Delta RMC151 - Manual (Page 826)

RMC70/150 and RMCTools User Manual
then these commands can be issued even though the axis is not at the correct starting
point. When the pressure/force command is issued, the axis will move toward the
requested profile (curve, sine wave, gearing relationship, etc.) as defined by the
transition command.
When the RMC powers up, transitions are disabled on all axes. To enable pressure/force
transitions, issue the Transition Rate Prs/Frc (64) command. Once this command has
been issued, it does not need to be issued again, unless you wish to specify a different
transition, or if you need to re-enable pressure/force transitions after disabling them. To
disable pressure/force transitions, issue the Transition Disable (Prs/Frc) (63) command.
This command will not affect any transitions that are in progress.
Transition Types
This command provides the following transition options:
• Seek (0)
The axis will move toward the requested profile using the Prs/Frc Rate and Prs/Frc
Accel Rate. When the pressure/force and pressure/force rate of the axis come close
to the position and velocity of the profile, the axis will "lock" onto the profile. Use this
option to get to the requested profile quickly and smoothly.
• Reach (1)
The axis will move toward the requested profile using the Prs/Frc Rate and Prs/Frc
Accel Rate. When the pressure/force reaches the pressure/force of the profile, the
axis will "lock" onto the profile. Notice that this option does not require the
pressure/force rates to be close when it locks on, and therefore may cause the axis to
jerk. Use this option to get to the requested profile as quickly as possible.
• Superimposed (2)
A trapezoidal move using the Prs/Frc Rate and Prs/Frc Accel Rate will be
superimposed onto the requested profile such that the axis will reach the profile.
Notice that since the move is superimposed onto the profile, the axis will not
necessarily move at the specified pressure/force rate and acceleration rate, but rather
at the sum of the rates and accel rates from the requested profile and superimposed
portions of the move.
This method will always guarantee that the axis will lock on to the requested profile,
even if the Prs/Frc Rate and Prs/Frc Accel Rate are slower than that of the
profile. The time it takes to lock on will be based on how far the current Target
Pressure/Force is from the profile and on the Prs/Frc Rate. For example, if the
Target Pressure/Force is 3, the requested profile is at 9, and the Prs/Frc Rate is 6, it
will take roughly one second to lock on. The "lock-on" of the Superimposed method
will usually be as smooth or smoother than Seek.
Choosing a Transition Type
In general, try the Seek method first. If it takes too long to lock on, switch to Reach. For
either of these methods, make sure to set the Prs/Frc Rate and Prs/Frc Accel Rate to
values higher than that of the profile it is trying to follow. Otherwise, the axis may never
catch up to the requested profile. Notice that if the master register is stopped, then all 3
methods will perform similarly.
If the transition is used for a gearing application, the behavior of any of the methods will
be the same if the master is not moving while the transition is taking place. If the master
is moving, and is a well-behaved Target Pressure/Force, then the Seek and Reach
methods will both behave very similarly. If the master is moving, but is noisy, such as an
analog reference signal, then the Reach method will "lock in" the quickest, but may
cause a jerk.
The Superimposed method is not as useful as the first two methods, but it can provide a
more predictable "lock-on", as described above. Also, this method will always guarantee
that the axis will lock on to the requested profile, even if the Prs/Frc Rate and Prs/Frc
Accel Rate are slower than that of the curve.
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