Siemens SINAMICS S120 Function Manual page 482

Function modules
9.8 Basic positioner
If a signal at binector input p2613 (reversing cam, MINUS) or at binector input p2614 (reversing
cam, PLUS) is detected during reference point approach, the search direction is reversed.
If the minus reversing cam is approached in the positive direction of travel or the plus reversing
cam in the negative direction of travel, fault F07499 (EPOS: reversing cam approached with the
incorrect traversing direction) is output. In this case, the wiring of the reversing cams (BI: p2613,
BI: p2614) or the direction of approach to the reversing cam must be checked.
The reversing cams are low active. If both reversing cams are active (p2613 = "0" and p2614
= "0"), the drive remains stationary. As soon as the reference cam is found, then
synchronization to the reference zero mark is immediately started (refer to step 2).
If the axis leaves its start position and travels the distance defined in parameter p2606 (max.
distance to reference cam) heading towards the reference cam without actually reaching the
reference cam, the drive remains stationary and fault F07458 (reference cam not found) is
issued.
If the axis is already located at the cam, when referencing is started, then traversing to the
reference cam is not executed, but synchronization to the reference zero mark is immediately
started (refer to step 2).
Note
The velocity override is effective during the search for the cam. By changing the encoder data
set, status signal r2684.11 (reference point set) is reset.
The cam switch must be able to supply both a rising and a falling edge. For a reference point
approach with evaluation of the encoder zero mark, for increasing actual position values the 0/1
edge is evaluated and for decreasing actual position values, the 1/0 edge. Inversion of the edge
evaluation is not possible at the sensor zero mark.
If the length measuring system has several zero marks which repeat at cyclic intervals (e.g.
incremental, rotary measuring system), you must ensure that the cam is adjusted so that the
same zero mark is always evaluated.
The following factors may impact the behavior of the "reference cam" control signal:
● Switching accuracy and time delay of reference cam switch
● Position controller cycle of drive
● Interpolation cycle of drive
● Temperature sensitivity of machine's mechanical system
Step 2: Synchronization to reference zero mark (encoder zero mark or external zero mark)
Reference cam available (p2607 = 1):
In step 2, the drive accelerates to the velocity specified in p2608 (zero mark approach velocity)
in the direction opposite to that specified using binector input p2604 (reference point approach
start direction). The zero mark is expected at distance p2609 (max. distance to zero mark). The
search for the zero mark is active (status bit r2684.0 = "1" (reference point approach active)) as
soon as the drive leaves the cam (p2612 = "0") and is within the tolerance band for evaluation
(p2609 - p2610). If the position of the zero mark is known (encoder evaluation), the actual
position of the drive can be synchronized using the zero mark. The drive starts the search for
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Function Manual, 06/2019, 6SL3097-5AB00-0BP2
Drive functions