Efficient Networks Siemens Sinamics S120 - Manual (Page 261)

Function modules
7.9 Basic positioner
Drive Functions
Function Manual, (FH1), 07/2007 Edition, 6SL3097-2AB00-0BP4
261
CAUTION
During adjustment with the rotary absolute encoder, a range is aligned symmetrically
around the zero point with half the encoder range within which the position is restored after
switch off/on. If position tracking is deactivated (2720.0 = 0), only one encoder overflow is
permitted to occur in this range (further details are given in chapter Position controller ->
Actual position value conditioning). Once adjustment has been carried out, the range must
not be exited because a unique reference between the actual encoder value and the
mechanical components cannot be established outside the range.
If the reference point p2599 is in the encoder range, the actual position value is set in line
with the reference point during adjustment. Otherwise, it is set to a corrected value in the
encoder range.
No overflow occurs with linear absolute encoders, which means that the position can be
restored within the entire traversing range after switch on/off once adjustment has been
carried out. During adjustment, the actual position value is set in line with the reference
point.
Reference point approach for incremental measurement systems
When the reference point approach (in the case of an incremental measuring system), the
drive is moved to its reference point. In so doing, the drive itself controls and monitors the
complete referencing cycle.
Incremental measuring systems require that after the machine has been powered-up, the
absolute dimension reference is established to the machine zero point. When powering-up
the position actual value x
0
in the non-referenced state is set to x
0
= 0. Using the reference
point approach, the drive can be reproducibly moved to its reference point. The geometry
with a positive starting direction (p2604 = "0") is shown in the following.