Yaskawa FSP Amplifier - Manual (Page 180)

FSP Amplifier User’s Manual Chapter 6: Servo Adjustment
6-13
The following wizard will help you to calculate your load inertia.
Estimation of equivalent load (
J
load
)
To tune your system, you should have an approximate estimation of the
Inertia (
J
load
) of the load attached to the motor.
If a cylinder load is mountain directly on motor axis you should
usefollowing formula to calculate load inertia:
32
4
d l
J
load
× × ×
=
ρ π
Where ρ is the characteristic weight of the load [kg/m^3].
L is the length and d is the diameter of the load [m].
Estimation of Equivalent Load ( J
load
)
Case 1: Load is a cylinder directly mounted or coupled to motor axis:
32
4
d l
J
load
× × ×
=
ρ π
ρ is the density of the load material [kg/m 3 ]
L is the length
D is the diameter of the load [m]
Case 2: Load is driven through a gear with ratio N:
Equivalent load on motor is:
2
N
J
J
load =
Case 3: Load is a mass driven by a ball screw having pitch:
2 Pitch M
load
J
×
= + J
screw
+J
coupling
J
load
, Æ Kg.m 2 , M
Æ Kg,
Pitch
Æ meter/radian
Other Cases: Make your own rough load inertia evaluations.