Actual Value Synchronization (Slip For 2-Encoder Systems) - Siemens SINUMERIK 840D sl Function Manual

Basics regarding the safety functions integrated in the system/drive
6.4 Actual value conditioning
$MA_SAFE_ENC_IS_GEAR_REVERSAL (gearbox direction of rotation reversal) is available
on the NC side for all gearbox stages.
If, a value of 1 (TRUE) is entered in MD SAFE_ENC_IS_GEAR_REVERSAL for a gearbox
stage, then this results in a direction of rotation reversal of the safety-relevant actual value,
and compensates the direction of rotation reversal of the mechanical gearbox.
The default value 0 (FALSE) of MD SAFE_ENC_IS_GEAR_REVERSAL for a gearbox stage
corresponds to the previous response, i.e. the safety-relevant actual value direction of rotation
is not reversed.
When parameterizing the system, ensure that the load-side actual value has the same sense
in the safety-relevant actual value systems (NCK and DRV). Otherwise, incorrect
parameterization of the direction of rotation reversal in one or in both actual value sensing
channels (NCK, DRV) results in an error in the crosswise data comparison (CDC).
Referencing:
When referencing, the positions of the NC and SI actual value systems are set to the same
value at a defined transfer time.
If, during referencing - after this transfer time - motion still occurs, e.g. until standstill is reached
- and the NCK and Safety Integrated (SI) actual value systems have a different direction of
rotation - from this transfer time on, these count in opposing directions, and result in an offset
between the actual values the NC and SI actual value system.
This must be taken into consideration for monitoring functions with absolute reference (SE,
SN)!
6.4.6

Actual value synchronization (slip for 2-encoder systems)

Description of function
When a 2-encoder system is used, SI actual values from the NC and the drive drift apart for
systems that have inherent slip. The reason for this is that the drive evaluates the motor
measuring system and the NC evaluates the direct measuring system after the gearbox.
There are the following two alternatives in order to avoid this:
● 1-encoder system without actual value synchronization
● 2-encoder system with actual value synchronization and therefore additional monitoring of
the load side
Slip tolerance
The actual value is synchronized through two channels. In both channels, machine data 36949
$MA_SAFE_SLIP_VELO_TOL / parameter p9549 "SI Motion slip velocity tolerance" is used
in which the maximum offset between the NCK and drive actual value is entered as velocity.
The tolerance value entered in MD36942 $MA_SAFE_POS_TOL is not relevant.
For the actual value synchronization, both channels correct their SI actual position to half the
determined actual value difference. Please note that the two SI actual positions no longer
display the correct absolute position. The NC actual position and the two SI actual positions
are different.
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Function Manual, 12/2017, 6FC5397-4BP40-6BA1
Safety Integrated