Rockwell Automation 1771-QA Stepper Positioning Assembly User Manual - Manual (Page 77)

3–55 Programming and Operation
Publication 1771-UM002A–EN–P – May 2000
If the resonant frequency is encountered, its effect can be dampened
or eliminated as follows:
•
If encountered in a steady state condition (at or near a chosen
final rate), increase the inertial load or change the final rate.
•
If encountered when accelerating or decelerating through the
resonant frequency, increase the rate of acceleration or
deceleration by programming shorter ramp or decel times.
In general, a stepper motor with no load is more apt to resonate than
one that has a load.
Accuracy of Ramp and Decel Times
Output accuracy (variation) varies from less than +2.5% at 20k Hz to
less than +1.0% at 1k Hz or lower (Table 3.C).
Table 3.C
Output Accuracy
Programmed Rate
Output Rate
Accuracy
20kHz-18.01kHz <+ 2.5%
18kHz-1.01kHz <+ 2.0%
1kHz-0Hz <+ 1.0%
The accuracy of the executed ramp or decel time will depend on the
programmed ramp or decel time, and the rate to which the ramp is
programmed or from which the decel is programmed. The
maximum variation in executed ramp and decel times is shown in
Table 3.D.
Table 3.D
Ramp and Decel Time Accuracy
Programmed Pulse
Rate 1
Variation in
Ramp/Decel
Time
20,000 to 2001Hz +5% 2
2,000 to 101Hz +10% 2
100 to 51Hz +25% 2
50 to 2Hz +50%
1 Rate achieved by a ramp, or the rate from which a decel begins.
2 In addition, 20ms could be added or subtracted to the value of the ramp or
decel times between 0 and 1 second.