Registration on virtual axes – Rockwell Automation GMLC Reference Manual User Manual
Page 702
Publication GMLC-5.2 - November 1999
Using Virtual Axes
665
Passively homing the virtual axis—or any axis—causes no motion. The
passive homing operation is complete when the physical axis, to which
the virtual axis is linked, is caused to move past its encoder marker pulse.
See Home Axis in the Function Blocks chapter of this manual for more
information on passive homing. The homing status of the virtual axis can
be checked using either its Homing_status variable, or an On Axis block,
as is the case with a physical axis.
During passive homing, the Marker_Distance variable for the virtual axis
is updated. The value of the Marker_Distance variable is equal to the
position of the axis when the marker occurred. The numerical change in
the actual position of the virtual axis caused by the passive homing
operation can thus be calculated as the value of the Marker_Distance
variable minus the axis’ Home Position, after passive homing is
completed. The Passively Home Axis and Calculate Position Change
module included in the GML Commander Module Library on your GML
Commander disk implements this calculation for Axis 0. See Marker
Distance in the Expression Builder chapter for more information on this
module.
A virtual axis can also be homed using a Redefine Position block to
directly set the actual position of the axis to the value that you want. See
Redefine Position in the Function Blocks chapter of this manual for more
information.
Registration on Virtual Axes
The Watch Control block can be used to set up a registration event for a
virtual axis. When a registration event occurs on a virtual axis, the
Registration_Position variable of the physical axis on the motion
controller to which the virtual axis is linked is not affected—only the
virtual axis’ Registration_Position is changed.