Rockwell Automation Publication MOTION-RM002H-EN-P-February 2018 547
If the sum of the Acceleration and Deceleration time is greater than the total time
as specified by the speed, the Acceleration and Deceleration time is reduced
proportionately so the total specified time in the Speed Parameter is met.
The Speed, when programmed in seconds, takes priority over Acceleration and
Deceleration, which in turn takes priority over Jerk. The move will always
complete in the specified total time. If the time is too short for the axes physical
limits, then a servo drive fault results.
If programmed, move parameters are inconsistent, then an attempt to fix the
inconsistency is done by giving priority to parameters in the following order (the
lower number has the higher priority):
1. Total move length. This parameter is always satisfied as programmed, it is
never changed.
2. Total move duration
3. Acceleration and Deceleration time
4. Acceleration and deceleration Jerk
• If the Acceleration Jerk time is greater than 50% of the Acceleration
Time, then the time is reduced so that the Acceleration completes in
the specified Acceleration Time. Similar calculations are performed for
the Deceleration Jerk times.
• If speed units are programmed in units of seconds, then acceleration
and deceleration must also be programmed in seconds. For this case, the
jerk can be programmed in either units of seconds or percentage of
time.
Tip:
Time based planning cannot be used for jogged moves (MAJ).
Time Based Planning is only functional for moves starting and ending at zero
velocity. An error generates if a move is started with a non-zero velocity or
acceleration. You have the option to wake-up a paused or dwelling move with a
time based move. See Dwells for more information.
The values of zero for acceleration, deceleration, or jerk times are permitted and
will generate infinite acceleration, deceleration, or jerk. A value of zero for speed
generates a runtime error. For an S-curve profile, an infinite jerk will change to a
trapezoidal profile.
All the existing functionality for the Time Based programming mode is supported
when you operate in Master Driven mode. Time becomes master distance in
Master Driven mode.
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