Siemens SINAMICS S120 Function Manual page 488

Function modules
8.8 Basic positioner
By using a reduction gear between the motor and the load (spindle), the drive detects
several revolutions of the motor per mechanical revolution of the load - and therefore also
several encoder zero marks.
The higher-level control/position control when referencing requires a unique reference
between the encoder zero mark and the machine axis (load/spindle). This is the reason that
the "correct" zero mark is selected using a BERO signal.
Example with a measuring gear
Figure 8-19
The diagram shows an application example for using referencing with several zero marks
per revolution with a measuring gear located between the motor/load and encoder.
As a result of the measuring gear, several encoder zero marks appear within one motor/load
revolution. Using the BERO signal, also here, the correct zero mark for referencing can be
selected from the several encoder zero marks.
Preconditions
● The position of the zero mark that has the shortest distance to the position when the
BERO signal switches is to be determined.
● The appropriate mechanical preconditions must be fulfilled when mounting the BERO.
● Preferred mechanical configuration
The BERO signal covers the zero mark, as in this case, the zero mark selection is
independent of the direction of rotation.
● In order to be able to precisely determine the position of the BERO (in relation to the
reference position of the encoder) even at higher speeds, this must be connected to a
fast Control Unit input.
488
Measuring gear between the motor and encoder
Function Manual, (FH1), 04/2014, 6SL3097-4AB00-0BP4
Drive functions