Technical data

Drive functions
7.1 Servo control
Function Manual
Function Manual, 06/2012, 6SL3097-4AB10-0BP4
175
7.1.18 Central probe evaluation
Description
Frequently, motion control systems have to detect and save the positions of drive axes at an
instant in time defined by an external event. For example, this external event may be the
signal edge of a probe. In this case, it may be necessary to evaluate several probes or save
the position actual values of several axes, triggered by a probe event.
For the central probe evaluation, the instant in time of the probe signal is detected and saved
by a central function. From the available sample values of the position signals of the various
axes, the position actual values at the probe instant are interpolated with respect to time in
the control. For SINAMICS S, two techniques have been implemented:
● For the probe evaluation with handshake, for each probe and positive and/or negative
probe edge, up to 1 measured value is evaluated each communication cycle / each four
DP cycles.
● With a parameterizable probe evaluation without handshake, the evaluation frequency of
the probe edges can be increased up to the communication frequency/application
frequency of the probe evaluation (= SERVO cycle of the higher-level control).
Precondition: T_DP = T_MACP (i.e. cycle ratio = 1:1, no cycle reduction ratio is possible).
Common features for central measuring with and without handshake
Both measuring techniques have the following points in common:
● PROFIBUS telegrams
● Synchronization between the control and drive as a precondition for measuring.
● System time: Resolution (0.25 µs), maximum value (16 ms)
● Time stamp: Format (drive increments, NC decrements)
● Monitoring functions (sign of life)
● Fault messages
● Incrementing
In the interface, the value "0" is not a valid time format and is used to express that a
measured value is not available.