Siemens SINUMERIK 840C - Manual (Page 913)

12 Functional Descriptions 03.95
12.18.6 Variable cascading of GI following drives (SW 4 and higher)
12.18.6 Variable cascading of GI following drives (SW 4 and higher)
Note:
The user must always make sure that the ring is never completely closed at any time; the
error message "NC-CPU timeout" (3085) will be output if the ring is closed with software
version 4.
There is no explicit "Monitoring for following axis rings" with separate alarm message and
suppression of the last GI link requested (which would close the ring).
If a GI ring has to be closed, re-sorting can be disabled with MD 5016, bit 7.
12.18.7 Gearbox interpolation chain
A gearbox chain is produced when a following drive acts in turn as the leading drive for
another following drive. In principle, different link structures can be configured within a gearbox
chain. However, it is not meaningful to create a gearbox chain consisting only of setpoint links
since all links can be derived from the first leading drive.
In a gearbox chain with actual value links, the dynamic response of the axes should improve
as the gearbox depth increases (increasing servo gain).
A gearbox chain with a mixture of link structures should be configured only if the individual GI
groupings fulfil the above conditions. Once an actual value link has been inserted in a chain, all
the following links must be of the actual value type.
Example: Setpoint link (K1) Actual value link (K2/K4) Actual value link (K2/K4)
LD1----------> FD1/LD2------------->FD2/LD3---------------->FD3
servo gain=0.5 servo gain=0.5 servo gain=0.7 servo gain=0.9
A gearbox chain must never be closed. It is not permissible to create a
feedback to a leading drive already in the chain;
e.g. LDx --> FDy/LDy --> FDx
This type of chain may be defined (see gantry axes), but it must be
ensured that these links are not active simultaneously.
12–138 © Siemens AG 1992 All Rights Reserved 6FC5197- AA50
SINUMERIK 840C (IA)