Rockwell Automation Publication MOTION-UM003K-EN-P - January 2019 327
Out of Box Configuration for PowerFlex Drives Appendix B
Why Does The Axis Reverse Direction When Stopped and Started?
While an axis is jogging at its target speed, you stop the axis. Before the axis
stops completely, you restart the jog. The axis continues to slow down and then
reverses direction. Eventually the axis changes direction again and moves in the
programmed direction.
Example
You use a Motion Axis Stop (MAS) instruction to stop a jog. While the axis is
slowing down, you use a Motion Axis Jog (MAJ) instruction to start the axis
again. The axis continues to slow down and then moves in the opposite
direction. Eventually it returns to its programmed direction.
Look For
Cause
When you use an S-curve profile, jerk determines the acceleration and
deceleration time of the axis:
• An S-curve profile has to get acceleration to 0 before the axis can speed
up again.
• If you reduce the acceleration, it takes longer to get acceleration to 0.
• In the meantime, the axis continues past 0 speed and moves in the
opposite direction.
S-curve profile in the
instruction that starts
the motion.
Stop Type is set to a specific type of
motion, such as Jog or Move.
The stopping instruction changes
the deceleration. For example, the
Change Decel operand of an MAS
instruction is set to No. This No
means that axis uses its maximum
deceleration rate.
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