Mitsubishi Electric CR800 Series, Специальные технические характеристики, Страница: 151 / 156

7Appendix
Inertia calculation method Appendix-138
7 Appendix
Appendix 1 ： Inertia calculation method
An allowable moment of inertia in the mechanical interface at the tip of the robot arm is determined. If a load
exceeding the allowable moment of inertia is put, on the tip of the arm, vibration during operation and an overload
alarm may occur. Therefore, consider the matching/appropriateness of the hand and load to be mounted on the tip
of the arm for the robot specifications when you select a robot. The following describes the load inertia calculation
method.
Calculate the total moment of inertia about the J4 axis.
I = Iz
1
+ Iz
2
+ W
1
L
1
2
+ W
2
L
2
2
L
1
L
2
W
1
W
2
I: total moment of inertia about the J4 axis
Iz: load inertia
W: mass (kg)
Rectangular shape Cylindrical shape
a
2
+ b
2
Load inertia: Iz = W·
12
r 2
Load inertia: Iz = W·
2
[Calculation example]
a
b
r
Hand
Workpiece
Center of gravity
of the hand
Center of gravity
of the workpiece
Total moment of inertia about the J4 axis
I = 0.0068 + 0.0012 + 2.5 x 0.05
2
+ 1.5 x 0.1
2
= 0.030 kg·m
2
The calculation result (0.030 kg·m
2
) is greater than the allowable inertia (rating) of 0.01 kg·m
2
for RH-6FRH.
However, if the center of gravity of the hand is aligned with the axis of rotation of J4 and the workpiece is held directly below the J4
axis, both L
1
and L
2
become zero and the total inertia around the J4 axis is calculated as follows.
I = 0.0068 + 0.0012 = 0.008 kg·m
2
< 0.01 kg·m
2
The result is smaller than the allowable inertia.
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50
100
2.5kg
1.5kg
Hand Workpiece
0.15 2 + 0.1 2
Load inertia: Iz
1
= 2.5×
= 0.0068kg·m 2 = 0.0012kg·m 2
12
0.04 2
Load inertia: Iz
1
=1.5×
2
150
100
40
Hand
Workpiece
Center of gravity
of the hand
Center of gravity
of the workpiece