Siemens SIMATIC FM 351 - Page 114

Modes and Jobs
9-28
FM 351 Positioning Module
C79000-G7076-C351-02
Data Used in the Channel DB
Address Name Type Initial Value Comment
15.0 START BOOL FALSE 1 = start positioning
15.2 DIR_M BOOL FALSE 1 = direction minus
15.3 DIR_P BOOL FALSE 1 = direction plus
15.7 DRV_EN BOOL FALSE 1 = activate drive enable
16.0 MODE_IN BYTE B#16#0 4/5= relative/absolute incremental
approach
17.0 MODE_TYPE BYTE B#16#0 Incremental dimension number 1 – 100,
254 or 255
34.0 PLOOP_ON BOOL FALSE 1 = loop traverse in plus direction
34.1 MLOOP_ON BOOL FALSE 1 = loop traverse in minus direction
34.2 EI_OFF BOOL FALSE 1 = do not evaluate enable input
Fictitious Target
If you start positioning with a target that is located in the direction opposite to that
set for the loop traverse, the FM 351 calculates a fictitious target for this target at
which it reverses direction and then approaches the target in the correct direction.
This fictitious target must be located at a position corresponding to at least half the
target range before the relevant software limit switch.
The distance between the fictitious target and the set target is calculated
depending on the direction:
Table 9-6 Calculating the Location of the Fictitious Target for a Loop Traverse
Settings
Location of the Fictitious Target
Parameter settings:
Loop + (force contact plus)
and travel in minus direction.
The fictitious target (target
f
) has the value:
Target
f
= target – switch-off diff. minus – switchover diff. plus
Start position
Target
Fictitious target
0
Parameter settings:
Loop – (force contact minus)
and travel in the plus direction.
The fictitious target (target
f
) has the value:
Target
f
= target + switch-off diff. plus + switchover diff. minus
Start position Target Fictitious target
0