Functional Safety; Safety Concept; Relevant Standards - Kübler Sendix 58 FS2 Instructions D'utilisation

3.4 Functional Safety

The encoders are designed for integration in safety-related
functions regarding rotational speed, rotation direction and
position. For this purpose, a superordinate, safe encoder
evaluation device or safety controller is required. Its encoder-
internal diagnostics do not allow the encoder to trigger on its
own initiative actions such as initiating a safe state. It belongs
to the Acquisition / Sensor category in the safety function.
Information about "functional safety"
The encoders described in this manual are, depending on the
variant selected, suitable for use in safety-oriented systems
up to SIL2 or SIL3 according to EN 61800-5-2 and up to PLd
or PLe according to EN ISO 13849-1 and in conjunction with
controllers or evaluation units that have the necessary dia-
gnostic function DC=90 % or DC=99 %.

3.4.1 Relevant Standards

The safety assessment of the encoder is based on the follow-
ing standards and safety classes:
Relevant Safety Integrity Level (SIL) according to EN
Standards 61800-5-2
Performance Level (PL) according to EN
ISO 13849-1
BA Sendix® 58xxFS2 / 58xxFS3 - R60049.0009 - 04
NOTICE

3.4.2 Safety Concept

3.4.2.1 Safe Incremental Encoder Function
To obtain safe incremental information with the encoder, the
encoder evaluation unit must check the validity of the analog
signals. For a speed determination with the correct algebraic
sign, as well as for correct incremental information, both the
sine signal and the cosine signal must be evaluated, e.g. us-
ing the function sin²(x) + cos²(x) = 1 and quadrant monitoring
of the resulting unit circle, e.g. by means of permanent speed
monitoring.
3.4.2.2 Safe Absolute Encoder Function
Loss of safety
The digital absolute information is not part of the certification.
The digital absolute position cannot be used alone to realize
safety functions.
To obtain safe information on the absolute position with the
encoder, the encoder evaluation unit must also count the in-
cremental information (relative position) and compare it with
the absolute position also provided by the encoder.
The comparison of the digital position data with the sine and
cosine signals allows continuously checking the reported pos-
ition and detecting a deviation of the two signals. Since this
function requires both the incremental information and the ro-
tation direction information for the check, the achievable
safety level is limited to this.
NOTICE
EN - 39