2.1 Selecting the Servomotor Capacity
2.1.1 Capacity Selection Example for a Rotary Servomotor: For Speed Control
2-2
2.1
Selecting the Servomotor Capacity
Refer to the following selection examples to select Servomotor capacities with manual calculations
rather than with the above software.
2.1.1
Capacity Selection Example for a Rotary Servomotor:
For Speed Control
1.
Mechanical Specifications
2.
Operation Pattern
3.
Motor Speed
4.
Load Torque
Item
Code
Value
Item
Code
Value
Load Speed
υ
L
15 m/min
Gear and Coupling
Moment of Inertia
J
G
0.40
×
10
-4
kg
m
2
Linear Motion
Section Mass
m
250 kg
Number of Feeding
Operations
n
40 rotations/min
Ball Screw Length
B
1.0 m
Feeding Distance
0.275 m
Ball Screw Diameter
d
B
0.02 m
Feeding Time
tm
1.2 s max.
Ball Screw Lead
P
B
0.01 m
Friction Coefficient
μ
0.2
Ball Screw Material
Density
ρ
7.87
×
10
3
kg/m
3
Mechanical Efficiency
η
0.9 (90%)
Gear Ratio
R
2 (gear ratio: 1/2)
External Force on Lin-
ear Motion Section
F
0 N
•
Load shaft speed
•
Motor shaft speed
n
M
=
n
L
· R
= 1,500
×
2 = 3,000 (min
-1
)
υ
L
Linear motion
s
ection
S
ervomotor
Coupling
Gear
Ball
s
crew
tc
ta
td
(m/min)
tm
t
15
υ
L
Motor
S
peed
Time (
s
)
t
= = = 1.5 (
s
)
ta
=
tm
−
= 1.2
−
= 1.2
−
1.1 = 0.1 (
s
)
tc
= 1.2
−
0.1
×
2 = 1.0 (
s
)
60
60
40
60
×
0.275
15
60
υ
L
If ta = td,
nL
= = = 1,500 (min
-1
)
PB
15
0.01
υ
L
TL
=
= = 0.4
3
(N
m)
2
π
R
(9.8
m
+
F)
PB
2
π ×
2
×
0.9
(9.8
×
0.2
×
250 + 0)
×
0.01
η
μ
