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

05.08
5.4.6 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 eval-
uates 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:
S 1–encoder system without actual value synchronization
S 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 MD 36942:
$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.
The actual values are synchronized in the crosswise data comparison clock cycle.
Actual value synchronization is also performed when a crosswise data comparison
of the SI actual position outputs an error.
Actual values are also synchronized after "referencing" and for "parking axis".
The currently determined and the maximum SI speed difference since the last
reset are displayed in the axis–specific service screen for diagnostic purposes.
In order to define the slip tolerance, in MD 36949: $MA_SAFE_SLIP_VELO_TOL
the maximum differential speed is set. As a result of an action, such as e.g. maxi-
mum acceleration when starting, gearbox stage changes with oscillation, a situa-
tion is created where the actual values drift apart. This value can be taken as nom-
inal value from the diagnostics screen "Maximum velocity difference", multiplied by
a factor of 1.5 and then entered into MD 36949.
Note
Actual values are only synchronized when there is an actual value difference
between the two channels of 2 mm or 2 m degrees in each SI monitoring clock
cycle.
© Siemens AG 2008 All Rights Reserved
SINUMERIK 840D sl/SINAMICS S120 SINUMERIK Safety Integrated (FBSI sl) – 05.2008 Edition
Basics on the Safety Functions Integrated in the System/Drive
5.4 Actual value conditioning
5-107