2-156 S Curve
Time to Max Speed
Note that S-curve time is defined for accelerating from 0 to maximum
speed. With maximum speed = 60 Hz, Ta = 2.0 sec, and S-curve = 25%,
acceleration time is extended by 0.5 seconds (2.0 * 25%). When
accelerating to only 30 Hz the acceleration time is still extended by the
same amount of time.
Crossing Zero Speed
When the commanded frequency passes through zero the frequency will
S-curve to zero and then S-curve to the commanded frequency.
The following graph shows an acceleration time of 1.0 second. After 0.75
seconds, the acceleration time is changed to 6.0 seconds. When the
acceleration rate is changed, the commanded rate is reduced to match the
requested rate based on the initial S-curve calculation. After reaching the
new acceleration rate, the S-curve is then changed to be a function of the
new acceleration rate.
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Seconds
Hz
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
0.0 1.0 2.0 3.0 4.0 5.0
Seconds
Hz
-80.0
-60.0
-40.0
-20.0
0.0
20.0
40.0
60.0
80.0
0.0 1.0 2.0 3.0 4.0 5.0
Seconds
Hz
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
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