Scaling The Input Variables; Principle Of Operation; Parameterization; Load Monitoring - Siemens Simatic Manual

Fail-safe function blocks for storage and retrieval machines

3.9.2 Scaling the input variables

The block expects the input of load limits or the actual load values as percentage to two decimal plac-
es, i.e. a value of 10000 corresponds to 100%. The user must make this scaling corresponding to the
reference variable of the module used.
For F-AI modules, for example, the reference variable is 27648. The F-library Distributed Safety (V1)
includes the "F_SCA_I" block specifically for this purpose.
The user must program this scaling himself if hardware with different reference variables is used.
Safety notes and instructions
The user must correctly calculate the load limit values corresponding to the re-
quirements laid down in EN528. The user must appropriately interconnect the
calculated limit values at the block.
3.9.3

Principle of operation

3.9.3.1

Parameterization

When parameterizing (assigning parameters) it should be observed that the following rela-
tionships must be able to be represented as integer multiple:
T_TEST / T_SAMPLE
T_SETTLE / T_SAMPLE
Further, the following relationships must exist between the input variables:
MINLOAD < MAXLOAD_STAT <= MAXLOAD_DYN
T_TEST > T_SETTLE > 0
The permissible value ranges of the individual inputs should be taken from the table describing
the inputs.
The block identifies if not all of the mentioned preconditions are satisfied, and this is signaled as
parameterizing error with the appropriately set DIAG bits.
Note
The block only checks the parameterization at the 1st call. This results in a sub-
sequent increased block performance.
As a consequence, reparameterization is not permitted when safety operation is
deactivated. The safety program must be regenerated and loaded each time that
any of the block operating parameters are changed.
3.9.3.2

Load monitoring

1. If two independent sources are used to measure the force, then these should be interconnect-
ed at LOAD1 or LOAD2 after scaling. If one measuring source is sufficient, then this is inter-
connected at both inputs.
2. If the difference between the two inputs is higher than the value parameterized at
MAXTOL_LOAD, then ERROR is set = 1 and DIAG bit is set to 0
3. In addition, the velocity parameterized at VMAX_RELEASE is output at SLS_THRESHOLD.
4. If both values lie within the window that can be parameterized using MAXTOL_LOAD, then us-
ing a positive edge at ACK, output ERROR and DIAG bit 0 can again be reset to 0.
5. Input MAXLOAD_MODE can be used to make a distinction between monitoring for steady-
state overload (MAXLOAD_MODE = 0) or dynamic overload (MAXLOAD_MODE = 1).
6. For MAXLOAD_MODE =0, as soon as the value at LOAD1 or LOAD2 exceeds the value pa-
rameterized at MAXLOAD_STAT, then this error is signaled using a 0 signal at
STAT_LOAD_OK.
7. In addition, ERROR is set to 1 and DIAG bit 1 is set
S7-Distributed Safety/SIMATIC Safety - fail-safe function blocks for storage and retrieval machines
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