Beckhoff AX8911, Документация

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Safe Motion functions
AX8911 47 Version: 1.2.0
7.4.3 Checking SafeDriveFeedback Position Valid
Each feedback system of AX8000 returns the Boolean information as to whether the current position data
have valid values.
There are 2 feedback systems for each axis. These are, for each axis, an OCT safety encoder on connection
X13 (or X23 if existent) and an EnDat 2.2 encoder on connection X21 (or X22 if existent).
Both feedback systems of an axis can be active at the same time and used within the safe logic.
WARNING
Position Valid
So that the axis positions can be used, the user must evaluate the Position Valid signal of the correspond-
ing feedback systems. Further feedback information is only entered if PositionValid = TRUE . If PositionVa-
lid = FALSE , the further feedback signals are frozen with their current values.
The address offsets for the signals SAFEDRIVEFEEDBACK Axis x Position Valid can be found in the
chapter Process image [
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38] .
7.4.4 Evaluation of AX8000 Status
In the case of an error or unexpected behavior of the AX8000 that is not signaled to the AX8911 and the
safety application, an expectation that can discover corresponding faulty behavior can be implemented via
an appropriate safety application.
The table below contains a list of possible tests that the user can implement.
Name Description Error reaction
Velocity Comparison of target and actual velocity. The actual
velocity is made available within the safety application
as a safe signal. The target velocity can be read via the
NC interface and transferred to the safety application.
Scaling can take place in the safety application or in the
standard PLC.
In addition, a "stuck at" error of the standard signal can
be detected within the safety application via the FB
Scale.
STO and brake + if applicable
service brake at safe output
Position Comparison of the actual and target positions from
safety application and NC controller. If the two positions
deviate too much from each other at runtime, this can be
detected by an FB Compare. A corresponding error
reaction can then be triggered within the logic. STO and brake + if applicable
service brake at safe output
7.4.5 Sample of an implementation in the TwinCAT Safety Editor
This sample shows a simple TwinSAFE project for an 1-axis device in which the activation of STO and the
brake takes place via a connection to a decentralized TwinSAFE logic (signal ActivateSTO executed within
the external safety logic in Category 4 / Performance Level e). The Restart signal also comes into the
AX8911 logic via this safe connection. If the result of the risk and hazard analysis is that the restart must be
implemented within the safety logic, then the restart must be wired to a safe input and then transferred to the
AX8911 via the FSoE connection.
In addition to the STO Signal, all module errors of the AX8911 are logically ORed and then fed to a negated
input of the FB ESTOP. The result of this is that the STO function is executed in the case of a module error
of the axis. This way, the axis can only be restarted when there is no error.