Siemens SINUMERIK MC Commissioning Manual page 196

Safety functions integrated in the drive
4.19 Safe actual value acquisition
Actual value synchronization
1)
Figure 4-31
The mean value of the actual values of both channels is calculated cyclically after actual value
synchronization (p9301.3 = 1) has been activated, for example, for systems or machines with
slip. The maximum slip defined in p9549 is monitored in the cross-check cycle (r9724). If "actual
value synchronization" is not enabled, the value parameterized in p9542 is used as tolerance
value for the crosswise comparison.
Safe motion monitoring
The properties of the actual value acquisition determine not only the encoders used, but also
the values for safe motion monitoring that can be achieved in the best case.
● Safe maximum speed (r9730)
The maximum speed (load side) that is permissible due to the acquisition of actual values
for safe motion monitoring functions is indicated in r9730. This parameter shows up to which
load velocity the safety-relevant encoder actual values (redundant coarse encoder position)
can still be correctly sensed as a result of the particular encoder parameterization.
The actual value acquisition clock (p9511) determines the frequency at which the actual
values are acquired. The longer the clock cycle, the higher the "safe maximum velocity." On
the other hand, a longer actual value acquisition clock cycle places a greater load on the
Control Unit. You must consider this when setting the optimum for your particular
application.
● Safe positioning accuracy (r9731)
This positioning accuracy can be achieved in the best case by acquiring the actual values.
If a 2-encoder system is used, the accuracy of the poorer encoder is indicated based on the
number of encoder pulses.
196
This deviation cannot be larger than the position difference that can occur at maximum slip
(p9549) during a cross-check cycle (r9724).
Example diagram of actual value synchronization
Safety Integrated (with SINAMICS S120)
Commissioning Manual, 02/2020, A5E46305916B AB