Siemens SINAMICS S120 Function Manual page 454

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Function modules

9.7 Position control

Example: Position range extension

With absolute encoders without position tracking, it must be ensured that the traversing range

around 0 is less than half the encoder range, because beyond this range, no unique reference

remains after switching on and off (see description on parameter p2507). This traversing range

can be extended using the virtual multiturn (p2721).

The following diagram illustrates an absolute encoder that can represent eight encoder

revolutions (p0421 = 8).

In this example, this means:

● Without position tracking, the position for +/- 4 encoder revolutions around r2521 = 0 LU can

be reproduced.

● With position tracking, the position for +/- 12 encoder revolutions (+/- 12 load revolutions

with load gear) can be reproduced (p2721 = 24).

Practical example:

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

means that +/- 131072 encoder revolutions or load revolutions can be reproduced.

For a rotary axis, a value for p2721 = p0421 is set for an encoder.

Virtual multiturn encoder (p2721)

The virtual multiturn resolution is used to set the number of resolvable load rotations for a rotary

absolute encoder with activated position tracking. It can be edited only for rotary axes.

With a rotary absolute encoder (p0404.1 = 1) with activated position tracking (p2720.0 = 1),

parameter 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

Position tracking (p2721 = 24), setting p2504 = p2505 =1 (gear ratio = 1)

Function Manual, 06/2019, 6SL3097-5AB00-0BP2

Drive functions