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Setting rotation time
Even if the torque that is generated by the rotary actuator is small, the parts could become damaged
depending on the inertia of the load. Therefore, the rotation time should be determined by calculating the
load
’s inertial moment and kinetic energy.
Moment of inertia
Inertia moment indicates scales how hard to rotate the object, and also how hard to stop rotating object.
An object started by the rotary actuator is getting to have inertia force. When the rotary actuator stops at
the stroke end, the actuator received big impact (kinetic energy) due to inertia force. Please refer below
for calculation of kinetic energy.
Allowable kinetic energy for the rotary actuator is limited. The limit of rotation time is obtained by
calculating inertia moment. Please refer following for obtaining inertia moment.
Basic inertia moment
2
r
m
I
m : Weight of load (kg)
r : Load center of gravity and distance of rotation axis. (m)
This shows inertia moment of “m (weight)” at “r” from the rotation axis. Calculation of inertia moment
depends on the shape of the object. Please refer the table on the next page for inertia moment
calculation.
2
I
2
1
E
E : Kinetic energy
J
I
I
II
: Inertia moment kg/m
2
ω : Angular speed
rad/s
r
m
Fig. (10) Inertia moment
2020-10-13 10:33
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