Siemens SINAMICS S120 Function Manual page 438

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7.7 Closed-loop position control

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 on the reproducible encoder range of

It is possible to activate position tracking for several DDS.

Virtual multiturn encoder (p2721)

The number of resolvable load rotations for a rotary absolute encoder with active position

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.

If the gear ratio 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 five load rotations before the same absolute value is achieved again.

In the case of linear axes, the virtual multiturn resolution (p2721) is preset to the multiturn

resolution value of the encoder (p0421), which is extended by six bits, (max. 32

positive/negative overflows).

The setting for p2721 cannot be edited again afterwards.

Example: Multiturn encoder:

For a linear axis, the value for p2721 is set to 262144 for an encoder with p0421 = 4096.

That means, +/- 131072 encoder revolutions or load revolutions can be reproduced in this

If, as a result of extension of the multiturn information, the displayable area of r2723 (32 bits)

is exceeded, the fine resolution (p0419) must be reduced accordingly.

Function Manual, (FH1), 01/2013, 6SL3097-4AB00-0BP3

Drive functions