Three-Encoder System - Siemens Simatic Manual

Storage and retrieval machines and safety functions
Figure 5: Two-encoder system, version 3
1.2.4

Three-encoder system

Sensing:
a) Sin/cos motor encoder via PROFIsafe telegram from SINAMICS S120. Two direct measuring sys-
tems using a standard telegram:

Position 1 via SINAMICS S120

Position 2 from distributed I/O with secure communication via an F module.
Figure 6: Three encoder system, version 1
b) Sin/cos motor encoder via PROFIsafe telegram from SINAMICS S120. Two direct measuring sys-
tems using a standard telegram:

Positions 1 and 2 via distributed I/O. One channel with secure communication via F mod-
ule.
Figure 7: Three encoder system, version 2
Three-encoder systems are used if a high degree of slip is to be expected, and as a result the motor en-
coder cannot be used to check the plausibility of the position. Instead, the plausibility of the position is
checked by making a cross comparison between the two direct measuring systems.
Safety notes and instructions
To identify a bus driver that has "frozen up", i.e. there is no longer any communi-
cation between the measuring system and CPU, there must be at least one fail-
S7-Distributed Safety/SIMATIC Safety - fail-safe function blocks for storage and retrieval machines
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