Rockwell Automation GMLC Reference Manual - Manual (Page 856)

Publication GMLC-5.2 - November 1999
Moves, Jogs, and Time-Lock Cams with Gearing, Position-Lock Cams, or Interpolated Motion 819
Connect the 0 (false) node of the On Expression block back to its input to
form a wait for position function and enter an expression that logically
combines the conditions for which you want to wait.
For example, the axis locked status condition does not check whether the
velocity of the axis is zero. If an axis has significant overshoot or ringing
at the end of the move, the axis locked condition becomes true before the
actual motion has settled out. In this case, use an expression of the
following form in the On Expression block to wait for the velocity of the
axis to be zero and the axis to be locked.
(Average_Velocity_AXIS0 = 0) && Lock_status_AXIS0
This technique can be extended to wait for other combinations of
conditions for many different applications.
Moves, Jogs, and Time-Lock Cams with Gearing, Position-Lock
Cams, or Interpolated Motion
When a move, jog, or time-lock cam is used in conjunction with gearing,
or a position-lock cam, or interpolated motion on the same axis, the
situation is a little different. In this case, the axis is locked
(Lock_status = 1) whenever the position error is less than the position
lock tolerance, regardless of whether the move, jog, or time-lock cam is
done or not.
Why the difference? Because in incremental motion applications (where
moves, jogs, and time-lock cams are used without gearing or position-
lock cams to position the axis to some specific point), it is most important
to know when the motion has finished and the axis is in position. The fact
that it is in position during the motion is of no consequence.