Harmonic Drive RSF Series, Руководство пользователя

Страница: 21 / 42

Chapter 2 Selection of the RSF supermini Series
RSF-super_V1_02
- 17 -
●
Example: 1
The load conditions are:
•
Rotary speed: 140r/min
•
Load moment of inertia: 0.9
×
10
-3
kg
･
m
2
•
Load torque is so small as to be negrected.
•
Acceleration/deceleration time is 0.03sec (30msec) or less.
(1) Compare these conditions with the “1-4 Specifications of RSF supermini actuators” and
temporarily select RSF-5A-50.
(2) Obtain J
A
=1.83×10
-4
kg ･ m
2
, T
M
=0.9 N ･ m, K
T
=0.54 N ･ m/A, and I
M
=2.2A from “1-4 Specifications of
RSF supermini actuators.”
(3) The friction torque of the actuator is T
F
= 0.54×2.2-0.9 = 0.29 N
･
m from Formula (3) on the
previous page.
(4) Therefore, the shortest acceleration time and deceleration time can be obtained from Formula (1)
and Formula (2), as follows:
t
a
= (0.183×10
-3
+0.9×10
-3
)×2× π /60×140/0.9 = 0.018 sec (18msec)
t
d
= (0.183×10
-3
+0.9×10
-3
)×2× π /60×140/(0.9+2×0.29) = 0.011 s (11msec)
(5) Because the assumed acceleration/deceleration time is 0.03sec (30msec) or less, the temporarily
selected actuator can be used for acceleration/deceleration, based on the result of (4).
(6) If the calculation results of the acceleration/deceleration time do not fall within the desired time
range, examine them again as follows.
•
Try to reduce the load moment of inertia.
•
Re-examine the gear ratio and gear head model.
2-4-5 Calculating equivalent duty
The load conditions, which are torque, speed,
moment of inertia, acceleration/deceleration time,
loading time, are limited by the actuator to drive the
load. To select the proper actuator, the equivalent
duty of the load should be calculated.
The %ED (percent equivalent duty) is:
100
t
t K t K t K
ED %
d Ld r Lr a La
×
× + × + ×
=
(4)
where, ta: acceleration time in second
td: deceleration time in second
tr: driving time in second
t: single cycle time in second
K
La
: duty factor for acceleration time
K
Lr
: duty factor for driving time
K
Ld
: duty factor for deceleration time
Ta, Tr, Td: output torque
ta
td
N
tr
Time
Speed
t: duty cycle
ts
Time
To
rq
u
e
Td
ts: stop time