Overview Of The Safety Functions Integrated In The System - Siemens SINUMERIK 840D sl Function Manual

Features of the two-channel, diverse structure
A two-channel, diverse structure is characterized by the following features:
● Two-channel structure with at least 2 independent computers (i.e. computers with different
hardware and software).
● Crosswise result and data comparison with forced checking procedure for the purpose of
detecting internal errors even in functions that are not often used (dormant errors).
● The computers can access data, reaction-free and decoupled at the shared (common)
interfaces (e.g. actual value input).
Detecting
The actual values of the individual axes are sensed by the sensor modules through two
channels and are provided to the drive and control.
In order to connect sensors and actuators in a safety-related fashion, their process signals
must be connected for further processing.
Evaluating
The safety-related functions are executed independently of one another by the NCK-CPU,
PLC-CPU and the drive CPUs. The CPUs cyclically and mutually compare their safety-related
data and results (crosswise data comparison). A test can be carried out - initiated by the CPUs
- to check the switch-off signal paths and actuators (forced checking procedure).
Reacting
When the integrated safety-related functions respond, the drive processors, the PLC processor
and/or the NCK processor can act on the connected actuators in a safety-related fashion in-
line with the actual situation. For example, the appropriate stop responses for the drives can
be initiated and the actuators shutdown via the switch-off signal paths.
3.2.1

Overview of the safety functions integrated in the system

The safety functions are available in all modes and can communicate with the process using
safety-related input/output signals. They can be implemented for each individual axis and
spindle.
● Safe shutdown (stops)
When a monitoring function or a sensor responds (e.g. a light grid), the drives are safely
controlled down to standstill, optimally adapted to the actual operating state of the machine.
● Safe monitoring of the acceleration (SBR)
Monitors the speed characteristic. The speed must decrease after a stop request.
● Safe standstill (SH)
The drive pulses are suppressed, allowing the energy feed to be safely and electronically
disconnected.
Safety Integrated
Function Manual, 12/2017, 6FC5397-4BP40-6BA1
3.2 Safety technology integrated in the system
Brief description
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