(converted
to motor
shaft):
TL [kg • m]
• Duty
cycle
Moreover,
the following
specifications
are needed
as positioning
characteristics:
• Detecting
resolution:
_ 0[ram/pulse]
• Stopping
accuracy:
--+_ [mm/rev]
41
• Ball screw
pitch:
PEmm]
I
• Number
of output
pulses
of PG: Fpc [pulses/rev]
12.1.2
SELECTION
OF SERVOMOTORS
When
the machine
configuration
is as shownin
Fig.
12.1, the motor
power
P required
to
drive
the moving
part
(table)
at a constant
speed
is given
by
(kW_......................................................
(1)
q
tt WV
P-
6.120x
77
Also,
acceleration
torque
T, required
for accelerating
in the acceleration
time
t (s) is given
by
GD_L ×NM
To -
375xt
+TL
(kgom_
.................................
(2)
where,
NM is the number
of revolutions
of motor
(rpm).
Then,
a motor
having
the capacity
satisfying
equations
(1)and
(2)shoul
tentatively
selected.
Its type should
be determined,
and the acceleration
torque
TA including
GD _ of the
motor
itself
must
be determined
from
the equation
shown
below.
TA = (GD2L +GD2M)
xNM
_ TL
Ekg ° mJ
..................
(3)
375 x t
q
234
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