Siemens SINAMICS S120 Function Manual page 274

Function modules
7.8 Closed-loop position control
Configuration of the load gear (p2720).
The following points can be set by configuring this parameter:
● p2720.0: Activation of position tracking
● p2720.1: Setting the axis type (linear axis or rotary axis)
● p2720.2: Reset position
Note
If position tracking of the load gear is activated with parameter p2720[0]=1 (position gear
load tracking) after the encoder is adjusted (p2507=3), the adjustment will be reset.
If the encoder is adjusted again when load position tracking is active, the load gear position
will be reset (overflows).
The permissible position tracking range is mapped onto the reproducible encoder range of
EPOS.
Position tracking can be activated in FW2.5 SP1 only for one DDS.
With FW version V2.6 and higher, position tracking can be active in more than one DDS.
Virtual multiturn encoder (p2721)
The number of resolvable load rotations for a rotary absolute encoder with active position
tracking
can be set by means of the virtual multiturn resolution.
It is only editable for rotary axes.
With a rotary absolute encoder (p0404.1 = 1) with activated position tracking (p2720.0 = 1),
p2721 can be used to enter a virtual multiturn resolution.
NOTICE
If the gear factor is not equal to 1, then p2721 always refers to the load side. The virtual
resolution, which is required for the load, is then set here.
In the case of rotary axes, the virtual multiturn resolution (p2721) is preset to the multiturn
resolution value of the encoder (p0421) and can be altered.
Example: Singleturn encoder
Parameter p0421 is preset to p0421 = 1. However, parameter p2721 can be altered
subsequently, e.g. the user can program p2721 = 5. As a result, the encoder evaluation
initiates 5 load rotations before the same absolute value is achieved again.
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Here, a rotary axis refers to a modulo axis (modulo offset can be activated through
higher-level control or EPOS). With a linear axis, position tracking is mainly used to
extend the position area (see section: Virtual multiturn encoder (p2721)).
The position values stored in non-volatile memory are reset in response to the following
events:
– When encoder replacement is detected.
– When the configuration of the encoder data set (EDS) is modified.
– When the absolute encoder is adjusted again.
Function Manual, (FH1), 10/2008, 6SL3097-2AB00-0BP5
Drive functions