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APPENDIX
App. - 24
(6) Load moment of inertia (converted into equivalent value on servo motor shaft)
Moving part
J
L1
= W •
2
S 10
-3
2
= 1.52 • 10
-4
[kg•m
2
]
Ball screw
J
L2
=
32
B
• D
B
4
•
n
1
2
= 0.24 • 10
-4
[kg•m
2
]
ρ = 7.8 • 10
3
[kg/m
3
] (iron)
Gear (servo motor shaft)
J
L3
=
32
G
• D
G1
4
= 0.03 • 10
-4
[kg•m
2
]
Gear (load shaft)
J
L4
=
32
G
• D
G2
4
•
n
1
2
= 0.08 • 10
-4
[kg•m
2
]
Full load moment of inertia (converted into equivalent value on servo motor shaft)
J
L
= J
L1
+ J
L2
+ J
L3
+ J
L4
= 1.9 • 10
-4
[kg•m
2
]
(7) Temporary selection of servo motor
Selection conditions
(a) Load torque < servo motor rated torque
(b) Full load moment of inertia < J
R
• moment of inertia of the servo motor
J
R
: Recommended load to motor inertia ratio
According to above conditions, HG-KR23 (rated torque: 0.64 N•m, maximum torque: 2.2 N•m,
moment of inertia: 0.221 • 10
-4
kg•m
2
) is selected temporarily.