Siemens Sinumerik 840D sl Programming Manual page 469

Optimization possibility
If the automatic optimization is selected (<Opt>="P") and if the parameter smoothing
distance (<Dist>) and angular tolerance (<angular tolerance>) are specified for the
following axis, then for tangential tracking, velocity steps of the slave axis as a result of steps
in the leading axis contour are smoothed. In this case, the following axis is controlled with
look ahead (refer to the diagram) in order to keep the deviation as small as possible.
Defining the angle change
The angular change limit at which an intermediate block is automatically inserted is defined
using the following machine data:
MD37400 $MA_EPS_TLIFT_TANG_STEP (Tangent angle for corner recognition)
Effect on transformations
The position of the rotary axis to which follow-up control is applied can act as the input value
for a transformation.
Explicit positioning of the following axis
If an axis, which is following your lead axes, is positioned explicitly the position is added to the
programmed offset angle.
All distance data are permissible (path and positioning axis motion).
Status of coupling
The status of the coupling can be interrogated in the NC part program using the system
variable $AA_COUP_ACT[<axis>]:
Value
0
1,2,3
Job planning
Programming Manual, 02/2011, 6FC5398-2BP40-1BA0
8.1 Tangential control (TANG, TANGON, TANGOF, TLIFT,
Meaning
No coupling active
Tangential follow-up active
Path traversing behavior
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