Rockwell Automation GMLC Reference Manual - Manual (Page 238)

Publication GMLC-5.2 - November 1999
Move Axis 201
Absolute Moves on Rotary Axes
When an axis is configured for rotary operation, the motion controller
handles absolute moves the same as with linear axes, except that when the
axis position exceeds the unwind parameter, axis position is unwound. In
this way, axis position never exceeds the unwind value, and never falls
below zero.
The specified position is interpreted trigonometrically and can be positive
or negative and can exceed the unwind value. Negative position values
are equivalent to their corresponding positive values (i.e. –90° is the same
as +270° etc.) and are useful when rotating the axis through zero. When
the position exceeds the unwind value, the axis moves through more than
one revolution before stopping at an absolute position.
Incremental Moves
When you select Incremental from the Move field, the axis moves the
specified distance at the specified speed, using the specified acceleration
and deceleration.
Changing the Move Distance
You can change the final destination of an incremental move while the
move is in progress (but not while the axis is accelerating or decelerating
with S curve or parabolic profiles) using another Move Axis block with
an additional incremental distance. The total distance moved by the Move
Axis blocks is the sum of the two distances.
You can also change the final destination of an incremental move while a
move is in progress, using another Move Axis block with a new absolute
position. In this case, the axis goes directly to the specified absolute
position without completing the incremental move. This action is
different from the case where an incremental Move Axis block follows an
absolute Move Axis block.