7Appendix; Appendix 1 ： Inertia Calculation Method - Mitsubishi Electric MELFA CR800 Series Special Specifications Manual

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.
Center of gravity
of the hand
L
1
[Calculation example]
Center of gravity
of the hand
50
Total moment of inertia about the J4 axis
I = 0.0068 + 0.0012 + 2.5 x 0.05
2
= 0.030 kg·m
The calculation result (0.030 kg·m
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 and L
1 2
I = 0.0068 + 0.0012 = 0.008 kg·m
The result is smaller than the allowable inertia.
I = Iz + Iz + W
1 2 1
Hand
Workpiece
W
1
W
2
Center of gravity
L
2 of the workpiece
Hand
Workpiece
2.5kg
1.5kg
Center of gravity
100
of the workpiece
2
+ 1.5 x 0.1
2 ) is greater than the allowable inertia (rating) of 0.01 kg·m
become zero and the total inertia around the J4 axis is calculated as follows.
2
< 0.01 kg·m
I: total moment of inertia about the J4 axis
2 2
L + W L Iz: load inertia
1 2 2
W: mass (kg)
Rectangular shape
a
2 2
a + b
Load inertia: Iz = W·
12
Hand
150
100
2
0.15
Load inertia: Iz = 2.5×
1
12
= 0.0068kg·m
2
2
Cylindrical shape
b
Load inertia: Iz = W·
Workpiece
40
2
+ 0.1
Load inertia: Iz =1.5×
1
2
= 0.0012kg·m
2 for RH-6FRH.
Inertia calculation method Appendix-138

7Appendix

r
r 2
2
2
0.04
2
2